INTRACRANIAL HYPERTENSION (IH) MEANS HIGH PRESSURE INSIDE THE SKULL.

Intracranial Pressure (ICP) is measured in millimeters of mercury (mmHg). Most scholars agree that on average, “normal pressure” should be between 5-15 mmHg, mild to moderate intracranial hypertension between 20-30 mmHg (which “requires treatment in most circumstances”), and an ICP of > 40 mmHg indicate “severe and possibly life-threatening intracranial hypertension.” [1] When high intracranial pressure is left untreated, it creates a “pushing effect” towards the only natural escape at the base of the skull (the foramen magnum) and the cerebellar tonsils in the pathway are pushed through the foramen magnum. [2]

Understanding the Monro-Kellie Doctrine (pressure-volume relationship)
The association between IH/IIH and Chiari Malformation appears to be a malicious intricate pathological circle. The cranium (skull) consists of brain matter, cerebrospinal fluid, and both venous and arterial blood. A hypothesis, referred to as the Monro-Kellie Hypothesis (now better known as the Monro-Kellie Doctrine), states, “The sum of volumes of the brain, CSF, and intracranial blood is constant. An increase in one should cause a decrease in one or both of the remaining two.” Therefore, if an abundance of cerebrospinal fluid (IIH or hydrocephalus), both cranial blood volume and brain matter should be forced to deplete. This depletion is usually directed in the path of least resistance – through the foramen magnum and into the spinal canal. When the brain matter closest to the bottom of the skull (cerebellar tonsils) is pushed through the foramen magnum and into the spinal canal (an Acquired Chiari Malformation), the tonsils act like a cork and blocks the flow of cerebrospinal fluid (regardless of the size of the tonsillar descent), which in turn, continues to raise intracranial pressure.[3]

 

More Symptoms of Intracranial Hypertension

Venous Hypertension
When an etiological cofactor exists (such as a space-occupying mass), it is considered Secondary Intracranial Hypertension (SIH); when no other cause was identified, it is known as Idiopathic Intracranial Hypertension (IIH) formerly known Pseudotumor Cerebri. However, recent studies on the connection between Intracranial Hypertension and Venous Hypertension might put an end to the “idiopathic” theory.

Oxygen-rich blood travels from the heart to the rest of the body through the arterial system, then the oxygen-depleted blood returns to the heart through the venous system. We have a host of small veins in our head and they dump into a series of large veins, called sinuses. Dural Venous Sinus Stenosis occurs when there is a narrowing of one or more of the venous sinuses (most commonly seen in the Transverse sinuses or transverse sigmoid sinus junction), which in turn compromises cerebral venous outflow. Transverse Sinus Stenosis (TSS) is most common in Idiopathic Intracranial Hypertension (IIH). Depending on the study that you are reading, it is proving to be present in 90-100% of IIH patients [4]. While its connection might sound obscure if you look at it from a Monro-Kellie perspective – The blood going into the head, cannot get out at the same speed (because of the narrowed sinus). When this inflow of blood remains constant and the outflow is hindered, the transverse sinus on that side (we have two transverse sinuses, one on each side) enlarges, forcing the CSF and brain matter to reduce to maintain the volume equilibrium. This reciprocation can happen when any of the sinuses or jugular narrow (stenosis). While scholars continue to debate whether TSS is a cause or consequence of IIH, surgeons continue to decompress us without checking our pressures or decompress (the most invasive treatment) in hopes that it will lower our pressures, and patients are left with untreated high pressure still causing a “pushing down effect” and an enlarged foramen magnum for our brains to be pushed down. [2] The sagging brain once again obstructs the flow of cerebrospinal fluid by plugging the foramen magnum, and that in turn raises the intracranial pressure even more. Or, the untreated high pressure blows through the duraplasty and causes a post-operative leak, known as a pseudomeningocele.

 

Reducing the Risks of Post-Op IH/IIH Complications
Brain MRIs often show indicators of Intracranial Hypertension (IH/IIH), therefore, we recommend that all Chiari patients have full brain MRIs and not just cervical MRIs.

• When the pressure builds inside of the dura mater the pressure pushes the dura and fluid inside of the crevice that holds the pituitary gland (the sella turcica or pituitary fossa). When the amount of fluid is equal to or greater than 50% and the pituitary gland size is 2mm, the condition is known as Empty Sella Syndrome. (Doctors now recognize that < 50% (where the pituitary gland size is 3-7mm) can also cause symptoms and they now refer to that as a partially empty sella.) [5]

• Slit like or flattened lateral ventricles from the increased pressure, however, when the Foramen of Monro (the aqueduct that connects the lateral ventricle to the third ventricle) is stenosed, the fluid will back-up and the lateral ventricle will not appear flattened. [6]

• Enlarged/swollen optical nerves (papilledema). [7]

• Low lying or herniated tonsils (often diagnosed as a Chiari Malformation). [2]

 

What We Recommend BEFORE DECOMPRESSION is considered:
If you have symptoms of IH/IIH accompanied by any of the MRI indicators mentioned above, it is both reasonable and prudent to ask your neurosurgeon to investigate further BEFORE DECOMPRESSION.

  • See a neuro-ophthalmologist to check for signs of papilledema, including Optical Coherence Tomography and Ultrasonographic B-scanning. [7]
  • Magnetic Resonance Venography (MRV, preferably with the ATECO technique) to check for venous stenosis of any of the cranial sinuses and/or jugular vein. Stenosis is not exclusive to the transverse sinus and it can happen in multiple sinuses simultaneously.
  • If overweight, consider trying to lose weight. Studies show that a weight loss of 5-10% of one’s overall body weight, when accompanied by a low-salt diet, can offer some to IH/IIH symptoms.[8]
  • Consider trying Diamox (Acetazolamide) and/or Topamax (Topiramate) to see if that improves the pressure headaches.
  • Request a lumbar puncture (spinal tap) to test your opening pressures. We recommend that it’s guided with fluoroscopy with a small gauge needle (and not the standard 22 gauge) that they allow to drip (as opposed to syringe pull) and ensure that someone is available to perform an epidural blood patch if necessary. Time should be allotted afterward to lay flat for several hours immediately following the procedure and for several days once returning home. The potential for CSF leaks is high for the EDS/Chiari patient. A doctor that marginalizes the risks ahead of time, will generally marginalize your symptoms when you are actively leaking.
  • ICP Bolt Monitoring can record the differences experienced in pressure over time, and how different positions affect ICP.

 

Note: When the intracranial pressure gets high enough, it can cause a cranial leak. This is especially true for the Ehlers-Danlos patient where the dura mater is thin and fragile. When a cranial leak decreases the intracranial pressure, the papilledema, empty sella, stenosis, and high-pressure headaches can sometimes start to revert to normal or near-normal, and the leak will affect any attempts to check intracranial pressure (reducing the pressure from what it was before the leak occurred), however the tonsillar herniation will usually remain if the pressure gets too low. [9]

 

TREATMENT OPTIONS:
If Venous Stenosis exists, stenting should be considered as leaving the sinus/jugular stenosed can post other health risks, and stenting is proving to have much better success with fewer complications requiring revisions. When medication fails to decrease ICP, and a stent is not an option, a Ventriculoperitoneal Shunt (VP Shunt) or Ventriculoatrial Shunt (VA Shunt) can be surgically placed to drain cerebrospinal fluid straight from the ventricle. Shunts are known for failing and often need a multitude of revisions, but even with all the revisions, it is less invasive than a decompression. Shunts under the foramen magnum should never be used as a means of controlling ICP.

For the IH/IIH patient, herniated tonsils should be assumed an Acquired Chiari Malformation (even if a small posterior fossa is evident), and by correcting the high pressure before decompression, the decompression will be less likely to fail.

 

Helpful Tips:
If you have IH/IIH, it is best to avoid caffeine, avoid progestin based birth control, and all EDS patients should try to avoid the use of fluoroquinolones such as ciprofloxacin (Cipro), levofloxacin (Levaquin/Quixin), gatifloxacin (Tequin), moxifloxacin (Avelox), ofloxacin (Ocuflox/Floxin/Floxacin), norfloxacin (Noroxin), due to the increased risk of aneurysm.

 

 


 

References: 

1 Rangel-Castillo, Leonardo, et al. “Management of Intracranial Hypertension.” Rangel-Castilla, Leonardo et al. “Management of intracranial hypertension.” Neurologic clinics vol. 26,2 (2008): 521-41, x. doi:10.1016/j.ncl. Feb. 2008, <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2452989/>.

2 Aiken, A.H., et al. “Incidence of Cerebellar Tonsillar Ectopia in Idiopathic Intracranial Hypertension: A Mimic of the Chiari I Malformation.” American Journal of Neuroradiology; Nov. 2012, <http://www.ajnr.org/content/33/10/1901>.

3 Mokri, B. “The Monro-Kellie Hypothesis: Applications in CSF Volume Depletion.” Neurology., U.S. National Library of Medicine, 26 June 2001, <https://www.ncbi.nlm.nih.gov/pubmed/11425944>.

4 Henderson, Fraser C., et al. “Neurological and Spinal Manifestations of the Ehlers–Danlos Syndromes.” American Journal of Medical Genetics Part C: Seminars in Medical Genetics, 21 Feb. 2017, <www.onlinelibrary.wiley.com/doi/10.1002/ajmg.c.31549/full>.

5 Pietrangelo, Ann. “Empty Sella Syndrome.” Healthline, Oct. 2017, <https://www.healthline.com/health/empty-sella-syndrome>.

6 Hingwala, Divyata R., et al. “Imaging signs in idiopathic intracranial hypertension: Are these signs seen in secondary intracranial hypertension too?.” Annals of Indian Academy of Neurology vol. 16,2: 229-33. doi:10.4103/0972-2327.112476, June 2013, <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3724081/>.

7 Mollan, Susan P., et al. “A practical approach to, diagnosis, assessment and management of idiopathic intracranial hypertension.” Practical neurology vol. 14,6: 380-90. doi:10.1136/practneurol-2014-000821. May 2014, <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4251443/>.

8 Thurtell, Matthew J., and Michael Wall. “Idiopathic Intracranial Hypertension (Pseudotumor Cerebri): Recognition, Treatment, and Ongoing Management.” Current Treatment Options in Neurology, U.S. National Library of Medicine, Feb. 2013, <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3554852/>.

9 Pérez, Mario A., et al. “Primary spontaneous cerebrospinal fluid leaks and idiopathic intracranial hypertension.” Journal of neuro-ophthalmology : the official journal of the North American Neuro-Ophthalmology Society vol. 33,4: 330-7. doi:10.1097/WNO.0b013e318299c292, Dec. 2014, <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4040082/>.

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TETHERED CORD SYNDROME (TCS) INVOLVES A STRETCHING OF THE SPINAL CORD, AND OFTEN YOUR MEDULLA OBLONGATA
AS WELL, WHICH LEADS TO A HOST OF NEUROLOGICAL PROBLEMS.

 

Before we talk about Tethered Cord Syndrome, let’s first talk about the anatomy associated with the spinal column (in layman’s terms).

•  The role of the vertebral column is to hold the spine strong (so it can be upright) and protect the spinal cord from injury. In a normal vertebral column, there are thirty-three vertebrae on each side (seven cervical vertebrae, twelve thoracics, five lumbar, five fused vertebrae in the sacrum and another four fused vertebrae in the coccyx).

•  Each vertebra in the upper twenty-four vertebrae is separated by intravertebral discs largely composed of the fibrous protein, collagen. The main role of these discs is to allow the vertebral column to move and flex.

•  The role of the spinal canal is to hold cerebrospinal fluid around the spinal cord, which not only cushions the cord against injury, but it also lubricates the cord, cleanses the cord, and brings essential nutrients that the spinal cord needs. The spinal canal is made up of several layers that form the meninges. These layers are also composed of high concentrations of collagen. The outermost layer of the meninges is the dura mater. The dura mater should be dense and strong, so cerebrospinal fluid cannot leak from it.

•  The spinal cord relays messages from the brain to the nerves that allow the body to function. When part of the spinal cord is compromised, it can inhibit signals from getting to the nerves from that point downward. The brainstem (midbrain, pons, and medulla oblongata) is attached to the spinal cord at the top (the medulla and spinal cord meet at what is called the cervicomedullary junction) and the spinal cord continues down to the mid/lower back. From there it becomes a delicate elastic band of fibrous collagen-based tissue called the filum terminale that extends from the conus medullaris (the lowest point of the spinal cord before it becomes the filum terminale) to the dural sac at the S2 level.1

Chiari Malformation has many conditions that can be associated with it (comorbid conditions) and sometimes those comorbid conditions can be at the root cause (etiological cofactor) or one of the causes along the way (pathological cofactor) to the tonsils being as low as they are (making the Chiari “secondary” to one or more “other” conditions). Tethered Cord Syndrome (TCS) is one of those pathological conditions.2 Like Chiari, it is a neurological disorder; however, it is one of the spinal cord.3

Tethered Cord happens when the sticky fibrous tissue of the filum adheres to fatty/scar tissue or the dura lining of the spinal canal.1 While this tethering can happen anywhere in the spinal canal, it is most common at the lumbosacral level.4 When the tethered filum pulls the spinal cord tightly enough that it causes neurological problems, it becomes known as Tethered Cord Syndrome (TCS). Tethered Cord is most common in patients with Spina Bifida (myelomeningocele, meningocele), Spina Bifida Occulta (lipomeningomyelocele, lipomyelocele) and patients with Ehlers-Danlos Syndromes (EDS), a Hereditary Disorder of Connective Tissue (HDCT) where one or more of the types of collagen (the most abundant protein in the human body) is mutated at a cellular level. Tethered cord can be congenital or acquired. It can be obvious in childhood or symptoms may not present themselves until adulthood. Some children may develop minor signs that are overlooked by untrained medical professionals and can progress slowly or rapidly over time.

More Symptoms of Tethered Cord Syndrome

A Tethered Cord Syndrome diagnosis can be somewhat of a challenge. The signs and symptoms of the condition are not always present and when they are, they are often not recognized, so it is important to know all indicators. People with Tethered Cord (TC) can have sacral dimples, discoloration, and hairy patches on their lower back that can lead a doctor to investigate further, however, some have no external signs at all. Some have kyphosis (rounded back) and scoliosis (curved spine). Sometimes radiological criteria are not met or are ambiguous, yet an Occult Tethered Cord (characterized by the presence of symptoms with normal conus position and inconclusive findings of the filum) can still exist.5 Symptoms can be elusive as well and can happen all at once or gradually over the course of many years. Many symptoms worsen due to activity; climbing stairs has been reported as causing pain that varies from uncomfortable to excruciating.

One of the reasons that Tethered Cord is often overlooked is that many neurosurgeons are not aware of the connection it can have with a Chiari Malformation and the medical tests used for determining if a tethered cord problem exists are not always accurate or accurately read.

 

Magnetic Resonance Imaging (MRI)

• A lumbar MRI is usually the first step. This gives a visualization of the spinal cord in relation to the surrounding vertebrae. The actual tethering is not always obvious on MRI, sometimes the only proof of the tethering is the pulling it creates on the spinal cord. Doctors will look for the position of the conus medullaris when looking for signs that the spinal cord is being pulled. The consensus amongst most surgeons is that a normal conus should be located from the T12 to the lower L2. There is much debate on the importance of establishing evidence of a low-lying conus.5 When conus reaches the lower L2 or below, doctors should be investigating why it’s low and consider if the cord might be tethered. When looking for the location of the conus, your position can make all the difference. MRIs are generally performed supine (lying down) and the cord is not pulled as tightly as it is when upright. For this reason, upright MRIs are becoming the method of imaging preferred by most neurosurgeons looking to confirm or deny if tethering exists in a patient showing symptoms. Other signs of tethering that might be visible in a lumbar MRI include an enlarged foramen magnum, thick or fatty filum, presence of fatty tissue inside the canal, or the filum might be pulling to one side of the canal.5

• A prone MRI of the lumbar region can be an invaluable tool for those where other MRIs indicate that the filum might be pulling to one side (usually the back side) of the canal. With prone MRIs, imaging is done while the patient is lying face down (as opposed to facing up, like most supine MRIs). If the anteroposterior conus movement of >10% of the canal width was evident from the supine to the prone, then the likelihood of it pulling to one side do to tethering is less likely and more conservative management might be better appropriate than a surgical release.6

• A cervical MRI can also show signs that a tethered cord might exist. The cervical spinal cord can sometimes appear narrow from it being pulled tight. The medulla oblongata can become elongated. This happens because the brainstem is attached to the top of the spinal cord and that cord is being pulled tight, essentially pulling everything down and tight. This elongation of the medulla from the tethering can cause secondary symptoms by itself, known as Dysautonomia.

· Low/herniated cerebellar tonsils consistent with what is seen in a Chiari Malformation. When the brainstem is herniated (where part/most of the medulla is below the foramen magnum) along with the cerebellar tonsils, it is considered a Chiari 1.5 (which should be a good indicator that you might be dealing with an Acquired Chiari Malformation, where the herniated tonsils are secondary to another condition). One study quoted that out of 2,987 patients with a tonsillar herniation of 5mm or greater, 14% met the diagnostic criteria (based on “generally accepted clinical and radiographic criteria”) and 63% of the 289 patients with tonsillar herniations of < 5mm.5

· A syrinx is common with Tethered Cord, as it causes a blockage of fluid at the foramen magnum. A syrinx can develop anywhere in the spine, usually in the lower cord, but with Tethered Cord Syndrome it can develop in the lower medulla (Syringobulbia) as well because of the low brainstem is at the point of the blockage of fluid from the Chiari Malformation.

Even with an upright MRI and every symptom listed, patients are often told they do not have Tethered Cord. This is simply due to a lack of education on the subject and medical bias between doctors. It is important to make sure that you have the images viewed by a neurosurgeon that is familiar not only with Tethered Cord but Chiari and Comorbids as well. (Nearly half of the large study quoted above were referred following a failed Chiari Decompression.5) The combination of the images and the patient’s symptoms should tell the neurosurgeon if surgical intervention is required. Patients often require several consultations before they can find a knowledgeable enough physician.

 

What We Recommend BEFORE DECOMPRESSION is considered:
If you have symptoms of TCS, especially if accompanied by any of the MRI indicators mentioned above, it is both reasonable and prudent to ask your neurosurgeon to investigate further before decompression is considered. A Tethered Cord Release Surgery prior to decompression may relieve the tension that is pulling the brainstem and cerebral tonsils downwards reducing the risk of a failed decompression. There is a chance with small tonsillar herniations that the Tethered Cord Release might allow the cerebellar tonsils to rise enough to the point that cerebrospinal fluid flow is reestablished to where decompression is no longer needed. However, failure to release a tethered cord prior to decompression surgery increases the likelihood of a failed decompression. (In fact, in the study quoted above, out of the 3,276 patients with herniated tonsils, 46% of them were referred for evaluation after a failed decompression surgery.5) An MRI of all three levels of the spine should be done to rule out other possible causes for leg/back symptoms along with urodynamic testing, an Electromyogram (EMG) Test and Nerve Conduction Study (NCS) of the lower limbs is also suggested.

 

TREATMENT OPTIONS:
For some, physical therapy can help with symptoms for a while. However, ultimately it will likely need to be surgically treated with a Tethered Cord Release.

Tethered Cord Release (TCR) Surgery involves the untethering of the spinal cord. An incision is made in the lumbar area, the filum terminale is separated and the factors that are tethering the spinal cord to the vertebrae are severed. Surgical treatment is not without risk and does not guarantee relief of symptoms. However, in a large study, up to 83% of adult patients report relief, 16% unchanged, and 1% report feeling worse.5 In children, the numbers are even better with 93% obtaining improved symptoms and 7% unchanged.5 Most patients describe the surgery as extremely painful for the first two weeks and “better than they ever remember feeling” (often because they have been tethered for much of their lives) after two weeks. The most common complication involves retethering (often from the scar tissue from the release) and multiple surgeries may be required over a lifetime. Finding a neurosurgeon experienced with TCRs and the surgical treatment of Ehlers-Danlos patients can sometimes help reduce the risks associated with scar tissue formation, but scar tissue can happen with even the best of neurosurgeons.

For the TCS patient, herniated tonsils really should be assumed an Acquired Chiari Malformation (even if a small posterior fossa is evident), and by correcting the tethered cord before decompression the decompression will be less likely to fail.

 

Special Note: There are other conditions that can present with similar symptoms. Diastasis Recti is a type of abdominal hernia common to pregnant women, those with obesity, and EDS patients. This separation in the abdominal muscles is known to sometimes cause lower back pain and many of the same pelvic floor problems seen with Tethered Cord Syndrome (TCS). Unlike TCS however, it does not usually require surgical treatment. If you suspect Diastasis Recti, we recommend that you talk to your Primary Care Physician about referring you to physical therapy to bring your abdominal muscles back together before considering Tethered Cord Release (TCR).7

 

 

 


 

References: 

1 Henderson, Fraser C., et al. “Neurological and Spinal Manifestations of the Ehlers–Danlos Syndromes.” American Journal of Medical Genetics Part C: Seminars in Medical Genetics, 21 Feb. 2017, <www.onlinelibrary.wiley.com/doi/10.1002/ajmg.c.31549/full>.

2 “Section of the Filum Terminale Surgery for Tethered Spinal Cord Syndrome in Patients with Chiari Malformation and Syringomyelia.” North Shore-Long Island Jewish Health System The Chiari Institute, Chiari Connection International, 02 Oct. 2006, <http://www.chiariconnectioninternational.com/docs/TCS_SFT_Explained.pdf>.

3 Quake. “Overview: Chiari Comorbidities & Etiological/Pathological Cofactors [Revised].” Chiari Bridges, 16 Nov. 2019, <https://chiaribridges.org/overview-chiari-comorbidities-etiological-pathological-cofactors/>.

4 Arslanoglu, A., et al. “Multidisciplinary Combined Approach for Tethered Spinal Cord Syndrome: Radiology, Surgery and Physical Therapy.” Balkan Military Medical Review, 2006, <https://pdfs.semanticscholar.org/8c30/18bf5bfbd6f3e7e5e9c3559bbbfdcac82e04.pdf>.

5 Milhorat, Thomas H., et al. “Association of Chiari malformation type I and tethered cord syndrome: preliminary results of sectioning filum terminale.” Surgical Neurology, Elsevier, July 2009. <https://www.sciencedirect.com/science/article/abs/pii/S0090301909002572>.

6 Aoun, Salah G., et al. “The Use of Prone Magnetic Resonance Imaging to Rule Out Tethered Cord in Patients With Structural Spine Anomalies: A Diagnostic Technical Note for Surgical Decision-making.” Cureus vol. 11,3 e4221. 11 Mar. 2019, doi:10.7759/cureus.4221. <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6510567/>.

7 “A Complete Guide to Diastasis Recti: Truths on Abdominal Muscle Separation.” Braceability, 05 June, 2018. <https://www.braceability.com/blogs/info/diastasis-recti>.

When you start to educate yourself on a condition like Chiari, your vocabulary will be challenged. Most of us study with a medical journal article opened in one tab and medical dictionary in the next. Amongst all the medical terminology you will tackle, there are probably a few terms as important to your understanding of Chiari than comorbidities and pathological/etiological cofactors. When two or more conditions tend to co-occur, they are said to be comorbid with one another. It makes no inferences of a causal relationship between the conditions, only that they co-occur. This co-occurrence deduces that a correlation exists, but when the nature of that correlation is not known, they are just said to be comorbidities. When a “causal relationship” is known or suspected, the conditions start being discussed in terms of pathology or etiology, which are similar, but not exactly the same thing.

An etiological cofactor exists when the “root cause” of a condition is known or believed to be known. That “root cause” is the etiological cofactor. When an etiological cofactor can cause a series of events or conditions that can become “direct causes” for other conditions, that series of events creates a pathology. Conditions along the path are called pathological cofactors. Understanding these cofactors is imperative in understanding Chiari and all of the comorbid conditions that accompany it.

ETIOLOGICAL COFACTOR:

Chiari Malformation often seems like a beast that wreaks havoc on our bodies on every level. Indeed it is, but as you can see from the diagram above, it really is not the “root” of everything that is going wrong. There is a bigger beast at work in so many of us, and its name is Ehlers-Danlos. It is not by chance that so many of us with Chiari have so many other conditions in common (especially conditions like Degenerative Disc Disease, arthritis and other connective tissue problems). It is not by chance that so many of us have a history of miscarriage and similar familial histories. It is not by chance that Chiari is more prevalent in females than males. And it is definitely not by chance that Chiari is running in families and they cannot find a definitive genetic link. They cannot find it because they are not looking at the beast hiding in the background.

Ehlers-Danlos Syndromes are a group of inherited disorders involving a genetic mutation in one or more of our bodies’ collagen. Collagen is the most abundant protein, making up 1/3 of the proteins in the human body, affecting our bones, skin, muscles, and connective tissue[1]. Collagen is often described as a “cellular glue” that helps hold the body together. When that glue fails to hold, everything seems to go awry; before and after birth: skulls can under-develop in utero, organs tend to prolapse, and bones begin to shift as joint laxity increases (including the bones/vertebrae at the craniocervical junction). Ehlers-Danlos is a primary “root cause” of Chiari Malformations and a majority of the other problems we have. The list in blue is far from being a complete list of conditions caused by EDS. They are commonly accompanied with Chiari because they can cause or attribute to a Chiari malformation (pathological cofactors).[2]

 

PATHOLOGICAL COFACTORS:

Cranial Settling occurs when the skull has dropped and the odontoid (C2/axis) enters into the foramen magnum (Basilar Invagination). This drop can further compromise the craniocervical junction and as it pushes everything down, it increases the likelihood of an Acquired Chiari Malformation.

Craniocervical Instability (CCI) & Atlantoaxial Instability (AAI) usually occurs with cranial settling and Basilar Invagination (BI). The settling and/or softening of tissue can cause a shifting of the C2 (resulting in CCI or AAI) and the cerebellar tonsils (which are already inclined to prolapse) simply drop down with each shift affecting ones ability to tilt/rotate their head.[3]

Intracranial Hypertension (IH – High Intracranial Pressure) occurs when your intracranial pressure (ICP) becomes elevated. This elevation can happen for a variety of reasons.

  1. Space Occupying Masses (cysts, tumors or hydrocephalus) take up space inside the skull causing a mass effect.”
  2. When no mass effect exists, many doctors look no further and give the diagnosis of Idiopathic Intracranial Hypertension.

Because the area of the skull is fixed in an adult cranium and partially fixed in that of a child, the elements inside the fixed space (CSF, blood volume and brain matter) tend to get pushed out wherever they can (the only place that they can escape without breaking through the dura is through the foramen magnum and the brain matter that’s closest to the foramen magnum is the cerebellar tonsils).[4]

Tethered Cord Syndrome occurs when the tissue inside the epidermis adheres to the spinal cord or filum terminale. While this tethering can happen anywhere along the spinal canal, it is most common in the lower lumbar and/or sacral spine. When this adhesion happens it creates a pulling down of the spinal cord and consequently, the brainstem located at the top of the spinal cord and the cerebellar tonsils just get pulled down with it.[5]

Intracranial Hypotension (Low Intracranial Pressure, often involving a CSF Leak) usually involves a cerebrospinal fluid leak or an over-draining shunt, we will highlight the former. Ehlers-Danlos patients tend to have weak dura matter. Tears/holes in the dura can happen anywhere in the dura surrounding the brain or spinal canal and they can happen completely spontaneously (without a known cause). When the leak occurs in the spinal canal, they can create a suctioning effect where cerebrospinal fluid (CSF) is being pulled down and out, causing the intracranial pressure (ICP) to drop. The cerebellar tonsils that are already prone to prolapse (due to EDS) end up getting suctioned downward with the CSF.[6] Cranial leaks often happen when high pressure is left untreated until the high pressure causes a leak in the dura mater. In cranial leaks, fluid usually leaks through the nose or ears (less common), and you can often taste the metallic taste of the cerebrospinal fluid in the back of your throat. While both spinal leaks and cranial leaks can cause low pressure and low-pressure symptoms, and while both can start, stop, and start again spontaneously, there is an increased risk whenever there is an opening where cerebrospinal fluid leaks outside of the human body (if cerebrospinal fluid can make it out of the body, microscopic bacteria can make it inside the same opening where it can enter in the meninges).[7]

Posterior Cranial Fossa Hypoplasia (PCFH) is the only etiological cofactor listed above that is definitely congenital. The role of collagen in bone development has been long-standing, especially its known contribution to certain conditions like Osteogenesis Imperfecta. However, more recent studies are discovering the role collagen plays in congenital posterior fossa anomalies. Posterior Cranial Fossa Hypoplasia is the most commonly “acclaimed” cause of Chiari malformations, but studies show, that even when all of the other causes above are factored out, only approximately 52% of those left (that fail to meet “the diagnosis criteria” for any of the above), have a small posterior fossa.[8]

 

COMORBIDITIES

While all of the conditions listed in the diagram are comorbidities, some are etiological/pathological cofactors of an Acquired Chiari (even though nearly 100% of us are told that our Chiari Malformation is congenital) and others have Chiari Malformation as their etiological/pathological cofactor:

Syringomyelia occurs when cerebrospinal fluid (CSF) is obstructed and a CSF filled cyst/cavity forms inside the spinal cord. This cyst is directly related to the obstruction of cerebrospinal fluid that can be caused by Chiari Malformation, Spinal Stenosis (a narrowing of the spinal canal, spinal cyst/tumor, a herniated disc), or irregular curvature of the spine (scoliosis). When that cyst/cavity extends into the medulla oblongata (the lowest part of the brainstem), it is called Syringobulbia, and it comes with a new set of symptoms consistent with the damage being done to the brainstem. So when Chiari Malformation exists with a syrinx, and there is no stenosis or disc problem in close proximity below it, the Chiari Malformation should be listed as the etiological cofactor for the syrinx. If more than just the Chiari Malformation is believed to be causing the syrinx, each would be more accurately described as a pathological cofactor.

Dysautonomia occurs when damage has been done to the brainstem or Vagus nerve. Whenever either of these is damaged, often from compression at/near the craniocervical junction, the autonomic nervous system can begin to dysfunction.

 

Confused? If you understand the causal relationships but find yourself wondering if a comorbid condition is an etiological or a pathological cofactor, think of it in terms of a domino effect. Only the first domino is the real etiological cofactor. All of the dominoes in between (on the path) are pathological cofactors. The important thing to remember in this array of medical terminology is that while everything is definitely not Chiari, it almost always shares a connection to it, and that is why so many of us have so many conditions and symptoms that doctors call unrelated! It is imperative in our fight that we know “what” we have and “why” it is happening. With such a broad spectrum of symptoms (like we all have), we must educate ourselves and not just believe the limited knowledge of our doctors.

*Revised November 2019

 


 

References: 

McIntosh, James. “Collagen: What Is It and What Are Its Uses?” Medical News Today, MediLexicon International, 16 June 2017, <www.medicalnewstoday.com/articles/262881.php>.

Quake. “The Chiari Malformation Ehlers-Danlos Connection (Short Version).” Chiari Bridges, 7 Dec. 2017, <www.chiaribridges.org/chiari-malformation-ehlers-danlos-connection-short-version>.

3 Hawkeye. “Overview: Craniocervical Instability and Related Disorders.” Chiari Bridges, 6 Dec. 2017, <www.chiaribridges.org/craniocervical-instability-related-disorders>.

4 Quake. “Brain Under Pressure – Understanding Intracranial Hypertension.” Chiari Bridges, 10 Dec. 2017, <www.chiaribridges.org/brain-pressure-understanding-intracranial-hypertension>.

5 Storm. “The Tethered Cord – Chiari Malformation Connection!” Chiari Bridges, 15 Dec. 2017, <www.chiaribridges.org/tethered-cord-chiari-malformation-connection>.

6 Argent. “Overview: Cerebrospinal Fluid Leaks.” Chiari Bridges, 10 Dec. 2017, <www.chiaribridges.org/cerebrospinal-fluid-leaks>.

7 Pérez, Mario A et al. “Primary Spontaneous Cerebrospinal Fluid Leaks and Idiopathic Intracranial Hypertension” Journal of neuro-ophthalmology : the official journal of the North American Neuro-Ophthalmology Society vol. 33,4 (2013): 330-7. doi:10.1097/WNO.0b013e318299c292, <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4040082/>

8 Quake. “Overview: Chiari Malformation.” Chiari Bridges, 6 Dec. 2017, <www.chiaribridges.org/chiari-malformation>.

You Might Have More Than A Migraine If…

 

High-Pressure Headaches
Those that suffer from high pressure tend to feel pressure behind the eyes (often mistaken for sinus headaches) and report feeling like their “head is going to explode” from the pressure. High-pressure headaches are generally characterized by being worse when laying down – often awaking in the middle of the night or first thing in the morning with a headache, and the headache tends to dissipate to some degree after being upright for a period of time (and that period of time is different for everybody). Caffeine generally exacerbates high-pressure headaches.

  • For more on Intracranial HYPERtension: https://chiaribridges.org/brain-pressure-understanding-intracranial-hypertension/
  • For a list of common high-pressure symptoms:: https://chiaribridges.org//glossary/symptoms-of-intracranial-hypertension/

 

 

Low-Pressure Headaches
Those that suffer from low-pressure headaches tend to report feeling like there is an invisible pressure pushing down from the top of the head, often making it feel like your “head is going to implode.” Low-pressure headaches are characterized by being worse when upright and relieved by laying down. Low-pressure headaches are typically a sign of a cerebrospinal fluid leak (CSF Leak). The longer that the leak has existed, the less obvious the positional element is – meaning the patient can be upright longer before they feel the pressure at the top of their head, and they tend to need to lay down longer before getting any measure of relief. Caffeine often helps relieve low-pressure headaches.

  • For more on Intracranial HYPOtension & CSF Leaks: https://chiaribridges.org//cerebrospinal-fluid-leaks/
  • For a list of common low-pressure symptoms:: https://chiaribridges.org//glossary/symptoms-of-intracranial-hypotension/

 

 

Occipital Headaches
Chiari headaches are felt at the occiput – at the base of the back of the skull and upper neck. They are generally tussive in nature, where they are exacerbated by valsalva maneuvers, which generally include: coughing, sneezing, heaving, laughing hard, or bearing down (like with a bowel movement or childbirth). These maneuvers reduce cardiac output (the amount of blood coming from the heart with each heartbeat), which in turn affects the attempted flow of cerebrospinal fluid, and it increases vagal stimuli.

  • For more on Chiari Malformation: https://chiaribridges.org//chiari-malformation/
  • For an expansive review of the name and definition of Chiari Malformation: https://chiaribridges.org//whats-in-a-name-chiari-malformation/

 

Connecting the Three Headaches

  • Untreated high pressure can cause cranial leaks (which leads to low pressure) – often accompanied by cerebrospinal fluid leaking through the nose or ears.

 

  • CSF leaks can sometimes seal on their own leading to rebound high pressure (which is temporary) or continued high pressure if they originally had high pressure.

 

 

  • Untreated low pressure can cause the brain to sag and as it sags the cerebellar tonsils can get lodged into the foramen magnum where it blocks the flow of cerebrospinal fluid, leading to occipital headaches (often diagnosed as a Chiari 1 Malformation).

 

  • Untreated spinal leaks can create a suctioning or pulling down effect where the cerebellar tonsils can get lodged into the foramen magnum where it blocks the flow of cerebrospinal fluid, leading to occipital headaches (often diagnosed as a Chiari 1 Malformation).

 

 

 

Major Problem Regarding Our Diagnoses & Treatment Options:

  1. Doctors and radiologists alike, tend to see the herniated tonsils and assume a small posterior fossa.
  2. Most do not check for high pressure or low pressure, even when directly asked and symptoms are present.
  3. When a posterior fossa decompression is finally offered, the high or low pressure is often left untreated which leads to a failed decompression.
  4. By the time sufferers get a name to go with their symptoms, we jump at the opportunity for relief.

 

 

The “Bobblehead Sensation” – When It Feels Like Your Neck Can No Longer Hold Up Your Head

While most of us experience this feeling either intermittently or continuously, it is generally related to structural instability issues:

 

 

  • Cervical Instability (also known as Sub-axial Instability, SAI) involves hypermobility of the C2/C3 to the C7 intervertebral discs. This condition (like most conditions involving the cervical spine) is a major cause of muscle spasms (in the neck and throughout the body at any point below the disc issues. When these neck spasms occur, they can cause the “Bobblehead sensation” where it feels like your neck can no longer hold up your head. This disc degeneration can lead to paralysis as discs compress the spinal cord.

 

 

Important Questions to Ask Your Neurosurgeons: https://chiaribridges.org/important-questions-for-your-neurosurgery-appointment/

 

 

INTRACRANIAL HYPERTENSION (IH) AND IDIOPATHIC INTRACRANIAL HYPERTENSION (IIH) ARE CONNECTED, BUT ARE NOT THE SAME THING AND THEREFORE SHOULD NOT BE USED INTERCHANGEABLY.

Intracranial Hypertension (IH) means high pressure inside the skull. Intracranial Pressure (ICP) is measured in millimeters of mercury (mmHg). Most scholars agree that on average, “normal pressure” should be between 5-15 mmHg and that 20-25 mmHg is when the ICP crosses the line into being IH. Pressure can be brought on by several different means: space-occupying masses such as hydrocephalus and cranial cysts/tumors; cranial edema (Encephalitis); trauma; stroke; aneurysm; certain infections/diseases (Meningitis), liver failure[1], kidney failure[2]; or as a side-effect of certain medications (such as: Tetracycline[3][5], Sulfasalazine[4], Lithium[5], excess amounts of Vitamin A, steroid use[6], growth hormone treatments[6], and the hormonal Intrauterine Device (IUD), “Mirena”[7]); however, sometimes the cause of the pressure is completely unknown. When an etiological cofactor exists, it is considered Secondary Intracranial Hypertension (SIH); when no other cause is identified, it is known as Idiopathic Intracranial Hypertension (IIH) or Primary Intracranial Hypertension (PIH).

Idiopathic Intracranial Hypertension (IIH) was first noticed in 1893, by the German physician Heinrich Quincke, who named it Serous Meningitis. As its absence of space occupying masses/lesions began to draw more thought, it was renamed Pseudotumor Cerebri (PTC) by Max Nonne in 1904. Sometime later, the term “Benign Intracranial Hypertension” began being used interchangeably with Pseudotumor Cerebri, to describe the fact that while it is sharing some of the same characteristics that a cranial tumor would cause, it is benign (not harmful), but arguments were made against it in that blindness is not indicative of being benign.”[6] The name finally settled as “Idiopathic Intracranial Hypertension,” which means IH of an unknown cause. No matter what you choose to call it, the pain and damage remains the same for those who have it.

 

UNDERSTANDING IDIOPATHIC INTRACRANIAL HYPERTENSION
IIH is a neurological disorder where the cerebrospinal fluid within the skull is elevated, without the presence of a space-occupying mass, edema (brought on by things such as trauma, infection, or disease), or any adverse reactions to certain medications. Studies show that IIH is more common amongst women between the ages of 20 and 50,[8] and there is a slight increase amongst those that are overweight. Some studies also suggest a connection between obstructive sleep apnea and transverse cerebral venous sinus stenosis.[9] Amongst the general population, IIH is believed to exist in 1/100,000 (0.00001). Amongst those that are 10% above their ideal body weight, the numbers increase to 13/100,000 (0.00013), and rising to 19/100,000 (0.00019) in those 20% above their ideal body weight.[10] Although doctors often tend to pass this off as merely a side effect of weight gain, the increase is slim and seems to decrease as the percentage of weight gain above ideal weight continues to rise above the 10% margin. Additionally, the weight factor excludes men and children under the age of 10, which may simply be because women are more likely than men to have comorbid conditions that would lead to Intracranial Hypertension. Studies show that the women to men ratio for Chiari Malformation is believed to be 3:1 and those with both Chiari Malformation and Ehlers-Danlos Syndromes 9:1[11]). However weight is not irrelevant with IIH, the overweight/obese patient population report finding improvement of some symptoms when weight loss of 5-10% of one’s overall body weight, when accompanied by a low-salt diet[12]. 

 

UNDERSTANDING THE IH/IIH CONNECTION: THE MONRO-KELLIE DOCTRINE
The association between IH/IIH and Chiari Malformation, appears to be a malicious intricate pathological circle. The cranium (skull) consists of brain matter, cerebrospinal fluid, and both venous and arterial blood. A hypothesis, referred to as the Monro-Kellie Hypothesis (or Monro-Kellie Doctrine), states, “The sum of volumes of brain, CSF, and intracranial blood is constant. An increase in one should cause a decrease in one or both of the remaining two.”[13] Therefore, if there is an abundance of cerebrospinal fluid (IIH or hydrocephalus), both cranial blood volume and brain matter should be forced to deplete. This depletion is usually directed in the path of least resistance – through the foramen magnum and into the spinal canal. When the cranial brain matter closest to the bottom of the skull (cerebellar tonsils) goes through the foramen magnum and into the spinal canal (an Acquired Chiari Malformation), it blocks the flow of cerebrospinal fluid, which in turn, continues to raise intracranial pressure.

 

SYMPTOMS OF INTRACRANIAL HYPERTENSION
Intracranial Hypertension (IH) can be either acute or chronic and comes with a variety of symptoms, many of which can help distinguish IH pain from typical pain associated with Chiari Malformation. A typical Chiari headache originates at the back of the skull (at the occiput), but IH headaches are usually described as pressure at the top of the head, that radiates downward. Headaches tend to be worse when laying down (which is opposite of low pressure headaches that are often relieved by laying down). Those that suffer from IH, often report waking up from sleep with a bad headache, and often a slight incline can help alleviate the headache pain. Pulsatile Tinnitus occurs when you hear a ringing in your ears that coincides with your heart beat. The tale-tell symptom of IH involves the damage done to the optical nervesPapilledema is when the optic discs swell in response to the increased cranial pressure.[14] Symptoms of Papilledema include: headaches behind the eyes, blurred vision, fleeting vision, dimmed vision, double vision, visual obscurations, decreased peripheral vision, and photopsia. Another source of IH damage is seen in the pituitary gland and is known as Empty Sella Syndrome (ESS). As the high intracranial pressure (ICP) tries to take over, cerebrospinal fluid finds its way to the sella turcica and starts filling it with spinal fluid (partially or completely)[15]. The intruding CSF attempts to envelope this depression in the sphenoid bone, and squeezes the pituitary gland, flattening it until it appears “empty.” While some initially suffer no symptoms of the damage done to the pituitary gland, most eventually develop a variety of hormonal issues, known as hypopituitarism.

 

DIAGNOSIS CRITERIA
Diagnosis of Intracranial Hypertension usually begins with investigating either the headaches or the vision problems. The least invasive test is having a neuro-ophthalmologist check behind your eyes for Papilledema. It is not considered conclusive in testing for IH, but it is essential in determining the extent of the damage to the optical nerves. Magnetic Resonance Imaging (MRI) of the brain can be useful in showing signs of Intracranial Hypertension. In cases where one or more space-occupying masses exists, further imaging and often biopsy may be required. The type of mass, its exact location, and the amount of damage that it is believed to be doing, will be used to determine the best treatment. If imaging gives an indication that the intracranial pressure is high, but no space-occupying mass exists, additional testing is usually necessary to confirm, some of which can be potentially be dangerous for those with Heritable Disorders of Connective Tissue (HDCT), such as Ehlers-Danlos Syndromes (EDS). Lumbar punctures (LP), also known as a spinal tap, are often used to test the opening CSF pressure, but by puncturing the dura (which is thinner than normal with Connective Tissue Disorders), the risk of a CSF leak is high. When an LP causes a CSF leak, the first indication is usually a post-dural-puncture headache (PLPH) and eventually, the intracranial hypertension will decrease, as the leak causes intracranial hypotension.[16] CSF leaks can escalate very quickly and can be difficult to identify and treat; therefore, we recommend that LPs be done only when absolutely necessary, and that they be done only under fluoroscopy, by qualified surgeons that fully understand the likelihood of Connective Tissue Disorders, the symptoms of leaks, and have a plan of action should those symptoms occur. Sometimes, ICP can fluctuate and have high spikes that cause problems, rendering LPs useless unless they are done at the precise time. When these spikes are suspected ICP monitoring bolts might be the better option, but still poses a risk of leaks.[17] 

 

TRANSVERSE SINUS STENOSIS (TSS)

Transverse sinus stenosis (TSS) occurs when there is a narrowing of the transverse sinus (dural venous sinus), which in turn can compromise cerebral venous outflow. TSS is common in idiopathic intracranial hypertension (IIH). Depending on the study that you are reading, it is proving to be present in 65-100% of those diagnosed specifically with IIH. Its direct connection seems relatively obscure, and there is no indication of its prevalence in intracranial hypertension (IH), but it is worth looking for and treating if found. While scholars remain undecided as to whether TSS is a cause or consequence of IH, if it does prove to be a cause of high pressure, IIH will likely no longer have an idiopathic element to it and it will become another etiology of Intracranial Hypertension. TSS can often be undetectable with standard Magnetic Resonance Imaging (MRI). The correct procedure would be Magnetic Resonance Venography (MRV, with the ATECO technique [18]), specifically looking for signs of stenosis, to include looking for fistula(s) and aneurysm(s). The lack of a fistula or aneurysms however, does not exclude the possibility of a TSS existing (remember it’s being found in 65-100% of those with IIH). Even with MRV, TSS can often be misinterpreted as “flow-related artifacts.” [18] Because the prevalence of TSS in IIH patients is high (some studies call it “universal”) [19], we recommend that all IIH patients have a MRV with the ATECO technique done before surgical treatment and that venous stenting be considered as a viable surgical treatment.

 

TREATMENT OPTIONS
Treatments for Idiopathic Intracranial Hypertension usually starts with weight loss and/or medicinal options; Diamox (Acetazolamide) and Topamax (Topiramate) are most frequently prescribed. Those with IH/IIH should avoid consuming caffeine, as it can increase pressure and therefore is counter-productive to treatment measures. Diamox is a carbonic anhydrase inhibitor and Topamax can also inhibit carbonic anhydrase, but is an anticonvulsant, often prescribed for the treatment of neuropathy and seizure disorders. Both are believed to successfully lower the production of cerebrospinal fluid. Topamax can also help suppress the appetite, which can help with weight loss, but it also comes with many side-effects like all nerve meds do. When medication fails to decrease ICP, a Ventriculoperitoneal Shunt (VP Shunt) or Ventriculoatrial Shunt (VA Shunt) are surgically placed to drain cerebrospinal fluid straight from the ventricle. Shunts are known for failing and often need a multitude of revisions. Venous stenting is not a new procedure, yet it is not readily offered. While there are studies indicating that the successful reduction of intracranial pressure can help with TSS. Stenting is not only a surgical treatment for the stenosis (which could significantly reduce the possibility of a life-threatening aneurysm in patients with a connective tissue disorder), but it is also a surgical treatment for intracranial hypertension as it “improves CSF resorption in the venous system.” [18] Therefore, it seems illogical to shunt (just dealing with the pressure) and leave such a potentially life-threatening condition untreated. [20] Studies are indicating as high as a 94% of patients being cured of all IIH symptoms as a direct result of venous stenting. [18] While all surgeries pose a risk of complications, and the statistics for stenting are likely inflated and skewed (like that of decompression surgeries), these statistics on stenting are definitely encouraging!

Intracranial Hypertension is a complex issue that should be explored whenever a Chiari Malformation exists, before a decompression surgery is performed. When both Intracranial Hypertension and Chiari Malformation are found to co-exist, the treatment should be in consideration of the correlation of the two, as they both are pathological co-factors of one another. Failure to recognize and treat Intracranial Hypertension before or soon after decompression surgery, will increase the likelihood of a failed decompression. While a decompression surgery can lower Intracranial Hypertension, as cerebrospinal fluid is once again allowed to flow, if space-occupying masses or a case of Idiopathic Intracranial Hypertension (where too much cerebrospinal fluid is being created) are left untreated, those problems will still exist after decompression surgery and the high pressure is likely to cause the cerebellar tonsils to fall once again.

*Revised October 2018

 


 

References:

Jalan, R. “Intracranial Hypertension in Acute Liver Failure: Pathophysiological Basis of Rational Management.” Seminars in Liver Disease., U.S. National Library of Medicine, Aug. 2003, <www.ncbi.nlm.nih.gov/pubmed/14523680>.

Chang, D, et al. “Benign Intracranial Hypertension and Chronic Renal Failure.” Cleveland Clinic Journal of Medicine., U.S. National Library of Medicine, <www.ncbi.nlm.nih.gov/pubmed/1525975>.

Holst, Anders Vedel, et al. “A Severe Case of Tetracycline-Induced Intracranial Hypertension.”Dermatology Reports, PAGEPress Publications, 31 Jan. 2011, <www.ncbi.nlm.nih.gov/pmc/articles/PMC4211491/>.

Sevgi, E, et al. “Drug Induced Intracranial Hypertension Associated with Sulphasalazine Treatment.” Headache., U.S. National Library of Medicine, Feb. 2008, <www.ncbi.nlm.nih.gov/pubmed/18070060>.

Kelly, S J, et al. “Pseudotumor Cerebri Associated with Lithium Use in an 11-Year-Old Boy.”Journal of AAPOS : the Official Publication of the American Association for Pediatric Ophthalmology and Strabismus., U.S. National Library of Medicine, Apr. 2009, <www.ncbi.nlm.nih.gov/pubmed/19393521>.

Aylward, Shawn C. “Intracranial Hypertension: Is It Primary, Secondary, or Idiopathic?”Journal of Neurosciences in Rural Practice, Medknow Publications & Media Pvt Ltd, 2014, <www.ncbi.nlm.nih.gov/pmc/articles/PMC4173226/>.

Etminan, Mahyar, et al. “Risk of Intracranial Hypertension with Intrauterine Levonorgestrel.”Therapeutic Advances in Drug Safety, SAGE Publications, June 2015, <www.ncbi.nlm.nih.gov/pmc/articles/PMC4519742/>.

“Pseudotumor Cerebri Information Page.” National Institute of Neurological Disorders and Stroke, U.S. Department of Health and Human Services, <www.ninds.nih.gov/Disorders/All-Disorders/Pseudotumor-Cerebri-Information-Page>.

Thurtell, Matthew J., et al. “An Update on Idiopathic Intracranial Hypertension.” Reviews in Neurological Diseases, U.S. National Library of Medicine, 2010, <www.ncbi.nlm.nih.gov/pmc/articles/PMC3674489/>.

10 Wani, Irfan Yousuf, et al. “Complete Ophthalmoplegia: A Rare Presentation of Idiopathic Intracranial Hypertension.” Annals of Indian Academy of Neurology, Medknow Publications & Media Pvt Ltd, 2015, <www.ncbi.nlm.nih.gov/pmc/articles/PMC4683894/>.

11 Henderson, Fraser C., et al. “Neurological and Spinal Manifestations of the Ehlers–Danlos Syndromes.” American Journal of Medical Genetics Part C: Seminars in Medical Genetics, 21 Feb. 2017, <www.onlinelibrary.wiley.com/doi/10.1002/ajmg.c.31549/full>.

12 Thurtell, Matthew J., and Michael Wall. “Idiopathic Intracranial Hypertension (Pseudotumor Cerebri): Recognition, Treatment, and Ongoing Management.” Current Treatment Options in Neurology, U.S. National Library of Medicine, Feb. 2013,<www.ncbi.nlm.nih.gov/pmc/articles/PMC3554852/>.

13 Mokri, B. “The Monro-Kellie Hypothesis: Applications in CSF Volume Depletion.” Neurology., U.S. National Library of Medicine, 26 June 2001, <www.ncbi.nlm.nih.gov/pubmed/11425944>.

14 Schirmer, Clemens M, and Thomas R Hedges. “Mechanisms of Visual Loss in Papilledema.”Journal of Neurosurgery, <www.thejns.org/doi/full/10.3171/FOC-07/11/E5>.

15 “Empty Sella Syndrome Information Page.” National Institute of Neurological Disorders and Stroke, U.S. Department of Health and Human Services, <www.ninds.nih.gov/Disorders/All-Disorders/Empty-Sella-Syndrome-Information-Page>.

16 Panikkath, Ragesh, et al. “Intracranial Hypertension and Intracranial Hypotension Causing Headache in the Same Patient.” Proceedings (Baylor University. Medical Center), Baylor Health Care System, July 2014, <www.ncbi.nlm.nih.gov/pmc/articles/PMC4059569/>.

17 Abraham, Mary, and Vasudha Singhal. “Intracranial Pressure Monitoring.” Journal of Neuroanaesthesiology,  <www.jnaccjournal.org/article.asp?issn=2348-0548;year=2015;volume=2;issue=3;spage=193;epage=203;aulast=Abraham>.

18 Ahmed, Wilkinson, et al. “Transverse Sinus Stenting for Idiopathic Intracranial Hypertension: A Review of 52 Patients and of Model Prediction.” American Society of Neuroradiology, July 2011. <www.ajnr.org/content/32/8/1408.long>.

19 Riggeal, Bruce, et al. “Clinical course of idiopathic intracranial hypertension with transverse sinus stenosis.” American Academy of Neurology, 2012. <www.ncbi.nlm.nih.gov/pmc/articles/PMC3589184/>.

20 Patel, et al. “Evaluating and treating venous outflow stenoses is necessary for the successful open surgical treatment of arteriovenous fistula aneurysms.” Society for Clinical Vascular Surgery, Volume 61, Issue 2. February 2015. <www.sciencedirect.com/science/article/pii/S0741521414014116>.

 

 

CHIARI MALFORMATIONS (PRONOUNCED: KEE-AH-REE) ARE STRUCTURAL DEFECTS IN WHICH THE CEREBELLUM, THE HIND PART OF THE BRAIN, DESCENDS BELOW THE FORAMEN MAGNUM INTO THE SPINAL CANAL.

While Arnold Chiari Malformation (Type 2) was first identified in the late 19th century by the Austrian pathologist Hans Chiari, much of the current medical knowledge has developed since 1985 with the expanded use of Magnetic Resonance Imaging (MRI). The number of patients diagnosed with Chiari malformations continues to increase, and with that increase Chiari Malformation is getting some of the attention the condition has always demanded.

Chiari malformations (“CMs”) are neurological disorders in which the cerebellum extends out of the skull and into the spinal canal, which in turn blocks the flow of cerebrospinal fluid, puts pressure on the brainstem and spine, and may result in varying degrees of nerve compression. Once thought to occur in 1 in 1000 people, it is now believed to be much more frequent of an occurrence. A 2016 pediatric study found it to occur in 1 in 100 children[1]. However, since the most common type (Type 1) tends to become symptomatic during late teens and early adulthood, it is likely to be much more common when adults are factored in. Females are more likely than males to have a Chiari Malformation (at a ratio of 3:1), and significantly higher amongst those with both Chiari Malformation and Ehlers-Danlos Syndrome (9:1)[2]. We affectionately refer to those that live with this condition, including the attendant pain and frequent disregard from the medical community, as Chiarians (regardless of whether they have had surgical intervention or not).

While some Chiarians are symptomatic throughout their lifetime, the vast majority of Chiarians (those with Type 1) develop symptoms in their late teens or early adulthood. Those symptoms can range from mild to crippling, and can become severe enough to cause paralysis (often associated with syringomyelia) or death.


WHAT CAUSES A CHIARI MALFORMATION?

Multiple factors have been identified which can either cause or attribute to Chiari malformations. Although they too were once thought to be rare, Acquired Chiari malformations are now being diagnosed in increasing numbers. A brief overview of what each of these labels entail, together with a summary of the different types of CM’s, is provided below:

  • Congenital Chiari, is believed to be caused by a posterior cranial fossa hypoplasia (PCFH)[3], which can also be caused by a connective tissue disorder such as Ehlers-Danlos.[4] While the cerebellum continued to grow in utero, the posterior skull failed to grow proportionately. Problems resulting from this size discrepancy continue and eventually the overcrowding of the hindbrain squeezes the cerebral tonsils downward into the opening of the spinal canal (cranial constriction). While the herniation of the cerebellar tonsil(s) can take place during gestation or after birth, because the cause is 100% congenital, and the process most likely began in utero, it is usually considered a Congenital Chiari Malformation when the only pathology found is a small posterior cranial fossa. In one large study, they found those with a Chiari Malformation and no associated etiological/pathological co-factors, with only slightly over 52% having a small PCF. When other co-factors were present, the number of Chiarians found with a small PCF plummeted, and therefore it should be considered acquired until proven otherwise.[5]

  • Acquired Chiari can have one or more possible pathological co-factors; any of which can result in the descent of the cerebellar tonsils. Many Chiarians often mistakenly conceptualize an Acquired Chiari Malformation as being brought on only by trauma; however, “acquired” is an antonym for “congenital,” so an Acquired Chiari Malformation in medical terms is one that a person was not born with. While this can include Acquired Chiari malformations resulting from trauma, it can also include Acquired Chiari malformations resulting from a variety of other medical conditions:

    Special care should be taken when any of these co-morbid conditions exist in conjunction with a Chiari Malformation. Before the consideration of decompression surgery, a plan should be developed which addresses each possible comorbid condition before decompression. This can reduce the likelihood of complications and/or a failed decompression surgery.

SEVEN TYPES OF CHIARI MALFORMATIONS WORTH DISCUSSING (asterisks “*” indicate commonly known types)

Chiari Zero:  The lower part of the cerebellum (the cerebral tonsils) are blocking the foramen magnum, but are not descended through. Because of the cerebellum’s position, it blocks the flow of cerebrospinal fluid and all the effects of that blockage are comparable to Type 1.

Diagnosis Requirements: Symptomology; MRI showing no herniation but the low-lying tonsils that are pressing against the top of the foramen magnum; MRI showing a syrinx (despite the name, Chiari Zero is classified under Syringomyelia and not Chiari Malformation – so a syrinx is technically required for diagnoses). [6][7]

Treatment Options: With few symptoms, non-surgical treatments might be recommended. When a syrinx is present, a decompression is often recommended before the syrinx has a chance to further develop and cause additional damage to the spine. However, even when a syrinx is present, all pathological cofactors should be explored and addressed prior to decompression surgery.

Chiari 0.5: In cases of Chiari 0.5, the lower part of the cerebellum (the cerebral tonsils) are descended through the foramen magnum, but descends < 5mm (which is the measurement that some doctors use to define Chiari). Usually labeled “tonsillar ectopia” on radiology reports, the symptoms and effects of the obstruction are generally the same as those experienced with Type 1 or Chiari 1.5.[3]

Diagnosis Requirements: Symptomology; MRI showing a herniation of < 5mm, unless already properly diagnosed with a Type 1 or Chiari 1.5; presence of a syrinx is not “required” for diagnosis, but as with Chiari Zero, it illustrates that it is causing a problem obstructing the flow of cerebrospinal fluid and may be relevant when deciding between various courses of treatment.

Treatment Options: The same as Type 1 or Chiari 1.5, respectively.

*Chiari Malformation Type 1: The most common type of Chiari Malformation, Type 1 is diagnosed when the cerebral tonsils descend below the foramen magnum. Medical professionals unfamiliar with current research surrounding Chiari Zero and Chiari 0.5 (and the symptomology surrounding the blockage of cerebrospinal fluid), believe that a tonsillar herniation of less than 5mm is simply a tonsillar ectopia and only diagnose a Chiari Malformation when the descent is > 5mm. However, the 5mm requirement is controversial, and many doctors now base their diagnoses not solely on measurements, but rather on symptomology and a combination of other factors, including cine MRI’s, a patient’s symptoms, and other relevant factors.[6] Many people with a Chiari Zero, Chiari 0.5, or Type 1 can be asymptomatic for a lifetime: one large study found that approximately 30% of those with a CM measuring between 5-10mm were asymptomatic.[8] If symptoms develop, they often present in adolescence or early adulthood. Anecdotal evidence supports the proposition that once symptoms start, the symptoms often progress rapidly until the damage is stopped surgically.

Diagnosis Requirements: Symptomology; MRI indicating at least one herniated tonsil (without the brainstem descending as well).[9]

Treatment Options: Prior to surgery any/all comorbidities should be explored and treated especially if you are found to have a normal sized posterior fossa. However, if you have classic Chiari 1 Malformation with a small posterior fossa, the risks of surgery should be weighed against the severity of symptoms and the impact that symptoms are having on the patient’s quality of life. It is often recommended to treat mild symptoms with medication, with surgical options typically reserved for cases in which symptoms cause more serious medical and quality of life problems. However, symptoms do tend to progress, and studies have shown a correlation between successful decompression surgery and the amount of time between the onset of any symptoms and surgical intervention[10]. See “Decompression Surgery” below.

Chiari 1.5: This type of CM (often referred to as a “Complex Chiari”) is often acquired as opposed to congenital.  Chiari 1.5 should be the diagnosis when the tonsil(s) and all/part of the lower brainstem (the medulla oblongata) has descended past the foramen magnum. This is usually indicative of another comorbid condition pushing the brainstem downward from above or pulling downward from below.[5][11][12]

Diagnosis Requirements: symptomology; MRI indicating at least one herniated tonsil AND a downward displacement of all/part of the brainstem; without the other radiological findings associated with Type 2.

Treatment Options: Treatment options can vary significantly from patient to patient depending on the cause of the Chiari 1.5. While a variety of medical options might initially be used to treat symptoms, it is extremely important that all possible causes and/or comorbidities are thoroughly investigated and treated prior to the consideration of decompression surgery. Failure to identify and treat any such conditions can increase the likelihood of a failed decompression and further complications such as brain slumping, increased cervical instability, etc.

*Chiari Malformation Type 2 (also known as Arnold Chiari Malformation): Type 2 involves a herniation of the cerebellar tonsils and lower part of the brainstem (the medulla oblongata). Unlike in Chiari 1.5, in Type 2 the fourth ventricle is usually herniated, all/part of the cerebellar vermis (the tissue connecting both halves of the cerebellum) is missing or herniated, the corpus callosum (nerve fibers connecting both hemispheres of the brain) is fully/partially absent (agenesis), and it is almost always accompanied by a myelomeningocele (the most serious form of Spina Bifida, a congenital neural tube defect where the spinal canal does not close properly).[13][14][15]

Diagnosis Requirements: While a myelomeningocele is usually evident and diagnosed at birth, a brain MRI should confirm the radiological aspects of Type 2.

Treatment Options: Myelomeningocele is usually treated surgically at birth. If other related problems develop, such as hydrocephalus and/or tethered cord, they are often dealt with surgically as they become problematic. While some with Type 2 are decompressed, anecdotal evidence reflects a general trend of an increased failure rate with decompression surgeries as compared to those with Type 1. Because of this, some neurosurgeons choose not to decompress those with Type 2.

*Chiari Malformation Type 3: Type 3 is a serious type of Chiari Malformation involving herniated cerebellar tonsils, brainstem, and fourth ventricle. However, in most cases of Type 3, a sac forms out of the back of the skull (encephalocele) that contains brain matter from the cerebellum and the meninges. Type 3 causes severe neurological problems that are evident at birth and has a high infant mortality rate.[16][17]

 *Chiari Malformation Type 4: Type 4 is the most severe type of Chiari Malformation, but does not involve a hindbrain herniation (and therefore arguments have been made that it is not a Chiari Malformation). Instead, it consists of an undeveloped or underdeveloped cerebellum. Most infants born with Type 4 die in infancy.[16][17]


S
URGICAL INTERVENTION 

Decompression surgery is currently the only available means of attempting to stop the progression of symptoms of a congenital chiari (with no other pathological cofactors), but decompression is not a cure (not even close). Statistics show that up to 69% of decompressed patients find some measure of relief from surgery (usually headaches)[18]. Most neurosurgeons will give only a 50% chance of helping each individual symptom. Some of the symptoms are irreversible once they develop. Recent studies show that there is a correlation between early surgical intervention and positive post-surgical outcomes.[19] However, we cannot over emphasize the importance of your doctors taking time to find, diagnose, and treat co-morbid conditions BEFORE decompression surgery. If they are not willing to consider comorbidities, they are probably not the doctor for you!

 

 

*Original version released January 2018, revised October 2018.


 

References:

1
Eltorai, Ibrahim M. “Rare Diseases and Syndromes of the Spinal Cord” Cham: Springer International Publishing: Imprint: Springer, 2016. Page 43, 15.2, <www.springer.com/us/book/9783319451466>.

2 Henderson, Fraser C., et al. “Neurological and Spinal Manifestations of the Ehlers–Danlos Syndromes.” American Journal of Medical Genetics Part C: Seminars in Medical Genetics, 21 Feb. 2017, <www.onlinelibrary.wiley.com/doi/10.1002/ajmg.c.31549/full>.

3 Sekula, Raymond F, et al. “Dimensions of the Posterior Fossa in Patients Symptomatic for Chiari I Malformation but without Cerebellar Tonsillar Descent.” Cerebrospinal Fluid Research, BioMed Central, 2005, <www.ncbi.nlm.nih.gov/pmc/articles/PMC1343586>.

4 Stagi, Stefano, et al. “The Ever-Expanding Conundrum of Primary Osteoporosis: Aetiopathogenesis, Diagnosis, and Treatment.” Italian Journal of Pediatrics, BioMed Central, 2014, <www.ncbi.nlm.nih.gov/pmc/articles/PMC4064514>.

5 Milhorat, Thomas H., et al. “Mechanisms of Cerebellar Tonsil Herniation in Patients with Chiari Malformations as Guide to Clinical Management.” Acta Neurochirurgica, Springer Vienna, July 2010, <www.ncbi.nlm.nih.gov/pmc/articles/PMC2887504>.

6 Isik, N, et al. “A New Entity: Chiari Zero Malformation and Its Surgical Method.” Turkish Neurosurgery., U.S. National Library of Medicine, <www.ncbi.nlm.nih.gov/pubmed/21534216>.

7 “JNS JOURNAL OF Neurosurgery OFFICIAL JOURNALS OF THE AANS since 1944.” The Resolution of Syringohydromyelia without Hindbrain Herniation after Posterior Fossa Decompression | Journal of Neurosurgery, Vol 89, No 2, <www.thejns.org/doi/abs/10.3171/jns.1998.89.2.0212?url_ver=Z39.88-2003&rfr_id=ori%3Arid%3Acrossref.org&rfr_dat=cr_pub%3Dpubmed>.

8 Elster, A D, and M Y Chen. “Chiari I Malformations: Clinical and Radiologic Reappraisal.”Radiology., U.S. National Library of Medicine, May 1992, <www.ncbi.nlm.nih.gov/pubmed/1561334>.

9 Wilson, Eugene. “Chiari.” CEDSA Home, <www.cedsa.org/index.php/59-quick-reference/73-chiari.html>.

10 Hindawi. “Surgical Management of Patients with Chiari I Malformation.” International Journal of Pediatrics, Hindawi, 28 June 2012, <www.hindawi.com/journals/ijpedi/2012/640127>.

11 Kim, In-Kyeong, et al. “Chiari 1.5 Malformation : An Advanced Form of Chiari I Malformation.”Journal of Korean Neurosurgical Society, The Korean Neurosurgical Society, Oct. 2010, <www.ncbi.nlm.nih.gov/pmc/articles/PMC2982921>.

12 Malik, Amita, et al. Chiari 1.5: A Lesser Known Entity. Annals of Indian Academy of Neurology, <www.annalsofian.org/article.asp?issn=0972-2327;year=2015;volume=18;issue=4;spage=449;epage=450;aulast=Malik>.

13 Wolpert, Samuel M, et al. “Chiari II Malformation: MR Imaging.” American Journal of Roentgenology, <www.ajronline.org/doi/pdf/10.2214/ajr.149.5.1033>.

14 Yumer, M H, et al. “Chiari Type II Malformation: a Case Report and Review of Literature.”Folia Medica., U.S. National Library of Medicine, <www.ncbi.nlm.nih.gov/pubmed/16918056>.

15 Kim, Irene. “Chiari II Decompression in Patients with Myelomeningocele in the National Spina Bifida Patient Registry (NSBPR).” <http://spinabifidaassociation.org/sbworldcongress/wp-content/uploads/sites/10/2017/04/B.4-Kim-Neurosurgery.pdf>.

16 “Chiari Malformation Fact Sheet.” National Institute of Neurological Disorders and Stroke, U.S. Department of Health and Human Services, <www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Chiari-Malformation-Fact-Sheet>.

17 “Chiari Malformations.” NORD (National Organization for Rare Disorders), <www.rarediseases.org/rare-diseases/chiari-malformations>.

18 14 Aliaga, L, et al. “A Novel Scoring System for Assessing Chiari Malformation Type I Treatment Outcomes.” Neurosurgery., U.S. National Library of Medicine, Mar. 2012, <www.ncbi.nlm.nih.gov/pubmed/21849925>.

19  Siasios, John, et al. “Surgical Management of Patients with Chiari I Malformation” International Journal of Pediatrics, Article ID 640127, Hindawi, 2012, <www.hindawi.com/journals/ijpedi/2012/640127>.

THE DEFINITION OF A CHIARI MALFORMATION HAS BEEN LONG DEBATED. IT REALLY IS NO WONDER THAT PATIENTS AND MEDICAL PROFESSIONALS ALIKE ARE CONFUSED. THEN, WITH US FULLY UNDERSTANDING ALL SIDES OF THE DEBATE, WE DEFINED A CHIARI MALFORMATION AS STRUCTURAL DEFECTS IN WHICH THE CEREBELLUM, THE HIND PART OF THE BRAIN, DESCENDS BELOW THE FORAMEN MAGNUM INTO THE SPINAL CANAL. THIS DEBATE IS BEING ANALYZED THIS YEAR, AS CERTAIN ORGANIZATIONS ARE BRAVING TO ATTEMPT TO BRING DOCTORS ALL UNDER ONE UNIFORM DEFINITION AND DIAGNOSTIC CRITERIA. THEREFORE, AMIDST ALL THE CONFUSION AND DEBATE, WE WANTED TO EXPLAIN THE FACTORS INVOLVED, AND WHY WE WENT WITH THE DEFINITION THAT WE DID, AND WHY ONE STANDARD IS SO IMPORTANT!

To better facilitate our explanation, we will call all associated terms by their specific medical names:

Tonsillar Ectopia (TE) = tonsillar herniation of any size
Posterior Fossa Hypoplasia (PFH) = an underdeveloped posterior fossa

 

Chiari Malformation Vs. Arnold Chiari Malformation

The most common type of Chiari is Type 1 (which includes a Chiari 1.5, where the brainstem is also below the foramen magnum). Many people use the term “Chiari Malformation” when diagnosed with Type 1, while others cling to the name “Arnold Chiari Malformation” with the same diagnosis. Is there a difference? The name “Chiari Malformation” came from Hans Chiari, an Austrian pathologist, who first discovered the malformation in the late 19th century.[1, 2] Julius Arnold, a German pathologist, later expanded on Chiari Type 2, and Type 2 took on his name “Arnold Chiari Malformation.” Therefore, technically speaking, a Chiari Malformation and an Arnold Chiari Malformation are not the same; Arnold Chiari Malformation is specific to Chiari Type 2 (which usually includes a myelomeningocele, the most serious form of Spina Bifida). However, they are used interchangeably by many, even by medical professionals and the misnomer is of little consequence one way or the other.[3]

 

Chiari Malformation = Posterior Fossa Hypoplasia Theory

Many ascribe to the theory that a Chiari Malformation ONLY consists of a posterior fossa hypoplasia (which means that the back of the skull is malformed, and therefore the cranial area (space) at the rear is too small). They believe that a tonsillar ectopia is only a symptom, and a Chiari Malformation can exist with or without an accompanying ectopia. This argument is not without merit, because much of what was initially being looked at by Hans Chiari were deformities in the posterior skull upon postmortem examination (so there wasn’t soft tissue to analyze). He originally attributed much to hydrocephalus, but expanded his research into the pons, medulla oblongata, and cerebellum (which can all be attributed to intracranial pressure as a pathology of a “tonsillar ectopia”). To ascribe to this belief would also mean that “Acquired Chiari Malformations” cannot exist, as one doesn’t “acquire” a small posterior fossa. And that would also mean that Chiari Type 2, Type 3 and Type 4 technically would not be a Chiari Malformation at all either, since their definitions do not require a posterior fossa hypoplasia. Perhaps type 3, which has an opening at the back of the skull, but no “small posterior fossa” is even implied in the definitions.

But to look at the full history of what became known as a Chiari Malformation, we can begin by looking at the research of a German pathologist, named Theodor Langhans. In his research in 1881 (a decade before Hans Chiari conducted his research on what became known as a Chiari Malformation), while looking at syringomyelia (“a cavity created in the spinal cord”), he noted a “change in the cerebellar cavity.” Upon dissection of the cerebellum, he described the cerebellar tonsils as “two symmetrical pyramidal tumors,” pushing the brainstem forward.[4] In fact, the other noted researchers: Nicholas Tulp (1593–1674), John Cleland(1835–1925), and Julius Arnold (1835–1915), all centered on the hindbrain hernia [herniation] without speculation as to its etiology/pathology. It is said that “many of the English translations of Chiari’s work contain inaccuracies.” But note that Chiari’s first paper was on “ectopia of cerebellar tissue,” and that he went on to define Type 1 as showing, “elongation of the tonsils and medial parts of the inferior lobes of the cerebellum into cone shaped projections, which accompany the medulla oblongata into the spinal canal.”[5] Which sounds like what is now known to be a Chiari 1.5. Much later, in 1938, at a time when the posterior fossa decompression became the popular surgical treatment for a Chiari Malformation, a Chiari 2 patient “underwent posterior fossa exploration with the authors not considering hindbrain herniation in their differential. Penfield and Coburn later stated that: ‘In retrospect it seems that we should have suspected the Arnold-Chiari malformation. Instead, a suboccipital craniotomy was carried out…” So even the early neurosurgeons seeking to perfect their surgical treatment felt that it was a mistake to concentrate on the posterior fossa and not take into account etiologies of the hindbrain herniation. That mistake is still going on 80 years later.[6]

The biggest problem that they are going to have with strictly defining a Chiari Malformation as a small posterior fossa resides in the fact that the diagnosis criteria for a Chiari Malformation only consists of ONE MEASUREMENT, the length of the tonsillar ectopia (how far the tonsils herniate below the foramen magnum). Generally, there are no measurements of the posterior fossa taken when radiologists make the initial diagnoses. Furthermore, most neurosurgeons see the radiology reports, and depending on symptomology, they make the decision to decompress or not to decompress without ever measuring the size of the posterior fossa. Most never look for (and often do not know about) etiological/pathological cofactors that could have been causing the tonsillar prolapse in the first place.

Where does this assumption leave us?
Unfortunately it leaves most of us with failed decompressions, fighting with our neurosurgeons that “something is still wrong.” These neurosurgeons look at their post-operative checklist and see that they successfully did everything surgically required in their out-of-date textbooks:
  1. Suboccipital bone was appropriately decompressed. ✔️
  2. Dura was opened and dura patch was successfully inserted. ✔️
  3. Lamina was successfully removed from the C1 (and sometimes the C2 as well). ✔️
They did all that was required of them based on the diagnoses presented! They don’t have time (or don’t care) to look beyond that, so once again, the idea of our continued symptoms are thought of as being psychosomatic.
 
While we applaud the efforts of those seeking to get a measure of consistency in how Chiari is defined, the truth remains that until the diagnosis criteria is changed as well, we are being diagnosed with Chiari Malformation based on our tonsillar herniation; it is presumed to be congenital; we are being surgically treated as though it is congenital, and we are ending up with failed decompressions. This confusion is beyond unacceptable, it’s reprehensible!
When it is all redefined, hopefully we will have a well defined diagnosis criteria, or it is all irrelevant. And the many that really did acquire what was assumed to be “congenital” who are now being told that they do not have Chiari Malformation at all, will be able to get lawyers for “an improper diagnosis” that lead to the incorrect brain surgery being done. There are surgeons coming around and finally seeing that there is merit to these studies that have been done since the late 1990s, that have shown a pushing/pulling effect that can cause the tonsillar ectopia that gets us diagnosed with a Chiari Malformation, and we applaud them for having the integrity to stand up and get it right. That’s exactly what we need and deserve!
If you were diagnosed with a Chiari Malformation and want to know how all of this might be affecting you, we encourage you first to find your initial radiology reports, and see if there were measurements taken of the posterior fossa. And then wait with that information… wait and see what changes are actually made to the definition. While you are waiting learn. Learn everything you can about every etiological/pathological cofactor, and every comorbidity. If it is “officially” redefined as a small posterior fossa, we will have to work together as a community (like we always do) to help lawyers see how we have been getting lost in the shuffle, year after year. If it’s not officially changed and Chiari continues to be defined as a structural defect involving the cerebellar tonsils, we will have to continue in our fight to make these cofactors of Acquired Chiari Malformation known!

 


 

References:

1 Tubbs, et al. “Hans Chiari (1851–1916).” Journal of Neurology, Pioneers in Neurology, Springer Berlin Heidelberg, 26 Mar. 2010, <https://link.springer.com/article/10.1007/s00415-010-5529-0>.

2 “Hans Chiari.” Whonamedit – Dictionary of Medical Eponyms, <www.whonamedit.com/doctor.cfm/1123.html>.

3 Tubbs, R. Shane, and W. Jerry Oakes. The Chiari Malformations: A Historical Context . 2013, <https://pdfs.semanticscholar.org/79dd/127d31820d612600c0b032225437295d86c3.pdf>.

4 Mortazavi, M M, et al. “The First Description of Chiari I Malformation with Intuitive Correlation between Tonsillar Ectopia and Syringomyelia.” Advances in Pediatrics., U.S. National Library of Medicine, Mar. 2011, <https://www.ncbi.nlm.nih.gov/pubmed/21361763>.

Pearce, J M S. “Arnold Chiari, or ‘Cruveilhier Cleland Chiari’ Malformation.” Journal of Neurology, Neurosurgery & Psychiatry, BMJ Publishing Group Ltd, 1 Jan. 2000, <https://jnnp.bmj.com/content/68/1/13>.

Mortazavi, Martin M., et al. “The First Posterior Fossa Decompression for Chiari Malformation: the Contributions of Cornelis Joachimus Van Houweninge Graftdijk and a Review of the Infancy of ‘Chiari Decompression.’” SpringerLink, Springer, Dordrecht, 6 Apr. 2011, <https://link.springer.com/article/10.1007%2Fs00381-011-1421-1>.

CHIARI (KEE-AR-EE) MALFORMATIONS ARE FAR FROM RARE, THEY ARE JUST RARELY UNDERSTOOD, EVEN BY MOST MEDICAL PROFESSIONALS. A CHIARI MALFORMATION EXISTS WHEN THE LOWEST PART OF THE HIND BRAIN (THE CEREBELLAR TONSILS) PROLAPSES INTO THE HOLE AT THE BOTTOM OF THE SKULL (FORAMEN MAGNUM), ENTERS THE SPINAL CANAL AND OBSTRUCTS THE FLOW OF CEREBROSPINAL FLUID (CSF), PUTS PRESSURE ON THE BRAINSTEM AND SPINE, AND MAY RESULT IN VARYING DEGREES OF NERVE COMPRESSION.

PREVALENCE OF CHIARI: Once thought to occur in 1 in 1000 people, it is now believed to be much more frequent of an occurrence. A 2016 pediatric study found it to occur in 1 in 100 children[1]. Since Chiari Malformation Type 1, the most common type, tends to become symptomatic during late teens and early adulthood, it is likely to be much more common when adults are factored in.

THE CONNECTION: Chiari malformations were originally believed to be caused by a posterior fossa hypoplasia (small area inside the back of the skull) and doctors speculated that lack of maternal prenatal care or drug abuse caused the deformity. However, as studies continue, they are finding that many with this hind brain herniation have connective tissue disorders, such as Ehlers-Danlos Syndromes. Ehlers-Danlos Syndromes involve a mutation in one of the collagen genes. Collagen is a protein that is often described as a “cellular glue” that helps hold the body together. When that glue fails to hold, everything seems to go awry; specifically, as related to Acquired Chiari Malformations: organs tend to prolapse, and bones begin to shift as joint laxity increases (including the bones/vertebrae at the craniocervical junction). They are finding that these acquired Chiari malformations are far more common than originally thought. There are many pathological co-factors that can cause or attribute to the formation of a Chiari Malformation, and most can be linked to these Heritable Disorders of Connective Tissues (HDCTs), including a posterior fossa hypoplasia. In one large study, they found those with a Chiari malformation and no associated co-factors, with only slightly over 52% having a small Posterior Cranial Fossa (PCF). When other co-factors were present, the number of Chiarians found with a small PCF plummeted and therefore it is should be considered acquired until proven otherwise.[2]

DIAGNOSES: A decade ago, it took 10-20 years from the onset of symptoms to be diagnosed and now it takes an average of 1-2 years, because medical professionals are slowly beginning to look for it. Magnetic Resonance Imaging (MRI) remains the best tool for diagnosis. Some medical professionals believe that a tonsillar herniation of less than 5mm is simply a tonsillar ectopia and only diagnose a Chiari malformation when the descent is > 5mm. However, the 5mm requirement is controversial and many doctors now base their diagnoses not solely on measurements, but rather on symptomology and a combination of other factors (including Cine MRI, a patient’s symptoms, and other relevant factors). Due to the prevalence of connective tissue issues, gravity often proves to be a significant factor and should be taken into account by use of an upright MRI whenever possible.[3] EDS should be diagnosed by a geneticist before surgery is considered.

TREATMENT OPTIONS: There is no cure for a Chiari malformation, but there are treatment options. When symptoms are minimal and not life-altering, pain management is usually offered. However, it is important to know that while medications may ease some symptoms, Chiari symptoms tend to be progressive. Decompression surgery is the only treatment available to attempt to halt the progression of the damage being done to your Central Nervous System (CNS). The most common reason that decompression surgeries fail, is undiagnosed co-morbid conditions, especially those that can be etiological/pathological co-factors. More than one surgery might be necessary to successfully treat a Chiari malformation and any/all co-morbid conditions and there is a correlation between early surgical intervention and positive surgical outcomes[4].

 


 

References:

1 Eltorai, Ibrahim M. “Rare Diseases and Syndromes of the Spinal Cord” Cham: Springer International Publishing: Imprint: Springer, 2016. Page 43, 15.2, <www.springer.com/us/book/9783319451466>.

2 Milhorat, Thomas H., et al. “Mechanisms of Cerebellar Tonsil Herniation in Patients with Chiari Malformations as Guide to Clinical Management.” Acta Neurochirurgica, Springer Vienna, July 2010, <www.ncbi.nlm.nih.gov/pmc/articles/PMC2887504>.

3 Henderson, Fraser C., et al. “Neurological and Spinal Manifestations of the Ehlers–Danlos Syndromes.” American Journal of Medical Genetics Part C: Seminars in Medical Genetics, 21 Feb. 2017, <www.onlinelibrary.wiley.com/doi/10.1002/ajmg.c.31549/full>.

4 Siasios, John, et al. “Surgical Management of Patients with Chiari I Malformation” International Journal of Pediatrics, Article ID 640127, Hindawi, 2012, <https://www.hindawi.com/journals/ijpedi/2012/640127>.

Once diagnosed, you will usually be referred to a specialist (not a Chiari Specialist, but an everyday, run-of-the-mill neurologist or neurosurgeon). They tend to come in one of two types: Either they are very passive and just want to wait and see how bad it gets, or they are very pro-surgery and while they will still usually give you a 50% chance of helping your symptoms, they will tell you how decompression surgery really is your best option. Both are problematic.

FOR THE ASYMPTOMATIC CHIARIAN:
Without a doubt, the passive approach is by far the best plan of action for the asymptomatic Chiari patient. Approximately 30% of those with a Chiari 1 malformation can go their entire lives without having symptoms (in fact, many remain undiagnosed and don’t even know they have it because they have no symptoms).[1] The Chiari is often discovered while looking for something else entirely and is therefore considered an “Incidental Finding.” While there is a chance that the Chiarian will become symptomatic one day, the risks of surgical complications exceed the potential benefit on something that has not and might not ever affect their life.

FOR THE SYMPTOMATIC CHIARIAN:
If the Chiarian is symptomatic, however, “Decompression Surgery is the only treatment available [at this time] to correct functional disturbances or halt the progression of damage to the central nervous system. Most individuals who have surgery see a reduction in their symptoms and/or prolonged periods of relative stability. More than one surgery may be needed to treat the condition.”[2] Despite the reasons for haste however, we do recommend slowing down and making sure that adequate testing is done to ensure that the Chiari is a “Congenital Chiari” formed only by a small posterior fossa, with no other etiological/pathological co-factors that could make it an “Acquired Chiari Malformation.” If not identified and addressed, these etiological/pathological co-factors can cause complications and even lead to a failed decompression surgery. (Note: most are told at diagnosis that it is a “congenital defect.” However, that is usually a presumption on their part, stemming from a lack of knowledge of Chiari and its comorbidities, and them giving too much credence to the paragraph or two on Chiari malformations in their medical school textbooks. That is not the reality that many are dealing with; so, testing is imperative!)

TESTING:
If you have been diagnosed with a Chiari malformation or a tonsillar ectopia (regardless of the size of tonsillar descent), you should have the following tests/images done.

1. A sleep study to check for Sleep Apnea.

Central Sleep Apnea (CSA) is more common with Chiari, especially when there has been damage to the brainstem or Vagus Nerve.

Obstructive Sleep Apnea (OSA) is commonly linked with obesity in the general population, it is also very common amongst those with Connective Tissue Disorders (such as Ehler’s-Danlos Syndrome).

• Both CSA and OSA can be present in the Chiarian with a Connective Tissue Disorder. When both are causing apnea, it becomes known as “Complex Sleep Apnea.”

• Sleep Apnea, regardless of the type, is a common “killer” amongst Chiarians.


2. A brain and full spine MRI (upright recommended) with and without contrast.

What they should be looking for in these MRIs:

a) Do you have a syrinx (Syringomyelia or Syringobulbia)?

• If you have either, that is proof that the blockage of CSF is significant enough to cause these potentially serious complications.

b) Is any part of your brainstem below the foramen magnum?

• If it is, you have a variant of Type 1, known as a Chiari 1.5[3] or Type 2, both indicate that there is something else going on causing the brainstem to herniate along with the cerebellar tonsils

c) Do you have a cyst/tumor causing increased intracranial pressure that is pushing the cerebellar tonsils down?

• If you have either, and they are operable, there is a chance that surgically removing it could decrease the intracranial pressure and allow the cerebellar tonsils (and brainstem if it is below the foramen magnum at all) to go to proper position. Furthermore, if the cyst/tumor is not addressed before, during, or soon after decompression surgery, the chances of your tonsils herniating again after decompression are high.[4]

d) Do you have Hydrocephalus causing increased intracranial pressure that is pushing the cerebellar tonsils down?

• If you do, there is a chance that the placement of a Ventriculoperitoneal Shunt could decrease the intracranial pressure enough to allow the cerebellar tonsils (and brainstem if it is below the foramen magnum at all) to go to their proper position. Furthermore, if the Hydrocephalus is not addressed before, during, or soon after decompression surgery, the chances of your tonsils herniating again after decompression are high.[5]

e) Do you have signs/symptoms of Idiopathic Intracranial Hypertension (often shows as excessive fluid above the lateral ventricles, with small, “slit-like” lateral ventricles; usually accompanied by Papilledema and/or