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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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>.

 

 

Most Chiarians go to see a surgeon with an expectation of them being knowledgeable in their field. However, while they might be a surgeon with a specialty of neurologically-based surgical procedures, their knowledge of Chiari and its comorbid conditions might not rank high in their practice. Make the most of your initial appointment by interviewing them and what they really know about Chiari Malformation. Be cautious of inflated success rates, as the scale on their decompression success/failure rates are not based on how their patients feel afterward, it is based on if they were successful with the aspects of the surgery (bone removal, opening the dura, adding the dural patch/graft, laminectomy). 

 

HERE IS A LIST OF CHIARI QUESTIONS WE RECOMMEND ASKING AT YOUR FIRST NEUROSURGERY APPOINTMENT:

 

General Questions:

  • In an average month, how many Chiari decompressions do you perform?
  • What do you believe causes a Chiari malformation?
  • Looking at my brain scan, is any part of my “brainstem” herniated (below the posterior fossa)?

 

Intracranial Hypotension (low pressure) Questions:
*Article to help you understand CSF Leaks & Intracranial Hypotension prior to your appointment.
If you have SYMPTOMS OF LOW INTRACRANIAL PRESSURE and/or suspect a cerebrospinal fluid leak, we recommend asking the following questions:

  • S.E.E.P.S.
    • Looking at my brain scan, do you see any Subdural fluid collections?
    • Looking at my brain scan, do you see an Enhancement of pachymeninges?
    • Looking at my brain scan, do you see an Engorgement of my venous structures? Should we do an MRV to make sure?
    • Looking at my brain scan, does my Pituitary appear to be enlarged?
    • Looking at my brain scan, does my brain appear to be Sagging?

If he/she answers affirmatively to any of the above S.E.E.P.S. questions, ask: 

  • What should be done to find/repair a potential leak?
  • Are you aware that it is common for CSF Leaks to not show up on MRI?
  • Are you willing to do a CT Myelogram and a  digital subtraction myelogram if I develop symptoms of a leak and none can be found on MRI?
  • Are you aware that it can often take multiple epidural blood patches to try and seal a leak, and sometimes when a blood patch fails to work, a surgical dural repair might be necessary?

 

Intracranial Hypertension (high pressure) Questions:
*Article to help you understand Intracranial Hypertension prior to your appointment.
If you have SYMPTOMS OF HIGH INTRACRANIAL PRESSURE, we recommend asking the following questions:

  • Looking at my brain scan, do I have cerebrospinal fluid in my sella turcica (Empty Sella Syndrome)?
  • Looking at my brain scan, do you see any evidence of my optic nerves are swollen (papilledema)?
    • If so, should I be referred to a neuro-ophthalmologist?
  • Looking at my brain scan, do my lateral ventricles appear small or flattened?
    • If so, do I need to have my pressures checked?
    • What are the symptoms of a CSF Leak, should one develop?
      • What is your plan of action if I should develop these leak symptoms?
      • Are you aware that it is common for CSF Leaks to not show up on MRI?
      • Are you willing to do a CT Myelogram if I develop symptoms of a leak, and none can be found on MRI?
    • Should a leak be found, are you aware that it can often take multiple epidural blood patches to try and seal a leak?

 

Tethered Cord Questions: 
*Article to help you understand Tethered Cord: Sorry, Coming Soon.
If you have SYMPTOMS OF TETHERED CORD, we recommend asking the following questions:

  • Looking at my brain/cervical scan, does my brainstem appear to be elongated?
  • Looking at my cervical scan, does my spinal cord appear to be stretched?
  • Looking at my lumbar scan, does my conus reach my L2/L3?
  • Looking at my thoracic and lumbar scan, does my spinal cord appear to be pulling to the back, or one particular side?
    • If so, should we do a prone MRI to see if it has actually adhered to that side?
  • Looking at my lumbar scan, do I appear to have fatty tissue inside the epidermis?
    • If the answer to any of these questions is affirmative, do you suspect that I have a tethered spinal cord?
    • If so, should we plan for a Tethered Cord Release before or soon after decompression surgery, so the likelihood of a failed decompression is reduced?
    • If I have urological issues, can I get a referral for urodynamic testing to rule out any other potential causes of my urological issues?

 

Craniocervical Instability (CCI) & Atlantoaxial Instability (AAI):
*Article to help you understand CCI & AAI prior to your appointment.
If you have SYMPTOMS OF CRANIOCERVICAL INSTABILITY or SYMPTOMS OF ATLANTOAXIAL INSTABILITY, we recommend asking the following questions:

  • Looking at my brain/cervical scans, what are the measurements of my clivoaxial angle and Grabb-Oakes?
  • Do these measurements meet the diagnostic criteria for Craniocervical Instability?
  • Looking at my flexion and extension imaging, how many millimeters of translation are there between flexion and extension?
  • Does Chamberlain’s Line cross my odontoid? If so, does it cross at a level that would indicate Basilar Invagination?
  • Looking at my rotational imaging, what is the percentage of uncovering of the right and left articular facets on rotation?
  • Do the percentages from my rotational imaging meet the diagnosis criteria for Atlantoaxial Instability?

 

IF A DIAGNOSIS CRITERIA IS MET IN ANY OF THE ABOVE, WE STRONGLY RECOMMEND THAT YOU WAIT ON DECOMPRESSION AND PURSUE THE TREATMENT OF SAID CONDITION(S) AND THAT OF EHLERS-DANLOS SYNDROME, AS EACH OF THESE CONDITIONS CAN BE PATHOLOGICAL TO AN ACQUIRED CHIARI AND EACH IS A STRONG INDICATOR THAT A CONNECTIVE TISSUE PROBLEM EXISTS. 

*The questions in this article will periodically change, as we are able to expand our recommended question suggestions.

 


*Original version released September 2018, revised November 2019.

 

 

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>.

Bridges are built as a means to assist people in getting over the things that obstruct their path. We are constantly facing obstacles when it comes to our health, so we decided to build a bridge! Chiari Bridges is a non-profit network built by Chiarians for Chiarians. Our goal is to provide information, substantiated by published studies, in a way that is easy to understand. We encourage readers, to not only read our articles, but look up every study for themselves and read that too. Print it out and sit down with a highlighter; read it as many times as necessary until you understand; then use it to talk to your doctors. Our doctors are under no obligation to read our articles, but they should be willing to read officially published studies from journals, especially those specific to their profession. As many of our authors are patients as well, all authors sharing original pieces will be writing under pseudo-ghost names, to protect them from being black-listed by their doctors. Chiari Bridges is not affiliated with any physician or medical group. You should in no way use this site as a replacement for diagnosis, treatment, or medical from a qualified medical professional. The information provided on our website is strictly for educational purposes, in order to help further the understanding of Chiari, and its associated conditions. Our goal is to share our collective experiences and the information we have gathered, with those in need of answers, that it may increase your knowledge and guide you in conversations with your doctors.