General Information Archives

Published: 19 January 2018

Written by Gaea

4 Comments

Categories: General Information

“Make it stop!”

“I can’t take this pain anymore!”

How many times have you, or your loved one, cried out these very words?

Pain from a Chiari headache can be brought on from the simplest of things – a sneeze, a cough, laughter, or bearing down when going to the bathroom. We never know when the headache is going to strike, how long it will last, or when it will end. We are unable to describe the intensity of the pain to others, and when asked to rate our pain on a scale of 1 – 10, we want to scream, “14!” The radiating, crushing pain of the headaches robs us of our ability to function for days on end. And depending on the extent of damage the Chiari has caused you may also have the burning, stabbing, and shooting involved with neuropathic pain and neuralgia. The frosting on the pain cake, perhaps? With the many co-morbid disorders that go hand in hand with Chiari, such as Ehlers-Danlos Syndrome, Intracranial Hypertension, Hydrocephalus, and Tethered Cord Syndrome, is it any wonder we cry out, “Make it stop!”?

Once finally diagnosed, whether you feel like you are losing your mind, or rejoicing over finally having answers, I guarantee you, this emotional roller coaster will still prove to be the ride of your life! Even if they say your Chiari was an “incidental finding,” I can almost guarantee that when you look back in hindsight, you will see that some of the signs of Chiari or its comorbid conditions were always there and you thought they were just “normal.” If you have a history (or familial history) of headaches made worse when you cough, sneeze, laugh, flinch, strain, or bend over; neck pain; stomach aches; ankle/knee/hip/elbow problems; hypermobile joints; dislocations; scoliosis; bulging/herniated discs; miscarriages; aneurysms; numbness; muscle wasting (atrophy); vision loss; double vision; or unexplained muscle/eye spasms (and the list could go on); then they are all probably related to Chiari and its comorbidities. If you just got a new diagnosis of “Chiari Malformation,” you might feel fear, with a sigh of relief to finally have a diagnosis to go with the many symptoms you have complained about for years. Whatever you are feeling right now, be sure to take the time to breathe and take care of you, because the battle is an accumulation of long and tiring rounds and odds are, Chiari Malformation is not the only problem you have going on.

By a wide margin, the hardest part of our fight is dealing with doctors. One would think it would be the never-ending pain, but when your doctors do not believe you, ridicule you, or outright verbally abuse you, it not only adds insult to injury, but it probably illustrates reasons that your doctor(s) just might be the ones that need counseling. As patients, we are paying for them to help us with our medical problems; what we get instead is usually a referral to a therapist because of their ineptitude. The absurd part of this circle of insanity is that when we make ourselves more knowledgeable about our condition(s), because we have no other choice, a doctor that understand the Hippocratic Oath would respond by making themselves more knowledgeable as well, so they can help their patients. Yet, what is far too common are doctors that do not want to know the results of studies, who are complacent with their fifteen minutes of Chiari education, and think if they talk a good game, patients can be manipulated into thinking maybe it’s all in their minds.

In a distant second, would have to be the heart-wrenching feeling we get when our loved ones put more stock in the opinions of our morally bankrupt doctors, even once we have shared study after study and article after article showing you that our doctors are wrong. What we go through, feeling like our bodies have betrayed us, knowing that our doctors have betrayed us (even if it is because they do not know any better), we need you in our corner. This is the fight of our lives, for our lives, and we should never have to do it alone! The energetic, feisty, loving person that you have loved so much over the years is still inside of us! When your brain falls into your spinal canal and your connective tissue is wasting away, there is no measure of motivation that is going to help fix it! We need help with our battle, someone in our corner! We don’t need judgement or motivational speeches; we need love and understanding – and an occasional shoulder to cry on. We need you to help us stay grounded and remind us that despite the pain and brokenness, we still have value in this world! Without a shadow of a doubt, we really need you!

What our bodies go through from head to toe really can only be understood by remembering the importance of your Central Nervous System in everything that you do. Every nerve in your body passes through the Foramen Magnum, where the Cerebellar Tonsils invaded, and in most cases, every single one of those nerves are damaged to some degree (and some of that damage is permanent). The headaches we get when we cough, sneeze, heave (or do anything that causes a bounce or even a slight movement of our skulls), can often only be compared to the pain of childbearing – rendering the pain rating scales useless for not having the angry face reaching around and trying to rip his skull out from the base. The neck pain consists of spasms (either continuous or intermittent). For most of us with HDCT, Craniocervical Instability makes our heads constantly feel like they weigh far too much for our weak necks to support (often described as a ‘bobblehead” feeling). Some might consider the pins and needles or ice pick stabbing pains behind our eyes, in our heads (neuralgia) or in our extremities (peripheral neuropathy) to be a crushing reality of life despite surgery.

Finally, this lack of awareness, education and research makes it even more difficult for those of us who find ourselves no longer able to work. The Social Security Administration has yet to add Chiari Malformation to its list of impairments which would automatically qualify for disability benefits (apparently, they do not know the importance of the Central Nervous System either). Although benefits can still be fought for and awarded, the fight becomes far more difficult than it needs to be. Chiarians often must fight for years, filing appeal after appeal, to prove that their reality is the reality.

Is their hope? Yes!

Through it all, and despite all the challenges that face us, we are many, and together, we are powerful! We can change all of this by becoming our own advocates and by raising awareness and dollars for research and awareness information that strives to educate the medical professionals that are treating us. This is our war to fight and being the warriors that we are, we must rise to the occasion – because LOSING IS NOT AN OPTION!

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Published: 19 January 2018

Written by Cheryl Isanogle

2 Comments

Categories: General Information

One of the biggest hurdles a Chiari patient may face is that of simply being diagnosed. Some studies cite an average of 5 years between the onset of symptoms significant enough for a patient to seek medical care and the patient receiving an accurate diagnosis of Chiari Malformation. Sadly, however, online support groups and message boards are peppered with the stories of patients who went undiagnosed, or more often, misdiagnosed, for decades. Patients are frequently misdiagnosed with conditions such as Fibromyalgia, Multiple Sclerosis, Chronic Fatigue Syndrome, Chronic Migraine, and various autoimmune disorders. Even more disturbing is the fact that in a study by Dr. Thomas Milhorat of over 300 patients diagnosed with Chiari, 59% had been diagnosed with a psychosomatic illness.^[^1] Diagnoses such as Hypochondriasis, Somatoform Disorder, Conversion Disorder, and a tricky little term some doctors use to disguise the fact that they believe their patient’s symptoms are “all in their head,” called ‘Functional Somatic Syndrome’ (which by definition does not necessarily imply a psychosomatic cause but are often interpreted by other medical professionals in that manner) are frequently written in patient’s medical records to account for their very real, medically explainable symptoms.^[^2] This often further undermines a patient’s efforts to find a diagnosis when they decide to try a new doctor, with their defiled medical records in tow, often without even realizing what has been written in their charts or what it actually means in ‘doctor speak.’

Diagnosis of Chiari Malformation is based upon the presence of Chiari symptoms, such as an occipital headache that is brought about or worsened by Valsalva maneuvers, neurological symptoms such as poor balance, numbness or tingling in the arms, weakness in the legs, etc. combined with the “gold standard” of imaging studies for Chiari, an MRI of the brain.^[^3] The MRI should show a tonsillar herniation that inhibits the normal flow of CSF fluid out of the Fourth ventricle of the brain and through the foramen magnum. When normal flow is in question, a CINE MRI may be conducted to determine how the CSF is flowing through the brain and upper spinal canal. There, are, however, controversial cases sometimes referred to as “Chiari Zero,” where no herniation exists, but interruption of flow and symptoms are present.^[^4]

So, with all these wonderful tests available, why is it so difficult to get a diagnosis? Well, first of all, most primary care physicians and neurologists alike are under-educated or outright miseducated about Chiari Malformation. It has always been presumed to be a relatively rare disorder, and with over 7,000 rare diseases known to modern medicine, medical schools cannot give a thorough education to medical students on everyone. However, since the advent and now fairly commonplace use of the MRI, it is becoming apparent that Chiari is not quite as rare as it was once thought to be. When a primary care physician is stumped by a patient’s complaints of headaches and neurological symptoms, it is only natural to refer that patient to a neurologist for evaluation. But even many neurologists are grossly uninformed about Chiari. Many patients, even with an MRI that shows a herniation, are told that their many varied symptoms can’t possibly be due to the herniation of their brain, even with numerous studies available which show otherwise. Some patients have even been told by neurologists and even neurosurgeons that “Chiari doesn’t cause headaches [pain].” In fact, most symptomatic patients experience severe headaches, nerve pain, and pain from related disorders such as Syringomyelia.

Furthermore, radiologists across the U.S. are using vastly different criteria from one another to determine whether a patient’s herniation constitutes a Chiari Malformation. Some are using criteria of a 3-5mm herniation, others a 7 mm herniation, and some are failing to look for a herniation altogether. The latest research, in fact, suggests that the size of the herniation does not matter at all. Some people with large herniations show no symptoms, while others with quite small herniations experience severe symptoms. Experts are now focusing more on whether the herniation blocks the normal flow of cerebrospinal fluid (CSF) in determining whether a patient may benefit from surgical intervention.

It is important to address the situation of “Incidental Findings” of Chiari Malformation. It is true that sometimes while having an MRI for an unrelated matter, a completely asymptomatic patient is found to have a Chiari Malformation. Unless this type of patient were to become symptomatic later, no treatment is necessary in these situations. However, if you look at radiology reports with a claim of ‘incidental finding of Chiari Malformation,’ you are likely to see that the reason mentioned for the imaging being done was to look for a cause of headaches or other known symptoms of Chiari. In these cases, these are absolutely not ‘Incidental Findings.’ Again, this is an example of the lack of education about Chiari.

For patients, the best piece of advice one can give on your road to diagnosis of your symptoms, whether due to Chiari or something else, is to trust yourself and never give up seeking answers. If you believe your symptoms are due to Chiari or that your MRI may have been misread, get a second opinion from a neurosurgeon that specializes in treating Chiari Malformation.

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References:

¹ Milhorat, T H, et al. “Chiari I Malformation Redefined: Clinical and Radiographic Findings for 364 Symptomatic Patients.” Neurosurgery., U.S. National Library of Medicine, May 1999, <www.ncbi.nlm.nih.gov/pubmed/10232534>.

² Mayou, Richard, and Andrew Farmer. “Functional Somatic Symptoms and Syndromes.” BMJ : British Medical Journal, BMJ, 3 Aug. 2002, <www.ncbi.nlm.nih.gov/pmc/articles/PMC1123778/>.

³“The Chiari I Malformation.” Chiari I | Chiari & Syringomyelia Foundation (CSF), <csfinfo.org/education/physician-information/chiari-i/>.

⁴Hofkes, S K, et al. “Differentiation between Symptomatic Chiari I Malformation and Asymptomatic Tonsilar Ectopia by Using Cerebrospinal Fluid Flow Imaging: Initial Estimate of Imaging Accuracy.” Radiology., U.S. National Library of Medicine, Nov. 2007, <www.ncbi.nlm.nih.gov/pubmed/17890352>.

Published: 19 January 2018

Written by Michelle Cole

3 Comments

Categories: General Information

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 Empty Sella Syndrome), which can cause enough cranial pressure that it can push your cerebellar tonsils down?

• If you do, there is a chance that a prescription for Diamox or Topamax, or the surgical placement of a Ventriculoperitoneal Shunt, could reduce the pressure enough to allow the cerebellar tonsils (and brainstem if it is below the foramen magnum at all) to go into proper position. Studies exist both in favor of shunting first and doing the decompression first; there are documented cases where unresolved IH has led to failed decompression surgeries, while other cases attribute a Chiari decompression as being that which resolved IH symptoms.^[6/7]

f) Do you have signs/symptoms of Tethered Cord Syndrome that could be pulling on the spine from below?

• If you do, there is a chance that a less invasive surgery known as a Tethered Cord Release, could stop the downward pulling of the spinal cord and allow the cerebellar tonsils (and brainstem if it is below the foramen magnum at all) to go into proper position. Furthermore, if the Tethered Cord is not addressed before, during, or soon after decompression surgery, the chances of your tonsils herniating again after decompression are high. (Note: not all Tethered Cords are easily visible by MRI, when they are not visible, it is called Occult Tethered Cord (OTC) and surgery on a OTC remains controversial.)^[8]

g) Do you have signs/symptoms of Intracranial Hypotension (CSF Leak) that could be pulling or creating a suctioning effect from below?

• If you do, there is a chance that a less invasive blood patch or a Dural Tear Repair Surgery, could stop the downward pulling/suctioning effect on the spinal cord and allow the cerebellar tonsils (and brainstem if it is below the foramen magnum at all) to go into proper position. Furthermore, if the leak(s) are not addressed before, during, or soon after decompression surgery, the chances of your tonsils herniating again after decompression are high. (Note: not all leaks are easily visible by MRI.)^[9]

h) Do you have signs of Spina Bifida (Myelomeningocele, Meningocele, or Spina Bifida Occulta)?

• While it is important to know if any of these exist, a Myelomeningocele would put you at an increased risk of having a Chiari Type 2. While all Chiari Malformations with a Myelomeningocele do not meet the standards for Type 2, 90% of those with a Myelomeningocele have a Chiari Type 2. Most neurosurgeons will not perform a decompression on someone with a Myelomeningocele because of the risk of further complications.^[10]

i) Do you have signs/symptoms of disc degeneration problems and/or stenosis, especially in the cervical spine where it can damage the Vagus Nerve?

• If you do, these could be another sign of a connective tissues disorder. If you have a syrinx above a herniated/bulging disc, there is a good chance that the disc is attributing to it. Herniated/bulging discs in the cervical spine can be quite troublesome. They can usually be addressed by a second procedure called an Anterior Cervical Discectomy and Fusion (ACDF), but if there are multiple cervical problems and Craniocervical Instability, some surgeons will opt to do a fusion at the time of decompression.^[11]

j) Do you have signs and symptoms of a cervicomedullary syndrome^[^12], which are often the result of Craniocervical Instability (CCI), Atlantoaxial Instability (AAI), or both. (CCI and AAI can be confirmed with: An upright c-spine MRI with flexion, extension, and neutral views or a 3D cervical CT with rotational views.)

• CCI/AAI can produce many of the same symptoms as Chiari 1 malformation, including occipital or craniocervical junction headaches made worse by Valsalva maneuvers. It has been theorized that CCI/AAI may also be capable of causing or worsening a herniation of the cerebellar tonsils, and it has been demonstrated that CCI can cause ventral brainstem compression and deformative stress injury to the brainstem.^[^13] Failure to diagnose and treat CCI before or along with decompression has also been linked to decompression failure. CCI and AAI, while rare in the general population, are relatively common in patients with HDCT’s (Heritable Disorders of Connective Tissue), such as Ehlers-Danlos Syndrome. CCI, when identified to be the root cause of significant symptoms, can be treated conservatively, and in the short term, with the use of a hard-cervical collar, physical therapy and, possibly, traction. More permanent treatment in the form of a fusion and stabilization surgery (fusing the occiput to C1, C2, and sometimes additional vertebrae).^[12/13]

3. A preliminary check for connective tissue disorder (especially Ehler’s-Danlos Syndrome). If preliminary results indicate the presence of a connective tissue disorder, genetic testing should be done to rule out more serious types.

IF NONE OF THESE PROBLEMS APPEAR TO EXIST:
Some doctors and patients prefer to wait and just treat the symptoms medically. That is your choice to make and you should never let anyone try to bully you or manipulate you into having surgery or not; although it is important to know that statistics show that those who have had a shorter duration of onset of symptoms and surgery tend to have a better surgical outcome.^[14]

Statistics show that 80% of decompressed patients report some relief from some of their symptoms; headaches are the most commonly reported symptom to gain relief (81%).

Most surgeons will give a 50% chance of relieving each symptom individually, with the exception of pain associated with damaged nerves.

While some surgeons prefer a conservative approach to surgery such as a “bone only” decompression or a “Minimally Invasive Subpial Tonsillectomy,”^[15] a full decompression usually consists of:

♦ Craniectomy: removal of part of the sub-occipital skull.

♦ Laminectomy of C1 (and sometimes C2): removal of the lamina from the vertebra.

♦ Duraplasty: opening of the dura (the outermost membrane enveloping the brain and spinal cord) and patching it so there is more room.

♦ Cerebellar Tonsillectomy: removal/cauterization of the cerebellar tonsils.

IS DECOMPRESSION SURGERY A CURE FOR A CHIARI MALFORMATION?
There is a fundamental problem with the question and what many neurologists and neurosurgeons believe about decompression surgery. For the patient, the symptoms are synonymous with the condition. If we continue to struggle living our lives because of these symptoms, having a doctor that refuses to validate that struggle, can add insult to injury. Decompression surgery should NEVER be considered a cure to the symptoms of a Chiari malformation, it is merely the only treatment available [at this time] to correct functional disturbances or halt the progression of damage to the central nervous system. The likelihood of continued symptoms is almost absolute, Decompression is only a means of reestablishing the flow of CSF between the brain and spinal canal (which is imperative). Once flow is restored, there should be some relief from many of the symptoms. Complications such as Syringomyelia should be reduced or resolved, so the possibility of paralysis is significantly reduced. With as bad as the pain and symptoms are, it really can get worse if left untreated. Finding a specialist that is not only experienced with decompression surgeries, but who fully understands the correlation and treatment of etiological/pathological co-factors and co-morbid conditions, substantially increases the likelihood of a positive surgical outcome.

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References:

¹ 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>.

² “Chiari Malformation Fact Sheet.” National Institute of Neurological Disorders and Stroke, U.S. Department of Health and Human Services, June 2017, <www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Chiari-Malformation-Fact-Sheet>.

³ 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/>.

⁴ Wang, J, et al. “Acquired Chiari Malformation and Syringomyelia Secondary to Space-Occupying Lesions: A Systematic Review.” World Neurosurgery., U.S. National Library of Medicine, Feb. 2017, <www.ncbi.nlm.nih.gov/pubmed/27894943>.

⁵ Graham, A, et al. “An Unusual Cause of Neck Pain: Acquired Chiari Malformation Leading to Brainstem Herniation and Death.” The Journal of Emergency Medicine., U.S. National Library of Medicine, Dec. 2012, <www.ncbi.nlm.nih.gov/pubmed/21215551>.

⁶ Fagan, L H, et al. “The Chiari Pseudotumor Cerebri Syndrome: Symptom Recurrence after Decompressive Surgery for Chiari Malformation Type I.” Pediatric Neurosurgery., U.S. National Library of Medicine, 2006, <www.ncbi.nlm.nih.gov/pubmed/16357496>.

⁷ Park, Michael S., et al. “Coexistent Chiari Malformation and Idiopathic Intracranial Hypertension: Which Should Be Treated First?- Case Report and Review.” JSM Neurosurg Spine, vol. 2, no. 3, ser. 1025, 20 Mar. 2014. 1025, <www.jscimedcentral.com/Neurosurgery/neurosurgery-2-1025.pdf>.

⁸ Milhorat, T H, et al. “Association of Chiari Malformation Type I and Tethered Cord Syndrome: Preliminary Results of Sectioning Filum Terminale.” Surgical Neurology., U.S. National Library of Medicine, July 2009, <www.ncbi.nlm.nih.gov/pubmed/19559924>.

⁹ Atkinson, J L, et al. “Acquired Chiari I Malformation Secondary to Spontaneous Spinal Cerebrospinal Fluid Leakage and Chronic Intracranial Hypotension Syndrome in Seven Cases.” Journal of Neurosurgery., U.S. National Library of Medicine, Feb. 1998, <www.ncbi.nlm.nih.gov/pubmed/9452230>.

¹⁰ Vandertop, William P., et al. Surgical Decompression for Symptomatic Chiari II Malformation in Neonates with Myelomeningocele. Oct. 1992, <www.thejns.org/doi/abs/10.3171/jns.1992.77.4.0541>.

¹¹ Dahdaleh, Nader S., and Arnold H. Menezes. Incomplete Lateral Medullary Syndrome in a Patient with Chiari Malformation Type I Presenting with Combined Trigeminal and Vagal Nerve Dysfunction. 2008, <www.thejns.org/doi/pdf/10.3171/PED.2008.2.10.250>.

¹² 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>.

¹³ Henderson, FC, et al. “Deformative Stress Associated with an Abnormal Clivo-Axial Angle: A Finite Element Analysis.” Surgical Neurology International, 16 July 2010, <www.europepmc.org/articles/PMC2940090/>.

¹⁴ Ma, J, et al. “Cerebellar Tonsillectomy with Suboccipital Decompression and Duraplasty by Small Incision for Chiari I Malformation (with Syringomyelia): Long Term Follow-up of 76 Surgically Treated Cases.” Turkish Neurosurgery., U.S. National Library of Medicine, 2012, <www.ncbi.nlm.nih.gov/pubmed/22664992>.

¹⁵ Beecher, Jeffrey S., et al. “Minimally Invasive Subpial Tonsillectomy for Chiari I Decompression.” Acta Neurochirurgica, Springer Vienna, 5 July 2016, <www.ncbi.nlm.nih.gov/pmc/articles/PMC4980444/>.