Category: Acquired Chiari Malformation

An Acquired Chiari Malformation is when the cerebellum extends out of the skull and into the spinal canal after birth; whether acquired from another inherited condition such as Ehlers-Danlos Syndromes, or one of the many developed conditions that can cause the pushing/pulling down on the brain or spinal cord: Intracranial Hypertension, Hydrocephalus, Cysts/Tumors, Tethered Cord Syndrome, Intracranial Hypotension (CSF leaks), etc. It is recommended that all Chiari Malformations are assumed to be acquired, until proven otherwise.

The Important Questions to Ask Your Neurosurgeon [Revised]
Most Chiarians go to see a surgeon with an expectation of them being knowledgeable in their field. However, while they might be a neurosurgeon, their knowledge of Chiari and its comorbid/pathological 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 Malformations. Be cautious of inflated success rates. Chiari decompression in general offers a just over a 50% success rate (which means it has a nearly 50% failure rate). Surgeons that claim a 100% (or near 100% success rate) are usually not basing their success on how their patients feel afterward, it is based on if they were successful with the aspects of the surgery:
Removal of the occipital bone ✓
Opening the dura and adding the patch/graft ✓
Laminectomy ✓
Cauterization/resection of cerebellar tonsils ✓

WE DESERVE BETTER THAN THAT!

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

General Questions:
- How do you define a Chiari Malformation?
- What do you believe causes a Chiari malformation?
  - Are all Chiari malformations from a small posterior fossa?
  - Do I have a small posterior fossa? If yes, how big is it? If size is unknown, was my posterior fossa measured? If not, why not? How did you come to the conclusion that I have a small posterior fossa?
  - How common do you believe Acquired Chiari malformations to be?
- Do you always recommend decompression surgery for all of your patients with herniated cerebellar tonsils? Why/why not?
- In an average month, how many Chiari decompressions do you perform? How many tethered cord releases? How many craniocervical fusions? What percentage of your practice is spent treating patients with these connective tissue related conditions?
- Looking at my brain scan, is any part of my “brainstem” herniated (below the posterior fossa)? If so, does that make me a Chiari 1.5?
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?
- Looking at my corpus callosum:
  - Does there appear to be a depression?
  - Is there an inferior pointing of the splenium?
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/or 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?
    
    If yes, are you aware of the risks of developing a CSF Leak from a lumbar puncture?
  - 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 mid/low L2?
- 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 questions.

*Original version released September 2018, revised 2023.
September 16, 2023
Overview: Chiari Comorbidities & Etiological/Pathological Cofactors [Revised]
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 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 condition of the syrinx. If more than just the Chiari Malformation is believed to be causing the syrinx, each would be more accurately described as pathological.

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, think of it in terms of a domino effect. Only the first domino is etiological. All of the dominoes in between (on the path) are pathological. 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:

¹McIntosh, James. “Collagen: What Is It and What Are Its Uses?” Medical News Today, MediLexicon International, 16 June 2017, <www.medicalnewstoday.com/articles/262881.php>.

²Quake. “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>.
November 16, 2019
A Mother’s Story

Today is 11th April, 2019. Spring is in the air, yet I struggle to appreciate its presence. My daughters are at school, my son is at home in bed yet again. Like so many other days he is unable to get up. My son is 19 years old and looks just like any other 19 year old. You would never guess that this 19 year old is fighting a tremendously unfair battle every single day and has done so for several years.

Let me rewind.

My son was around 9 years old when he first complained of a lack of feeling on his right side and regular headaches. Doctors in Ireland, where we were living at the time, told him to drink more fluids after his daily soccer practice and put the numbness down to a trapped nerve. When he was 14 years old and living in Canada, he was told exactly the same by doctors there. However, when I finally insisted on him being referred to a neurologist, this very neurologist laughed at my son for wasting his time. He was told that it was all in his head. I vividly remember telling him off myself in the carpark on our way home.

I also remember being disappointed about his worsening school reports, blaming the onset of teenage years for his inability to concentrate and retain information. Blurred vision was also dismissed when his eye test came back just fine. Doctors didn’t grow concerned until he was 16 years old and living in France when a routine soccer medical check-up showed a sudden scoliosis deterioration from 8 degrees to 40 degrees. Subsequent MRIs showed Chiari Malformation (CM) with extensive Syringomyelia.

Neurosurgeons were quick to reassure him that all should be fine after a decompression surgery. Nevertheless, I spent hours researching these unknown rare conditions and found two experienced neurosurgeons, one in England and one in Belgium, for second opinions. Whereas surgeons in France took a more traditional approach and talked about inserting a shunt, both these surgeons warned strongly against this and so we made the decision to go to Belgium for the surgery. We felt well informed and were full of hope when my son embarked on his healing process 3 years ago.

Let me tell you where we are now.

Doctors in Europe tell us that my son is one of the unlucky few as his health has drastically deteriorated. Scar tissue has attached itself to his brain tonsils but that only explains part of his deteriorated health. So I embarked on a mission to get to the bottom of these problems. Surely there was hope to be found in the health system in France, one of the best in the world! After countless appointments with multiple health professionals, we were dumbfounded by the complete lack of understanding, knowledge and pure arrogance in relation to CM and its associated conditions, which resulted in my son’s mental health being questioned yet again.

I started carrying out my own research, which clarified the distinct link between brain disorders and compromised immune/digestive systems. Whereas his doctors are reluctant to make that link, the evidence is clear. 18 months after surgery, my son got struck down by glandular fever. Again, we were hopeful that this would only be a temporary setback. Today however, my son suffers from chronic fatigue syndrome as well as dysautonomia.

At our wits end last summer, we turned to a hospital in the United States that specialized in Chiari Malformation. Our first consultation with its Managing Director turned out to be an eye opener. This neurosurgeon could literally finish our sentences. My son was finally understood. It turns out that doctors in Europe had failed to diagnose another condition, Ehlers-Danlos Syndrome (EDS), which caused craniocervical instability. This in itself can be a debilitating condition but the combination of craniocervical instability with brain decompression surgery can be a death sentence. He further explained that such patients are deemed to benefit from Occipitocervical Fixation (OC) Fusion surgery. However, this surgery has not yet received the green light for these conditions from Health Services in Europe.

Armed with a diagnosis of Complex Chiari, we faithfully returned to my son’s French doctors, only to be met, yet again, by a lack of understanding. My request for an upright flexion/extension MRI was seen as outlandish and peculiar. Turns out, an upright MRI is not yet available in France. Instead they still rely on flexion/extension X-ray images which fail to adequately detect craniocervical instability.

In recent discussions, our son’s Belgian neurosurgeon cautiously recognizes the link between CM and EDS. However, as these studies are in their infancy in Europe, doctors still carry out decompression surgeries without checking for EDS. He also questions the durability of an OC Fusion but agrees that much more extensive research needs to be carried out in Europe and that my son is extremely unfortunate this hasn’t happened yet.

So where does this leave my son? In the land of limbo. Knowing that Europe is trailing some 10 years behind the States in this field. France, with its inherent reluctance to change, probably closer to 15 years. School is no longer an option for my son as his brain fog and memory loss have become more and more of a problem, his fatigue too debilitating and his headaches too frequent.

We are tired of fighting the system, tired from having to spell out the name of his conditions to health professionals, tired of being misunderstood. There are days I avoid going out as I don’t want to answer people’s well-meant questions. There are days I am ashamed of the anger that wells up inside me when friends air their worries about their children’s school results. There are days I feel like I am being punched in the stomach when I see his friends play a soccer match. People tell me I am strong. I don’t agree. I wish I had been strong all those years ago and believed my son over his doctors.

My son is my hero. My son is a fighter. My son has generally done what health professionals told him to do, taken every medication health professionals told him to take, followed the advice health professionals told him to take, yet the system continues to let him down. When I look into my son’s eyes, I still see this steadfast determination but I now also see pain and disillusionment. My son believed me when I told him we would overcome this together. My son believed me when I told him the worst would be over soon. My son doesn’t believe me anymore. I feel that I have failed him.

Complex Chiari diagnosed so late is a life sentence. It has brought pain, sadness and isolation, not only to my son but to my entire family. My husband and I are learning to compartmentalize, enjoy moments. We live in hope that our son’s better periods will begin to lengthen and pick ourselves up every time these come to an abrupt end. We have to. We owe it, not only to our son but to our daughters too.

We continue our journey through the unknown, thankful for the sources of information coming from the United States, usually met with skepticism and resistance by French health professionals. However, one thing I have learned from our journey so far is that we cannot fight these conditions and health services alone. Surely there must be more people out there in Europe. Surely, as a group we can start making a difference. Let’s unite! Let’s educate! Let’s raise awareness! Our children deserve so much better! Our children deserve to be heard, supported, and at the very least, understood!

June 11, 2019
Overview: Chiari Malformation [Revised]
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:
  - Heritable Disorders of Connective Tissue (HDCTs), most commonly Ehlers-Danlos Syndromes (EDS), make the tonsils more prone to prolapse below the foramen magnum.
  - Multiple conditions are known to create a pushing/pulling effect that can result in a tonsillar herniation. These conditions include: Intracranial Hypertension (IH)^, Atlantoaxial Instability and Craniocervical Instability (AAI/CCI), Tethered Cord Syndrome (TCS), and Intracranial Hypotension (cerebrospinal fluid leaks), Hydrocephalus, and a variety of cysts and brain tumors.^[^2]
  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]

SURGICAL 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!

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*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>.
October 4, 2018
What’s In A Name? An Expansive Review of the Name and Definition of Chiari Malformation
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!

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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>.

⁵Pearce, 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>.

⁶Mortazavi, 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>.
September 4, 2018
The Chiari Malformation Ehlers-Danlos Connection

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 BRAIN STEM 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].

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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>.

January 19, 2018
Overview: Complications Associated With A Chiari Decompression

From Intracranial Hypertension (formerly known as Pseudotumor Cerebri), Hydrocephalus, Tethered Cord Syndrome, to conditions related to the presence of a connective tissue disorder, such as Ehler’s-Danlos Syndrome, the primary reason for post-decompression complications seen in the Chiari Patient Community continues to be largely related to undiagnosed and untreated comorbid conditions. Time and time again, we see decompression failure, or a recurrence of symptoms after decompression, because there are other underlying conditions that need to be addressed. For this reason, we strongly recommend that patients get evaluated for the possibility of these known comorbid conditions before undergoing decompression surgery, unless circumstances require emergency surgery. (More information about the testing we recommend can be found in “The Treatments” article). Potential complications of decompression surgery may vary, depending upon the specific technique used, such as whether a duraplasty is performed, and how much bone is removed during a suboccipital craniectomy. The most common complications are infection, CSF leak, and Pseudomeningocele in adult patients.

INFECTIONS

Surgical site infections:
A surgical site infection is a risk of any surgery. While hospitals and surgical staff strive to maintain a sterile environment, hospitals are known for harboring pathogens, including many that are antibiotic resistant. Patient factors, including diabetes, age, being overweight, and being a smoker can also increase a patient’s risk of developing a post-operative infection.^[^1] Antibiotics are typically given post-surgically (and sometimes before surgery) in order to reduce the risk of infection. Some infections require wound revision surgery, to remove pus and infected tissue in order to improve healing.

MENINGITIS

Meningitis is an additional surgical risk when the dura is opened during a decompression. It is characterized by inflammation of the meninges, the linings of the brain. There are three main types of meningitis: aseptic, bacterial and chemical.

CSF Meningitis/Blood (left); CSF Meningitis (middle); CSF (right)

♦ Aseptic Meningitis is by far the most common type, and is generally less severe than the bacterial type. Most cases of aseptic meningitis are caused by viruses, but may rarely be fungal, autoimmune, parasitic or drug-induced.^[^2] The treatment for aseptic meningitis is usually supportive care.^[^3] Chemical meningitis is also a risk any time surgery or other procedures or treatments are performed on the brain or spine.^[^4]

♦ Bacterial Meningitis is much more serious and can be life threatening. Three types of bacteria cause most cases: streptococcus pneumoniae, Group B streptococcus, and Neisseria meningitidis. Typical treatment includes antibiotics and supportive care.

CSF LEAKS

Duraplasty leak:
Post-decompression CSF leaks are a risk of decompression surgery whenever the dura is opened. The risk of a CSF leak dramatically increases with the presence of untreated hydrocephalus^[^5], intracranial hypertension (IH)^[^6], and connective tissue disorders, such as Ehlers-Danlos Syndrome. Nationwide statistics indicate that the risk of a CSF leak post-duraplasty is 10-15%. However, some surgeons report a significantly lower incidence of CSF leaks in their patients.^[^7] The use of biologic glue to seal the dural suture line has greatly reduced the incidence of post-duraplasty CSF leaks. A common sign of a leak is clear fluid leaking from the incision site.

Pseudomeningocele:
A pseudomeningocele is a type of CSF leak, where the leak creates a pocket in the muscles in the back of the neck. It is one of the most common complications of duraplasty. While some surgeons have managed to keep the incidence of pseudomeningocele low in their patients, some report an incidence as high as 18%.^[^8] A study at Vanderbilt University at 2013 showed that the development of a pseudomeningocele after decompression significantly reduced the benefit of decompression at one-year post-op on pain, disability and quality of life.^[^9] A smaller pseudomeningocele may re-absorb on its own. However, with large and persistent PM’s, the duraplasty may adhere to the cerebellar tonsils, blocking flow and making a revision surgery more difficult. There is much debate among neurosurgeons as to whether doing routine duraplasty as part of decompression outweighs the risks. Some argue that duraplasty increases the risk of complications, while others say that failure to perform duraplasty often results in inadequate decompression, reduced benefit, and the need for additional surgeries. Some experts argue that duraplasty using the patient’s own pericranial tissue and using water-tight sutures and biologic glue minimizes the risk of a leak and makes routine duraplasty the best option for most patients. A squishy pocket of fluid is often seen near the base of the skull and a PM can be confirmed and monitored with an MRI. In some cases, a surgeon may try draining the pocket of fluid with a needle and syringe.

BLEEDING AND ANESTHESIA-RELATED COMPLICATIONS

Excessive Blood Loss:
Excessive blood loss is a risk of any major surgery, but can be minimized by a careful surgical technique. Patients with connective tissue disorders may have an increased risk of bleeding complications, due to fragile blood vessels, particularly with vascular EDS or vascular crossover symptoms. Cessation of blood-thinning medications, such as warfarin, aspirin and NSAIDS also reduces the risk of bleeding.

Anesthesia Risks:
While risks of general anesthesia are quite low, the risk may be higher if you or someone related to you has had previous adverse interaction to general anesthesia. Some EDS patients are also prone to anesthesia issues, such as requiring more anesthesia or ineffectiveness of local anesthetics. Therefore, it is important to inform your anesthesiologist of your pertinent medical history.^[^10]

BONY REGROWTH

Regrowth of the bone removed during decompression is a risk associated with the pediatric patient population, particularly patients under the age of 2. Surgeons have reported as much as a 50% incidence of bony regrowth in patients under the age of 5, and as much as 80% in patients under age 2. Regrowth of bone may result in the need for future surgery.^[^5]

CRANIOCERVICAL INSTABILITY

While Craniocervical Instability is not uncommon among those with connective tissue disorders, it is pretty rare in the general population. However, aggressive bone removal during decompression surgery can create an unstable craniocervical junction. It is important to discuss with your surgeon how much bone they plan to remove, and the risks and benefits of laminectomy, particularly if you also have a connective tissue disorder, which increases your risk for developing instability.

CEREBELLAR SLUMPING (PTOSIS)

Cerebellar slumping (aka cerebellar ptosis) occurs as a result of too much bone being removed around the foramen magnum that there is no longer enough bone to support the weight of the cerebellum. The brain slumps downward toward the spine, re-herniating the cerebellar tonsils, and often compressing the cerebellum itself against the back of the skull and brain stem. This can often result in worse symptoms than the patient had before decompression. Surgical techniques have been developed to revise the decompression and provide more support to the cerebellum.^[^11]

OCCIPITAL NEURALGIA

Occipital neuralgia is nerve pain, often accompanied by numbness and/or tingling, of the occipital nerve in the back of the head. It can be caused by compression of or damage to the occipital nerve. While the presence of a Chiari malformation itself can cause compression of the cranial nerves, including the occipital nerve, decompression surgery can also cause occipital neuralgia. This can be due to compression of the nerve from the use of retractors to hold apart musculature during surgery, or the build-up of scar tissue around the nerve. More conservative treatment of occipital neuralgia may include medications, such as lidocaine patches and medication that target nerve pain, physical therapy, cutaneous nerve stimulators, and nerve root blocks. Severe and persisting occipital neuralgia may require surgical decompression of the nerve or occipital neurectomy, surgical removal of the occipital nerve.^[^12]

SCAR TISSUE AND ADHESIONS

Like with occipital neuralgia and pseudomeningocele, the development of scar tissue and adhesions can cause symptoms to return or failure to relieve symptoms after a decompression surgery. Adhesions and scar tissue can develop wherever tissue is cut, including the dural graft, cauterized tonsils and the skin incision. Scar tissue and adhesion can inhibit or block CSF flow and often require revision surgery to remove the scar tissue. A careful selection of the graft material used for a duraplasty may reduce the risk of developing adhesions and scar tissue.^[^13]

DECOMPRESSION FAILURE

While perhaps technically not a complication, the failure rate of decompression surgery to alleviate symptoms deserves a mention here. While proper complications can often result in the failure of a decompression to relieve symptoms, or in fact, may make them worse than before decompression, even complication-free decompressions surgeries have a high rate of failure, as much as 40%, depending upon the study. Some reasons for decompression failure in the absence of the above-listed complications include failure to diagnose and treat comorbid conditions that may be causing symptoms, an inadequate decompression (failure to create enough space by removing bone and performing a duraplasty), and some or all of the symptoms being due to another cause, such as migraines. In cases of an inadequate decompression, a more aggressive decompression revision surgery may provide relief. In cases where a comorbid condition exists, that condition must be diagnosed and treated. However, there are still a small percentage of patients who do not get relief, even with further decompression and other treatments. The reason for this is not clearly understood.^[^5]

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References:

¹Torpy, Janet M. “Postoperative Infections.” JAMA, American Medical Association, 23 June 2010, <www.jamanetwork.com/journals/jama/fullarticle/186132>.

²Ramachandran, Tarakad S. “Aseptic Meningitis Treatment & Management.” Aseptic Meningitis Treatment & Management: Approach Considerations, Medical Care, Prevention, 22 Aug. 2017, <www.emedicine.medscape.com/article/1169489-treatment>.

³“Meningitis.” Meningitis | Brain & Spine Foundation, <www.brainandspine.org.uk/meningitis>.

⁴McDaniels, Edison. “Chiari Decompression Surgery.” Neurosurgery101-TheBlog, 3 Apr. 2013, <www.surgeonwriter.com/chiari-4/>.

⁵Trumble, Eric. “Chiari Overview & Surgical Issues.” Chiari and Syringomyelia Foundation, Chiari and Syringomyelia Foundation, 13 Oct. 2015, <www.csfinfo.org/videos/physician-lecture-videos/csf-lectures-archive/chiari-overview-surgical-issues/>.

⁶“Chiari Surgery.” Chiari Surgery | Mayfield Chiari Center, 10 Dec. 2017, <www.mayfieldchiaricenter.com/chiari_surgery.php>.

⁸“Pseudomeningocele Following Chiari Surgery Decreases Quality of Life.” CHIARI MEDICINE, 17 May 2015, <www.chiarimedicine.com/blog/2015/5/17/pseudomenigocele-following-chiari-surgery-decreases-quality-of-life>.

⁹Parker, S. L., et al. “Effect of Symptomatic Pseudomeningocele on Improvement in Pain, Disability, and Quality of Life Following Suboccipital Decompression for Adult Chiari Malformation Type I.” Journal of Neurosurgery., U.S. National Library of Medicine, Nov. 2013, <www.ncbi.nlm.nih.gov/pubmed/24010974>.

¹⁰“The Risks of Anesthesia and How to Prevent Them.” WebMD, WebMD, 2016, <www.webmd.com/a-to-z-guides/anesthesia-risks-what-patients-should-know>.

¹¹“Surgical Technique Alleviates Cerebellar Slumping.” Cerebellar Slumping, 31 May 2007, <www.conquerchiari.org/articles/surgery/techniques/cerebellar-slumping.html>.

¹²Mueller, Diane. “Occipital Neuralgia and Chiari Malformation.” CHIARI MEDICINE, 4 Apr. 2013, <www.chiarimedicine.com/blog/2013/4/4/occipital-neuralgia-and-chiari-malformation>.

¹³Attenello, Frank J., et al. Suboccipital Decompression for Chiari I Malformation: Outcome Comparison of Duraplasty with Expanded Polytetrafluoroethylene Dural Substitute versus Pericranial Autograft. 4 Sept. 2008, <www.link.springer.com/article/10.1007/s00381-008-0700-y>.

January 19, 2018