Cerebellar tonsillar ectopia herniation and Chiari 1 malformation
Ross Hauser, MD
For many people, cervical instability can cause a wide array of cardiovascular like, neurological like and psychological like syndromes and symptoms. Most of the time and unfortunately for these people the connection is not initially made. For others the connection is made too late after inappropriate treatments and surgeries have been performed. Cervical instability can cause these problems because the cervical sympathetic ganglion, spinal cord, brain stem and cerebellum have an affinity or connection to the cervical spine. For context, the superior cervical sympathetic ganglion is part of our flight-fight response. It is part of a messaging network that sends crucial instructions though out the body. The uniqueness of the superior cervical sympathetic ganglion is that it is the only ganglion (in simplest terms a nerve station that relays nerve messages) that innervates the head and neck. If this important structure is “pressured” by development of a herniation or Chiari or its location is moved, causing a stretching to the nerves, the messaging to the head and neck becomes distorted.
While the brain stem and cerebellum are normally protected inside the cranium, in some genetic conditions such as Arnold Chiari malformations, the cerebellum and/or brain stem can actually extend into the foramen magnum and are affected by cervical conditions, especially related to atlantoaxial (C1-C2) instability.
Another lesser known condition called cerebellar tonsillar ectopia can occur which again involves the cerebellar tonsils blocking vital structures in the foramen magnum, but this condition generally occurs with a trauma such as a whiplash injury. Sometimes Arnold Chiari malformations or cerebellar ectopia can cause symptoms by themselves, but I find that symptoms most often occur with upper cervical instability. In other words, sometimes both conditions are required for symptoms to occur. Since the whole nervous system via the spinal cord has to use the neck as a conduit to get to the brain, it is easy to see how instability, especially at occiput-atlas-axis area (upper cervical spine) where the opening is most narrowed, could affect many of the bodily functions and give a host of unusual symptoms. More commonly, though, cervical instability gives innumerable symptoms because of its close association with the autonomic nervous system ganglia.
Discussion points of this article:
- Cervical instability and Cerebellar tonsillar ectopia. Another missing diagnosis of mysterious symptoms?
- 30% of the people who had cerebellar tonsillar ectopia herniation greater than 5 mm were asymptomatic.
- If 2 mm herniations are asymptomatic what about 5, 10, 15 mm or more?
- The key for many people is that the syrinx may be causing the symptoms.
- The Importance of Cerebrospinal Fluid Flow.
- Increased intracranial hypertension by blocking cerebrospinal fluid flow at the foramen magnum.
- Chiari malformation (cerebellar tonsillar ectopia) causes symptoms because herniated tonsils combined with upper cervical instability block the normal flow of cerebrospinal fluid.
- When surgery is recommended for Chiari 1 malformation or Cerebellar tonsillar ectopia and when surgery is needed.
- Whiplash and cerebellar tonsil ectopia.
Cervical instability and Cerebellar tonsillar ectopia. Another missing diagnosis of mysterious symptoms?
Cerebellar tonsillar ectopia, or downward herniation of the cerebellar tonsils, is defined as caudal (away from) herniation of the cerebellar tonsils through the foramen magnum. I suggest as others have that Cerebellar tonsillar ectopia as being trauma-induced and Arnorld Chiari 1 malformation to be congenital, though some would disagree. When Chiari 1 malformations begin to cause symptoms in adults who were previously asymptomatic, I believe that it is upper cervical instability that has caused cervicotonsillary compression syndrome, moving the Chiari 1 patient from asymptomatic to symptomatic.
This article is a companion article to our piece: Chiari malformation: Non-surgical alternatives to Chiari decompression surgery
What are we seeing in this image?
Cerebellar tonsillar ectopia can be easy to spot on MRI. In the illustration below, used to more clearly define the talking point that the cerebellar tonsils are caudal or inferior to a line drawn from the basion or most anterior (front) point of the foramen magnum to the opisthion or the posterior (back) point of the foramen magnum, known as the basion opisthion line or McRae’s line. While the hernia is easy to see, there is no consensus as to how much herniation is significant because the degree of tonsillar herniation is not always related to the severity of symptoms
The most important point in regard to treatment is whether or not the cerebellar tonsillar ectopia is causing symptoms and is there an upper cervical instability component. If there is cervical instability present, it is my belief that this should be treated with Prolotherapy (explained below) and if symptoms persist then consider surgical evaluation for one or both (cerebellar tonsillar ectopia and upper cervical instability) of the conditions. The symptoms of both conditions are very similar and because C1-C2 fusion with craniectomy for cerebellar tonsillar ectopia is a big operation it is best to try conservative treatment first.
Cerebellar tonsillar ectopia is easy to spot on MRI, as it is simply noting that the cerebellar tonsils are caudal or inferior to a line drawn from the basion or most anterior point of the foramen magnum to the opisthion or the posterior point of the foramen magnum, known as the basion opisthion line or McRae’s line. While the hernia is easy to see, there is no consensus as to how much herniation is significant because the degree of tonsillar herniation is not always related to the severity of symptoms.
What are we seeing in this image?
Normal anatomy versus Chiari malformation of the cerebellum. With the size of the posterior fossa too small, the cerebellar tonsils may herniate through the foramen magnum of the skull into the spinal canal. The tonsils block the flow of cerebrospinal fluid and may cause fluid buildup inside the spinal cord, called a syrinx.
30% of the people who had cerebellar tonsillar ectopia herniation greater than 5 mm were asymptomatic.
In early research there was first discussion on the extent of the herniation as measured in millimeters. Many patients we see understand that they have a herniation measured this way but they are not sure to what extent this herniation means other than it must be effecting them some how. Yet in this early research doctors found that people with significant herniation of the tonsils hade no symptoms and remained asymptomatic.
In this first study from 1986, doctors wrote in the American journal of neuroradiology (1) “It has been noted that a low degree of ectopia of the cerebellar tonsils on MRI is of questionable significance. (Note: The MRI reveals cerebellar tonsillar ectopia but the patient does not complain of specific symptoms). (The researchers then measured) measured the position of the cerebellar tonsils with respect to the inferior aspect of the foramen magnum in 200 normal patients and in 25 patients with a firm diagnosis of Chiari I malformation.
- In the normal group, the mean position of the tonsils was 1 mm above the foramen magnum with a range from 8 mm above the foramen magnum to 5 mm below.
- In the patients with Chiari I malformations, the mean position was 13 mm below the foramen magnum with a range from 3 mm below the foramen magnum to 29 mm below. Fourteen percent of normal patients had tonsils extending slightly below the foramen magnum.
- MRI demonstration of less than 2 mm of tonsillar ectopia is probably of no clinical significance in the absence of syringomyelia.
If 2 mm herniations are asymptomatic what about 5, 10, 15 mm or more?
In this next study doctors tried to lay a a road map where they could correlate the amount of herniation with the amount of symptoms. In this 1992 study from Department of Radiology, Bowman Gray School of Medicine, Wake Forest University (2) researchers examined clinical findings and magnetic resonance images in 68 patients with Chiari I malformations with the goal to analyze and identify those radiologic features that correlated best with clinical symptoms.
The first thing the researchers noted was a statistically significant of a more female predominance of the malformation was observed, with a female: male ratio of approximately 3:2.
- Associated skeletal anomalies were seen in 24% of patients.
- Syringomyelia, a disorder in which a CSF-filled cyst or syrinx, forms within the central canal of the spinal cord, was detected in 40% of patients, most commonly between the C-4 and C-6 levels.
- Of the 25 patients who presented with spinal symptoms, 23 (92%) proved to have a syrinx at MR imaging.
- When the syrinx extended into the medulla, however, brain stem symptoms predominated.
- Patients with objective brain stem or cerebellar signs had the largest mean tonsillar herniations.
- Patients with tonsillar herniations greater than 12 mm were invariably symptomatic, but approximately 30% of patients with tonsils herniating 5-10 mm below the foramen magnum were asymptomatic at MR imaging.
- “Incidental” Chiari I malformations are thus much more common than previously recognized, and careful clinical assessment remains the cornerstone for proper diagnosis and management.
The key for many people is that the syrinx may be causing the symptoms
The key may be the syrinx causing the symptoms, because in another study, this one from Department of Neurological Surgery, Johns Hopkins Hospital, (3) 25 patients who had Chiari 1 and were asymptomatic, the average cerebellar tonsillar descent was 11.4 mm, but only 1 of these was found to have syringomyelia.
Above I cite three studies, one from 1986, one from 1992, and one from 2000. It should be pointed out that all three of these papers sought to help doctors understand and classify the role of cerebellar tonsillar descent and the formation of a syrinx in helping identify a treatment path and proper diagnosis. Yet a 2020 paper, more than 30 years later still cites the controversies surrounding diagnosis and classification of the patient’s problem.
Writing in December 2020 in the journal Neurosurgical review (4) , neurosurgeons in Italy made these observations: “Cerebellar tonsil herniation comprises a spectrum of disorders sharing a common neuroimaging finding consisting of downward displacement of the cerebellar tonsils through the foramen magnum and into the upper cervical spinal canal. This not uncommon condition may result from a large host of congenital or acquired causes, and confusion regarding its classification and pathogenesis still exists. Terminology also remains heterogeneous, including inconsistencies in the usage of the “Chiari 1 monicker.”
The combination of craniocervical bony abnormalities, anatomic CSF restriction, and reduced compliance leads to symptoms in adult Chiari malformation Type I.
In the study below, the researchers use the term “compliance.” In this context, compliance describes the mechanical compliance that maintains correct change in fluid within the spinal canal by way of maintaining the changes in the inside pressure of the spinal cord. This compliance helps regulate the intracranial pressure with movement.
A team of researchers published January 2022 findings in the journal Medical hypotheses (12) to question the prevailing theory of Chiari malformation Type I. In this paper the researchers note that is is thought that Chiari malformation Type I : “focuses on the underdevelopment of the posterior cranial fossa (the back base of the skull where brainstem and cerebellum are located) which results in tonsillar herniation. Symptoms are believed to be due to the herniation causing resistance to the natural flow of cerebrospinal fluid (CSF) and exerting a mass effect (herniation) on nearby neural tissue. However, asymptomatic cases vastly outnumber symptomatic ones and it is not known why some people become symptomatic. Recently, it has been proposed that Chiari malformation Type I symptoms are primarily due to instability of either the atlanto-axial (AA) or the atlanto-occipital (AO) joint and the cerebellar tonsils herniate to prevent mechanical pinching. However, only a small percentage of patients exhibit clinical instability and these theories do not account for asymptomatic herniations.”
To answer these problems the researchers suggested that answer may lie in “a combination of craniocervical abnormalities which leads to tonsillar herniation and reduced compliance of the cervical spinal canal. Specifically, abnormal atlanto-occipital (AO) and/or atlanto-axial (AA) joint morphology leads to chronic cervical instability, often subclinical, in a large portion of CMI patients.”
This then becomes a problem of an overworking of the suboccipital muscles as they try to compensate for the instability.
The researchers continue: “Over time, the repeated, involuntary activation of these muscles leads to mechanical overload of the myodural bridge complex, altering the mechanical properties of the dura it merges with. As a result, the dura becomes stiffer, reducing the overall compliance of the cervical region. This lower compliance, combined with CSF resistance at the same level, leads to intracranial pressure peaks during the cardiac cycle (pulse pressure) that are amplified during activities such as coughing, sneezing, and physical exertion.”
This increase in pulse pressure reduces the compliance of (it narrows) the cervical subarachnoid space which increases the CSF wave speed in the spinal canal, and further increases pulse pressure in a feedback loop (a possible explanation of intercranial hypertension). Finally, the abnormal pressure environment induces greater neural tissue motion and strain, causing microstructural damage to the cerebellum, brainstem, and cervical spinal cord, and leading to symptoms.”
The Importance of Cerebrospinal Fluid Flow
What are we seeing in this image?
Inferior (looking up into skull) view of CT scan showing obstruction of the foramen magnum by malrotation of the atlas. Atlas malrotation can cause increased intracranial hypertension by blocking cerebrospinal fluid flow at the foramen magnum. (Shown by the arrow). This person while helped by atlas adjustments, also had Prolotherapy injections (described below) to treat their upper cervical instability. The combination helped alleviate their symptoms.
Increased intracranial hypertension by blocking cerebrospinal fluid flow at the foramen magnum
While the pathophysiology of syringomyelia is not fully understood, as demonstrated by the research above, current prevailing theories suggest that increased pulse pressure in the subarachnoid space forces cerebrospinal fluid (CSF) through the spinal cord into the syrinx. A 2006 paper in the Neurosurgical review (5), “Unraveling the riddle of syringomyelia” describes the formation of syringomyelia and it has to do with cerebrospinal fluid pressure.
“It is generally accepted that the syrinx consists of cerebrospinal fluid. The here-proposed intramedullary (within the medulla) pulse pressure theory instead suggests that syringomyelia is caused by increased pulse pressure in the spinal cord and that the syrinx consists of extracellular fluid. A new principle is introduced implying that the distending force in the production of syringomyelia is a relative increase in pulse pressure in the spinal cord compared to that in the nearby subarachnoid space. The formation of a syrinx then occurs by the accumulation of extracellular fluid in the distended cord. . . .In Chiari I malformations, the systolic CSF pulse pressure and downward motion of the cerebellar tonsils are significantly increased. This leads to increased spinal cerebrospinal fluid velocities and, as a consequence of the Bernoulli theorem (this is a theory of fluid dynamics and how fluid pressure works, decreased fluid pressure in narrow regions of the spinal cerebrospinal fluid pathways. . . The here-proposed concept has the potential to unravel the riddle of syringomyelia and affords explanations to previously unanswered clinical and theoretical problems with syringomyelia. It also explains why syringomyelia associated with Chiari I malformations may develop in any part of the spinal cord including the medullary conus.”
Chiari 1 malformations have been shown to increase the pressure within the subarachnoid space, especially in the cervical region where most syrinxes are located. As noted in the 2006 paper just discussed, syringomyelia preferentially develops where the systolic CSF flow causes a suction effect on the spinal cord, i.e., at or immediately caudal to physiological or pathological encroachments of the spinal subarachnoid space.
In Chiari 1 malformation, the cerebellar tonsils partially occlude the subarachnoid space at the foramen magnum. This creates enlarged cervical subarachnoid pressure waves that compress the spinal cord from without, not from within, and propagates syrinx fluid caudally with each heartbeat, leading to syrinx progression. It is interesting that after simple decompressive extra-arachnoidal surgery, there is disappearance of the abnormal shape and position of the tonsils, suggesting that the Chiari 1 malformation of the cerebellar tonsil is acquired, not congenital. This was described in a 1999 paper from the Surgical Neurology division, National Institute of Neurological Disorders and Stroke, National Institutes of Health at Bethesda, Maryland and published in the Journal of neurosurgery.(6)
“The progression of syringomyelia associated with Chiari I malformation is produced by the action of the cerebellar tonsils, which partially occlude the subarachnoid space at the foramen magnum and act as a piston on the partially enclosed spinal subarachnoid space. This creates enlarged cervical subarachnoid pressure waves that compress the spinal cord from without, not from within, and propagate syrinx fluid caudally with each heartbeat, which leads to syrinx progression. The disappearance of the abnormal shape and position of the tonsils after simple decompressive extraarachnoidal surgery suggests that the Chiari I malformation of the cerebellar tonsils is acquired, not congenital. Surgery limited to suboccipital craniectomy, C-I laminectomy, and duraplasty eliminates this mechanism and eliminates syringomyelia and its progression without the risk of more invasive procedures.”
If the cervical spinal canal is statistically significantly more narrowed in patients with syrinx than in those without a cervical syrinx, then couldn’t cervical instability, which also narrows the cervical spinal canal with motion, be the cause of syrinx?
A paper (7) from the Department of Neurology, Massachusetts General Hospital, the Department of Radiology, Mayo Clinic, Rochester, the Department of Radiology, University of California San Francisco, the Department of Radiology, University of California San Diego, and the Department of Radiology, University of Wisconsin discusses this narrowing of the cervical spinal canal.
“The cervical spine in Chiari I patient with syringomyelia has significantly different anteroposterior (in the front of the cervical spine and in the back of the cervical spine) diameters than it does in Chiari I patients without syringomyelia.” The researchers then tested the hypothesis that patients with idiopathic (unknown and spontaneous) syringomyelia also have abnormal cervical spinal canal diameters.
Study learning points
- Fifty idiopathic syringomyelia patients with 50 age-matched controls were studied.
- Idiopathic syringomyelia patients subjects had one or more syrinxes varying from 1 to 19 spinal segments.
- Spinal canal diameters narrowed from C1 to C3 and then enlarged from C5 to C7 in both groups.
- Diameters from C2 to C4 were narrower in the Idiopathic syringomyelia patients than in controls.
- The ratio of the C3 to the C7 diameters was also smaller in Idiopathic syringomyelia patients than controls.
- Collectively, the spinal canal diameters in the Idiopathic syringomyelia patients were significantly different from controls.
As mentioned above, there is a connection between narrowing of the cervical spinal canal in patients with syrinx than in those without a cervical syrinx So the question again, couldn’t cervical instability, which also narrows the cervical spinal canal with motion, be the cause of syrinx?
Chiari malformation (cerebellar tonsillar ectopia) causes symptoms because herniated tonsils combined with upper cervical instability block the normal flow of cerebrospinal fluid.
Chiari malformation (cerebellar tonsillar ectopia) causes symptoms because herniated tonsils combined with upper cervical instability block the normal flow of cerebrospinal fluid (CSF). Instead of moving in an easy, pulsating movement through this opening, the fluid begins to force its way through like a bursting dam or a rip tide, pushing the tonsils down even farther and exerting pressure on the brainstem and spinal cord. Sometimes the cerebrospinal fluid can accumulate inside the spinal cord, forming a syrinx and further damaging it. Symptoms may not appear until late childhood and adulthood, causing severe headaches, neck pain, dizziness, numbness in the hands, and a host of other symptoms. The list of symptoms again is very similar to the one that occurs with upper cervical instability, craniocervical syndrome, whiplash associated disorders, and post-concussion syndrome, giving credence to the notion that they all may have a common etiology of disrupted nervous system activity in the head and neck region and various other systems. When Chiari 1 malformations begin to cause symptoms in adults who were previously asymptomatic, I believe that it is upper cervical instability that has caused cervicotonsillary compression syndrome (CTCS), moving the Chiari 1 patient from asymptomatic to symptomatic.
Cerebellar tonsillar ectopia is thought to occur because of caudal (at the back) mechanical traction (pulling) from C1 subluxation, as the cervical spinal cord at that level is centered in the neural canal by denticulate (dentate) ligaments. (These ligaments are extensions of pia mater that anchor the spinal cord to the dura mater.) These ligaments keep the spinal cord from impacting upon the anterior and posterior portion of the bony spinal canal and keep it in place as the spinal bones move in various directions. When the cervical spine goes through full extension and full flexion, potentially compressing the spinal cord during extension and stretching it during flexion. It is this anchoring of the spinal cord at the foramen magnum and upper cervical area by the dentate ligaments that keep normal neck movements from putting mechanical traction on the brainstem and pulling it through the foramen magnum.
With upper cervical instability, however, the tension from the dentate ligaments at the upper cervical segments could start to compress the cervical spinal cord and obstruct fluid flow through the cervicomedullary junction. The neural pathways could also be damaged by vascular compromise thought to be due to misalignments of the upper cervical vertebrae.
What are we seeing in this image?
There are two illustrations. The A illustration demonstrates a normal cervical alignment at C1/C2. The second or “B” illustration demonstrates mis-ailgnment. As can be seen, the axial canal space for the upper spinal cord and/or brainstem and cerebrospinal fluid is severely compromised when the atlas misaligns. Symptoms can range from suboccipital and head pain and pressure to severe neurological compromise. Please see our article on treatments for Atlas displacement c1 forward misalignment.
Cervical spinal instability can be of varying degrees. As the instability progresses, especially in the C1 region where the space for the spinal cord is especially narrow because of the dens of C2, the cross sectional area of the spinal canal decreases which can lead to compression of any nervous tissue in that space including the spinal cord, brainstem or cerebellar tonsils. There are many mechanisms by which structural instability in the upper cervical region can cause neurological injury including mechanical compression, ischemic changes, or alterations in CSF flow.
Atlantoaxial instability would cause a functional narrowing of the spinal canal and encroach on vital structures in the area or disrupt cerebrospinal fluid flow. It has been shown that that there is an increased prevalence of having Chiari malformation type 1 in patients with occipitoatlantoaxial hypermobility with hereditary disorders of connective tissue (Ehlers Danlos Syndrome). This was suggested in a paper from Department of Neurosurgery, The Chiari Institute, Harvey Cushing Institute of Neuroscience, North Shore-Long Island Jewish Health System published in the Journal of neurosurgery. Spine. (8)
The encroachment onto the cerebellar tonsils as seen by upright MRI was also reducible by cervical traction or returning to the supine position. This would suggest the Chiari malformation lesion is from upper cervical instability. In one study, 65 patients with Chiari malformation were treated by atlantoaxial fixation (arthrodesis/fusion) for atlantoaxial instability. This research was presented by Dr. Autl Goel of the Department of Neurosurgery, King Edward VII Memorial Hospital and Seth G.S. Medical College and published in the Journal of neurosurgery. Spine. (9)
- Sixty-three patients improved after surgery, and the improvement was sustained. One patient died during the surgery. One patient had persistent symptoms. So overall 97% (63/65) patients improved clinically (include brainstem function) from the operation. Fifty-five percent of repeat MRIs showed an improvement of the syrinx. Dr. Goel, who did the surgeries, commented, “Given our analysis, we understand that both Chiari Malformation and syringomyelia are secondary results of subtle and longstanding atlantoaxial instability. As we continue to treat more such cases using only atlantoaxial fixation, we find that tonsils quite frequently migrate back to their original position and that the syrinx cavity collapses following a surgical procedure that focuses only on atlantoaxial fixation.
Based on our results with resolving upper cervical instability with Comprehensive Prolotherapy, we concur with the Dr. Goel that when the atlantoaxial instability is resolved the majority of the symptomatology that the person suffered with abates. I have used Prolotherapy to stabilize the vertebral segments suspected of causing a syrinx and the patients symptoms improved.
When surgery is recommended for Chiari 1 malformation or Cerebellar tonsillar ectopia and when surgery is needed.
Surgery can be recommended when it is not needed, surgery can also be needed, period. The primary surgical treatment for Chiari 1 malformation or Cerebellar tonsillar ectopia that is obstructing cerebrospinal fluid flow is decompression or enlargement of the posterior fossa to establish normal cerebrospinal fluid pathways. The compression by the cerebellum is felt to obstruct the normal venting of the cerebrospinal fluid in and out of the craniocervical subarachnoid space, throughout the cardiac cycle. Many people who end up with craniectomy, had not even considered other treatments prior to the surgery because no one thought that upper cervical instability may be causing their symptoms. It makes sense though, As the subarachnoid space is most crowded at the craniocervical junction, that by stabilizing or limiting C1-C2 motion, Prolotherapy, for example, could also open up the subarachnoid space and allow appropriate cerebrospinal fluid flow in appropriate patients. So the most conservative decompressive treatment when cervical instability is the cause of nerve or spinal cord compression in my opinion is Prolotherapy.
According to neurosurgeon Dr. Joel Franck, whom I have collaborated with, the essential radiological feature of craniocervical syndrome is lateral C1-C2 ligamentous instability, which he recommends to be diagnosed with digital motion x-ray. (The digital motion x-ray or DMX is explained below). He believes many of the symptoms are from transient vertebral artery compression. When these vertebral segments are fused, the symptoms of cranial cervical syndrome abate. The patient who has headache that never goes away is likely to have this condition and difficulty clearing out CSF from the brain. Eventually toxins accumulate and start damaging the brain. This is one potential mechanism of traumatic encephalopathy as occurs in football players. When the cervical instability is resolved by fusion and the CMJ decompressed by craniectomy the horrific headaches subside. When a person has a combination of C1-C2 instability and cerebellar tonsillar ectopia, it causes a compression of the cervicomedullary junction, which is an even more serious condition. When symptoms become severe, a decompressive surgery is performed. The surgery relieves the compression of the brain stem and spinal cord and improves circulation of the spinal fluid. I would not be writing about this condition if not for the fact that many people with this condition respond to Prolotherapy before or after the surgery. In some people the extensive surgery does help and is tremendous, but if it doesn’t or the person does not want to have surgery, a second opinion by a Prolotherapist is a good idea.
Digital motion X-Ray C1 – C2
The digital motion x-ray is explained and demonstrated in the video below. This is one of our tools in demonstrating cervical instability in real-time and motion. Most injuries to the upper or lower cervical spine are not identified by standard or static x-rays, CT scans, or MRIs. Functional or dynamic imaging technology, which images a person while joints are under stress or in extremes of motion is more sensitive in diagnosing instability. Digital motion x-rays or stress cervical radiographs are obtained using open-mouth projections in neutral, left, and right cervical lateral flexion as well as rotation to reveal a significant lateral offset of one of the lateral masses of C1 on C2.
The clinical signs of upper cervical instability can vary from no symptoms or relatively diffuse complaints to signs and symptoms of extreme importance or seriousness. When clinical symptoms are present, assessing the degree of instability by objective means including digital motion x-ray helps in determining the treatment course.
In my article Ross Hauser, MD. Reviews of Diagnostic Imaging Technology for Cervical Spine Instability, I discuss DMX and compare it to standard digital imaging in varying cervical spine instability issues including Cerebellar tonsillar ectopia herniation and Chiari 1 malformation.
My office gets many emails from all over the world from patients with various MRI findings and they wonder if they are a Prolotherapy injection candidate. This email is one example: This email has been edited for clarity purposes.
I had stand up MRI and CINE flow study (CSF flow) because I am experiencing significant back and head pain and my laydown MRIs kept coming back unremarkable. The report of the upright MRI are:
- C0-C1: Encroachment of the cerebellar vermis and tonsils on the foramen magnum associated with capsulosynovial proliferative change of the atlanto-odontoid articulation, the so called ‘Chiari 0’ anatomy. Asymmetric widening of the left lateral atlantodental interval (4.88mm versus 3.25mm on right). Abnormal signal in the alar ligament (suggestive of injury).
- C1-C2: Hypertrophy of the atlantodental articulation with posterior capsulosynovial proliferation producing mild encroachment of the anteroposterior dimension of the central spinal canal. Abnormal signal in the transverse ligament. Loss of the normal anatomic relationship of C1 and C2, consistent with atlantoaxial rotatory instability.
- Pathokinesiology (motion views)
- Flexion: Anterolisthesis of C3 on C4 and C4 on C5. Widening of the posterior disc space heights at the C3-C4, C4-C5 and C5-C6 levels consistent with insufficiency of the posterior longitudinal ligament. Widening of the interspinous intervals at the C3-C4, C4-C5 and C5-C6 levels as a manifestation of insufficiency of the capsular and interspinous ligamentous complex.
- Extension: Retrolisthesis of C3 on C4 and C4 on C5.
- CSF view and flow: Distension of the CSF spaces in the Meckel cave regions, accompanied by dural ectasia of the optic nerve sheaths (both correlated with increased intracranial pressure).
- The cerebellar tonsillar ectopia is producing interference with normal CSF migration through the foramen magnum…after adjustment of C1, there is much more uniform CSF flow through the foramen magnum.
If one looks through all this, it appears from the MRI that the person’s upper cervical instability (C1-C2) is blocking CSF flow. Other parts of the scan signified it was blocking arterial flow as well. The manipulation she received partially restored flow. So my office emailed this person back to let her know that Prolotherapy would also be an option for treatment. Again, as in this person’s case, headache pain caused by cerebellar tonsillar herniation can also be relieved when the blockage of hindbrain CSF flow is normalized.
This case brings up a good point about headaches and blockage of hindbrain CSF flow. In one study on patients with Chiari 1 malformation, patients with frontal or generalized headaches were 10-times less likely to demonstrate obstructured CSF flow on Cine phase-contrast MRI of the craniocervical junction and 8-times less likely to have tonsillar descent greater than 7 mm compared with patients with occipital headaches. This was demonstrated in a paper from the Department of Neurosurgery, Johns Hopkins Medical Center.(10)
So in patients with cerebellar tonsillar ectopia, occipital headache is the one that best correlates clinically with obstructed CSF flow. In some people the tonsillar descent into the foramen magnum is enough to block CSF flow, but I would propose that the obstruction is from upper cervical instability. The combination of CSF obstruction and occipital headache has a common etiology in upper cervical instability and on many occasions have been successfully treated even within the last month with Prolotherapy at Caring Medical Regenerative Medicine Clinics.
Another interesting point is that even patients with significant Chiari 1 malformation with syrinx showed neurological improvement, including a decrease in the syrinx, with atlantoaxial fixation. This suggests that even Chiari malformations, or at least some of them, are due to upper cervical instability. It is well known that genetic ligamentous disorders such as Ehlers Danlos Syndrome have a higher incidence of occipitoatlantoaxial hypermobility and associated Chiari 1 malformation than controls. Compared to a group consisting of both healthy patients and those with just Chiari 1 malformation, patients with hereditary disorders of connective tissue (such as Ehlers Danlos Syndrome) as well as Chiari 1 malformation had significant X-ray and CT evidence of upper cervical instability.
Whiplash and cerebellar tonsil ectopia
Cerebellar tonsillar ectopia must be distinguished from the congenital condition Arnold-Chiari syndrome. Arnold-Chiari syndrome consists of four variations, only one of which, Type I, occurs in middle age adults. Although actual cerebellar tonsillar herniation occurs through the foramen magnum, generally it is not trauma related. It exhibits far more herniation than whiplash induced Cerebellar tonsillar ectopia, is associated with a cervical syrinx and a tethered lower spinal cord. There is some evidence that AC Type I can be symptomatically activated by trauma, but this is rare. In short, whiplash induced Cerebellar tonsillar ectopia is not Arnold Chiari Type I. Cerebellar tonsillar ectopia is caused by the trauma of the motor vehicle crash or other whiplash trauma and is not congenital.
In 2010, doctors at the Department of Public Health and Preventive Medicine, Oregon Health and Science University School of Medicine published their findings which they wrote were the “first to demonstrate a neuroradiographic difference between neck pain patients with and without a recent history of whiplash trauma.” The paper was presented in the journal Brain injury (11) These are the findings as they relate to cerebellar tonsillar ectopia presented in summary points:
- Cerebellar tonsillar ectopia may become symptomatic following whiplash trauma. The purpose of the present study was to assess the frequency of Cerebellar tonsillar ectopia in traumatic vs non-traumatic populations.
- Cervical MRI scans for 1200 neck pain patients were reviewed; 600 trauma (cases) and 600 non-trauma (controls).
- Half of the groups were scanned in a recumbent position and half were scanned in an upright position. Two radiologists interpreted the scans for the level of the cerebellar tonsils.
- Cerebellar tonsillar ectopia was found in 5.7% and 5.3% in the recumbent and upright non-trauma groups vs 9.8% and 23.3% in the recumbent and upright trauma groups. (Note the highest reading by far was in the upright MRI interpretation. 14% of Cerebellar tonsillar ectopia diagnosis would have been missed in the recumbent MRI.
I am going to summarize and refer you to our article Injury and abnormalities at the cervicomedullary junction. The cervicomedullary junction (CMJ) is the place where the brain meets the spinal cord and is an area that is commonly injured after traumas such as whiplash. The CMJ involves the structures that are located just above, through, and below the foramen magnum, the opening in the occipital bone through which many vital structures enter and leave the brain cavity. These structures include the:
- spinal cord-brain stem junction
- vertebral veins, which drain the brain during the upright position
- vertebral arteries, which supply blood to the brainstem
- cerebellum and inner aspects of the temporal and occipital lobes of the brain
- subarachnoid space of the cord, which contains cerebrospinal fluid
All structures that have an impact on our discussion above.
Currently there are few non-surgical options for treatment to disorders at the cervicomedullary junction. We have discussed surgery above. The primary treatments are non-surgical (pinless) halo ring reduction or traction to realign the craniocervical junction. If the realignment is realized then the patient would have his/her neck immobilized with the hopes that the neck would settle into a more natural shape. If this does not work, cervical spine fusion is then called for.
Caring Medical has published dozens of papers on Prolotherapy injections as a treatment in difficult to treat musculoskeletal disorders. Prolotherapy is an injection technique utilizing simple sugar or dextrose. Our research documents our experience with our patients.
In many cases, Prolotherapy injections cannot replace surgery. Prolotherapy cannot open up the foramen magnum, but a neurosurgeon can. If upper cervical instability is found, Prolotherapy injections can be started along with splinting the neck in the best possible alignment. If this relieves the vast majority of the symptoms, it can be assumed that the symptoms were from upper cervical instability. If symptoms do not resolve, then neurosurgery for the cervicomedullary problems needs to be considered.
To recap: The primary surgical treatment for Chiari 1 malformation or CTE that is obstructing CSF flow is decompression or enlargement of the posterior fossa to establish normal CSF pathways. The compression by the cerebellum is felt to obstruct the normal venting of the CSF in and out of the craniocervical subarachnoid space, throughout the cardiac cycle. Many people who end up with craniectomy, had not even considered Prolotherapy prior to the surgery because no one thought that upper cervical instability may be causing their symptoms. It makes sense though, as the subarachnoid space is most crowded at the craniocervical junction, that by stabilizing or limiting C1-C2 motion, Prolotherapy could also open up the subarachnoid space and allow appropriate CSF flow in appropriate patients. So the most conservative decompressive treatment when cervical instability is the cause of nerve or spinal cord compression is Prolotherapy.
Summary and contact us. Can we help you? How do I know if I’m a good candidate?
We hope you found this article informative and it helped answer many of the questions you may have surrounding Injury and abnormalities at the cervicomedullary junction. . . Just like you, we want to make sure you are a good fit for our clinic prior to accepting your case. While our mission is to help as many people with chronic pain as we can, sadly, we cannot accept all cases. We have a multi-step process so our team can really get to know you and your case to ensure that it sounds like you are a good fit for the unique testing and treatments that we offer here.
Please reach out to the Hauser Neck Center Patient team here
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This article was updated June 20, 2022