Injury and abnormalities at the cervicomedullary junction

Ross Hauser, MD

This is a companion article to Chiari malformation: Non-surgical alternatives to Chiari decompression surgery

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

It is compression on these structures which have been linked to the various and myriad symptomology in the patients we see. Please see my related articles for follow-ups to the discussion I present here: Treating neurologic-like symptoms by addressing cervical spine instability and disrupted blood flow into the brain, Cervical Spine Instability, Vein blockage, fluid build up and intracranial hypertension, Symptoms, and conditions of cervical spine compression causing internal jugular vein stenosis, and Symptoms and conditions of Craniocervical Instability.

What are we seeing in this image? The place of the brainstem in the cervical spine and how upper cervical instability can impact the brainstem.

The vast array of neurologic-like, vascular, and cardiovascular-like symptoms suffered by patients in whiplash related or cervicomedullary junction degeneration of injury can be explained by examining the position of the brain stem in the cervical spine and how instability at the C1 or C2 levels can cause these bones to start wandering around and compressing nerves, arteries, and veins.

The brainstem is the inferior (deep inside)-most portion of the brain and contains the pons (the largest area of the brainstem responsible for being the conduit or connection between the brain and the cranial nerves), midbrain (which for the most part controls the nerves of audio/visual) and medulla (respiratory and cardiovascular function connections), each having extremely important functions that involve the communication between the brain (central nervous system) and the periphery (the out nerves). The lowest portion of the brainstem, the medulla, is continuous with the upper cervical spinal cord. It is the part of the brainstem that is most affected by upper cervical instability. It contains the functional centers that control autonomic nervous system activity that regulates respiration, heart rate, and digestive processes. The medulla also controls movement, relaying of somatic sensory information from internal organs, and control of arousal and sleep. It also contains the cardiac, respiratory, vomiting, and vasomotor centers regulating heart rate, breathing, and blood pressure. The last seven cranial nerves also emerge from the medulla. When the medulla nerve tracts are not working correctly, symptoms can include:

weakness or paralysis on one side of the body
loss or decreased sense of touch
weakened position sense
weakness of muscle tone
decreased pain and temperature sensation
difficulty swallowing
vertigo
vomiting
loss of coordination

Many of these symptoms are seen in patients with upper cervical instability. It is important to remember that many important nerve tracts go through the brain stem, including the corticospinal (muscle power), posterior column-medial lemniscus pathway (fine touch, vibration, and proprioception sensation), and the spinothalamic tract (pain, temperature, itch, and crude touch).

Please see my related articles for follow-ups to the discussion I present here: Thermoregulatory instability – Neck pain and inability to maintain consistent body temperature, Cervical disc disease and difficulty swallowing – cervicogenic dysphagia, Cervical Vertigo, and Cervicogenic Dizziness – Neck pain and dizziness.

Since humans spend most of their time upright, it is important when evaluating someone for an issue related to the cervicomedullary junction that they are scanned by motion x-rays and MRI in the upright position. With today’s technology, it is not only possible to find alterations that show instability in the biomechanics of the cervical spine, but also alterations in the blood flow, venous drainage, and CSF flow under the effects of gravity. It is common now to find upright MRIs where a person can get an MRI in the seated upright position. The scan is taken with the neck in the neutral, maximally flexed, and then extended position. With upright motion MRIs, not only are upper and lower cervical instability being documented but also how this can compress the structures of the cervicomedullary junction. Downward herniation of the cerebellar tonsils or tonsillar ectopia can be documented as well.

What we have is in aging patients, those who did not have some type of corrective treatment in the cervical spine area that addressed cervical instability, suffered from degenerative Chiari malformation problems because of a narrowing or compression of the CSF space

In June 2021, a team of researchers writing in the medical journal Cerebellum (1) discussed the compression of structures in the cervicomedullary junction focusing on the cerebellar tonsils. They note that Chiari malformation type I (CMI) is detected in scans as the cerebellar tonsils extend below the foramen magnum. They also note that “to date, the relationships among adult age, brain morphometry (the measure of the volume of various parts of the brain), surgical status, and symptom severity in Chiari malformation type I are unknown.” To answer this question the researchers set out to better understand the relationships among these variables.

They looked at:

Adult Chiari malformation type I patients (80% female) who either had (150 patients) or had not (151 patients) undergone posterior fossa decompression surgery. What they found was “Age differences in self-reported pain were (brought about) by anterior CSF space in the cervical spine area-and this effect was particularly (noticeable) for non-decompressed Chiari malformation type I patients. As Chiari malformation type I patients age, the anterior CSF space decreases, and this is associated with increased pain-especially for non-decompressed CMI patients.”

What we have is in aging patients, those who did not have some type of corrective treatment in the cervical spine area that addressed cervical instability, suffered from degenerative Chiari malformation problems because of a narrowing or compression of the CSF space.

This problem is demonstrated in the illustration below: The caption reads 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 the cerebrospinal fluid and may cause fluid build up inside the spinal cord (a syrinx).

Cervicomedullary Compression Syndrome (CMCS)

When there is downward herniation of the cerebellar tonsils and/or brainstem into the foramen magnum causing symptoms, I simply call the condition cervicomedullary compression syndrome, whether CTE or Chiari 1. The symptoms of CMCS, CTE, Chiari 1, and upper cervical instability are basically identical. Individuals with CMCS (and for that matter cerebellar ectopia and Chiari 1 Malformation) can have many of the same symptoms we have been discussing including neck pain, balance problems, muscle weakness, numbness, or other abnormal feelings in the arms and legs, dizziness, and a host of others. As some patients do not want to have neurosurgery, they often seek out a consultation for more conservative care.

There are four types of Chiari malformations, Types 1-4, with each more involved than the last. Types 2-4 generally cause significant neural compromise and are evident at birth. At the Hauser Neck center, we typically get consulted when someone discovers that they have a craniocervical junction problem that showed up on MRI. It is sometimes very difficult to find a physician that understands the triad of upper cervical instability, Chiari I, and Cerebellar Tonsillar Ectopia. They can be associated with syringomyelia as well as hydrocephalus, an excessive buildup of CSF in the brain. Both are serious problems and necessitate a neurosurgical consult, as a shunt to drain the excess fluid may be needed to relieve the pressure. However, if these were discovered after a trauma such as a whiplash injury, the cause could be what I have termed CMCS or cervicomedullary compression syndrome, and appropriate motion x-ray and MRI studies need to be done.

CMCS occurs when there is a compression of the vital structures that coarse into the cranium through the foramen magnum including the medulla oblongata, vertebral arteries, spinal accessory nerve, and of course cerebrospinal fluid. Because the compression occurs where the cervical spinal cord meets the brainstem at the medulla oblongata it is appropriate to call the compression syndrome CMCS. Cervical instability explains why symptoms occur. In other words, why do some people who are discovered to have CTE on MRIs have symptoms and others do not. I would propose that those who have symptoms have upper cervical instability and those without symptoms have stable cervical spines.

Whenever any of the structural fluids (arterial, venous, cerebrospinal) are compressed, various types of neurological and neurological-like symptoms can occur along with resultant pain. CMCS results from a combination of a low-lying cerebellar tonsil and upper cervical instability. It is this compression from upper cervical instability that moves CTE from asymptomatic to symptomatic. The condition is acquired, generally from a whiplash-type injury, unlike Chiari Type 1 which is genetic. There are times, however, when a genetic Chiari malformation, when combined with upper cervical instability, will also cause symptoms.

It should be noted that some people also have symptoms when the cerebellar tonsils are at or just below the McRae line. This is arguably referred to as Chiari 0 malformation. Dr. Franck and I would say these patients have CTE. In many of these patients diagnosed with Chiari 1 malformation (CTE), the missing diagnosis is upper cervical instability, a condition that needs to be evaluated and be treated if present, to resolve the symptoms.

What are we seeing in this image? Upper cervical instability and cerebellar tonsillar ectopia

Your attention is drawn to the lower half of this illustration. We see ligament damage represented between the C1 – C2 vertabrae. This can cause compression, cerebellar tonsillar ectopia, and blockage of the spinal fluid flow at the C1-C2 area.

What Does This Mean for the Patient?

When a patient is given a diagnosis that they apparently had from birth, it begs the question “Doctor, if you are saying my diagnosis is Chiari malformation then why did it become symptomatic now? If the person had it for 30 years of their life and they have symptoms now, it may be that either the low lying tonsils on the x-ray are from a ligament injury or the symptoms of migraine headaches, suboccipital headaches and neck pain are actually not from the MRI finding, but from upper cervical instability. It can be true to say that this person who suffered for all these years had a missing diagnosis – upper cervical instability.

Cerebellar tonsillar ectopia can result from whiplash injuries

Whiplash injury to the cervical ligaments causes many destructive effects on the structures in and around the neck. With whiplash and corresponding alar and transverse ligament injury, C1 capsular synovitis (inflammation in the cervical joints) develops as a mass lesion at the ventral spinal canal at the level of the odontoid (C2 – Dens). With putative (assumed) damage to the dentate ligaments (the spinal cord ligaments that hold the spinal cord in place within the spinal column), cerebellar tonsillar ectopia (CTE) occurs and the cervicomedullary junction will be directly be compressed in flexion (head in the chin) versus extension (head in the air). These findings are clearly demonstrable with upright positional MRI scanning. Compression of these regions of the central nervous system is naturally manifested, again, as varied symptoms. Additionally, the pulsatile CSF flow across the foramen magnum from the cranium to and from the spinal canal is transiently obstructed by these post-whiplash phenomena as demonstrable via Cine MRI.

Of interest is the fact that in a well-cited 2010 study led by the Department of Public Health and Preventive Medicine, Oregon Health and Science University School of Medicine, researchers followed 1,200 patients. Tonsillar ectopia was identified in 1 in 4 trauma patients versus 1 in 18 non-trauma patients, further confirming that cerebellar tonsillar ectopia can result from whiplash injuries. (2)

A December 2020 paper built on this idea of “discovering missing diagnosis” in problems of tonsillar herniation. Here a team of Italian neurosurgeons writing in the journal Neurosurgical Review (3) suggested: “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” (label).

Of interest in this discussion of the inconsistency of diagnosis was the fact that some physicians were and are publishing cases that trauma can cause cerebellar tonsillar ectopia to become symptomatic, which they are calling Chiari 1 Malformations. (4,5)

What all of this means is that the finding of cerebellar tonsillar herniation (whether you call it CTE or Chiari Malformation doesn’t matter from a clinical standpoint) doesn’t mean anything itself, much like seeing a degenerated disc or herniated disc on an MRI of the cervical spine. It has to be correlated with the patient, which means one has to consider the biomechanics of the cervical spine in each particular patient. Is there cervical instability present? If so, it would be optimal to treat this with a conservative approach before contemplating a decompressive surgery to open up the cervicomedullary junction. However, if by the various scans it appears that there is cervicomedullary junction compression causing the symptoms, then neurosurgical consultation should be made.

Non-Surgical Options: Prolotherapy

There are not many non-surgical options for injury and abnormalities at the cervicomedullary junction. 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.

Injections

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.

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.

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1 García M, Eppelheimer MS, Houston JR, Houston ML, Nwotchouang BS, Kaut KP, Labuda R, Bapuraj JR, Maleki J, Klinge PM, Vorster S. Adult Age Differences in Self-Reported Pain and Anterior CSF Space in Chiari Malformation. The Cerebellum. 2021 Jun 9:1-4. [Google Scholar]
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