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Craniocervical Instability

Craniocervical Instability Ribbon

Craniocervical Instability Awareness Ribbon

Spinal instability can occur anywhere along the spine as a potential complication of Ehlers-Danlos Syndrome (EDS) and other connective tissue disorders. The main spinal instability that can occur in the craniocervical junction are Craniocervical Instability and Atlantoaxial Instability


Craniocervical Instability (CCI) also known as Syndrome of Occipitoatlantialaxial Hypermobility, is instability in the craniocervical junction (skull and atlas) and can lead to structural instability putting pressure on the brainstem and upper cervical spine resulting causing Cervical Medullary Syndrome


This is diagnosed by MRI with images in both flexion, extension and rotation. Some doctors prefer these MRIs to be done in an upright MRI machine, while others prefer supine MRIs due to the better quality of the images. Some form of traction is often used to demonstrate that the symptoms are linked to the structural issues seen in the imaging. There is some debate about imaging needed, we always recommend the type of imaging the doctor you are seeing/want to see requests. This will save you money and potentially radiation exposure from CT/Xray that might not be relevant for your specific case. 

Treatment can be conservative through physiotherapy and wearing a hard collar. In some cases, surgery is required to fuse the skull to the spine. Further fusion down the spine may occur depending on how much subaxial instability is found further down. A hard collar must be worn under the direction of a health professional as this can cause muscle to weaken and worsen issues if not used correctly or from prolonged use.

Symptoms of Cervical Medullar Syndrome can include:


Heat intolerance

Orthostatic Intolerance


Delayed Gastric Emptying

Chronic Fatigue

Brain Fog

  • Neck Pain

  • Central Sleep Apnoea

  • Facial pain and/or numbness

  • Balance Issues

  • Muscle Weakness

  • Dizziness/Vertigo

  • Gag reflex reduction

  • Swallowing issues

  • Tinnitus - Ringing in ears

  • Nausea and/or vomiting

  • Nystagmus (irregular down-beat eye movements

  • Paralysis

Atlantoaxial Instability (AAI) can occur separately or in conjunction with CCI. This is similar to CCI, but the instability (excessive movement) occurs between the first and second cervical vertebrae (C1 and C2). In the cervical spine C1 (Atlas) and C2 (Axis), this atlantoaxial joint allows the head to rotate.

Diagnosis is AAI uses dynamic imaging with an MRI or CT with the neck in rotation (looking left and right). Symptoms are similar to what has been listed for CCI and are often exacerbated when looking left/right this can cut off the arteries in the neck. 

As with CCI treatment can range from conservative (physio, neck brace) or may require a fusion of C1 and C2. 

Cranial Settling (CS)

Vertical instability in the craniocervical junction can result in the skull sinking down the spine which causes the top of the spine (Dens) to impinge up into the brainstem. 

Craniocervical Instability, Atlantoaxial Instability and Cranial Settling can all occur at once, or someone may only have 1 or 2. While these can occur in patients with EDS, those who have EDS and have had a Chiari decompression are at greater risk. It is advised for those who have both to speak to a qualified surgeon who understands the risks. They may require both the Chiari decompression and the fusion to stabilise the neck. This can be difficult as the bone removed for Chiari is a common area to fuse. The 2022 Chiari consensus has highlighted the need to assess patients with Chiari 1.5 for spinal instability before a standard decompression. 

Instability can occur anywhere in the spine and fusion may be needed anywhere on the spine and in some rare cases the entire skull to spine area fused. Fusing decreases your range of motion and should be done as the last possible treatment option. Instability in the spine (Spondylisthesis) can occur when the vertebrae slip either too far forward (Anterolisthesis) or backward (Retrolisthesis) over the other vertebrae. A displacement of of the vertebrae by 3mm has been noted in research articles as the amount of displacement in the cervical region needed for diagnosis. Some radiological places may not "small" displacements of less than this. Most research focusses on the lumbar region not the cervical so this can cause confusion, but small amounts of slippage is considered acceptable and not something requiring immediate surgical attention. As always discussion concerns with your doctor.

CCI/AAI in Australia

Until around late 2018/2019 there was very little help available for these conditions in Australia. This is improving slowly. There are upright MRI scanners available in both Sydney and Melbourne with the Sydney site seeing a fair share of patients with craniocervical junction instabilities. Sydney has had the most surgeries but they are still in small amounts but interest and recognition is growing with doctors. 


There has been some interest on the patient boards with Chiropractors diagnosing via DMX imaging. There is no reputable research about this so far to recommend this route. If this changes we will update in the future. Due to this and the neurosurgeons not using this type of imaging we do not carry any information on imaging places or Chiropractors doing DMX scans. American surgeons using this seem to use this for additional information of lower cervical instability in conjunction with other scans, but it still has not become a standard imaging among doctors.   

We are endeavouring to have a separate site up specifically in relation to CCI/AAI in Australia. Till then there is the online awareness page mentioned above and a Facebook Support Group.

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