Craniocervical Instability (CCI), also known as the Syndrome of Occipitoatlantialaxial Hypermobility, is a structural instability of the craniocervical junction which may lead to a pathological deformation of the brainstem, upper spinal cord, and cerebellum.
It primarily occurs in patients with Ehlers-Danlos Syndrome and other hereditary disorders of connective tissue..
How does Craniocervical Instability occur?
About 1 in 15 people with EDS will go on to develop CCI due to a lack of connective tissue support at the craniocervical junction.
While some EDS patients present with this condition after a head and neck injury (such as whiplash), for the most part this condition tends to manifest gradually through repetitive stretch injuries from actions as simple as turning one’s head.
These stretch injuries can result in one or more (and in many times, all) of the following:
- Nerve dysfunction: deformative stress of repetitive stretching of the cranial-cervical nerves can lead to cell dysfunction and nerve death in this area.
- Thickened odontoid capsule (pannus formation): when joints are hypermobile, pannus may grow in a tumor-like fashion where it may erode articular cartilage and bone. When this occurs on the odointoid bone (a bone in our upper neck that acts as our head’s axis) it can compress the brainstem.
- Retroflexed Odontoid: Loose ligaments can misalign the proper angle of the odontoid bone causing it to push backwards, compressing the brainstem.
- Chiari Malformation: a downward displacement of the cerebellar tonsils (part of the brain) that puts pressure on the cerebellum and brainstem, progressively damaging them over time, and blocking the flow of cerebral spinal fluid (CSF).
- Cranial Settling: the skull sinking downward onto the spine. In severe cases basilar invagination occurs, where the tip of the odontoid process projects above the foramen magnum (the opening at the bottom of the skull).
Unsurprisingly, the histopathological changes in neurons that are undergone in these situations would not show up on any routine diagnostic test.
In many cases, however, Chiari (4), cranial settling (5), and a retroflexed odontoid (3) may be demonstrable on MRIs, but typically only when imaged in the upright position. This would explain why many of these patients’ diagnostic imaging reports state negative results.
What are the Symptoms of Craniocervical Instability?
a heavy headache: a constant to near constant headache that can be described as feeling like the head is too heavy for the neck to support (feeling like a “bobble-head”)
a pressure headache: an impairment of CSF flow causes intracranial pressure which would be aggravated by “valsalva maneuvers” such as yawning, laughing, crying, coughing, sneezing or straining.
Dysautonomia: brainstem compression can lead to a dysfunctional autonomic nervous system (the involuntary regulator of all body functions).
Plust various other symptoms.
How is Craniocervical Instability Diagnosed:
Upright MRI and Rotational 3d CT scans are the standard imaging techniques used to determine if CCI is present in individuals with EDS
A definitive diagnosis of CCI can be made by a technique known as Invasive Cervical Traction (ICT). ICT is an inpatient procedure where the paitent’s head is pulled upward by a pulley system. If, over the course of 48 hours, the patient’s symptoms are cleared, CCI is confirmed.
Because ICT is rarely available in typical hospitals, as an alternative a doctor may simply pull the patient’s head up off the spine in the doctor’s office. If there is a reduction in pain and symptoms, it confirms the diagnosis. Patients may also have an extreme worsening of symptoms if their head is pushed downward.
What is the treatment for Craniocervical Instability?
Craniocervical fusion: a procedure in which the skull is pulled upward (cervical traction), placed into the corrected position, and then the occipital bone of the skull is fused to the upper cervical vertebrae to hold the corrected position.
In patients who also have a Chiari Malformation, the droopy and damaged cerebellar tonsils may be shrunk with electrocautery. This shrinkage ensures that there is no blockage of CSF flow out of the 4th ventricle.