Rarest of the Rare: Chiari Patients Who Also Need Fusion

Dec. 7, 2016

chiari back of headPediatric neurosurgeon Dr. Richard Anderson sees a lot of patients with Chiari malformation. In this rare condition, part of the base of the brain is squeezed down into the spinal canal. The most common kind of Chiari, called Chiari I, is usually diagnosed in childhood, adolescence or young adulthood.

Not all cases of Chiari I need surgical treatment. But when surgery is necessary, neurosurgeons like Dr. Anderson can perform a procedure that provides more space for the brain by removing a small area of bone. The surgeon can tailor the specifics of the operation for each patient. This procedure is almost always all that is needed.

But in rare cases of Chiari I, the malformation also comes along with instability of the joint between the base of the skull and the top of the spine. In these cases, an additional procedure, a fusion between the base of the skull and the top of the spine, is needed.

In a fusion, a joint is fixed, usually with rods, plates and screws, so that it no longer moves. Fusion between the base of the skull and the top of the spine is called craniovertebral fusion (cranium = skull; vertebrae = bones of the spine).

Only a small number of patients (less than 5 percent) with a Chiari I malformation will need this type of fusion.

The rarity of these cases, however, means they are not always identified and properly treated with fusion during surgery, says Dr. Anderson. When this happens, symptoms will likely persist, and the patient will probably end up needing a second surgery.

According to Dr. Anderson, to avoid multiple surgeries, it is necessary to identify patients who need fusion before their Chiari surgery takes place.

The problem is that no single symptom or X-ray finding can always diagnose joint instability. Instead, a combination of symptoms and X-ray findings together can suggest that the joint is unstable. This is where it becomes extremely important for surgeons to look for the signs and symptoms more often present in this group.

Chiari patients with an unstable joint are much more likely than other Chiari patients to have symptoms of headache, hyperreflexia (overactive reflexes) and dysphagia (trouble swallowing). Their X-rays are also more likely to show other specific signs.

For example, patients with unstable joints are more likely to have ventral brainstem compression or a condition called basilar invagination. This is a specific misalignment of the bones at the top of the neck.

Dr. Anderson recently taught neurosurgeons about this joint instability and its treatment at a meeting of the Congress of Neurological Surgeons. He focused on the details that can help a neurosurgeon diagnose the condition.

The neurosurgeons in attendance can take that knowledge back to their practices and be on the lookout for those rarest of the rare cases: Chiari patients whose symptoms may only be completely resolved with a fusion.

Learn more about Dr. Richard Anderson on his bio page here.

Image credit: ©JanBaby/pixabay

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