Asymptomatic Chiari Type I malformation: should patients be advised against participation in contact sports?

Chiari type I malformation (CM-I) is characterised by caudal displacement of the cerebellar tonsils through the foramen magnum, crowding the craniocervical junction. It is being increasingly diagnosed in asymptomatic patients due to the widespread availability of MRI, and there are case reports of these patients suffering sudden death or neurological injury following head or neck trauma, raising the issue of whether they should be prohibited from contact sport participation, given the likelihood of frequent trauma. General neurosurgical opinion is that patients who are symptomatic and those with an associated spinal cord syrinx should be offered foramen magnum decompression, however asymptomatic patients without syringomyelia are not offered this in the majority of cases.

The authors performed a full review of the published literature, including all case reports, case series, studies and literature reviews regarding CM-I and either contact sports or trauma, excluding patients that had undergone surgical intervention and those becoming symptomatic in circumstances other than head or neck trauma.

21 case reports of CM-I patients deteriorating following trauma were identified, including four cases of sudden death following head or neck injury. However, studies of large samples of CM-I patients are yet to capture an incident of sudden death or acute neurological deterioration, suggesting that the risk is very low. CM-I patients may have an increased risk of concussion and post-concussion syndrome compared to the background population however.

Overall, the authors feel that there should be no restriction of sports participation for CM-I patients, but a discussion to make them and their families aware of the possible increased risks is important.