Images in Neurosurgery
These photographs show the hypoglossal nerve traversing a fenestrated right vertebral artery, just proximal to the vertebrobasilar junction. The branching pattern is normal, with no aneurysms or arteriovenous malformations. Incidence of fenestration ranges from 0.23% to 1.95% for all vertebral/basilar arteries. Most fenestrations (>70%) are extracranial and occur at the C1-C2 level. Fenestration—which differs from duplication—is possibly a persistent segment of the embryonic hypoglossal or proatlantal intersegmental arteries. Most basilar fenestrations are in the proximal portion. Fenestrations are usually asymptomatic.