An anatomical study of the neurovascular relationships at the trigeminal root entry zone.

We aimed to study the neurovascular relationships at the trigeminal root entry zone in the normal population to help determine the pathogenesis of trigeminal neuralgia. We studied 50 fresh cadavers asymptomatic for trigeminal neuralgia or other facial pain during life and examined the 100 trigeminal root entry zones (REZ) using either a transtentorial (34 cadavers) or an infratentorial approach (16 cadavers). A vascular relationship was seen in 39 REZ (39%). There was an arterial relationship in 34 REZ (superior cerebellar artery in 23, anterior inferior cerebellar artery in 7, and pontine branches of the basilar artery in 4). A venous relationship was seen in 5 REZ. There was vascular contact only in 28 REZ, displacement of the nerve in 7 and grooving of the nerve in 4. We concluded that a neurovascular relationship at the trigeminal root entry zone is not uncommon in an asymptomatic population. The incidence of a vascular relationship in the Indian population seems similar to that in other major series. Electron microscopic studies of the nerve at the site of vascular contact in normal and symptomatic populations may help determine the exact pathogenesis of trigeminal neuralgia.