Microsurgical relationships of the superior cerebellar artery and the trigeminal nerve.

Comparison and distortion of the trigeminal nerve by a tortuous and elongated superior cerebellar artery (SCA) is postulated to be a frequent cause of trigeminal neuralgia. This theory and the use of operative therapy in which the offending arterial loop is separated from the trigeminal nerve has created a need for more detailed information on the relationship of the SCA and the trigeminal nerve. In order to meet this need, 50 trigeminal nerves and the adjacent SCA were examined in 25 adult cadavers. Twenty-six of the 50 nerves examined had a point of contact with the SCA, but it was uncommon for the arterial contact to produce distortion of the nerve. In six instances, the contact was at the pontine entry zone of the trigeminal nerve, the site of arterial compression postulated to be associated with trigeminal neuralgia. Four trigeminal nerves (8%) had a point of contact with the anterior inferior cerebellar artery (AICA). The fact that large arteries are commonly in contact with the trigeminal nerve is important not only because of the controversial relationship of neurovascular contact to trigeminal neuralgia, but because of the possibility that major vessels may be encountered and injured during rhizotomy and other posterior fossa operations on the trigeminal nerve.