Neurinomas of the trigeminal nerve

Summary

Neurinomas of the trigeminal nerve are rare. Based on an analysis of the published cases and on six additional cases of our own classification into three types is proposed:

• Type I: neurinoma of the roots in the posterior fossa,

• Type II: neurinoma of the Gasserian ganglion,

• Type III: neurinoma of the trigeminal branches.

This classification allows a better adaptation of the surgical procedure to the individual case.

The trigeminal nerve originates from a sensory root and a motor root which emerge from the pons and gain the middle cranial fossa floor over the apex of the petrousrigde before forming the Gasserian ganglion. The three branches of the trigeminal nerve originate at the Gasserian ganglion¹⁰. Neurinomas of this nerve are relatively rare, as there are only 183 published cases. A study of the literature reveals that their incidence among brain tumours is from 0.2 to 0.4% according to the authors^{1, 7, 13, 14, 16}. Based on the published material and six personal cases and also on the anatomical, clinical and neuroradiological findings three major types of neurinomas of the trigeminal nerve can be distinguished according to their origin: neurinomas developed in the posterior fossa (type I) on the nerve roots, neurinomas of the Gasserian ganglion (type II) developed in the temporal fossa and neurinomas of the branches of the trigeminal nerve (type III).Transitional forms between the various types are possible and express special conditions of development.

Each of these topographical forms has a specific clinical and radiological picture and each requires specific surgical treatment. This will be demonstrated by analysing our own six cases and the cases reported in the literature.