THE TRIGEMINAL NERVE

The trigeminal nerve is described in terms of segmental anatomy and re gional pathology. The common brain stem lesions are neoplasms, vascula r disease, and demyelinating processes. Common lesions affecting the c isternal segment and Meckel's cave are schwannoma, meningioma, epiderm oid, vascular ectasia, and aneurysm. Common lesions affecting the cave rnous segment include meningioma, trigeminal schwannoma, lymphoma, met astasis, and vascular lesions. Skull base abnormalities include chordo ma, chondrosarcoma, metastasis, bone dysplasias, and Paget's disease. The peripheral divisions of the trigeminal nerve are commonly involved by adjacent inflammatory disease in the sinuses, perineural spread of malignancy, and schwannoma. Unfortunately, the anatomic site of a les ion cannot be accurately predicted on the basis of clinical symptomato logy. Successful imaging evaluation must include the entire course of the trigeminal nerve from the brain stem and upper cervical cord throu gh the peripheral branches.