The trigeminal nerve.

The trigeminal nerve is described in terms of segmental anatomy and regional pathology. The common brain stem lesions are neoplasms, vascular disease, and demyelinating processes. Common lesions affecting the cisternal segment and Meckel's cave are schwannoma, meningioma, epidermoid, vascular ectasia, and aneurysm. Common lesions affecting the cavernous segment include meningioma, trigeminal schwannoma, lymphoma, metastasis, and vascular lesions. Skull base abnormalities include chordoma, 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 lesion cannot be accurately predicted on the basis of clinical symptomatology. Successful imaging evaluation must include the entire course of the trigeminal nerve from the brain stem and upper cervical cord through the peripheral branches.