TRIGEMINAL NEUROPATHY - EVALUATION WITH MR-IMAGING

Neuropathy of the trigeminal nerve can involve its full course, from i ts nuclei in the brain stem to its peripheral branches. The nerve can be divided into four segments-brain stem, cistern, the Meckel cave and cavernous sinus, and extracranial-and consideration of the pathologic entities by these locations simplifies the differential diagnosis. Mu ltiple sclerosis, infarct, and glioma are the most common abnormalitie s in the brain stem leading to trigeminal neuropathy. The most common cisternal cause is neurovascular compression, followed by acoustic and trigeminal schwannomas, meningiomas, epidermoid cysts, lipomas, and m etastases. Trigeminal neuropathy arising from the Meckel cave and cave rnous sinus is frequently due to meningiomas, trigeminal schwannomas, epidermoid cysts, metastases, pituitary adenomas, and aneurysms. Malig nant tumors, which may demonstrate perineural tumor spread, are the mo st common extracranial cause. Because the clinical findings do not per mit accurate lesion localization, magnetic resonance imaging must be u sed to visualize the entire course of the fifth cranial nerve. The sta ndard study should include T2-weighted images of the whole brain and h igh-resolution axial and coronal T1-weighted images of the skull base obtained with and without contrast material enhancement.