Etiology of Trigeminal Neuralgia Trigeminal neuralgia is usually caused by Compression of the trigeminal nerve at its root by an aberrant loop of an intracranial artery (eg, anterior inferior cerebellar artery, ectatic basilar artery) Less often, a venous loop that compresses the 5th cranial (trigeminal) nerve at its root entry zone into the brain stem Other less common causes include compression by a tumor, an arteriovenous malformation, an aneurysm, and occasionally a multiple sclerosis plaque at the root entry zone (usually in younger patients), but these causes are usually distinguished by accompanying sensory loss and other deficits.