Unilateral atrophy of the masticatory muscles and mandibular ramus due to pure trigeminal motor neuropathy: a case report.

Pure trigeminal motor neuropathy is a very unusual disease that is characterized by trigeminal motor paralysis without trigeminal sensory disturbances and without the involvement of the other cranial nerves. We report a case of pure trigeminal motor neuropathy in a 70-year-old woman. The diagnosis was based on the results of clinical, electromyographic, and radiologic examinations. Only the motor branch of the left trigeminal nerve was damaged. Atrophy of the left-side masticatory muscles and jaw resulted in facial asymmetry. Magnetic resonance imaging (MRI) of the head and face did not detect any pathologic lesion, with the exception of atrophy and fatty infiltration of the muscles innervated by the left trigeminal motor nerve. The etiology of the patient's pure trigeminal motor neuropathy was undetermined. Patients with suspected trigeminal motor neuropathy should undergo MRI of the head and face to evaluate the sequelae of denervation and to detect an intracranial or extracranial lesion.