Case report: Unilateral masticatory atrophy caused by pure trigeminal motor neuropathy

Pure trigeminal motor neuropathy (PTMN) is characterized by trigeminal motor weakness without signs of trigeminal sensory dysfunction or involvement of other cranial nerves. We describe a rare case of an 83-year-old man with weakness and atrophy of the right masticatory muscle without any sensory disturbance. Brain computed tomography and magnetic resonance imaging revealed atrophy and fatty infiltration of the right masticatory muscle. Electromyography revealed abnormal spontaneous activity, chronic neurogenic motor unit potentials, and reduced interference patterns in the right temporalis and the masseter muscles. The patient was diagnosed with PTMN based on the clinical symptoms and examinations. Our case presents a rare clinical manifestation with unclear etiology.