Trigeminal Motor Neuropathy with Weakness and Atrophy of the Muscles of Mastication

This is a man who was diagnosed with polio in childhood, which involved the motor (VIII) division of the right trigeminal nerve. The motor portion of the trigeminal nerve innervates the muscles of mastication (temporalis, masseter - both of which demonstrate wasting in this patient - as well as the medial and lateral pterygoids), in addition to the tensor tympani, tensor veli palatine, mylohyoid and anterior belly of the digastric muscles. Given weakness of the jaw musculature on the right side, opening the mouth causing deviation of the jaw towards the side of the weakness - e.g., right sided trigeminal motor neuropathy causes rightward jaw deviation due to unopposed action of the left muscles of mastication. [[Number of Videos and legend for each: 1, patient with right trigeminal motor neuropathy with atrophic masseter and temporalis and jaw deviation to the right.]]