Electrophysiologic investigation of mandibular nerve injury.

Isolated lesions of the mandibular branch of the trigeminal nerve have only rarely been reported. We report the occurrence of an isolated lesion of the mandibular nerve associated with a unilateral mandibular fracture, and its substantiation electrophysiologically. A 65-year-old man was involved in a motor vehicle accident resulting in multiple fractures, including a unilateral mandibular fracture and temporomandibular joint dislocation. No evidence of intracranial pathology by CT scan was noted and the neurologic examination was nonfocal except for dysfunction of the mandibular nerve ipsilateral to the fracture site. Bilateral facial nerve latency and blink reflexes were normal. EMG evaluation of the muscles of facial expression and mastication demonstrated denervation confined to the muscles innervated by the mandibular branch of the trigeminal nerve. In patients complaining of facial sensory dysfunction, malocclusion, or weakness of muscles of mastication after mandibular fracture, an electrophysiologic examination can assist in evaluating cranial nerve integrity.