Hemifacial spasm following a blow to the mandible causing blunt injury to the peripheral facial nerve.

A 40-year-old male presented with hemifacial spasm manifesting as paroxysmal spontaneous twitches in the left peribuccal region persisting for 3 months. The symptoms began 7 days after an accident, when a signboard hit his left mandibular angle. Physical examination showed no trauma-related change in his face, and no neurological abnormality except for the twitches. Magnetic resonance imaging also showed no abnormalities of the facial nerve and adjacent regions. Electrophysiological studies showed synkinesis, so hemifacial spasm caused by peripheral facial nerve injury was suspect- ed. The symptoms subsided 4 months after the injury. Blunt injury to the facial nerve branches might cause hemifacial spasm.