Facial nerve injury and hemifacial spasm. We studied evidence of facial nerve damage in patients with hemifacial spasm. Three types of evidence of nerve damage were analyzed: objectively measured weakness in eyelid protractor strength, clinically evident weakness of muscles innervated by the seventh nerve, and clinically evident aberrant seventh nerve regeneration. Of the 60 patients in the study, 54 (90%) had at least one of these features of seventh nerve damage. Objectively measured eyelid protractor weakness was noted in 27 of 58 patients (47%) who were tested. Clinically apparent weakness of at least one of four facial muscle groups was noted in 42 of 60 patients (70%). Aberrant seventh nerve regeneration was documented in 25 of 60 patients (42%). These findings indicate that facial nerve damage is common in patients with hemifacial spasm. 