Electrophysiology Helps Differentiate Facial Palsy and Hemifacial Spasms

Electrophysiologic studies are important for diagnosing and predicting prognosis in both facial nerve lesions and hemifacial spasm. To delineate the pathophysiologic mechanisms of these entities and to differentiate between them, the author of this review describes the typical electrophysiologic findings in each.

The main methods used to record voluntary and evoked activity in facial muscles include electromyography, conduction studies of the facial nerve, transcranial magnetic stimulation to elicit motor evoked potentials, and blink-reflex studies. Studies at different times in the months after facial palsy onset can help to identify characteristic pathologic changes. In facial palsy, recording of synkinesias and abnormal blink-reflex findi…