Ephaptic transmission in hemifacial spasm: a single-fiber EMG study

In two patients with hemifacial spasm (HFS), single-fiber EMG recordings in facial muscles demonstrated low jitter in the late responses produced by stimulation of peripheral branches to other facial muscles. Surgical decompression of the facial nerve in one patient was followed by clinical improvement and disappearance of the abnormal late responses. These observations are consistent with the hypothesis that there is ephaptic transmission among peripheral branches of the facial nerve at the site of compression in HFS.