F-waves of the facial muscles in healthy control subjects and in patients with peripheral facial nerve disturbance

• Published in: Electromyography and clinical neurophysiology Vol. 39; no. 3; p. 167
• Main Authors: Ishikawa, M, Namiki, J, Takase, M, Kojima, A, Kawase, T
• Format: Journal Article
• Language: English
• Published: Belgium 01-04-1999
• Subjects: Adult; Electric Stimulation; Electromyography; Facial Muscles - physiopathology; Facial Nerve - physiopathology; Humans; Muscle Contraction - physiology; Peripheral Nervous System Diseases - physiopathology; Reaction Time - physiology; Sleep - physiology
• ISSN: 0301-150X

F-waves were recorded from the mentalis muscles with surface electrodes following stimulation of the marginal mandibular branch of the facial nerve in healthy control subjects during wakefulness, non-REM (rapid eye movement) sleep and voluntary contraction and in patients with Bell's palsy and acoustic neurinoma. The F-wave of the facial muscles results from the backfiring of antidromically activated alpha motoneurons in the facial motonucleus. Therefore, first, the F-waves were not easily elicited in patients with any disturbance in the proximal segment of the facial nerve (Bell's palsy and acoustic neurinoma). Second, the F-waves were affected by excitability of the facial motonucleus; the F-waves were inhibited significantly during sleep and enhanced significantly during voluntary contraction compared with those at rest during wakefulness. When the stimulation strength was set submaximum for M-waves, F-waves were elicited but H-waves, which have lower threshold than M-waves, were not elicited in the facial muscles, unlike the case of the extremities. Measurement of the F-waves of facial muscles is a new method for estimating excitability of the facial motonucleus unless there is any disturbance of the proximal segment. Fundamental characteristics of the facial F-waves were shown in the present study and measuring facial F-waves is clinically applicable for investigation of both excitability of the facial motonucleus and facial peripheral nerve disturbance.