title: F-waves of the facial muscles in healthy control subjects and in patients with peripheral facial nerve disturbance.
abstract: 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.
authors.affiliation: Department of Neurosurgery, Saitama National Hospital, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Ishikawa
authors.forename: J
authors.initials: J
authors.lastname: Namiki
authors.forename: M
authors.initials: M
authors.lastname: Takase
authors.forename: A
authors.initials: A
authors.lastname: Kojima
authors.forename: T
authors.initials: T
authors.lastname: Kawase
mesh_terms: D000328:Adult; D004558:Electric Stimulation; D004576:Electromyography; D005152:Facial Muscles / Q000503:physiopathology*; D005154:Facial Nerve / Q000503:physiopathology*; D006801:Humans; D009119:Muscle Contraction / Q000502:physiology; D010523:Peripheral Nervous System Diseases / Q000503:physiopathology*; D011930:Reaction Time / Q000502:physiology; D012890:Sleep / Q000502:physiology