[Transcranial magnetic stimulation of the facial nerve--identification of the actual excitation site in the cat].
The site where transcranial magnetic stimulation excites the facial nerve was studied in 6 cats. Transcranial magnetic stimulation of the facial nerve was recorded from the left mentalis muscle. A figure-of-eight shaped magnetic coil was used, and coil induction direction had more influence on the facial nerve evoked compound muscle action potentials (CMAPs) than the coil position. No change could be detected in the CMAPs before and after craniotomy, after cerebellar lobectomy and after exposure of the facial nerve in the facial canal. The facial nerve was stimulated electrically at the porus, meatal portion, geniculum and horizontal portion. The latencies of the CMAPs for each portion were measured and compared with the magnetic response, which was coincidental with that of the meatal portion. The facial nerve was then transected distally from the porus, and CMAPs following magnetic stimulation were recorded at each step. The CMAPs disappeared when the nerve was transected at the fundus. The results of both approaches in this study led to the conclusion that transcranial magnetic stimulation excites the facial nerve at the meatal portion.
Department of Neurosurgery, Keio University School of Medicine, Tokyo, Japan.
K
K
Gotoh
T
T
Ohira
J
J
Namiki
Y
Y
Ajimi
M
M
Ishikawa
R
R
Shiobara
S
S
Toya
M
M
Takase
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D002415:Cats; D004576:Electromyography; D005071:Evoked Potentials / Q000502:physiology; D005154:Facial Nerve / Q000502:physiology*; D005260:Female; D008297:Male; D009132:Muscles / Q000502:physiology; D010812:Physical Stimulation; D050781:Transcranial Magnetic Stimulation