Transcranial magnetic stimulation of the facial nerve: where is the actual excitation site?
The site where excitation on the facial nerve to transcranial magnetic stimulation occurs was studied by recording the muscle responses of 13 patients who had facial nerve lesions at different locations, and by comparing the latencies of muscle responses to transcranial magnetic and direct electrical stimulation of the facial nerve recorded in another 5 patients undergoing posterior fossa surgery. The results of both approaches of this study led independently to the conclusion that magnetic stimulation acts within the proximal part of the facial canal. It is suggested that the cerebrospinal fluid (CSF) conducts the magnetically induced stimulation currents into the labyrinthine segment of the facial canal, where the facial nerve is still surrounded by CSF for about 10 mm.
Rösler
K M
KM
Department of Neurology, Berne University Hospital, Switzerland.
Schmid
U D
UD
Hess
C W
CW
D000200:Action Potentials; D000328:Adult; D002555:Cerebrospinal Fluid / Q000502:physiology; D004553:Electric Conductivity; D004558:Electric Stimulation; D005154:Facial Nerve / Q000502:physiology* / Q000503:physiopathology; D005158:Facial Paralysis / Q000503:physiopathology; D006801:Humans; D009044:Motor Cortex / Q000502:physiology / Q000503:physiopathology; D009132:Muscles / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D050781:Transcranial Magnetic Stimulation