1991 Volume 1991 Issue Supplement51 Pages 119-126
Hemifacial spasm (HFS) is characterized by involuntary contructions of the mimetic muscles, and it is usually accompanied by synkinesis. When spasm and synkinesis spread to the stapedius muscle, tympanic noise (tinnitus due to the stapedius muscle contruction)arise. In the present study,57 patients with HFS who had normal tympanogram and stapedius reflex were examined by impedance audiometry to determine the spasm and synkinesis of the stapedius muscle before and after microvascular decompression. Only 18patients complained of tympanic noise, but 54 showed the stapedius muscle spasm and synkinesis. After operation, in all cases tynpanic noise disappeared and 50 patients showed neither spasm nor synkinesis of the stapedius muscle. During the operation,5 of these patients were also recorded by electrical stimulation on supraorbital nerve using needle electrodes inserted through the external auditory meatus. Synkinetic responses of the stapedius muscles could be recorded in 4 cases, and these abnormal potentials disappeared after intraoperative procedures. These results suggests that spasm and synkinesis spreads to the stapedius muscle even in patients without tynpanic noise, and these disappear during the microvascular decompression operation.
