Tinnitus due to Abnormal Contraction of Stapedius Muscle

The authors observed eight cases of intermittent tinnitus which appeared during the course of recovery from peripheral facial nerve paralysis of various etiology. The tinnitus occurred whenever a certain mimic facial muscle contracted voluntarily or involuntarily. As the tinnitus in each case didn't dispaaeared by medical treatment or other conservative therapy, tympanotomy via extenal auditory meatus was made. Under the operating microscope, contraction of the stapedius muscle synchronous with contraction of the mimic facial muscle was observed. The tinnitus had disappeared completely immediately after the tendon of stapedius muscle was sectioned. Thus the existence of tinnitus due to abnormal contraction of stapedius muscle was confirmed. Further, tinnitus in each cases was considered to be an expression of abnormal associated movement involving the stapedius muscle during the course of the recovery from facicl nerve paralysis. Changes of the minimum audible. threshold (air conduction) were measured in each case during the stapedius muscle contracted without sound stimulation, and the results showed a good accordance to the results obtaind from the theoretical and experimental works which had been reported by several authors. In a conclusion, the authors stressed the importance of the stapedius muscle tinnitus in the study of pathogenesis of tinnitus, facial nerve paralysis, as well as in the study of middle ear function.