A Report of Further Impedance Studies of the Acoustic Reflex

The result of acoustic stimulation of the middle ear muscles was studied using subjects in whom one or the other muscle contraction was known to be ineffective. Otosclerosis presented a condition of an intact pair of muscles but a stapes unresponsive to the contraction of the stapedius muscle. Bell’s Palsy represented a condition of a paralyzed stapedius muscle but an otherwise normal middle ear system. Through surgical intervention the ears of otosclerotic patients were altered by sectioning of the stapedius muscle and insertion of a prosthesis, while in other patients an exploratory tympanotomy verified that the middle ear was without pathology and then one or the other of the middle ear muscles was sectioned. All except one of these instances would eliminate the response of the stapedius muscle only, while the other would only eliminate the tensor tympani response. In each instance of restriction of response of the stapedius muscle the acoustic reflex could not be elicited. On the other hand, when the remainder of the system was intact and only the tensor tympani sectioned, the acoustic reflex appeared normal. These observations would strongly support the contention that the tensor tympani is not responsive to acoustic stimulation.