Studies in Impedance Audiometry: III. Middle Ear Disorders

Results of impedance audiometry were analyzed in 454 consecutive patients with conductive hearing loss. Completely successful results were obtained on 428 patients (94%). Tympanometry results indicated that type A patterns were usually associated with otosclerosis or other ossicular chain fixations and type B and C patterns were usually found in otitis media. Maximum static compliance values had only limited diagnostic value due to overlap between conductive and normal groups. Stapedial reflex could not be elicited in most patients. When reflexes were observed in otosclerotic ears, an unusual pattern characterized by negative deflections at onset and termination of a sound appeared. In a subgroup of 154 patients with unilateral conductive loss, results showed that amount of AC-BC gap necessary to abolish stapedial reflex was approximately 25 dB with sound in bad ear and approximately 5 dB with probe-tip in bad ear.