Primary malleus fixation: diagnosis and treatment.

Abstract

Primary malleus fixation occurs in an otherwise normal middle ear without evidence of congenital deformity and without chronic inflammatory changes. It occurs in the latter decades of life and is frequently associated with sensorineural presbycusis. We believe it is a ligament ankylosis with osteoarthritis related to the aging process. The diagnosis of malleus fixation is facilitated through the use of a modified Siegle pneumatic otoscope in conjunction with the Zeiss binocular microscope. The literature pertaining to this subject as well as the more historical reports are reviewed. Goodhill has written extensively on malleus fixation. The audiologic test results in the fixed malleus cases reviewed for this study often presented a misleading picture, sometimes mimicking stapedial otosclerosis with a characteristic Carhart's notch and sometimes indistinguishable from sensorineural presbycusis. Usually speech discrimination scores fell in the very good to excellent range. Weber tests, whether performed by tuning forks or audiometrically, almost always lateralized to the suspect ear. Impedance frequently failed to conform to the expected fixed malleus pattern of low static compliance and absent acoustic reflexes; there was an equal number of low compliance and normal range compliance tympanograms and 15% of the total number of our cases had abnormally high compliance tympanograms. Stapedial reflexes are normally expected to be absent with lateral ossicular fixation, but this was not a consistent finding with contralateral test stimulation. The decision for surgical treatment is dependent on the audiological findings and the potential hearing gain. The technique described consists of the removal of the incus and the head of the malleus and the reconstruction of a sound conducting pathway from the handle of the malleus to the mobile stapes or from the mobile stapes to the under surface of the tympanic membrane using a prosthesis-ossicle arrangement. Malleus fixation occurs far more often than it is diagnosed. Surgical correction can result in a worthwhile hearing gain even when the air-bone gap is narrow or nonexistent. The technique of ossicular reconstruction is dictated by the anatomical findings. Some form of autograft ossicular reconstruction from the malleus handle to the stapes is most frequently utilized. Otosclerosis with stapes fixation sometimes causes a lateral ossicular fixation due to degenerative disease and fibrosis. In this instance a stapedectomy is performed as the primary procedure with subsequent revision as necessary to eliminate the lateral obstruction.