Masking level difference before and after surgery in unilateral otosclerosis.

The object of this paper was to evaluate the binaural hearing in 20 patients suffering from unilateral otosclerosis. Binaural performance was assessed at a test frequency of 500 Hz using masking level difference (MLD) before and after surgery. The postsurgical results showed abnormal MLDs in patients in whom stapedotomy had successfully corrected the threshold asymmetry. Three possible hypotheses regarding this phenomenon were investigated: (1) cochlear damage, (2) auditory deprivation and (3) a mechanical middle ear anomaly due to the surgical prosthesis or healing processes. The analyses suggest that the conductive hearing loss may effect central auditory processing resulting in poor binaural hearing (auditory deprivation theory).