Bone conduction improvement after surgery for conductive hearing loss.

The objective is to evaluate change in post-operative bone conduction in patients who underwent surgery for conductive/mixed hearing loss due to various reasons. The study design is of retrospective case review and tertiary referral center setting. Five-hundred patients with unilateral conductive/mixed hearing loss were divided into five equal groups (each representing different causes for pre-operative hearing loss), who underwent appropriate surgical correction and had a follow-up audiogram available. The intervention comprises surgery (like myringoplasty and ossiculoplasty with closed or open cavity mastoidectomy for chronic otitis media, stapes mobilization for tympanosclerosis and stapedotomy for otosclerosis) for conductive/mixed hearing loss. Significant improvement or worsening in bone conduction was defined as 15 dB or more improvement or worsening of bone conduction threshold at least in two frequencies between 500 and 4000 Hz. All the other groups also showed a consistent pre-operative bone conduction reduction with an equally consistent improvement in post-operative bone conduction improvement to a varying degree with otosclerosis group having maximum percentage of patients with post-operative bone conduction improvement (60%). The measurement of bone conduction is not necessarily a true reflection of the function of the inner ear. Middle ear makes a contribution to bone conduction and correction of a middle ear conductive lesion causes an apparent improvement in inner ear function. The apparent inner ear hearing loss caused in this way may be reversible to some extent.