Otosclerosis

Otosclerosis is a condition where one or more foci of irregularly laid spongy bone replace part of normally dense enchondral layer of bony otic capsule in the bony labyrinth. This condition affects one of the ossicles (the stapes) resulting in hearing loss, tinnitus, vertigo or a combination of symptoms. The term otosclerosis is something of a misnomer. Much of the clinical course is characterized by lucent rather than sclerotic bony changes, so the disease is also known as otospongiosis. Otosclerosis is a condition where one or more foci of irregularly laid spongy bone replace part of normally dense enchondral layer of bony otic capsule in the bony labyrinth. This condition affects one of the ossicles (the stapes) resulting in hearing loss, tinnitus, vertigo or a combination of symptoms. The term otosclerosis is something of a misnomer. Much of the clinical course is characterized by lucent rather than sclerotic bony changes, so the disease is also known as otospongiosis. This is an inherited disease. The primary form of hearing loss in otosclerosis is conductive hearing loss (CHL) whereby sounds reach the ear drum but are incompletely transferred via the ossicular chain in the middle ear, and thus partly fail to reach the inner ear (cochlea). This usually will begin in one ear but will eventually affect both ears with a variable course. On audiometry, the hearing loss is characteristically low-frequency, with higher frequencies being affected later. Sensorineural hearing loss (SNHL) has also been noted in patients with otosclerosis; this is usually a high-frequency loss, and usually manifests late in the disease. The causal link between otosclerosis and SNHL remains controversial. Over the past century, leading otologists and neurotologic researchers have argued whether the finding of SNHL late in the course of otosclerosis is due to otosclerosis or simply to typical presbycusis.