Describe otosclerosis with its clinical features and management.

Nature and Pathology

• Otosclerosis is a primary disease of the otic capsule in which normal enchondral bone is replaced by spongy, highly vascular new bone, which later becomes sclerotic.
• Fixation of the stapes footplate produces a progressive conductive hearing loss in an ear that looks entirely normal.
• The name is a misnomer: the active disease is otospongiosis, the sclerotic phase coming later. It is confined to the otic capsule, which is the only bone in the body that normally undergoes no remodelling

Clinical Features and Diagnosis

• The classical presentation is a young adult, often a woman, with progressive deafness and a normal-looking drum — and it is the combination of a significant conductive loss with a normal ear that makes the diagnosis
• Hearing loss — bilateral in 70 to 80%, though often asymmetrical; slowly progressive over years; and conductive at first, becoming mixed as cochlear involvement supervenes
• Paracusis willisii — hearing better in noisy surroundings, which is characteristic and is explained by others raising their voices while the background noise is filtered out

Management

• Three options must be offered and discussed: observation, a hearing aid, or surgery. A hearing aid is a legitimate first choice and works well in otosclerosis.
• Stapedotomy (or stapedectomy) is the definitive operation: through a permeatal approach, the stapes superstructure is removed, a small fenestra made in the footplate, and a prosthesis placed from the incus to the fenestra. Stapedotomy with a small fenestra has replaced total stapedectomy, giving better results and fewer complications
• Results are excellent — closure of the air-bone gap to within 10 dB in 90%
• The rules of case selection matter — operate on the worse ear first; require an air-bone gap of at least 20 to 30 dB and adequate cochlear reserve; and never operate on an only hearing ear, since there is a dead-ear risk of 1%
• Other contraindications — active otosclerosis with a marked Schwartze sign; active middle ear infection; a patient whose occupation involves flying, diving or extremes of pressure; poor general health; and the very elderly, in whom an aid is simpler
• Complications — sensorineural loss or a dead ear (1%); vertigo, transient; perilymph fistula; reparative granuloma; prosthesis displacement or incus necrosis causing late recurrence; a floating or depressed footplate.
• Sodium fluoride may be used in cochlear otosclerosis with a progressive sensorineural loss, on the basis that it promotes maturation of the active focus; the evidence is limited, and it does not help the conductive component
• Cochlear implantation for far-advanced otosclerosis with profound loss, noting that facial nerve stimulation is commoner in these implanted ears because current spreads through demineralised bone
• Counsel about pregnancy, which may accelerate progression, and about the hereditary pattern
• The disease is otospongiosis before it is sclerosis, the active vascular phase preceding the dense one
• The otic capsule is the only bone that does not remodel, which is why a focus of remodelling there is pathological
• Pregnancy accelerates it, and the history should be asked for directly in any young woman with progressive conductive loss
• Penetrance is incomplete at about forty per cent, so the absence of a family history means very little
• Measles RNA has been found in otosclerotic foci, and the incidence has fallen since vaccination became widespread
• The fissula ante fenestram is the usual site, which is why stapes fixation is the usual consequence
• A soft voice suggests conductive loss and a loud voice sensorineural.
• The Schwartze sign indicates active vascular disease and is a relative contraindication to immediate surgery
• Superior canal dehiscence mimics otosclerosis but has present acoustic reflexes and sound-induced vertigo
• Ask about the Tullio phenomenon; vertigo provoked by loud sound points away from otosclerosis and toward dehiscence
• Offer the hearing aid honestly; the cochlea is normal so an aid works very well, and surgery is not the only option