Otosclerosis
On this page
Direct answer
Conductive hearing loss in a young adult woman, with a positive family history, a normal ear canal and a pink glow through the drum, is otosclerosis until proved otherwise. The disease is a primary localised dystrophy of the bony otic capsule in which spongy vascular new bone — the fault lies most often at the fissula ante fenestram, just anterior to the oval window — fixes the stapes footplate and creates a painless, progressive conductive loss, usually bilateral. Rinne turns negative, Weber lateralises to the worse ear, absolute bone conduction stays normal, and the audiogram shows an air–bone gap with the Carhart notch at 2000 Hz. Surgery (stapedotomy with a piston prosthesis) reliably restores hearing; a hearing aid and, for active cochlear disease, sodium fluoride therapy are the alternatives.
What you must remember
- Demographics: young adults, twice as common in women, worse in pregnancy (hormonal influence), familial in about half of cases with autosomal dominant tendency and variable penetrance.
- Site of predilection: the fissula ante fenestram, anterior to the oval window; cochlear (labyrinthine) otosclerosis additionally invades the inner ear and mixes in a sensorineural component.
- Schwartze sign — a flamingo-pink hue of the promontory seen through the tympanic membrane — indicates active, vascular disease.
- Paracusis Willisii: the patient hears better in noisy surroundings, because speech is raised above the patient's soft voice level while normal listeners are masked — characteristic of conductive loss.
- Audiometric triad: conductive air–bone gap, Carhart notch (bone conduction dip at 2000 Hz), tympanogram type As, and absent stapedial reflexes.
- Stapedotomy (small fenestra with a 0.4–0.6 mm teflon or platinum piston from incus to vestibule) has largely replaced total stapedectomy; hearing improves in the great majority, with a small risk of dead ear.
- Sodium fluoride has been used traditionally to hasten maturation of the active spongy focus and protect the cochlea in cochlear otosclerosis.
- Far advanced disease can present with a seemingly "dead" ear and a false negative Rinne — masking or the Stenger test clarifies.
A typical exam case, worked end to end
A 28-year-old woman, three months postpartum, reports slowly worsening hearing in both ears for four years; her mother uses a hearing aid. She has no ear discharge, no tinnitus beyond a mild low-pitched hiss, and no vertigo. Otoscopy shows a normal canal and an intact, translucent drum with a faint pink reflex on the left.
Follow the diagnostic chain the way the viva expects. Tuning forks at 512 Hz: Rinne negative bilaterally, worse on the left; Weber lateralises left; absolute bone conduction equal to the examiner — a conductive loss with an intact cochlea. Pure tone audiometry confirms bilateral conductive loss, say 45 dB on the left, with bone conduction near normal except for a 15 dB dip at 2000 Hz — the Carhart notch, an artefact of stapes fixation that disappears after successful surgery (overclosure). Tympanometry shows reduced compliance (As) with normal middle ear pressure, and stapedial reflexes are absent, abolished before the gap becomes large.
Now the decision. She wants hearing, not tablets. Options are a hearing aid — perfectly reasonable, zero operative risk — or stapedotomy. Under local or general anaesthesia, the tympanomeatal flap is raised, the stapes superstructure removed, a small hole made in the fixed footplate, and a piston wire crimped onto the incus long process so vibrations drive the perilymph directly. Expect an air–bone gap closure to under 10 dB in most hands; warn about taste disturbance from chorda tympani handling, and about the rare but real sensorineural loss and vertigo. If she instead chooses observation with a hearing aid, nothing is lost — surgery remains available later.
Where students slip
Two confusions recur every year. First, candidates read the Carhart notch as sensorineural disease because it sits on the bone conduction line; it is a mechanical artefact of stapes fixation at 2000 Hz and its disappearance (overclosure) after surgery confirms exactly that. Second, they forget that otosclerosis is only one cause of a conductive gap — the differential includes ossicular discontinuity, tympanosclerosis, congenital stapes fixation and middle ear effusion — and the differentiating pattern is exactly what the objective tests provide: As tympanogram with absent reflexes in otosclerosis versus Ad with absent reflexes in discontinuity. A final trap is the cochlear otosclerosis patient who presents with mixed or purely sensorineural loss, a positive family history and Schwartze sign; the exam expects you to say the diagnosis is clinical-plus-imaging (high-resolution CT may show a hypodense halo around the cochlea) rather than audiometric alone.
Frequently asked questions
Which site is most commonly involved in otosclerosis?
The fissula ante fenestram, an embryological cleft anterior to the oval window; disease there anchors the stapes footplate and produces conductive hearing loss.
What is the Carhart notch and why does it matter?
A bone conduction threshold dip at 2000 Hz produced by stapes fixation; it is a conductive artefact, and its disappearance after stapedotomy confirms the mechanical nature of the loss.
Why do patients with otosclerosis hear better in noise?
Paracusis Willisii — background noise raises speakers' voices above the patient's conductive threshold, so they follow conversation better than normal listeners do in the same din.
What does tympanometry with acoustic reflexes show in otosclerosis?
A type As curve (reduced compliance at normal pressure) with absent stapedial reflexes — the stiffness pattern that separates it from the hypermobile Ad pattern of ossicular discontinuity.
What are the surgical options and their principal risks?
Stapedotomy with piston insertion (or stapedectomy) restores hearing in most patients; risks include sensorineural hearing loss, vertigo, facial palsy, chorda tympani injury with dysgeusia and perilymph gush.