What otosclerosis is
The inner ear sits inside the densest bone in the body. In otosclerosis, small areas of that bone are replaced by softer, more active bone, and later by new hard bone. The process is painless and invisible from outside. It becomes noticeable when it reaches the oval window — the opening where the stapes, the third and smallest of the middle-ear bones, sits like a piston against the fluid of the inner ear.
When the footplate of the stapes becomes fixed in new bone, the piston stops moving freely. Sound still reaches the eardrum, the eardrum still vibrates, the malleus and incus still move — but the movement is not delivered into the cochlea. The result is a conductive hearing loss: the inner ear is fine, but the sound is not getting in.
Otosclerosis typically appears between the ages of 20 and 45, is more often diagnosed in women, and affects both ears in most people, usually to different degrees.
How it sounds and feels
- Gradual hearing loss, often noticed first for low, soft voices or in one ear on the telephone.
- Hearing sometimes seems better in background noise (paracusis), because people raise their voices and the background is attenuated by the conductive loss.
- A quiet, low voice of your own — people with conductive loss often speak softly, because they hear their own voice well through bone.
- Tinnitus is common, usually a low hum or rush, and often improves when hearing improves.
- Dizziness is uncommon and, if prominent, points towards another diagnosis or an additional problem.
Diagnosis
Otosclerosis is a clinical and audiological diagnosis. The eardrum looks normal. The audiogram shows air-conduction thresholds worse than bone-conduction thresholds — an air-bone gap — often with a characteristic dip in bone conduction around 2 kHz (the Carhart notch), which is a mechanical artefact of stapes fixation rather than true inner-ear damage.
Tympanometry usually shows a normal or stiff (As) curve, and the stapedial reflex is absent or shows an early on-off pattern. A CT scan is not required to make the diagnosis, but is useful in selected situations: an unusual audiogram, previous surgery, a possible alternative cause of conductive loss, or when planning surgery in a difficult ear.
Differential diagnosis of a normal eardrum with an air-bone gap
Stapes fixation is the most common cause, but not the only one. Consider congenital or acquired malleus or incus fixation, ossicular discontinuity after trauma, tympanosclerosis, and — importantly — third-window lesions such as superior semicircular canal dehiscence and enlarged vestibular aqueduct. Third-window lesions typically show a low-frequency air-bone gap with present stapedial reflexes, supranormal bone conduction, and reduced cervical VEMP thresholds. Operating on a dehiscence as if it were otosclerosis does not close the gap and can harm the inner ear; when reflexes are present or symptoms include sound- or pressure-induced vertigo, obtain a temporal-bone CT before recommending surgery.
Your options
There are three reasonable responses, and moving between them over time is normal.
Observation. If the loss is mild and not troubling, doing nothing yet is a legitimate choice. Repeat the audiogram every one to two years, or sooner if hearing changes. Nothing is lost by waiting; stapes fixation is not an emergency and surgical results do not depend on operating early.
Hearing aids. Because the inner ear is usually healthy, otosclerosis is one of the hearing losses that hearing aids treat best. Amplification is precise, speech understanding is typically excellent, and there is no risk to the inner ear. The costs are the ones that come with any device: daily use, maintenance, cosmetics for some, and the fact that amplification does not restore natural sound transmission.
Stapedotomy. The fixed footplate is bypassed: a small opening is made in it and a tiny prosthesis connects the incus to the inner-ear fluid. In most suitable ears this closes the air-bone gap and makes a hearing aid unnecessary. Against this stand a small but irreversible risk of worse inner-ear hearing, temporary dizziness and taste change, and the possibility that the result changes over years.
The hearing aid or stapedotomy page compares these on equal terms. The stapedotomy page describes the operation itself.
What tips the balance
- The size of the air-bone gap. A large, stable gap with good bone conduction is where surgery has the most to offer.
- The opposite ear. In an only-hearing ear, or when the other ear has already been operated with an uncertain result, the calculation changes.
- Speech scores and bone conduction. When the inner ear is also affected (mixed loss), closing the gap helps less and a hearing aid may still be needed afterwards.
- Your priorities. Independence from a device, work, music, the ability to tolerate a small surgical risk, time available for recovery.
- Future options. Whatever is decided now should not close off what may be needed in twenty years.
Bilateral disease
When both ears are affected, the first operation is normally proposed for the worse-hearing ear, and the second is only considered once the result of the first is stable — typically after six months to a year. Many people choose surgery on one side and a hearing aid on the other, which gives good binaural hearing with a single surgical risk.
On the other sites
- otosclerose.nl — independent patient information on otosclerosis in English and Dutch, with a clinical layer for professionals, an audiogram simulator with an age- and sex-dependent reference band (ISO 7029), an air-bone gap explainer and a printable question list (tools currently in Dutch).
- grolman-orl.fr — otosclerosis and stapedotomy as handled in the Colombiers practice, in French, English and Italian.
Common questions
Is otosclerosis hereditary?
It runs in families in a substantial minority of cases, with variable expression: a parent may have had a mild, unrecognised loss. Many people have no known family history. Having the gene pattern does not mean the hearing loss will become severe.
Does otosclerosis always get worse?
It usually progresses slowly over years, then often stabilises. Pregnancy and hormonal changes are traditionally reported to accelerate it, though the evidence is mixed. Progression is one reason to repeat the audiogram at intervals rather than decide everything at the first visit.
Can otosclerosis affect both ears?
Yes; it is bilateral in roughly two-thirds to three-quarters of cases, often asymmetrically. This matters: the state of the second ear is one of the most important factors in any decision about the first.
Is there a medication for otosclerosis?
Sodium fluoride and bisphosphonates have been used to slow the bone process, particularly when the inner ear is involved. The evidence is weak and the practice varies between countries. Neither reverses stapes fixation.
This page provides general educational information. It cannot replace an individual assessment, which depends on a full history, examination, audiometry and, where relevant, imaging. If you have sudden hearing loss, severe pain, facial weakness, severe dizziness or discharge with fever, seek medical care promptly.