Otosclerosis: progressive hearing loss with a normal eardrum

Otosclerosis is the most common cause of progressive hearing loss in a young to middle-aged adult whose eardrum looks entirely normal on examination. A focus of abnormal bone remodelling in the otic capsule — the dense bone surrounding the inner ear — gradually fixes the stapes footplate at the oval window, stiffening the ossicular chain and reducing sound transmission. The result is a slowly worsening conductive hearing loss that often takes years before the person realises how much they have lost.

Because the eardrum looks normal and the condition progresses gradually, it is regularly misattributed to earwax, eustachian tube dysfunction, or simply “getting older.” The diagnosis is made with a hearing test, not a visual examination, and early identification opens access to very effective treatment options — including a straightforward surgical procedure with excellent outcomes.

A. Core clinical — the AU general-practice framework

Who gets otosclerosis

Per RACGP guidance and the Bhutta 2019 clinical practice guideline:

• Clinically symptomatic disease affects approximately 0.3–0.4% of Australians of European descent; histological otosclerosis (foci visible on temporal bone specimens) is found in 7–12% of the population, most of whom are never symptomatic
• Female to male ratio approximately 2:1 — women present earlier and may progress faster, possibly related to hormonal effects on bone remodelling
• Typical onset 20–40 years, occasionally in adolescence or later after menopause
• Bilateral in approximately 70%, though one side often progresses faster than the other
• Positive family history in around 50% — autosomal dominant inheritance with incomplete penetrance of about 40%; several genetic loci have been identified but routine genetic testing is not used in clinical practice
• Much rarer in East Asian, sub-Saharan African, and Aboriginal and Torres Strait Islander populations

Symptoms

• Gradually progressive hearing loss over months to years — noticed as difficulty on the phone, in quiet settings, or with soft voices
• Low-pitched tinnitus — often the first symptom
• Paracusis Willisii — paradoxical improvement in noisy environments; almost pathognomonic when reported
• Mild balance symptoms in approximately 25% of cases; severe vertigo is not typical and should prompt consideration of an alternative diagnosis
• Aural fullness in some patients

Ask specifically about family history of progressive hearing loss or stapes surgery, any hormonal triggers (pregnancy, combined oral contraceptive, hormone replacement therapy), and occupational noise exposure which may coexist and compound the loss.

Examination

• Otoscopy — the tympanic membrane is normal in appearance; the absence of retraction, effusion, perforation, tympanosclerotic plaques, or cholesteatoma is the critical discriminating finding
• Occasionally a faint pinkish hue is visible through the eardrum over the promontory — the Schwartze sign — indicating active otospongiotic disease
• Tuning-fork tests at 512 Hz — Weber lateralises to the worse ear (the opposite direction to sensorineural loss); Rinne is negative (bone conduction heard longer than air conduction) when the conductive hearing loss exceeds 25 dB

Investigations

Pure-tone audiometry (MBS item 11324) is the diagnostic investigation. Characteristic findings:

• Air-bone gap — typically 25–60 dB, low-frequency predominant
• Carhart notch — a dip in bone conduction at 2,000 Hz (~10–15 dB); this is an audiometric artefact of the mechanical fixation, not a sign of sensorineural damage
• Mixed hearing loss if cochlear involvement is present

Tympanometry (MBS item 11332) typically shows a type As pattern — normal pressure peak but reduced compliance — reflecting the stiffened ossicular chain. A flat type B tympanogram would suggest middle-ear fluid and argue against otosclerosis.

CT of the temporal bones (MBS item 56013) is ordered by the ENT surgeon pre-operatively to confirm the fenestral focus, assess cochlear anatomy, and exclude alternative pathology. It is not part of the GP-initiated assessment.

MRI of the internal auditory meatus is only needed if the hearing loss is asymmetric or has a sensorineural component, to exclude a vestibular schwannoma.

Differential diagnosis (conductive loss, normal eardrum)

• Ossicular discontinuity — trauma history, larger air-bone gap (40–60 dB), type Ad (deep) tympanogram
• Superior semicircular canal dehiscence — autophony, Tullio phenomenon (sound-induced vertigo), low-frequency conductive loss with intact stapedial reflexes; CT confirms
• Paget’s disease of bone — older patient, raised alkaline phosphatase, bony changes elsewhere
• Congenital ossicular fixation — childhood-onset conductive loss, syndromic features in some
• Eustachian tube dysfunction — fluctuating, type C tympanogram, nasal symptoms

B. Evidence — treatment options compared

Per the Bhutta 2019 CPG, eTG, and ASOHNS, three options are supported for fenestral otosclerosis:

1. Hearing aid

• Reversible, no surgical risk, provides immediate benefit
• Behind-the-ear or receiver-in-canal aids work well because cochlear reserve is preserved — the problem is purely conductive
• Trial period is mandatory before purchase; eligible patients can access subsidised aids through the Hearing Services Program
• Does not halt progression of the underlying bony process

2. Stapedotomy (surgery)

• The definitive treatment; preferred over the older stapedectomy in current Australian practice
• A small fenestra (~0.6 mm) is drilled or lasered in the fixed footplate, and a titanium or Teflon piston bridges the gap from the incus to the oval window
• Outcomes: approximately 90% of patients achieve closure of the air-bone gap to within 10 dB at one year per Cochrane review meta-analyses and the Bhutta CPG
• Main serious risk: profound sensorineural hearing loss in the operated ear (~1%); other risks include temporary dizziness, taste alteration from chorda tympani handling (usually resolves), tinnitus changes
• Bilateral surgery is staged — one ear at a time, minimum 6 months apart, with confirmation that the first ear is stable and the patient is satisfied

3. Observation

• Appropriate when loss is mild and functional impact is minimal; review audiogram annually and revisit treatment preference as it progresses

Medical therapy — sodium fluoride (proposed to inhibit otospongiotic activity) and bisphosphonates (alendronate — studied in a small pilot RCT for cochlear otosclerosis) have limited or no robust evidence and are not standard in Australian practice.

Cochlear implant is assessed for patients with severe-profound sensorineural hearing loss from cochlear otosclerosis who are no longer candidates for stapedotomy. Facial nerve stimulation post-implant is a known complication specific to cochlear otosclerosis; specialist centres account for this in surgical planning.

C. Audiological rehabilitation and lifestyle considerations

A hearing aid trial should be offered to all patients as the first step, regardless of surgical candidacy, because it provides immediate functional benefit and does not foreclose surgical options. The Hearing Services Program through Hearing Australia is the key publicly funded pathway in Australia.

Protecting cochlear reserve is important for long-term hearing outcomes:

• Avoid loud noise without hearing protection — recreational and occupational noise adds sensorineural loss on top of the conductive deficit
• Avoid ototoxic medications when alternatives exist (aminoglycosides, high-dose loop diuretics, cisplatin) — discuss with your GP before starting any new medicine

Tinnitus co-existing with otosclerosis often improves after successful stapedotomy, but not always. If tinnitus remains burdensome, tinnitus retraining therapy and sound enrichment strategies can help; a mental health plan via your GP can provide access to a psychologist experienced in tinnitus management.

Workplace adjustments — phone amplification, FM systems, loop induction systems, quieter workstation placement — help maintain employment while awaiting or recovering from surgery. Document these with your employer if applicable.

Driving and commercial licences — significant hearing loss alone is not an automatic bar for standard licensing; commercial licence holders should check the Austroads Assessing Fitness to Drive standards for their vehicle class.

D. Australian operations

Referral pathway:

1. GP confirms the clinical suspicion based on history (progressive hearing loss, normal eardrum, family history, paracusis Willisii), tuning-fork findings, and audiogram
2. Refer to audiology for a formal PTA plus tympanogram if not already done — Hearing Australia can arrange this under the Hearing Services Program for eligible patients
3. Refer to ENT surgeon with the audiogram results, tympanogram, and clinical findings for surgical option discussion and pre-operative CT if surgery is planned
4. Hearing aid trial can run in parallel with the ENT referral for eligible patients through Hearing Australia

MBS items relevant to the GP investigation pathway:

• GP consultation: items 23, 36, 44; complex chronic: items 132, 133
• ATSI health assessment (includes hearing component): item 715
• 75+ assessment: item 707
• GPCCMP from 1 July 2025: items 965 and 967 for ongoing chronic hearing loss
• Audiometry: item 11324; tympanometry: item 11332
• CT temporal bone: item 56013 (ENT-ordered pre-operatively)
• Stapedotomy: MBS item 41476 (ENT specialist); cochlear implant: 41617
• Mental health care plan where hearing loss is contributing to depression or social isolation: items 2715 and 2717

Hearing Services Program eligibility — pensioner concession card holders, DVA Gold/White card holders for hearing-related conditions, Centrelink sickness allowance recipients, NDIS participants, ADF members, and Aboriginal and Torres Strait Islander adults aged 50 and above (threshold lowered from 55). Full details at hearingservices.gov.au.

Telehealth — follow-up consultations after audiometry results or post-operative reviews from ENT are increasingly available via telehealth, particularly for rural and remote patients.

E. Special populations

Women planning pregnancy — discuss the historical association between pregnancy and accelerated progression with an ENT surgeon before conception if otosclerosis is confirmed. Some surgeons recommend completing stapes surgery before a planned pregnancy; others support monitoring through pregnancy with trimester audiograms. This is a shared decision.

Aboriginal and Torres Strait Islander peoples — otosclerosis is rare in Aboriginal and Torres Strait Islander populations, but conductive hearing loss from other causes (chronic otitis media, chronic suppurative otitis media) is highly prevalent. The hearing test findings differ: type B or type C tympanogram, visible TM pathology, and a different audiometric profile. Audiology access via the 715 Health Assessment provides an equitable entry point for any form of hearing loss.

Adolescents and young adults — otosclerosis can begin in the teens. Early-onset progressive conductive loss with a family history warrants audiological assessment and ENT referral even in young people, as the sooner the diagnosis is established, the sooner audiological support and surgical planning can begin.

Older adults with cochlear otosclerosis — when the cochlear otosclerotic focus produces significant sensorineural loss, a cochlear implant may restore useful hearing. Refer to a cochlear implant centre early enough in the progression to preserve implantation candidacy; very dense cochlear otosclerosis can make electrode insertion difficult.

When to escalate

Refer urgently or contact ENT sooner when:

• Sudden change in hearing — otosclerosis causes gradual loss; sudden worsening suggests acute sensorineural loss or perilymph fistula and needs urgent assessment
• Asymmetric or predominantly sensorineural loss — needs MRI of the internal auditory meatus to exclude a vestibular schwannoma before attributing to cochlear otosclerosis
• New severe vertigo or facial weakness — not typical of otosclerosis; consider alternative pathology
• Any otorrhoea or visible tympanic membrane pathology — indicates a different diagnosis (chronic suppurative otitis media, cholesteatoma)
• Post-stapedotomy — sudden hearing drop, severe vertigo, facial weakness, or significant taste change after surgery require urgent ENT review for prosthesis displacement, perilymph fistula, or infection

What this article is and is not

This is general health information drawn from current Australian general practice and ENT guidelines — RACGP, Therapeutic Guidelines, ASOHNS, and the Bhutta 2019 otosclerosis clinical practice guideline — together with Cochrane review data on stapes surgery outcomes. It does not constitute personal medical advice and does not create a doctor–patient relationship.

Diagnosis of otosclerosis and decisions about hearing aids versus surgery are made with your GP, audiologist, and ENT surgeon, taking into account your audiogram, tympanogram, functional impact, family-planning considerations, and personal preference.

For Australian consumer-friendly information: HealthDirect — Otosclerosis, Better Health Channel, Hearing Australia, and Deafness Forum Australia.

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Sources cited

1. RACGP — Hearing loss in adults (Australian Family Physician)
2. Therapeutic Guidelines — Ear conditions (eTG complete)
3. ASOHNS — Australian Society of Otolaryngology Head and Neck Surgery
4. Hearing Australia — Hearing Services Program
5. Department of Health — Hearing Services Program
6. HealthDirect — Otosclerosis
7. Better Health Channel — Hearing problems
8. Bhutta MF et al. Otosclerosis clinical practice guideline. Otolaryngol Head Neck Surg 2019
9. Cochrane — Stapes surgery for otosclerosis
10. Austroads — Assessing Fitness to Drive
11. Deafness Forum Australia