Sensorineural and Conductive Hearing Loss
Hearing loss categorized by site of pathology: conductive (outer/middle ear) vs sensorineural (cochlea/CN VIII/central).
Also known as: hearing loss, SNHL, conductive hearing loss, presbycusis, sudden sensorineural hearing loss, SSNHL
Overview
Hearing loss is a reduction in auditory acuity. Conductive hearing loss (CHL) results from impaired sound transmission through the external or middle ear. Sensorineural hearing loss (SNHL) results from damage to the cochlea, cochlear nerve, or central auditory pathways. Mixed loss has both components.
Epidemiology
Affects ~15% of US adults; prevalence rises with age — ~50% of adults ≥75 have disabling hearing loss. Presbycusis is the most common form of adult SNHL. Sudden SNHL incidence ~5-27/100,000/year.
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Risk factors
- Age (presbycusis — high-frequency SNHL)
- Chronic noise exposure (occupational, recreational firearms, music)
- Ototoxic medications: aminoglycosides (gentamicin, tobramycin), platinum chemotherapy (cisplatin), loop diuretics (high-dose furosemide), salicylates, vancomycin, macrolides
- Family history (otosclerosis, hereditary SNHL)
- Head trauma, barotrauma
- Recurrent otitis media → conductive loss
- Congenital infections (CMV, rubella, syphilis), neonatal hypoxia, hyperbilirubinemia
- Cardiovascular disease, diabetes, smoking
Pathophysiology
Sound is conducted from pinna → EAC → TM → ossicles → oval window (mechanical) → cochlea → hair cells → CN VIII → brainstem → cortex (neural). CHL: cerumen, effusion, TM perforation, ossicular fixation (otosclerosis) or discontinuity. SNHL: cochlear hair cell loss (presbycusis, noise-induced), endolymphatic hydrops (Meniere), retrocochlear (vestibular schwannoma), or central lesions.
Clinical presentation
Symptoms
- Difficulty understanding speech, especially in noisy settings
- Asking others to repeat; increasing TV/radio volume
- Tinnitus (often associated with SNHL)
- Vertigo or imbalance (suggests inner ear or CN VIII)
- Ear fullness or aural pressure (effusion, Meniere)
- Otalgia, otorrhea (otitis media, externa, cholesteatoma)
Signs / physical exam
- Otoscopy: cerumen, effusion, perforation, retraction pocket, mass
- Weber test: tuning fork on midline forehead. CHL lateralizes to AFFECTED ear. SNHL lateralizes to UNAFFECTED ear.
- Rinne test: tuning fork on mastoid, then at ear canal. Normal/SNHL: AC > BC (positive Rinne). CHL: BC > AC (negative Rinne).
- Whisper test, finger rub for bedside screening
- Speech recognition disproportionately poor for the degree of pure-tone loss suggests retrocochlear (CN VIII) pathology
Classic findings
CHL: negative Rinne (BC > AC), Weber lateralizes to affected ear. SNHL: positive Rinne, Weber lateralizes to unaffected ear.
Differential diagnosis
- Cerumen impaction — Conductive loss, ear fullness, exam shows occluding wax; treat with ceruminolytic, irrigation, or curettage
- Otosclerosis — Progressive conductive loss in young adult, family history, Schwartze sign (pink TM), low-frequency loss; surgical stapedectomy or hearing aid
- Presbycusis — Gradual bilateral high-frequency SNHL in older adult, difficulty understanding speech in noise; hearing aids
- Noise-induced hearing loss — Bilateral SNHL with notch at 4 kHz on audiogram; occupational/recreational noise exposure
- Sudden sensorineural hearing loss (SSNHL) — ≥30 dB loss over ≥3 contiguous frequencies within 72 h; idiopathic in 90%; urgent oral corticosteroids + MRI to exclude vestibular schwannoma
- Meniere disease — Episodic vertigo + low-frequency SNHL + tinnitus + aural fullness; low-salt diet, diuretics, intratympanic steroids/gentamicin
- Vestibular schwannoma (acoustic neuroma) — Unilateral progressive SNHL, tinnitus, imbalance; MRI internal auditory canal with gadolinium
- Cholesteatoma — Conductive loss, foul otorrhea, retraction pocket or attic perforation; CT and surgical excision
- Ototoxic drug exposure — Bilateral SNHL temporally related to aminoglycoside, cisplatin, or loop diuretic; high-frequency loss earliest
Diagnostic workup
Diagnostic criteria
Type determined by audiogram: CHL = air-bone gap ≥10 dB with normal bone conduction. SNHL = both AC and BC thresholds elevated with no air-bone gap. Mixed = elevated BC plus an air-bone gap. SSNHL = ≥30 dB SNHL across ≥3 contiguous frequencies developing within 72 h.
Labs
- Not routine; consider TSH, ANA, RPR/FTA-ABS, Lyme, autoimmune panel in atypical or rapidly progressive SNHL
- Genetic testing (GJB2/connexin 26) for congenital nonsyndromic SNHL
Imaging
- Pure-tone audiometry — defines type, severity (mild 26-40 dB, moderate 41-55, moderately severe 56-70, severe 71-90, profound >90 dB), and configuration
- Tympanometry — middle ear pressure/effusion
- Speech audiometry — word recognition score
- MRI internal auditory canals with gadolinium — asymmetric SNHL, sudden SNHL, retrocochlear symptoms
- CT temporal bone — conductive loss with normal otoscopy (otosclerosis, ossicular abnormality, cholesteatoma extent)
- Newborn hearing screen — otoacoustic emissions (OAE) and/or automated auditory brainstem response (AABR) before discharge
Diagnostic algorithm
| Test | Normal | Conductive Loss | Sensorineural Loss |
|---|---|---|---|
| Weber (midline forehead) | Midline | Lateralizes to AFFECTED ear | Lateralizes to UNAFFECTED ear |
| Rinne (mastoid then EAC) | AC > BC (positive) | BC > AC (negative) on affected side | AC > BC (positive) bilaterally |
| Audiogram | All thresholds <25 dB | Air-bone gap ≥10 dB; BC normal | Both AC and BC elevated; no air-bone gap |
| Tympanometry | Type A | Type B (effusion) or As (otosclerosis) | Type A |
| Typical etiologies | — | Cerumen, OME, perforation, otosclerosis | Presbycusis, noise, ototoxicity, Meniere, vestibular schwannoma |
Treatment
First-line
- Cerumen impaction: ceruminolytic (carbamide peroxide), warm-water irrigation, or curettage under direct visualization
- Conductive loss from OME persisting >3 months with hearing loss: tympanostomy tubes
- Otosclerosis: hearing aids OR surgical stapedectomy/stapedotomy
- Presbycusis and chronic SNHL: hearing aids; cochlear implant if severe-to-profound bilateral SNHL with poor aided speech recognition
- Sudden SNHL: oral corticosteroids (prednisone 1 mg/kg/day × 7-14 days, then taper) within 2 weeks of onset; intratympanic dexamethasone salvage if oral course incomplete response
- Counsel on hearing protection (earplugs/muffs) for ongoing noise exposure
Second-line / adjunct
- Intratympanic dexamethasone for SSNHL — primary or salvage therapy, especially if systemic steroids contraindicated (diabetes, immunosuppression)
- Cochlear implantation for severe-to-profound bilateral SNHL with limited benefit from hearing aids
- Bone-anchored hearing aid (BAHA) for unilateral SNHL or chronic conductive loss
- Auditory rehabilitation, lip-reading instruction, assistive listening devices
- Treat underlying cause: discontinue ototoxic medication, manage Meniere with diet/diuretic, surgical removal of vestibular schwannoma when appropriate
Complications
- Speech and language delay in untreated congenital/early-childhood hearing loss
- Social isolation, depression
- Cognitive decline and increased dementia risk in untreated adult hearing loss
- Falls (linked to age-related hearing loss)
- Reduced occupational performance and earning capacity
PANCE pearls
- Weber lateralizes to BAD ear in conductive loss; to GOOD ear in sensorineural loss.
- Sudden SNHL is an ENT emergency — give oral steroids within 2 weeks AND order MRI internal auditory canals (5-10% have vestibular schwannoma).
- Universal newborn hearing screening: failed screen → confirmatory audiologic evaluation by 3 months; intervention by 6 months ('1-3-6 rule').
- 4 kHz notch on audiogram = noise-induced hearing loss.
- Bilateral conductive loss in a young adult with family history and normal otoscopy → otosclerosis.
References
- AAO-HNS 2019 — Chandrasekhar SS et al. Clinical Practice Guideline: Sudden Hearing Loss (Update). Otolaryngol Head Neck Surg 2019;161(1S):S1-S45
- USPSTF 2021 — Screening for Hearing Loss in Older Adults. JAMA 2021;325(12):1196-1201 (I statement)
- AAP/JCIH 2019 — Joint Committee on Infant Hearing. Year 2019 Position Statement. J Early Hear Detect Interv 2019
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