Conductive vs Sensorineural Hearing Loss: How to Tell Them Apart
Both conductive and sensorineural hearing loss present with decreased hearing, and both can be unilateral or bilateral, gradual or sudden. The core axis that separates them is anatomical: conductive loss arises from a mechanical problem in the external or middle ear (blocking sound transmission to the cochlea), whereas sensorineural loss arises from damage to the inner ear (cochlea) or the vestibulocochlear nerve (CN VIII). Weber and Rinne tuning-fork tests are the fastest way to localize the lesion at the bedside.
How to tell them apart
| Feature | Conductive Hearing Loss | Sensorineural Hearing Loss |
|---|---|---|
| Site of lesion | External or middle ear — a mechanical obstruction to sound conduction | Inner ear (cochlea) or cochlear nerve (CN VIII) |
| Weber test (tuning fork on forehead) | Lateralizes to the affected (abnormal) ear | Lateralizes to the normal (unaffected) ear |
| Rinne test (air vs. bone conduction) | Rinne negative — bone conduction ≥ air conduction in the affected ear | Rinne positive but diminished — air conduction still > bone conduction, though overall reduced |
| Representative causes | Cerumen impaction, otitis media/externa, tympanic membrane perforation, otosclerosis, cholesteatoma, ossicular chain disruption | Presbycusis, noise-induced loss, ototoxic drugs (aminoglycosides, loop diuretics, cisplatin), Ménière's disease, vestibular schwannoma, sudden sensorineural hearing loss |
| Otoscopy findings | Often abnormal — cerumen plug, bulging/erythematous or perforated TM, pearly white mass (cholesteatoma); TM normal in otosclerosis | Typically normal external canal and tympanic membrane |
| Associated symptoms pointing to etiology | Ear pain, otorrhea (including foul-smelling in cholesteatoma), fullness from obstruction | Episodic vertigo, tinnitus, and aural fullness (Ménière's); progressive unilateral loss with disequilibrium (vestibular schwannoma) |
| Reversibility | Often correctable (cerumen removal, treating infection, stapedectomy, surgical repair) | Frequently permanent; management often supportive (hearing aids) or directed at the underlying cause |
| Red-flag workup | Otoscopy and treatment of the mechanical cause usually suffices | Asymmetric sensorineural loss requires MRI to rule out vestibular schwannoma |
The reasoning
Start by localizing the lesion, not by guessing the disease. The Weber and Rinne tuning-fork tests are the anchor: Weber lateralizing to the bad ear plus a negative Rinne pins the problem to sound conduction in the external or middle ear, while Weber lateralizing to the good ear with a positive-but-diminished Rinne places the lesion in the cochlea or CN VIII. Then use otoscopy to identify a mechanical cause (wax, infection, perforation, cholesteatoma) that confirms a conductive picture; a normal exam with sensorineural tuning-fork findings shifts you toward inner ear or nerve pathology. Finally, let the associated features refine the etiology — episodic vertigo with tinnitus and aural fullness suggests Ménière's, while progressive asymmetric loss mandates MRI to exclude vestibular schwannoma.
Key tests
- Weber test: lateralizes to the affected ear in conductive loss, but to the normal ear in sensorineural loss.
- Rinne test: negative (bone conduction ≥ air conduction) in conductive loss; positive but diminished (air > bone conduction) in sensorineural loss.
- Otoscopy: reveals a mechanical cause (cerumen, bulging/perforated TM, cholesteatoma) in conductive loss, whereas the canal and TM are usually normal in sensorineural loss.
- Audiometry: shows an air-bone gap (conductive component) in conductive loss, as in otosclerosis with a normal TM; sensorineural loss shows reduced air and bone conduction together.
- MRI with gadolinium: obtained for asymmetric sensorineural loss to identify an enhancing cerebellopontine angle mass (vestibular schwannoma) — not indicated for a straightforward conductive lesion.
What they share
- Decreased hearing (hypoacusis) as the presenting symptom
- Can present unilaterally or bilaterally
- May be accompanied by tinnitus
- Can have a progressive, gradual onset (e.g., otosclerosis vs. presbycusis) or a sudden onset
Pitfalls
- Confusing Weber lateralization: it goes TOWARD the affected ear in conductive loss but AWAY (to the normal ear) in sensorineural loss — reversing these is a classic exam trap.
- Forgetting that Rinne remains 'positive' (air > bone) in sensorineural loss, just globally reduced; only conductive loss flips Rinne to negative.
- Missing that otosclerosis has a normal tympanic membrane on otoscopy despite causing conductive loss — a normal-looking ear does not exclude a conductive cause.
- Failing to order MRI for asymmetric sensorineural hearing loss and thereby overlooking a vestibular schwannoma.
- Overlooking that a single etiology like cholesteatoma can begin as conductive loss but erode further and cause vertigo or facial nerve palsy, blurring the clean division.
Practice this the way the exam tests it — on branching cases where your decisions shape the patient.