What is the approach to differential diagnosis of sensorineural hearing loss?

Differential Diagnosis of Sensorineural Hearing Loss

Initial Diagnostic Approach

The first critical step is to distinguish sensorineural hearing loss (SNHL) from conductive hearing loss (CHL) using tuning fork tests (Weber and Rinne) at initial presentation, followed by formal audiometry within 14 days to confirm the diagnosis. 1, 2

Bedside Differentiation: Tuning Fork Tests

Perform Weber and Rinne tests immediately to categorize the hearing loss:

• Weber test: Place a vibrating 256 or 512 Hz tuning fork at the midline forehead or maxillary teeth 2

  • SNHL: Sound lateralizes to the unaffected ear 2
  • CHL: Sound lateralizes to the affected ear 2

• Rinne test: Place vibrating tuning fork on mastoid bone, then move to ear canal entrance 2

  • SNHL: Positive result (air conduction > bone conduction) in both ears 2
  • CHL: Negative result (bone conduction > air conduction) in affected ear 2

Audiometric Confirmation

Obtain formal audiometry within 14 days of symptom onset to confirm SNHL, defined as ≥30 dB hearing loss at 3 consecutive frequencies occurring within 72 hours. 1, 3

Categorizing SNHL: Idiopathic vs. Secondary

History and Physical Examination Red Flags

Assess specifically for features suggesting non-idiopathic causes: 1

• Bilateral sudden hearing loss: Suggests autoimmune, infectious, or toxic etiologies 1
• Recurrent episodes: Consider autoimmune inner ear disease, Menière's disease, or migraine-associated hearing loss 1
• Focal neurologic findings: Mandates urgent evaluation for stroke or central nervous system pathology 1
• Vertigo with hearing loss: Consider Menière's disease, labyrinthitis, or posterior circulation stroke 4, 3

Common Etiologies by Category

Primary (Idiopathic) SNHL accounts for the majority of cases when no identifiable cause is found after appropriate workup 3, 5

Secondary SNHL causes to systematically exclude: 5

• Neoplastic: Acoustic neuroma (vestibular schwannoma), cerebellopontine angle tumors 4, 6, 5
• Vascular: Posterior circulation stroke, vertebrobasilar insufficiency 7, 5
• Infectious: Viral labyrinthitis, meningitis, Lyme disease 4, 5
• Autoimmune: Systemic lupus erythematosus, Cogan syndrome, granulomatosis with polyangiitis 7, 5
• Traumatic: Temporal bone fracture, perilymphatic fistula, noise trauma 6
• Toxic: Aminoglycosides, cisplatin, loop diuretics 7
• Metabolic: Hypothyroidism, diabetes mellitus 7

Mandatory Workup for Retrocochlear Pathology

All patients with confirmed SNHL must be evaluated for retrocochlear pathology using MRI (preferred) or auditory brainstem response (ABR) testing. 1

• MRI with gadolinium is the gold standard for detecting acoustic neuromas and cerebellopontine angle lesions 1, 4, 6
• ABR testing is an alternative when MRI is contraindicated (pacemakers, severe claustrophobia, financial constraints) 1, 4
• Timing is not specified in guidelines, but should be ordered during initial evaluation 1

What NOT to Do

Avoid routine head CT in the initial evaluation—it has very low yield, exposes patients to unnecessary radiation, and cannot detect early brainstem infarcts or small acoustic neuromas. 1

Do not obtain routine laboratory tests (CBC, metabolic panel, inflammatory markers) in patients with sudden SNHL unless history and physical examination suggest specific systemic disease. 1

Anatomic Classification for Differential

Cochlear (Sensory) SNHL

Imaging findings on CT or MRI may reveal: 6

• Bony labyrinth abnormalities: Demineralization (otosclerosis), congenital deformities, traumatic lesions, erosive processes 6
• Membranous labyrinth abnormalities: Enhancement on MRI (inflammation), hemorrhage, obliteration 6

Retrocochlear (Neural) SNHL

Requires high-resolution MRI evaluation of: 6

• Internal auditory canal 6
• Cerebellopontine angle 6
• Brain stem 6
• Thalamus and temporal lobe 6

Progressive vs. Sudden SNHL

For progressive SNHL specifically, expand the differential to include: 7

• Hereditary: Genetic syndromes, familial progressive hearing loss 7
• Developmental: Congenital inner ear malformations 7
• Degenerative: Presbycusis, though this is typically bilateral and symmetric 7

Critical Pitfalls to Avoid

Do not delay audiometric confirmation beyond 14 days—this is essential for accurate diagnosis and treatment decisions. 1

Do not assume bilateral symmetric hearing loss is simply age-related presbycusis without excluding autoimmune or toxic causes, especially if progression is rapid. 7

Do not skip retrocochlear imaging—acoustic neuromas can present with sudden hearing loss as the only symptom, and early detection significantly impacts surgical outcomes and morbidity. 1, 4

Remove impacted cerumen before establishing a diagnosis, as it causes conductive hearing loss that can confound the clinical picture. 2