A 68-year-old woman from Mumbai presents with sudden onset unilateral hearing loss in the left ear over 48 hours, accompanied by vertigo and tinnitus. She denies ear discharge or trauma. Otoscopy is normal. Weber test lateralizes to the right ear. Rinne test shows air conduction better than bone conduction on the left. Pure tone audiometry reveals a 50 dB hearing loss at 4 kHz with no air-bone gap. Tympanometry is normal. What is the most likely diagnosis?

Explanation

## Diagnosis: Sudden Sensorineural Hearing Loss (SSNHL) ### Clinical Reasoning **Key Point:** Sudden sensorineural hearing loss is defined as a loss of ≥30 dB over ≥3 contiguous frequencies occurring within 72 hours. This patient meets all criteria: acute onset (48 hours), significant loss (50 dB at 4 kHz), and no air-bone gap. **High-Yield:** The absence of an air-bone gap is the critical finding that excludes conductive pathology. In SSNHL: - Both air conduction (AC) and bone conduction (BC) thresholds are equally elevated - No ABG (AC − BC ≤10 dB) - Rinne test shows AC > BC (normal relationship preserved, but both elevated) - Tympanometry is normal (rules out middle ear pathology) ### Audiometric Pattern ```mermaid flowchart TD A[Sudden hearing loss < 72 hours]:::outcome --> B{Air-bone gap present?}:::decision B -->|Yes, ABG ≥ 20 dB| C[Conductive loss]:::outcome B -->|No, ABG ≤ 10 dB| D[Sensorineural loss]:::outcome D --> E{Unilateral?}:::decision E -->|Yes| F[SSNHL]:::outcome E -->|No| G[Bilateral SSNHL<br/>rare]:::outcome F --> H[Urgent MRI + Corticosteroids]:::action ``` ### Differential Diagnosis: Acute Hearing Loss | Feature | SSNHL | Acute OME | Ossicular Dislocation | |---------|-------|-----------|----------------------| | **Onset** | Hours–72 h | Days–weeks | Acute (post-trauma) | | **Air-bone gap** | None (≤10 dB) | Present (20–40 dB) | Present (20–50 dB) | | **Tympanometry** | Normal (Type A) | Flat (Type B) | Normal or reduced | | **Otoscopy** | Normal | Fluid level, dull TM | Normal or hemotympanum | | **Vertigo** | Common | Rare | Rare unless labyrinthine | | **Tinnitus** | Common | Uncommon | Uncommon | **Clinical Pearl:** The triad of sudden hearing loss + vertigo + tinnitus suggests **labyrinthitis** or **viral inner ear infection**, the most common cause of SSNHL. Other etiologies include: - Vascular insufficiency (anterior inferior cerebellar artery thrombosis) - Autoimmune inner ear disease - Viral infection (mumps, measles, HSV, CMV) - Idiopathic (60% of cases) ### Why Normal Tympanometry Excludes Middle Ear Pathology **Tip:** Tympanometry Type A (normal compliance, normal pressure) rules out: - Otitis media with effusion (Type B: flat) - Eustachian tube dysfunction (Type C: negative pressure) - Ossicular fixation (Type A with reduced compliance) This single test confirms the pathology is **beyond the middle ear** (i.e., cochlea or retrocochlear). ### Management 1. **Urgent MRI with contrast:** Rule out retrocochlear pathology (acoustic neuroma, MS) 2. **Corticosteroids:** High-dose oral or IV within 2 weeks of onset (best efficacy within 72 hours) 3. **Audiometry:** Repeat at 1–2 weeks to assess recovery 4. **Counseling:** Spontaneous recovery occurs in 30–60% of cases **High-Yield:** SSNHL is a medical emergency. Delay in treatment worsens prognosis. Corticosteroids initiated within 72 hours have the best evidence for recovery.