A 35-year-old woman from Tamil Nadu presents with a 3-year history of painless, progressive hearing loss and recurrent ear discharge from the right ear since childhood. She reports occasional vertigo triggered by loud sounds (Tullio phenomenon). On otoscopy, a white, pearly mass is visible in the posterosuperior external auditory canal. Tragal pressure causes vertigo and nystagmus. Weber test shows conductive hearing loss on the right. What is the most likely diagnosis and what is the underlying mechanism of the Tullio phenomenon?

Explanation

## Diagnosis: Cholesteatoma with Labyrinthine Fistula ### Clinical Presentation Analysis **Key Point:** The white, pearly mass in the posterosuperior EAC with sound-induced vertigo (Tullio phenomenon) indicates cholesteatoma with labyrinthine fistula. ### Diagnostic Features | Feature | Finding | Interpretation | |---------|---------|----------------| | **Mass appearance** | White, pearly | Keratinous debris of cholesteatoma | | **Location** | Posterosuperior EAC | Typical site for cholesteatoma | | **Tullio phenomenon** | Vertigo with loud sounds | Labyrinthine fistula with abnormal sound transmission | | **Tragal pressure vertigo** | Positive | Fistula test — confirms labyrinthine involvement | | **Conductive hearing loss** | Present | Ossicular erosion or fixation | | **Chronic otorrhoea** | Since childhood | Long-standing disease with bone erosion | ### Pathophysiology of Tullio Phenomenon **High-Yield:** Tullio phenomenon occurs when a labyrinthine fistula (usually lateral semicircular canal) allows direct sound pressure transmission to the membranous labyrinth, bypassing normal ossicular mechanics. ```mermaid flowchart TD A[Cholesteatoma expands]:::outcome --> B[Erodes lateral SCC]:::outcome B --> C[Labyrinthine fistula created]:::outcome C --> D[Sound pressure directly stimulates membranous labyrinth]:::action D --> E[Abnormal vestibular input]:::outcome E --> F[Vertigo + nystagmus]:::urgent G[Tragal pressure] --> H[Increases EAC pressure]:::action H --> I[Transmits through fistula]:::action I --> F ``` ### Mechanism of Fistula Test 1. **Normal ear:** Tragal pressure increases EAC pressure but does not reach labyrinth (intact osseous labyrinth) 2. **Fistula present:** Pressure transmitted directly through bony defect to membranous labyrinth 3. **Result:** Stimulates vestibular end organs → vertigo and nystagmus (Hennebert sign) **Clinical Pearl:** A positive fistula test (tragal pressure causing vertigo) is highly specific for labyrinthine fistula and indicates advanced cholesteatoma with bone erosion. ### Tullio Phenomenon: Mechanism **Key Point:** Sound-induced vertigo occurs because: - Normal route: Sound → ossicles → oval window → perilymph → normal vestibular response - Fistula route: Sound → EAC → fistula → membranous labyrinth → abnormal direct stimulation → vertigo The fistula bypasses normal impedance matching, allowing excessive pressure transmission. ### Complications Indicated by These Findings **Warning:** Labyrinthine fistula indicates: - Advanced bone erosion (high surgical risk) - Risk of labyrinthitis ossificans (permanent sensorineural hearing loss) - Risk of meningitis (if erosion extends to dura) - Risk of facial nerve paralysis (if facial canal eroded) ### Management **High-Yield:** Urgent surgical intervention (mastoidectomy with ossiculoplasty) is indicated to: 1. Remove cholesteatoma 2. Prevent intracranial spread 3. Prevent labyrinthitis ossificans 4. Restore hearing if possible