## Clinical Interpretation This patient has a **conductive hearing loss** with normal otoscopy and tympanometry, indicating normal middle ear pressure and tympanic membrane. The air-bone gap of 35 dB at 2 kHz is pathognomonic for ossicular dysfunction (likely stapes fixation, ossicular discontinuity, or incus erosion). ## Diagnostic Rationale **Key Point:** When conductive hearing loss is confirmed audiologically but otoscopy and tympanometry are normal, imaging is mandatory to identify the ossicular lesion before surgical planning. **High-Yield:** The normal tympanogram rules out: - Otitis media with effusion - Tympanic membrane perforation - Eustachian tube dysfunction This narrows the differential to ossicular pathology, which requires **structural imaging**. ## Why HRCT Temporal Bone? | Finding | Diagnosis | Surgical Implication | |---------|-----------|---------------------| | Fixed stapes footplate | Otosclerosis | Stapedectomy | | Incus erosion/discontinuity | Chronic otitis media / trauma | Ossicular reconstruction | | Malleus fixation | Congenital anomaly | Ossiculoplasty | | Normal ossicles | Stapes fixation (early otosclerosis) | Stapedectomy ± imaging | **Clinical Pearl:** HRCT has superior sensitivity (>95%) for detecting ossicular discontinuity, stapes fixation, and erosive lesions compared to plain radiographs. It is the gold standard for preoperative planning in conductive hearing loss with normal otoscopy. ## Management Algorithm ```mermaid flowchart TD A[Conductive hearing loss + normal otoscopy]:::outcome --> B{Tympanometry normal?}:::decision B -->|Yes| C[Ossicular pathology suspected]:::outcome C --> D[HRCT temporal bone]:::action D --> E{Stapes fixation?}:::decision E -->|Yes| F[Stapedectomy]:::action E -->|No| G[Ossicular reconstruction]:::action B -->|No| H[Eustachian tube dysfunction / OME]:::outcome H --> I[Conservative management ± grommet]:::action ``` 
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