A 4-year-old boy with acute suppurative otitis media and a bulging tympanic membrane develops spontaneous perforation with purulent discharge. The child has persistent fever and otalgia despite antibiotic therapy for 5 days. The mastoid region shows mild tenderness and postauricular swelling. Which investigation is most appropriate to assess for mastoiditis?

## Investigation for Suspected Mastoiditis Complication ### Clinical Context: ASOM with Perforation and Persistent Symptoms **Key Point:** When acute suppurative otitis media progresses to mastoiditis (evidenced by postauricular swelling, tenderness, and persistent symptoms despite antibiotics), high-resolution CT temporal bone is the investigation of choice to confirm bony involvement and guide surgical intervention. ### Why HRCT Temporal Bone in This Scenario? HRCT is the gold standard for detecting mastoiditis because it: 1. **Visualizes bony architecture** = shows loss of mastoid air cell definition, coalescence of air cells, and cortical erosion 2. **Detects subperiosteal abscess** = critical for surgical planning (cortical mastoidectomy vs. simple drainage) 3. **Identifies complications** = facial nerve canal erosion, sigmoid sinus thrombosis, intracranial extension 4. **High sensitivity and specificity** = superior to plain radiographs or clinical examination alone 5. **Guides surgical approach** = determines extent of mastoidectomy needed ### HRCT Findings in Mastoiditis | Finding | Significance | | --- | --- | | Loss of air cell definition | Early mastoiditis | | Coalescence of air cells | Suppurative mastoiditis | | Cortical erosion | Subperiosteal abscess formation | | Facial nerve canal erosion | Risk of facial nerve paralysis | | Sigmoid sinus thrombosis | Intracranial extension | **Clinical Pearl:** In a child with ASOM, perforation, and clinical signs of mastoiditis (postauricular swelling, tenderness, fever despite antibiotics), HRCT is essential before surgical intervention to define the extent of disease and plan the appropriate procedure. **High-Yield:** HRCT temporal bone is the imaging modality of choice for all suspected complications of ASOM (mastoiditis, intracranial extension, facial nerve involvement); it should be obtained urgently in this clinical scenario. ### Why NOT the Other Options? - **Otoacoustic emissions (OAE)**: Measures cochlear function; does not assess bony structures or mastoid pathology; irrelevant for diagnosing mastoiditis - **Tympanometry with acoustic reflex testing**: Assesses middle ear mechanics and ossicular chain function; cannot visualize mastoid bone or detect osteitis; inappropriate for suspected mastoiditis - **Impedance audiometry**: Functional test of middle ear compliance; does not provide anatomical information about mastoid air cells or bony erosion