A patient with atticoantral (unsafe) CSOM is found to have erosion of the tegmen tympani on HRCT and presents with meningismus and photophobia. Lumbar puncture shows turbid CSF with polymorphonuclear pleocytosis. What is the MOST likely route of spread?

• A Direct extension through the eroded tegmen tympani into the middle cranial fossa ✓
• B Hematogenous spread via the dural venous sinuses
• C Retrograde thrombophlebitis via the superior petrosal sinus
• D Spread via the internal auditory meatus

Explanation

Erosion of the tegmen tympani (roof of the middle ear cleft) by cholesteatoma allows direct extension of infection into the middle cranial fossa, leading to meningitis or epidural/subdural abscess. This is the direct extradural route. The tegmen separates the middle ear from the middle cranial fossa dura; once eroded, bacteria can directly reach the meninges. Lateral sinus thrombosis occurs via the posterior tegmen/mastoid route. The internal auditory meatus is not a common route for cholesteatoma spread.

Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.