A CT temporal bone in a patient with cholesteatoma shows erosion of the lateral wall of the epitympanum (scutum). This finding is pathognomonic of which type of cholesteatoma, and which route of spread is most likely?

• A Pars flaccida (attic) cholesteatoma spreading via the posterior route into the aditus and antrum ✓
• B Pars tensa cholesteatoma spreading via the posterior route into the sinus tympani
• C Pars flaccida (attic) cholesteatoma spreading via the anterior route to the cochleariform process
• D Congenital cholesteatoma with erosion of the tegmen tympani

Explanation

Scutum erosion on CT is characteristic of pars flaccida (attic) cholesteatoma. These cholesteatomas typically spread posteriorly from the Prussak's space via the aditus ad antrum into the mastoid antrum and air cells. Anterior spread toward the cochleariform process and tensor tympani may occur but is less common. Pars tensa cholesteatomas tend to spread into the sinus tympani and facial recess regions.

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

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Written and medically reviewed by the StethoPrep medical team.