Imaging Findings in Auto-Atticotomy

BACKGROUND AND PURPOSE:An acquired attic cholesteatoma may spontaneously drain externally into the external auditory canal, leaving a cavity in the attic with the shape of the original cholesteatoma but now filled with air, a phenomenon referred to as “nature''s atticotomy” or auto-atticotomy. We describe and quantify the CT appearance of the auto-atticotomy cavity as it pertains to the appearance of the scutum and the lateral attic wall.MATERIALS AND METHODS:Twenty-one patients with erosion of the scutum and loss of the lower attic wall on MDCT were identified during a 5-year span. Images were assessed for measureable widening of the space between the ossicles and the lower lateral attic wall in the axial and coronal planes. Three measurements of the lateral attic were made on the axial images. Findings were compared with the same measurements in 20 control subjects.RESULTS:The 21 patients had a characteristic blunting of the scutum with loss of the lower lateral attic wall and widening of the lateral attic, consistent with an auto-atticotomy. There was a statistically significant (P < .001) widening of the lateral attic dimensions in the axial plane in the patients with auto-atticotomy.CONCLUSIONS:Spontaneously evacuated cholesteatoma may mimic a surgical atticotomy on MDCT. Scutal erosion and attic enlargement with a smoothly contoured bony remodeling of the lower lateral attic wall in a patient with no history of surgery suggest that a cholesteatoma was previously present and spontaneously drained.

An atticotomy is a surgical approach through the external auditory canal to the attic of the middle ear, whereby the scutum and the lower lateral wall of the attic are surgically removed for access. An auto-atticotomy (also called “nature''s atticotomy”) refers to an enlarged lateral attic with absence of the scutum and lower lateral wall of the attic in a patient without a history of surgery.^1–3 This entity results from a deep retraction pocket or a cholesteatoma that has eroded the bone and then spontaneously drained into the external auditory canal. The wall of the original cholesteatoma remains, and so the air-filled defect is lined by keratinizing squamous epithelium. The appearance of an atticotomy and an auto-atticotomy is similar on CT. The purpose of this article was to describe the findings of auto-atticotomy on multidetector CT of the temporal bone.