Thirty-five consecutive patients with the clinical diagnosis of fenestral otosclerosis were evaluated with high-resolution computed tomography (CT). Twenty-six were diagnosed as having this disorder by CT evidence of abnormal bony excrescences at or adjacent to the oval window. The diagnosis was made upon examination of 1.5-mm-thick targeted sections obtained at 0.5-mm intervals in the axial projection. Coronal sections were also included. Sections were also evaluated for evidence of plaque formation elsewhere in the lateral wall of the labyrinth and for surgical obstacles such as an abnormally wide cochlear aqueduct, a high jugular vein, and a dehiscent facial nerve. It is concluded that fenestral otosclerosis may be accurately diagnosed with proper CT techniques.

Ninety patients who had suspected or confirmed fenestral or cochlear otosclerosis underwent CT examination. Foci of demineralization in the otic capsule were discovered in 20 ears (12 patients). Audiometric studies of the 12 patients revealed sensorineural hearing loss (SNHL) with distinct correlation of CT findings with progressivity and with involvement of the frequency level subtended by the specific area of the cochlea involved. Foci of abnormal increased density, presumably representing the healed phase of this disorder, were found less frequently than expected. There was a predilection for the basilar turn. All patients had static SNHL in the higher frequencies. The healed phase of this disorder is probably not consistently diagnosable with CT.

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