PMC6948323_01
Pure tone audiometry (PTA) of left ear (a) and right ear (b) showing bilateral severe conductive hearing loss. Note bilateral intact unmasked bone conduction (BC) (marked by arrowheads) and profound flat air conduction (AC) loss (marked by X for left and circle for right ear) across all frequencies resulting in significant air-bone conduction (ABC) gap.
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There was a large air-bone gap of 60 dB (AC 88 dB and BC 28 dB) in the right ear while 62 dB (AC 92 dB and BC 30 dB) in the left ear (Figure 2).
(a) High resolution axial CT Temporal bone images at the level of round window (a), stapes and oval window (b), and tympanic facial nerve (c). Absence of bilateral round ((a), dark arrows) and oval windows ((b), dark arrows) with tympanic facial nerve covering the site of oval window (C, arrows). Stapedial anomalies present with aplastic crura on the right and nearly intact left stapes except hypoplastic anterior crus (white arrows, (b)). Note skull base dysmorphism with abnormal orientation of internal auditory canal (IAC) and kissing carotid canals (marked as C in Figures 3(a)-3(c)).
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Absence of oval window (Figure 3(b), dark arrows) with retained thick bony plate without a defect into the vestibule. Note aplastic crura of the stapes on the right and relatively well developed stapes on the left side except the hypoplastic anterior crus (Figure 3(b), white arrows).
Coronal high resolution CT Temporal bone image showing bilateral dehiscent tympanic segments of facial nerve (arrows), abutting the lateral wall of the bony labyrinth due to its inferio-medial anomalous course.
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