PMC7783446_01
Pre- and postoperative (3-month) pure tone audiograms.
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F1
Preoperative audiometry indicated severe mixed hearing loss in the right ear, with moderate conductive hearing impairment in the left ear (Figure 1). The postoperative pure tone audiogram revealed a mild increase at 500, 1,000, and 2,000 Hz and a mild decrease at 250 and 4,000 Hz for bone conduction thresholds (Figure 1). An improvement to moderate hearing loss in the VSB-aided hearing threshold was confirmed at 3 months (Figure 1).
High-resolution computed tomography and magnetic resonance imaging. Multidetector computed tomography 1.0 mm-collimated coronal (a), and 0.5-mm collimated right (b) and left (c) sagittal oblique (so called Poschl plane) reformatted images obtained at admission in the emergency unit. Images according to the Poschl plane clearly show 5.5 and 3.5 mm-wide dehiscence of the bone overlying the right and the left superior semicircular canals, respectively (black arrows). These findings are consistent with clinical and audiometry findings. 1.5T magnetic resonance 3D-true fast imaging with steady-state free precession coronal (d), right (e), and left (f) sagittal oblique reformatted images obtained 2 months before as outpatient did not show the dehiscence (arrowheads). Note that right (g) and left (h) magnetic resonance 3D volume rendering anterior views shows thinning of both the lateral crus of both the superior semicircular canals, mainly in the left side (white arrow).
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F2
A temporal bone 1.5-T MRI with 3D reconstruction performed two months before did not show the bilateral dehiscence (Figures 2d-h).
Transcanal identification of round window (white arrow), reshaping of the niche, and positioning of the floating mass transducer of the Vibrant Soundbridge.
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F3
After identification and reshaping of the RW niche, a vibroplasty was performed paying particular attention to correctly plugging the round window and coupling it with the floating mass transducer (FMT) of the VSB (Figure 3).
Plugging of the round window with FMT, cartilage, and perichondrium (tragus) (white arrow). These autologous tissues also helped to seal off the floating mass transducer in the round window niche. Intraoperatively hearing evaluation with RW electrocochleography (black arrow).
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FMT in the round window niche. Furthermore, VSB hearing outcomes were monitored with electrocochleography using a cotton-wick recording electrode placed on the hypotympanum (Figure 4). Minimal drilling of the cortical temporal bone posterosuperior to the external auditory meatus was necessary to house the implant receiver and extra wire (Figure 4).