3.2 Surgery findings
Five ears underwent CI using traditional retroauricular straight
incision 3∼3.5cm in length. Four ears were performed using conventional
facial recess and round window approach(Table 2). Case 3 underwent
simultaneous bilateral CI surgery. Left ear used retrofacial approach
due to anteromedially displaced mastoid segment FN.
Individually, full electrode array insertion and excellent
intraoperative
electrically
Evoked Compound action potential was achieved in right ear of Case 1.
Case 2 had right aural atresia but normal cochlear nerve dimensions in
the operation ear (Figure 1). Since the mastoid was completely
sclerotic, and the semicircular canal was aplasia, only the dura and
sigmoid sinus were used as anatomical landmarks during mastoidectomy.
Drilling out of the superficial mastoid bone exposed a strip-like
fibrous tissue resembling the vertical segment of the facial nerve, but
facial nerve monitoring ruled out the possibility (Figure 1). The
mastoid segment of the facial nerve was exposed gradually by removing
the overlying bone with a fine diamond drill in the deep part of the
mastoid, with the assistance of facial nerve monitoring. Covert round
window niche was identified in front of the nerve and after removing the
overhanging bone and fibrous tissue, the round window was exposed. 7 of
the 12 electrodes were inserted through the enlarged round window.
Congenital dehiscent facial canal of the tympanic and pyramid segment
were confirmed in the right ear, which had facial paralysis
postoperatively. The patient underwent a secondary exploratory operation
7 days later, and the main trunk of facial nerve demonstrated no
reaction to monitoring probe. facial paralysis recovered to Brackmann
Level Ⅰ about 1 year later. Only partial insertion was achieved in left
ear of case 4.