Cochlear Apex Triangulation Utilizing Ct Measures And Middle Ear Landmarks.

OBJECTIVE

To better characterize the cochlear apex in relation to surgically relevant landmarks to guide surgeons and improve procedural success of apical electrode placement.

STUDY

DESIGN

Retrospective image analysis.

SETTING

Tertiary referral center.

PATIENTS: Cochlear implant recipients with available preoperative computed tomography (CT) imaging.

INTERVENTION: None.

MAIN OUTCOME MEASURE: Cochlear dimensions and cochlear apex distance measures to surgically relevant middle ear landmarks and critical structures.

RESULTS

Eighty-two temporal bone CT scans were analyzed utilizing multiplanar reformats. The average lateral width of promontory bone over the cochlear apex was 1.2 mm (standard deviation [SD], 0.3). The anteroposterior distance from the round window (avg, 4.2 mm; SD, 0.5), oval window (avg, 3.3 mm; SD, 0.3), cochleariform process (avg, 2.3; SD, 0.5), and superior-inferior distance from the cochleariform process (avg, -0.9; SD, 0.8) to the cochlear apex were measured. The relationship of the cochlear apex to critical structures was highly variable.A newly developed stapes vector was created and found to mark the posterior/superior boundary of the apex in 94% of patients. When a vector parallel to the stapes vector was drawn through the round window, it marked the anterior/inferior boundary of the cochlear apex in 89% of patients.

CONCLUSIONS

This study assists in characterizing cochlear apex anatomy and its relation to surrounding structures as a means of improving procedural accuracy and reducing trauma during apical cochleostomy. Understanding both distance relationships and expected boundaries of the apex could help to inform future surgical approaches.