HRCT and MRI Temporal bone: Decision making in cochlear implant surgery

Introduction The selection of the side of the ear and the technique for cochlear implant is based on various functional and anatomical factors. Systematic evaluation of HRCT and MRI temporal bone is necessary in selection of the ear for the implant as well to decide the technique, which is either cochleostomy, extended round window or round window approach. It also predicts the degree of difficulty and challenges encountered during the surgical procedure.

Objective To determine the role of HRCT and MRI temporal bone in predicting the difficulty of cochlear implant surgery.

Methods This was a prospective study carried out at a tertiary referral center where 70 patients with bilateral profound sensorineural hearing loss were evaluated by HRCT and MRI temporal bone and subsequently underwent cochlear implantation.Radiological findings were studied and were correlated to intraoperative findings. Based on it difficulty of surgical procedure could be predicted and surgical approach could be planned preoperatively.

Results Mean distances :- Facial Nerve(FN) and Mastoid Cortex- 15.6mm ± 3.93mm

- FN and Sigmoid Sinus- 10.4mm ± 3.09mm

- FN-Chorda Tympani - 3.22mm ± 0.9mm

- FN- Round Window – 3.85mm ± 1.34mm

Technique:-Extended Round window- 59,Round window-3 &amp; Cochleostomy- 8 patients There was excellent correlation between the imaging and intra op findings. (p<0.001)

Conclusion HRCT and MRI temporal bone both are road map for cochlear implant surgery.In addition the handedness of the patient and audiological preponderance help to determine the side of implant. This is important in developing country like ours (India) where government funds for only unilateral implant. Hence the decision of the surgeon is important regarding which ear to be implanted for excellent outcome and prognosis

Publication History

Article published online:
10 June 2020