MDCT Assessment of the Cochlear-Carotid Interval

The close anatomic course between the cochlea and the carotid artery presents a possible surgical risk during increasingly popular cohlear implant surgery. The purpose of this study was to determine the normal range of the this region termed "cohlear- carotid interval" (CCI) by 64-slice multi-detector computed tomography (MDCT) in the population. The study investigated 1105 patients who had undergone temporal MDCT. The CCI measured by two observers from 0.5 mm thick coronal images with confirmation on axial and sagittal planes. Among 1105 patients and 2210 temporal sides CCI measured 0.0 mm unilaterally in eight (0.7%) and bilaterally in two patients (0.1%) with a score of ten in the total population (0.9%). Total scores ranged from 0.0 to 6 mm for right CCI and 0.0 to 5.9 mm for left CCI. The CCI showed no significant relationship with sex (P=.096) and there were no significant differences between readers (P=.457) and sides (P=.879). A positive correlation (r=0.741) was found between right and left CCI. The present study demonstrated that the CCI varies considerably between 0.0 mm and 6 mm independently of sex in the population. Understanding the importance of CCI and preoperative knowledge of thin or absent bone allows the radiologist to play a crucial role in alerting the surgeon to prevent penetration of the carotid canal during cochlear implant surgery.