The importance of carotid-cochlear interval in the etiology of hearing loss.

Carotid-cochlear interval (CCI) is the minimal distance between petrous segment of internal carotid artery (ICA) and basal turn of cochlea. Pulsations of the ICA might create fluid pressure changes and direct stimulation of hair cells on the basilar membrane of basal turn of cochlea which is responsible for mid-tone frequencies. The purpose of this study was to investigate whether CCI has a role in the etiology of mid-tone hearing loss and to obtain reference measurements of CCI on MRI. A total of 117 subjects were consecutively enrolled into this retrospective study during a 4 month period. All examinations were performed on a 1.5 T MRI system. The images were transferred to the workstation and reformatted. The CCI was measured on reformatted 3D FIESTA images. The audiologic findings were correlated. We reviewed the temporal MRI studies of 90 consecutive patients [M/F: 48/42, Mean age 45.6 ± 16.6 (10-78)]. As a total 180 sides were evaluated. The CCI ranged from 0 to 9 mm. The CCI didn't exhibit a significant association with subject age or gender. There were no significant differences between readers or sides. There were statistically significant correlation between CCI and level of frequency and degree of hearing loss (p = 0.004 and p = 0.002). The knowledge of CCI is essential prior to otosurgical procedures. There was linear correlation among CCI and level of frequency and degree of hearing loss. CCI of the group including all types of middle frequency hearing loss was longer compared to the normal group.