Is There a Correlation Between Vascular Loops in the Cerebellopontine Angle and Unexplained Unilateral Hearing Loss?

Objective: This study was a retrospective analysis of patients who had received magnetic resonance imaging scans of the internal auditory canal (IAC) to evaluate unexplained asymmetric hearing loss. The study aimed to correlate structural features of vascular loops formed by the anterior inferior cerebellar artery (AICA) within the cerebellopontine angle and IAC with asymmetric hearing loss. Study Design: High-resolution thin-section T2 fast spin echo magnetic resonance imaging scans of 58 patients with asymmetric sensorineural hearing loss were obtained; the structure of the AICA was graded on both sides using 2 scoring systems. The grading senior head and neck radiologist was blinded to the clinical history. The first scoring system used was the Chavda classification, which is based on the anatomic location of the AICA loop. This system identified 92 loops within the cerebellopontine angle; 22 loops extending less than halfway into the IAC and 2 loops extending more than halfway into the IAC. A second classification system was used simultaneously to describe the extent of contact between the AICA loop and the vestibulocochlear nerve. The second system identified 24 loops that were not in contact with the nerve, 60 in which the loop was running adjacent to the nerve but not displacing it; 12 loops were identified that were displacing the vestibulocochlear nerve, and 24 loops were identified running between the facial and the vestibulocochlear nerve. Four loops were classified as both displacing the vestibulocochlear nerve and running between the facial and vestibulocochlear nerves. Tinnitus was present in addition to hearing loss. In 48 of the 58 patients, the statistical analysis was repeated for these patients. Results: No statistically significant association was found between loops classified by the Chavda system and hearing loss. No statistically significant association was present between loops that made no contact with the nerve, ran adjacent to the nerve, or displaced the nerve. A statistically significant association was found between loops that ran between the facial and vestibulocochlear nerve and hearing loss, with a p value of 0.0162. The subset who had tinnitus in addition to hearing loss had similar results, with the only significant association being found between loops running between the facial nerve and the vestibulocochlear nerve, and a p value of 0.0433 was obtained. Conclusion: A correlation between vascular loops and hearing loss did not exist in the majority of the patients in this study. The subset of patients that had a vessel between the facial and vestibular cochlear nerves deserve further investigation.