Can vascular loops cause otological symptoms?

Abstract

Objective. To determine the evidence for a relationship between vascular loops in contact with the vestibulocochlear nerve (CN VIII) and otological symptoms. Method. A systematic review and meta-analysis. Comprehensive search strategy using MEDLINE, EMBASE, CINAHL, Cochrane Library, Clinical Evidence, and Cochrane Central Register of Trials. Reference lists cross-referenced and authors contacted for missing data. No language restrictions. Included studies: (1) compared symptoms in subjects with vascular loops contacting CN VIII to subjects without; or (2) compared the prevalence vascular loops in contact with CN VIII in symptomatic ears to contra-lateral asymptomatic ears. Study quality systematically appraised. Results. Five studies met the inclusion criteria. A statistically significant association was demonstrated for the prevalence of vascular loops in contact with CN VIII, in subjects with unilateral sensorineural hearing loss: pooled odds ratio (OR) 2.0 (95% confidence interval [CI]:1.5, 2.6). No significant association was demonstrated for non-pulsatile tinnitus. A highly significant increase in prevalence of contacting vascular loops in contact with CN VIII was demonstrated in subjects having pulsatile tinnitus, with pooled OR: 78.8 (95% CI: 10.9, 821.8). Conclusions. Vascular loops in contact with CN VIII are a normal variant. Subjects with unilateral hearing loss were twice as likely to have these vascular loops in the symptomatic ear than the asymptomatic ear. Subjects with pulsatile tinnitus were 80 times more likely to have a contacting vascular loop than patients with non-pulsatile tinnitus. This suggests in some cases a causal relationship exists for pulsatile tinnitus, and surgical intervention may be occasionally indicated.