The association of vascular loops within the internal auditory meatus or contacting the vestibulo-cochlear nerve with audio-vestibular symptoms. A systematic review and meta-analysis.

Background: Intrameatal vascular loops (IVL) entering the internal auditory meatus (IAM) and neurovascular contact (NVC) with the vestibulo-cochlear nerve (CN VIII) have been proposed to have a relationship with audio-vestibular symptoms.

Purpose: This systematic review and meta-analysis aimed to determine whether the presence of IVLs and CN VIII NVC on magnetic resonance imaging (MRI) is associated with tinnitus, sensorineural hearing loss (SNHL) or vertigo and any specific subtypes.

Data sources: All studies comparing the presence of IVL or CN VIII NVC in ears with these audio-vestibular symptoms and controls were identified through MEDLINE, EMBASE, Web of Science Core Collection, Scopus and Cochrane Register of Controlled Trials databases.

Study selection: 16 studies and 3,455 ears (1526 symptomatic ears and 1929 control ears) were included.

Data analysis: Meta-analysis was performed using a bivariate random effects model. Pooled odds ratios (ORs) were calculated, and heterogeneity was evaluated with Cochran's Q test with statistical significance defined as p<0.05.

Data synthesis: There was no significant association between the presence of undefined tinnitus or SNHL and that of IVL (OR 0.90 95% CI 0.47, 1.70; OR 0.67, 95% CI 0.36, 1.25) or CN VIII NVC (OR 1.15, 95% CI 0.68, 1.95; OR 0.89, 95% CI 0.33, 2.40). However, the subgroup of sudden onset SNHL was associated with IVL (OR 1.34, 95% CI 1.04, 1.73) (p=0.02). There was no significant difference in the prevalence of IVL (OR 0.97, 95% CI 0.64, 1.48) or CN VIII NVC (OR 0.99, 95% CI 0.42, 2.32) between ears with undefined vertigo and control ears. However, there was an association between the presence of CN VIII NVC and the specific diagnosis of vestibular paroxysmia (OR 13.19, 95% CI 2.09, 83.16) (p=0.006).

Limitations: Our meta-analysis is limited by selection bias, small number of eligible studies and moderate heterogeneity.

Conclusions: IVL or CN VIII NVC on MRI are unrelated to symptoms of undefined tinnitus, SNHL and vertigo. However, CN VIII NVC is associated with vestibular paroxysmia whilst IVL is associated with sudden onset SNHL.

Abbreviations: AICA = anterior inferior cerebellar artery, CI = confidence interval, CN = cranial nerve, CPA = cerebellopontine angle, IAM = internal auditory meatus, NVC = neurovascular contact, OR = odds ratio, SNHL = sensorineural hearing loss, SoSNHL = sudden onset sensorineural hearing loss.