Potential Confounding Factors May Influence the Association Between Configurations of the Vertebrobasilar System and the Incidence of Idiopathic Sudden Sensorineural Hearing Loss and Canal Paresis

The Association of Vascular Loops within the Internal Auditory Meatus or Contacting the Vestibulo-Cochlear Nerve with Audiovestibular Symptoms: A Systematic Review and Meta-Analysis

BACKGROUND

Intrameatal vascular loops (IVL) entering the internal auditory meatus and neurovascular contact (NVC) with the vestibulocochlear nerve (cranial nerve [CN] VIII) have been proposed to have a relationship with audiovestibular symptoms.

PURPOSE

This systematic review and meta-analysis aimed to determine whether the presence of IVLs and CN VIII NVC on 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 audiovestibular symptoms and controls were identified through MEDLINE, EMBASE, the Web of Science Core Collection, Scopus, and the Cochrane Register of Controlled Trials databases.

STUDY SELECTION

Sixteen studies and 3455 ears (1526 symptomatic ears and 1929 control ears) were included.

DATA ANALYSIS

Meta-analysis was performed using a bivariate random effects model. Pooled ORs were calculated, and heterogeneity was evaluated with the Cochran Q test with statistical significance defined as P < .05.

DATA SYNTHESIS

There was no significant association between the presence of undefined tinnitus or SNHL and 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 = .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 = .006).

LIMITATIONS

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

CONCLUSIONS

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

Vertebrobasilar System Laterality and Idiopathic Sudden Sensorineural Hearing Loss

INTRODUCTION

The etiology of idiopathic sudden sensorineural hearing loss (ISSNHL) remains elusive, with vascular compromise as a proposed cause. This study aimed to explore the correlation between the vertebrobasilar vascular system laterality (VBVSL) and ISSNHL laterality.

METHODS

We conducted a retrospective analysis of consecutive patients diagnosed with ISSNHL from 2015 to 2020. The VBVSL pattern was established via magnetic resonance imaging scans by a neuroradiologist. ISSNHL occurring contralaterally to the basilar artery (BA) curvature or ipsilaterally to the dominant vertebral artery (VA) was designated as a "positive match," with all other scenarios classified as a "negative match."

RESULTS

Our study included 191 ISSNHL patients (median age 57 years, 89 males, 93 right ears). The majority of patients did not exhibit a positive match between ISSNHL laterality and the sides of BA curvature or dominant VA (28.8% and 36.6% for BA and VA, respectively). Notably, VA-positive match patients were significantly older than VA-negative match patients (59 vs. 53 years, p = 0.043), with a similar trend observed in BA-positive match compared to BA-negative match (59 vs. 54.5 years, p = 0.057). However, there was no significant difference in any other clinical, audiometric, or outcome factors between the positive and negative match groups.

CONCLUSION

The findings suggest no association between VBVSL and ISSNHL laterality. Furthermore, patients in the positive match group did not exhibit distinct clinical or audiometric features compared to those without a match.

Neurovascular conflict and sudden unilateral sensorineural hearing loss: coincidence or coexistence?

OBJECTIVE

To study the association between neurovascular conflict (NVC) of the 8th cranial nerve (CN8) and unilateral sudden sensorineural hearing loss SSNHL (SSNHL).

METHODS

A systematic literature search of "MEDLINE" via "PubMed," "Embase," and "Google-Scholar" was conducted. Meta-analysis of pooled data was performed for NVC prevalence of SSNHL affected ears versus controls.

RESULTS

The literature search identified 941 publications, of which, 9 included in qualitative synthesis (1030 ears) and 5 in quantitative synthesis (484 ears). NVC was as prevalent as 0.8-69% for affected ears and as 19-57% for controlled ears. No association between MRI protocol and NVC prevalence was proved. An odds ratio of 1.05 (95% confidence interval = 0.79-1.39) was calculated for association of NVC in unilateral SSNHL ears versus controls.

CONCLUSION

The prevalence of NVC of CN8 in unilateral SSNHL affected ears is not significantly bigger than controls. Hence, NVC of CN8 is probably NOT associated with unilateral SSNHL.

LEVEL OF EVIDENCE: 1