Internal auditory meatus vascular loops and vestibulocochlear neurovascular contact on MRI: Are they associated with pulsatile tinnitus?

TL;DR

This study found no link between certain vascular structures in the ear and pulsatile tinnitus, suggesting they are not a cause.

Contribution

The study provides evidence against the clinical relevance of IAM vascular loops and vestibulocochlear NVC in unilateral pulsatile tinnitus.

Findings

No significant difference in vascular loops or neurovascular contact between tinnitus and control ears.

Depth, angulation, or location of these structures did not influence the likelihood of tinnitus.

The study argues against analyzing these structures for pulsatile tinnitus.

Abstract

To compare the presence of internal auditory meatus vascular loops (IVLs) or vestibulocochlear neurovascular contact (CN8-NVC) between unexplained unilateral pulsatile tinnitus (PT) ears and contralateral asymptomatic ears. Furthermore, to investigate whether IVL depth or angulation, or CN8-NVC location is associated with the presence of PT.

Single-centre retrospective case-controlled study of patients undergoing three-dimensional T2-weighted MRI for unexplained unilateral PT from January 2012 to July 2021. Two blinded observers recorded the presence of IVLs or CN8-NVCs, whilst evaluating IVL depth and angulation. Proportions of ears with IVLs or CN8-NVCs were compared between PT ears and contralateral control ears with McNemar’s test. Mann–Whitney U or Student’s t-test compared the depth and angulation of IVLs and the location of CN8-NVC with respect to the transition zone between ears with and without PT.

Three hundred thirty-seven patients were evaluated (250 female; mean age 47 ± 16 years). There was no significant difference between the proportion of IVLs (19.3% vs 25.2%; p = 0.06) or CN8-NVCs (59.9% vs 65.6%; p = 0.12) in PT ears as compared to contralateral control ears. There was no significant difference in IVL depth (median loop-fundus distance 6.5 mm vs 6.8 mm; p = 0.45), IVL angulation (median interlimb distance 3.1 mm vs 3.3 mm; p = 0.54), or CN8-NVC location within the transition zone (p = 0.58) between ears with and without PT.

Unexplained unilateral PT is not associated with the presence of an ipsilateral IVL or CN8-NVC. Likelihood of PT is not influenced by depth or angulation of an ipsilateral IVL, nor by whether CN8-NVC is at the transition zone.

Question
The relevance of internal auditory meatus (IAM) vascular loops or vestibulocochlear NVC in the context of PT remains uncertain.

Findings
Likelihood of unilateral PT was not influenced by the presence, depth, or angulation of IAM vascular loops, nor by the presence or location of vestibulocochlear NVC.

Clinical relevance
This study argues against the analysis and reporting of IAM vascular loops or vestibulocochlear NVC in the context of PT, and it gives the clinician confidence to reassure the patient that these are unlikely to be an aetiology.

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