To investigate the impact of configurations of the vertebrobasilar system on the incidence of idiopathic sudden sensorineural hearing loss (ISSNHL) and canal paresis (CP).
Retrospective case review.
Tertiary referral center.
Two hundred and forty-eight consecutive patients diagnosed with ISSNHL and 152 patients with unilateral CP of an uncertain cause who were managed between January 2011 and December 2017. The contralateral side of 144 patients with Bell's palsy or cerebellopontine angle tumor served as a control.
All patients underwent magnetic resonance cisternography. CP was diagnosed based on caloric testing.
Main Outcome Measures:
1) Branching patterns of the anterior/posterior inferior cerebellar artery (AICA/PICA) in the cerebellopontine angle area. 2) The direction of the basilar artery (BA) curvature. 3) Vertebral artery (VA) dominance.
The incidence of vascular loops of the AICA/PICA entering the internal acoustic canal was significantly higher on both the affected and unaffected sides in patients with ISSNHL and CP in comparison to controls (p < 0.05). The curved BA was observed more frequently in the ISSNHL and CP groups than in the control group (p < 0.05), whereas the direction of the BA curvature was not associated with the laterality of ISSNHL or CP. The incidence of asymmetric VA in CP patients was significantly higher than that in controls (p = 0.0304), while no significant difference was observed between ISSNHL patients and controls. Remarkably, while the incidence rate of irregular vascular configurations was high in both the ISSNHL and CP groups, there was no marked difference between the affected and unaffected ears of the ISSNHL and CP groups.
Our results indicate that the vascular configurations of the vertebrobasilar system do not directly cause ISSNHL and CP. Instead, they suggest the presence of confounding factors that influence the vascular configurations and the development of ISSNHL and CP.