The Impact of Vascular Loops in the Cerebellopontine Angle on Audio-Vestibular Symptoms: A Systematic Review

Abstract

It has been suggested that vascular loops in the cerebellopontine angle and internal auditory canal are involved in the etiology of audio-vestibular symptoms. Several studies have focused on the compression of the eighth cranial nerve by vascular loops but have yielded contradictory results regarding their clinical significance. The aim of this study was to investigate whether vascular loops in this region correlate with audio-vestibular symptoms and which loop features – if any – can potentially lead to symptom manifestation. This systematic review was conducted according to the PRISMA guidelines. We performed on PubMed a literature search from November 2005 to October 2020. The search strategy included the following keywords (“vascular loops” OR “AICA loops” OR “vascular compression syndrome”) AND (“hearing loss” OR “tinnitus” OR “vertigo”). Fifteen studies were eligible and included in the analysis. Overall, the studies encompassed a total of 11,788 patients included in this review. The significantly larger group of patients (70%), in which no correlation of symptoms with vascular loops was found, suggests that vascular loops are probably anatomic variations in a substantial majority of cases with an uncommon subset causing some audio-vestibular symptoms. Even within the papers claiming a correlation, there is a multitude of symptoms that did not correlate with vascular loops. It has been suggested by most authors that magnetic resonance imaging should be performed to exclude the role of a vascular loop in the etiology of audio-vestibular symptoms only when vascular compression syndrome is suspected based on clinical indications and not routinely. Further studies would be useful in order to detail the relationship between the vascular structures and the nervous system.

Vascular Loop of the Anterior Inferior Cerebellar Artery (AICA) as a Cause of Sensorineural Hearing Loss (SNHL): A Case Report

“…Attempts have been made to elucidate the exact pathophysiology of SNHL/tinnitus caused by vascular loops, with theories including direct compression of the nerve by the loop, demyelination of the nerve due to contact with the artery, and reduced perfusion leading to hypoxia of the nerve [13][14]. In the present study, no obvious compression of the vestibulocochlear nerve indicates that the symptoms may have been caused by hypoxia or micro compression.…”

Radiological presence of vascular loops in the cerebellopontine angle region in patients with unilateral Ménière’s disease

“…The presence of vascular loop in the CPA-IAC region is not included in any diagnostic criteria for vestibular disorders except for vestibular paroxysmia (VP) [ 20 ], in which the neurovascular compression has been considered as the underlying mechanism. In fact, due to the lack of objective diagnostic test, vascular compression is a diagnosis of exclusion and patients with this syndrome are often misdiagnosed [ 3 , 5 ]. The causal relationship between audio-vestibular symptom and the presence of vascular loops in CPA-IAC region is still controversial.…”

“…Our results showed that imaging findings based on the Kazawa classification system did not correlate with the lateralization, Ménière’s stage, EcochG, and caloric test findings in unilateral MD, which is in line with the results of a systematic review. Papadopoulou et al included 15 studies for systematic review and found that, the radiological results did not consistently correlate with audio-vestibular symptoms in about 70% of the included patients, suggesting that vascular loops may be an anatomical variant in a significant majority of cases [ 3 ]. Of note, the etiologies underlying these audio-vestibular symptoms were undefined in most cases.…”

“…Bo Liu is the first corresponding author, Yangming Leng is the second corresponding author and Yue Zhou is the third corresponding author. such as sensorineural hearing loss (SNHL), tinnitus, vertigo, and its clinical significance [1,3].…”

“…Jannetta introduced the concept of neurovascular compression in 1975 to explain the pathogenesis of trigeminal neuralgia and performed the first microvascular decompression of the cranial nerve in a patient with this condition [ 2 ]. Until now, although vascular compression is widely accepted as a cause of trigeminal neuralgia and hemifacial spasm, there is still controversy regarding vascular compression of the vestibulocochlear nerve resulting in audio-vestibular symptoms, such as sensorineural hearing loss (SNHL), tinnitus, vertigo, and its clinical significance [ 1 , 3 ].…”