Vascular Loop of Anterior Inferior Cerebellar Artery Causing Disabling Tinnitus, Vertigo, and Hearing Loss - A Review

The vascular anatomy of the anterior inferior cerebellar artery (AICA) is highly variable. In respect to the neurovascular relationship in the internal auditory canal (IAC), the AICA is intimately related with vestibulocochlear and facial nerve. Vascular loop of AICA, especially located in the IAC, is rare. This vascular loop of the IAC may result in the compression over the vestibulocochlear nerve. Microvascular compression of the eighth cranial nerve is an important cause for disabling tinnitus, vertigo, and hearing loss. Disabling tinnitus and vertigo due to intrameatal vascular loop of AICA compression, the vestibulocochlear nerve can be treated with help of drilling the internal acoustic meatus and separate the vascular loop from the vestibulocochlear nerve. The intrameatal AICA and vestibulocochlear nerve conflict produce specific pathological features and their surgical treatment is also invariably challenging. Decompression of the vestibulocochlear nerve by the opening of the IAC and transposition of the AICA is thought to be an effective treatment modality for radiologically confirmed cases with clinical presentations of unilateral sensorineural hearing loss and pulsatile tinnitus. The aim of this review article is to describe the details of vascular anatomy, etiopathology, clinical presentations, diagnosis, neurophysiology, and current treatment of the vascular loop of AICA in IAC which often pose challenge to the clinicians.