Origin and Course
The anterior inferior cerebellar artery arises from the lower third of the basilar artery (a. basilaris), an unpaired vessel formed by the union of the right and left vertebral arteries at the pontomedullary junction.
During digital subtraction angiography (DSA), blood flow in the AICA may be preserved during occlusion of the distal basilar artery because it anatomically arises proximal to the obstruction site.
Areas of Supply
The AICA supplies structures in the posterior cranial fossa. Its vascular territory includes:
- Cerebellum: Supplies the anterolateral parts of the inferior surface of the hemispheres, a small anteroinferior portion of the hemispheres, including the flocculus and adjacent structures.
- Brainstem (Medulla Oblongata): Supplies the lateral zone of the medulla oblongata, particularly the region of the olivary nucleus.
Anatomical variability: The supply area of the AICA is inversely related to the territory of the ipsilateral posterior inferior cerebellar artery (PICA). In some individuals, the anterior inferior cerebellar artery may supply regions of the cerebellum that are normally supplied by the posterior inferior cerebellar artery.
Branches of the Artery
A specific branch of the AICA is the labyrinthine artery (a. labyrinthi), which may also arise directly from the basilar artery.
The labyrinthine artery enters the internal acoustic meatus (meatus acusticus internus) together with the vestibulocochlear nerve (n. vestibulocochlearis), where it divides into two groups of branches:
- Cochlear branch (r. cochlearis) — runs along the axis of the cochlea, forms arterial glomeruli, and supplies the basilar membrane, spiral organ, and the periosteum of the osseous labyrinth.
- Vestibular branches (rr. vestibulares) — supply the membranous vestibule, including the utricle, saccule, and the ampullae of the semicircular ducts.
Clinical Significance
Pathologies associated with the anterior inferior cerebellar artery have severe neurological consequences:
- Ischemic stroke: Unilateral hearing loss is described in anterior inferior cerebellar artery stroke. Cerebellar infarctions are dangerous due to the limited space in the posterior cranial fossa: even small infarctions cause a significant increase in intracranial pressure. Compression of the cerebral aqueduct or the fourth ventricle leads to obstructive hydrocephalus.
- Aneurysms: The origin of the anterior inferior cerebellar artery is a reported location for aneurysms in endovascular treatment guidelines. If endovascular intervention is not feasible, microsurgical management should be considered.
- Cranial nerve compression: Vascular loops of vertebrobasilar arteries, including the AICA, may lie close to cranial nerve roots and cause irritation at their non-myelinated root entry zones.