Microsurgical anatomy of the anterior inferior cerebellar artery- systematic review with meta-analysis

PURPOSE: The anterior inferior cerebellar artery (AICA) is a major vessel of cerebellopontine angle (CPA) and one of main cerebellar arteries. Many studies described a variety of AICA variants, however it has never been systematically reviewed and pooled in order to provide the neurosurgeons with the standardized knowledge in regard to most common types, including their clinical associations. This study aimed to determine AICA's microsurgical anatomy, including its morphometry, branching, origin, relationships with cranial nerves, as well as their respective neurosurgical considerations, such as tumor resection, decompression and bypass procedures. METHODS: Major databases (PubMed, Embase, Science Direct, Scopus, and Web of Science) were systematically searched up to November 2024. A total of 64 studies (n = 15,529 arteries) were included. RESULTS: The AICA originated from the basilar artery (BA) in 90.1% (95% CI:77.2-98.4; p < 0.001) of the general population, and had a unilateral branching pattern in 85.5% (95% CI: 78.4-89.6;p < 0.001). It was in contact with the abducens nerve (CN VI) up to 82.2% (95% CI: 54.7-100.0; p < 0.001) in general population. Regarding the facial-vestibulocochlear complex (CN VII-VIII), we found AICA to be located between CN VII and CN VIII in 60.6% (95% CI: 11.5-56.1;p < 0.001). AICA loops, were as common as 58.3% (95% CI:34.7-80.2;p < 0.001) in the general population, ranging up to 77.1% (95% CI:18.7-100.0;p < 0.001) in the South Korean population and just 18.0% (95% CI:1.0-45.1;p < 0.001) in the Turkish population. CONCLUSIONS: Neurosurgeons should remember that the AICA can present with many variants, which can produce various neurological symptoms, and increase the risk of iatrogenic lesions during numerous neurosurgical procedures.