The impact of perforating arterial branches on microvascular decompression for hemifacial spasm

Microvascular decompression (MVD) is the definitive surgical procedure for hemifacial spasm (HFS), with reported success rates exceeding 90%. However, the complexity of neurovascular compression varies between patients, and the presence of perforating arteries at the root exit zone (REZ) may hinder optimal decompression. This study aimed to analyze anatomical patterns and characteristics of perforating arterial branches at the REZ, and to evaluate their potential impact on the MVD procedure and surgical outcomes.

The authors conducted a retrospective review of high-quality intraoperative images and videos of patients who underwent MVD for HFS between January 2017 and October 2022. Inclusion criteria were pure arterial compression and a minimum postoperative follow-up of 6 months. Patient demographics; number of perforators within a 5-mm radius of the REZ and their length, direction, and involvement in facial nerve decompression; and postoperative outcomes were assessed.

One hundred five patients met the inclusion criteria. The mean patient age was 55.6 (SD 11.2) years, with a male-to-female ratio of 1:1.63 and a mean follow-up duration of 24.4 (SD 28.1) months. Favorable outcome reached 89.5% (94/105 patients), and persistent complications occurred in 3.81%. The compressing vessel was solely the anterior inferior cerebellar artery (AICA) in 28.6% of patients, the posterior inferior cerebellar artery (PICA) in 38.1%, and a combination in the remainder. The median number of perforators per patient was 2, with notable differences in length and vascular territory: AICA perforators were significantly shorter and more likely to supply the cranial nerve (CN) VII-VIII complex (p < 0.05). Furthermore, AICA perforators interfered more frequently with decompression than those from the PICA (53.3% vs 22.5%, p < 0.05). Postoperative outcomes did not differ significantly between groups.

The anatomical characteristics of perforating branches vary depending on the parent vessel. AICA perforators are usually shorter and more often supply the CN VII-VIII complex, thereby posing a greater challenge during MVD compared to PICA branches. Nonetheless, with appropriate surgical expertise, neuroendoscopic visualization, and adjunctive intraoperative monitoring, favorable outcomes can still be reliably achieved.