Surgical strategy for hemifacial spasm caused by vertebrobasilar dolichoectasia: interposition technique versus transposition technique

This study aimed to retrospectively evaluate clinical outcomes, recurrence, and complications associated with interposition and transposition techniques for the management of vertebrobasilar dolichoectasia (VBD) in patients with hemifacial spasm (HFS). We retrospectively reviewed 102 consecutive patients with VBD-associated HFS who underwent first-time MVD between January 2018 and August 2021. All patients initially underwent an attempt at interposition. Interposition was performed when the vertebrobasilar artery could be adequately mobilized without excessive tension and satisfactory decompression of the facial nerve root exit zone (REZ) could be achieved. Transposition was selected when marked vascular tortuosity, limited mobility, excessive vascular tension, or inadequate decompression made interposition unsuitable. Sixty-three patients underwent interposition and 39 underwent transposition. Because surgical allocation was determined by intraoperative vascular anatomy rather than randomization, the two groups were considered anatomically selected observational cohorts. Clinical outcomes were assessed immediately after surgery, at discharge, 1 month, 1 year, and the final 3-year follow-up. Recurrence-free survival was evaluated using Kaplan–Meier analysis, and Cox proportional hazards analysis was performed to estimate the hazard ratio for recurrence. At immediate postoperative assessment, excellent outcomes were observed in 55/63 patients (87.3%) in the interposition group and 33/39 patients (84.6%) in the transposition group, while effective outcomes (excellent or good) were observed in 61/63 (96.8%) and 38/39 (97.4%), respectively. The distribution of immediate postoperative outcomes did not differ significantly between the groups ( P = 0.864). Effective outcome rates were 61/63 (96.8%) versus 38/39 (97.4%) at discharge, 62/63 (98.4%) versus 38/39 (97.4%) at 1 month, 61/63 (96.8%) versus 37/39 (94.9%) at 1 year, and 58/63 (92.1%) versus 35/39 (89.7%) at the final 3-year assessment, respectively. No statistically significant between-group differences were observed at any of these time points. During follow-up, recurrence occurred in 4/62 patients (6.5%) after interposition and 3/38 patients (7.9%) after transposition (Fisher's exact P = 1.000). Kaplan–Meier analysis demonstrated similar recurrence-free survival between the groups (log-rank P = 0.684), and Cox analysis showed no significant difference in recurrence risk (HR, 0.733; 95% CI, 0.156–3.450). Postoperative complications occurred in 8/63 patients (12.7%) and 4/39 patients (10.3%), respectively (Fisher's exact P = 1.000). Both interposition and transposition were associated with satisfactory clinical outcomes in patients with VBD-associated HFS when selected according to intraoperative vascular anatomy. Transposition may be particularly useful when the vertebrobasilar artery cannot be adequately mobilized or when interposition results in excessive vascular tension or insufficient decompression. However, because treatment allocation was determined by intraoperative anatomy and the number of recurrence events was small, the present study does not establish equivalence, non-inferiority, or superiority of either technique.