Muscle pad interposition technique in microvascular decompression for primary hemifacial spasm: a single-center case series and systematic review.

Objective: Primary hemifacial spasm (HFS) is a rare neurological condition characterized by involuntary contractions of hemifacial mimic muscles. Microvascular decompression (MVD) with the interposition technique, in which a Teflon spacer is inserted between the nerve and the offending vessel, is the most commonly used treatment. However, the authors' institution has used autologous muscle pledgets for more than 15 years as an alternative spacer material, with satisfactory results. They report a single-center study of 75 consecutive patients treated with interposition MVD using autologous muscle pledgets between November 2012 and March 2023.

Methods: All patients had a minimum follow-up of 1 year. Surgical outcomes were assessed using the Japanese grading system of Kondo and colleagues, which evaluates both the efficacy of surgery and complications. Furthermore, a systematic review of recent series on HFS treated by the interposition technique was done, to compare the present study results and outcomes.

Results: Among the 75 patients, 31 (41.3%) were male, the median age was 52 years, and the median duration of the disease was 5 years. In 51 patients (68.0%), the neurovascular conflict (NVC) was due to single-vessel compression, while multiple vessels were found in 24 cases (32.0%). Complete resolution of HFS was achieved in 84% of patients, with an additional 6.7% reporting occasional mild spasms. Delayed resolution occurred in 18.7% of cases, typically within 30 days postsurgery. The overall complication rate was low, with 8.0% experiencing hearing deficits and 1.3% reporting persistent dysphonia. According to the Japanese grading system, excellent results (complete disappearance of HFS and no complications) were obtained in 62 patients (82.7%) and good results in 7 (9.3%). Involvement of the vertebral artery (VA) was associated with poorer outcomes, with a significant reduction in achieving complete resolution (OR 0.23, p = 0.031).

Conclusions: Interposition MVD using autologous muscle pads represents an effective and durable treatment for HFS, particularly when the offending vessel is not a large-caliber artery, such as the VA or basilar artery (BA). The present study results are in line with those of the best series evaluating long-term resolution of the spasm and surgical complications. Despite a limited rate of recurrences, the described technique provides a high rate of spasm resolution, minimal complications, and high patient satisfaction. In the case of an NVC near the VA or BA, interposition with stiffer materials or the transposition technique may ensure a higher rate of HFS control.