Effect of Prior Botulinum Toxin A Treatment on Persistence and Recurrence of Hemifacial Spasm Following Microvascular Decompression Surgery

Background: The two main treatment options for hemifacial spasm (HFS) are botulinum toxin A (BTX) and microvascular decompression (MVD); each therapy carries its own advantages and disadvantages. BTX treatment is low risk and highly effective, with efficacy in reducing spasms ranging from 75 to 100%. However, reinjection is required every 3 to 6 months and tachyphylaxis may develop. Thus, there is a high cost and potentially limited effectiveness of long-term BTX therapy. Meanwhile, surgical MVD is a one-time procedure that allows more definitive treatment and has a reported success rate of 90%. However, an unwanted outcome of MVD may be HFS persistence or recurrence, rates of which range from 10 to 40% and 5 to 10%, respectively.

It is not uncommon for patients to initially receive BTX injections and later undergo MVD if the neurotoxin eventually fails to adequately control spasms. However, knowledge about the effect of BTX treatment on outcomes after MVD is scarce. Some authors postulate that repeated BTX injections induce terminal motor axon growths that may lead to poly-innervation of muscle fibers and increased muscle excitability over time, thus limiting the effectiveness of MVD.

The purpose of this study was to evaluate whether prior administration of BTX affects outcomes after MVD for HFS. We also analyzed potential factors associated with HFS persistence or recurrence after MVD, including intraoperative neurophysiological monitoring with lateral spread response (LSR).

Methods: We performed a historic cohort of patients with HFS who underwent first-time MVD by a single surgeon from 2013 to 2023. Patients were categorized into two groups based on their treatment history: those with no prior BTX treatment (control) and those treated previously with BTX (BTX). We assessed group differences in demographics, pre-operative clinical data, and post-operative clinical outcomes categorized as follows: (1) HFS persistence, (2) HFS recurrence, or (3) HFS remission. Chi-square tests and logistic regression analyses were used to assess factors associated with HFS persistence and recurrence.

Results: A total of 40 patients with HFS were included in the study and the length of postoperative follow-up ranged from 6 weeks to 8 years. There were 18 patients in the control group (52.11 ± 12.86 years, 56% female). Twenty-two patients were in the BTX group (60.27 ± 11.34 years, 82% female). Thirty-one patients (78%) achieved complete HFS remission after first-time MVD. The HFS remission rate in the BTX group (16/22, 73%) was not significantly different from that of the control group (15/18, 83%; p = 0.48). Five patients (13%) had HFS persistence and four patients (10%) had HFS recurrence. Although not statistically significant, the BTX group had a higher persistence rate (4/22, 18%) compared to the control group (1/18, 6%, p = 0.36). There was no statistical difference in HFS recurrence rates between the control (2/18, 11%) and the BTX groups (2/22, 9%, p = 1.00). We did not identify any demographic or perioperative factors significantly associated with HFS persistence or recurrence.

Conclusion: Prior BTX treatment does seem to impact the outcome of MVD for the treatment of HFS.

Publication History

Article published online:
07 February 2025