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.
