Assessing Changes in Hand Tactile Sensitivity After Glabellar Botulinum Toxin Treatment.

Purpose: We aimed to assess behavioral changes in tactile sensitivity in patients receiving cosmetic glabellar botulinum toxin-A injections.

Methods: In this prospective cohort study, we conducted quantitative sensory testing on 20 patients receiving 15 to 35 units of glabellar botulinum toxin-A treatment between October 1, 2022 and March 8, 2023. We used modified Von Frey filaments to exert forces between 0.25 mN and 512 mN to the dorsal hand just prior to botulinum toxin-A injections. Filament tips were uniform, rounded, and 0.5 mm in diameter to prevent nociceptor activation. This process was repeated 4 to 6 weeks after injection to assess for any change in minimal mechanical detection thresholds.

Results: Minimal mechanical detection thresholds decreased (patients detected smaller amounts of force) overall, in patients with prior botulinum toxin-A treatment, and in patients without prior botulinum toxin-A treatment: 5.34 mN to 4.33 mN (p = 0.22), 6.43 mN to 5.97 mN (p = 0.31), and 4.44 mN to 3.00 mN (p = 0.53), respectively.

Conclusions: Our results suggest that the plastic changes observed in previous studies do not necessarily result in clinically significant manifestations when utilizing small to moderate amounts of botulinum toxin-A for aesthetic correction of glabellar lines, thus highlighting the safety of botulinum toxin-A for this indication. Further research is required to gain a comprehensive understanding of whether hand-associated cortical activity is altered after aesthetic amounts of botulinum toxin are injected.