Influence of vitamin D on muscle strength and botulinum toxin dosage through surface electromyography.

[PURPOSE] To evaluate the influence of patients' serum vitamin D levels on muscle strength characteristics and whether it impacts the durability of botulinum toxin (BT) treatment.

[METHODS] The muscle strength of the frontal and corrugator muscles was evaluated before and after the application of TB with pre- and post-application control measurements, and at weeks 2, 5 and 12. The effect of vitamin D on muscle strength and its interaction with BT were investigated in 20 patients. The muscle contraction force was measured by surface electromyography.

[RESULTS] The results revealed statistically significant differences between the frontal measurement groups at weeks 2 and 5, as well as for the corrugator in the same weeks and at week 12. Regarding vitamin D, significant differences were observed only in the initial group with vitamin D > 30 ng/mL compared to < 30 ng/mL for the frontal muscles. Patients with higher levels of vitamin D had higher average muscle strength compared to those with lower levels in all evaluations.

[CONCLUSIONS] It was observed that vitamin D influences muscle strength and the necessary dosage of BT.