Laryngeal dystonia and vocal tremor response to botulinum toxin injection.

[PURPOSE] The main objective of this study was to compare laryngeal dystonia (LD) and vocal tremor's (VT) response to botulinum toxin injection.

[METHODS] Retrospective study including every patient with LD or VT injected with botulinum toxin guided by electromyography, from January 1, 2010, to September 30, 2022, at a tertiary hospital centre. Improvement was assessed with the VHI-10, grade of dysphonia in a visual analogue scale (VAS; 0-10), GRBAS(I) scale (0-3) and maximum phonation time (MPT).

[RESULTS] A total of 77 patients were included, 44 patients with LD and 33 with VT. There were no differences between groups on pre-treatment VHI-10, grade of dysphonia in the VAS, MPT and G, R, B, A and I at diagnosis (p > 0.05). S was significantly higher in patients with LD (p < 0.001). After the first injection, both groups showed an increase in the grade of dysphonia on the VAS and a decrease in VHI-10, G, S and I (p < 0.05), with a higher variation in the VAS and S parameters in the LD group compared to VT (p < 0.05). In the 54 patients that performed two or more injections, G, S and I had a higher decrease in patients with LD when compared to patients with VT (p < 0.05).

[CONCLUSION] BTX injection was successful in improving the VHI-10, grade of dysphonia on the VAS and G, S and I in the GRBAS-I scale for both DT and VT. LD seems to have a better response to BTX in comparison to VT.