Laryngeal dystonia and vocal tremor response to botulinum toxin injection

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

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).

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).

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.