BoNT injection therapy is effective established therapy for focal spasticity of the upper limb and is commonly used for upper limb focal dystonia. BoNT limb injections may be performed using anatomical landmarks, EMG, E-stim and US guidance. A limited number of studies have attempted to compare these injection guidance techniques with inconclusive results.

Two center, randomized, cross-over, assessor-blinded trial. Patients with focal hand dystonia or upper limb spasticity, on stable BoNT therapy for at least 2 previous injection cycles, were enrolled. Patients were randomized to either E-stim or US. Procedure-related discomfort at the end of the procedure and efficacy/adverse effects at one month after the procedure were assessed. At 3 months after the first procedure, the patients crossed over to the other guidance method, with similar repeat assessments. Repeated measures ANCOVA was used with linear mixed model covariate selection.

20 subjects enrolled, 12 males, 10 upper limb spasticity and 10 dystonia. There was no difference between the two localization techniques in benefit or weakness after injection, as measured by both patient-reported visual analog scale (VAS, 0-100, least square mean 51.5mm with US and 53.1 with E-stim) or clinician global impression of change (CGI). There was a significant difference in perceived discomfort, with E-stim perceived as more uncomfortable by patients, VAS LS mean 34.5 vs 19.9 for E-stim and US, respectively (p=0.0082). There were no serious adverse events.

E-stim and US guidance procedures yield similar benefit and weakness. E-stim was perceived more uncomfortable by patients. Additional analyses, including the effects of each guidance method on procedure duration, correlation between muscle weakness and efficacy, and subgroup analyses by condition, are ongoing.