Inferior parietal lobule stimulation in task-specific focal hand dystonia: A randomized, crossover clinical trial

Abstract

Abstract OBJECTIVE: To determine the effect of inhibitory repetitive transcranial magnetic stimulation (rTMS) delivered to the left inferior parietal lobule (IPL) on the severity of task-specific focal hand dystonia. METHODS: In this randomized, sham-controlled, double-blind crossover study, participants received single sessions of low-frequency (1 Hz) inhibitory rTMS (1200 pulses) and sham stimulation to the left IPL. At baseline and after each session, we assessed the Writer’s Cramp Rating Scale (WCRS), kinematic analysis using an electrogoniometer, a torsiometer, and the patient-reported improvement on a Likert scale. RESULTS: We recruited 16 right-handed patients with task-specific focal hand dystonia [age: 33.3 ± 11.7 years, 13 male). The mean WCRS score at baseline was 5.8 ± 3.4 in group A (where first 1 Hz rTMS and then sham was applied) and 13.4 ± 5.2 in group B (where first sham and then 1 Hz rTMS were applied). An inhibitory rTMS protocol applied to the left IPL resulted in a statistically significant improvement in the WCRS total score [WCRS difference real minus sham mean (SD): −1 (1.3), (95% confidence interval (CI): −2, −1), p = 0.002] and writing movement score [WMS mean difference (SD): −1 (1.4), CI: (−2, 0), p = 0.005], irrespective of the sequence in which they received the intervention. Secondary outcomes were similar between the groups. CONCLUSION: In patients with task-specific focal hand dystonia, a single session of rTMS to the left IPL resulted in a modest reduction of focal hand dystonia severity. The results serve as a proof-of-concept for future studies to assess the clinical effects of multiple sessions of left IPL inhibition to modulate the abnormally hyperexcitable premotor–parietal–putaminal circuitry in task-specific focal hand dystonia.