Abstract Details

Dystonia is a network disorder. The inferior parietal lobule has extensive projections to the premotor cortex which is found to be aberrant in FHD. Modulation of motor areas via stimulation of the IPL may have downstream effects on M1 hand area.

To assess the effect of an inhibitory rTMS protocol to the left inferior parietal lobule on dystonia severity in patients with focal hand dystonia (FHD).

We conducted a randomized, sham control, double-blind, crossover study. All participants received single sessions of low frequency (1Hz) inhibitory rTMS [Intervention] and  Sham stimulation [Control] over the left IPL in random order. Each stimulation session lasted for 20 minutes and 300 pulses in 4 blocks were delivered at 90% RMT to the anatomically localized left IPL. At baseline and the end of each session of rTMS and sham stimulation, WCRS, kinematic analysis using electrogoniometer and torsiometer and subjective improvement by Likert scale were assessed.

We recruited 16 right-handed patients with task-specific FHD [mean age: 25.1 (range 19-54)years, gender(men-13), mean duration of symptoms: 8.3 (range 1-25 years)]. The mean WCRS score at baseline was 5.8 ± 3.4 in group A (received 1Hz rTMS initially) and 13.4 ± 5.2 in group B ( received sham stimulation initially). An inhibitory rTMS protocol applied to the left inferior parietal lobule resulted in significant improvement in dystonia severity measured by the WCRS total score (WCRS difference REAL minus SHAM mean (SD):-1(1.3), 95% CI -2,-1, p= 0.002) and Writing Movement Score (WMS  difference REAL minus SHAM mean (SD): -1(1.4), C.I. -2 to 0, p=0.005) and thus significant treatment effect within individual subjects, irrespective of the sequence in which they received the intervention.

In patients with task-specific focal hand dystonia, an inhibitory TMS protocol delivered to the inferior parietal lobule may modulate the abnormally hyperexcitable premotor-parietal-putaminal circuitry and reduce FHD severity.