Abstract
Though the pathophysiology of dystonia remains uncertain, two primary factors implicated in the development of dystonic symptoms are excessive cortical excitability and impaired sensorimotor processing. The aim of this study was to determine the functional efficacy of an intervention combining repetitive transcranial magnetic stimulation (rTMS) and sensorimotor retraining. A randomized, single-subject, multiple baseline design with crossover was used to examine participants with focal hand dystonia (FHD) (n = 9). Intervention: 5 days rTMS + sensorimotor retraining (SMR) vs. Five days rTMS + control therapy (CTL) (which included stretching and massage). The rTMS was applied to the premotor cortex at 1 Hz at 80% resting motor threshold for 1200 pulses. For sensorimotor retraining, a subset of the Learning-based Sensorimotor Training program was followed. Each session in both groups consisted of rTMS followed immediately by 30 min of the therapy intervention (SMR or CTL). Contrary to our hypothesis, group analyses revealed no additional benefit from the SMR training vs. CTL. When analyzed across group however, there was significant improvement from the first baseline assessment in several measures, including tests of sensory ability and self-rated changes. The patient rated improvements were accompanied by a moderate effect size suggesting clinical meaningfulness. These results provide encouragement for further investigation of rTMS in FHD with a need to optimize a secondary intervention and determine likely responders vs. non-responders.
Highlights
Focal dystonia is a movement disorder that can affect any body part and severely impair a person’s ability to function in their daily life
Group Results Effect of the Two Different Interventions on Behavior and Corticospinal Excitability Results of the two factor RM ANOVA revealed no significant intervention (CTL vs. SMR) × time (Pre-test, Post-test, Follow up) interactions in any measure, indicating there was no superior benefit or neurophysiologic change to the sensorimotor retraining intervention with repetitive transcranial magnetic stimulation (rTMS) compared to control with rTMS (Table 3)
One participant (#7) in the control therapy (CTL)-SMR group reported a worsening of symptoms at the first post-test that returned to normal at follow-up (GROC change of -4)
Summary
Focal dystonia is a movement disorder that can affect any body part and severely impair a person’s ability to function in their daily life. In task specific hand dystonia, the dystonia manifests when a person attempts to execute specific tasks such as writing, typing, or playing a musical instrument. Most often these tasks are related to a repetitive action, often done in the context of an occupation, impairing the ability to work and reducing quality of life. There is evidence to suggest that the problem may be related to faulty sensorimotor integration (for review, Abbruzzese and Berardelli, 2003; Quartarone et al, 2014) Another abnormality in FHD is that of plasticity. It has been demonstrated that decreases in M1 inhibition facilitate the induction of plasticity (Hess et al, 1996; Di Lazzaro et al, 2006), the abnormally increased plasticity in dystonia could be related to the abnormally decreased motor cortical inhibition that is found in patients with dystonia (Hallett, 2011)
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