Abstract
The treatment of writer’s cramp (W’sC) is essentially based on the use of botulinum toxin. However, additional treatments are sometime required to prolong the effects of the toxin, compensate for its progressive loss of efficacy in some subjects, and re-educate handwriting (e.g., rehabilitation strategies). Low-frequency repetitive transcranial magnetic stimulation (rTMS) has been employed to improve W’sC, but with short-lasting and controversial outcomes. We report on the effects of a long-lasting low-frequency rTMS paradigm on W’sC symptoms. A 25-year-old male with a diagnosis of simple W’sC was enrolled in the study. He underwent an objective assessment using the Writer’s Cramp Rating Scale (WCRS) and the 1-min writing test. Further, we recorded muscle activation of the upper limb during handwriting using an EMG wireless system. The patient was provided with 1,200 biphasic magnetic pulses delivered at 1 Hz over the left premotor cortex (PMC), 15 times scheduled every 2 days, thus covering a period of 5 weeks, followed by 10 days of rest. This block of stimulations was practiced other four times, for a period of 6 months. The patient showed a gradual clinical improvement with the progression of the treatments. W’sC symptoms totally disappeared and all the clinical scores showed a significant improvement after rTMS completion. Such improvement lasted up to 1 year after the end of the treatment. Moreover, we detected a long-lasting improvement in sensorimotor plasticity as measured by a paired associative stimulation protocol. Our case suggests that the long-lasting application of 1 Hz rTMS to PMC is a safe and potentially valuable tool to improve W’sC symptoms enduringly, probably by reverting maladaptive plasticity mechanisms within the sensory-motor areas of the hemisphere contralateral to the dystonic hand.
Highlights
Writer’s cramp (W’Sc) is a task-specific dystonic movement disorder characterized by involuntary cramping of muscles of the hand, forearm, or upper arm selectively triggered by writing (Sheehy and Marsden, 1982; Stahl and Frucht, 2016), with a noticeable impairment of writing
cortical silent period (CSP) duration was 98 ms, motor evoked potential (MEP) amplitude increase induced by rapid paired associative stimulation (rPAS) was very large (Table 1)
It lacked of topographic specificity, i.e., MEP amplitude showed a very large increase in both the abductor pollicis brevis (APB) and first dorsal interosseous (FDI) muscles
Summary
Writer’s cramp (W’Sc) is a task-specific dystonic movement disorder characterized by involuntary cramping of muscles of the hand, forearm, or upper arm selectively triggered by writing (Sheehy and Marsden, 1982; Stahl and Frucht, 2016), with a noticeable impairment of writing. Additional treatments are required to prolong the effects of the toxin, compensate for its progressive loss of efficacy in some subjects, and re-educate handwriting (i.e., rehabilitation strategies). Recent studies examining the effects of repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation to augment current rehabilitation techniques offered some encouraging results (Cho and Hallett, 2016; Erro et al, 2017; Quartarone et al, 2017). RTMS can induce effects on cortical excitability that outlast the stimulation itself By means of these effects, rTMS can modulate the sensorimotor plasticity, potentially fostering the rehabilitative outcomes in W’sC (Cho and Hallett, 2016; Erro et al, 2017; Quartarone et al, 2017). Cases of long-lasting 1 Hz rTMS paradigm applied to patents with W’sC have not been previously reported in the literature
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