Abnormalities of the sensory system have been proposed as causative factors for dystonia By mapping the human cortical hand somatosensory area of 6 patients with focal dystonia of the hand, we found an abnormality of the normal homuncular organization of the finger representations in the primary somatosensory cortex (S1). Although a remote antecedent event or even a developmental anomaly cannot entirely be ruled out, our findings may support the concept that abnormal plasticity is involved in the development of dystonia.

The objective of this study is to assess the safety and efficacy of repetitive transcranial magnetic stimulation (rTMS) for gait and bradykinesia in patients with Parkinson's disease (PD). In a double-blind placebo-controlled study, we evaluated the effects of 25 Hz rTMS in 18 PD patients. Eight rTMS sessions were performed over a 4-week period. Four cortical targets (left and right motor and dorsolateral prefrontal cortex) were stimulated in each session, with 300 pulses each, 100% of motor threshold intensity. Left motor cortex (MC) excitability was assessed using motor evoked potentials (MEPs) from the abductor pollicis brevis. During the 4 weeks, times for executing walking and complex hand movements tests gradually decreased. The therapeutic rTMS effect lasted for at least 1 month after treatment ended. Right-hand bradykinesia improvement correlated with increased MEP amplitude evoked by left MC rTMS after individual sessions, but improvement overall did not correlate with MC excitability. rTMS sessions appear to have a cumulative benefit for improving gait, as well as reducing upper limb bradykinesia in PD patients. Although short-term benefit may be due to MC excitability enhancement, the mechanism of cumulative benefit must have another explanation.

The results support the hypothesis that A(2A) receptor mechanisms contribute to symptom production in PD and that drugs able to selectively block these receptors may help palliate symptoms in levodopa-treated patients with this disorder.