Improvement of Secondary Fixed Dystonia of the Upper Limb After Chronic Extradural Motor Cortex Stimulation in 10 Patients

Abstract

Fixed dystonic postures secondary to ischemic, traumatic, or postsurgical lesions located in the basal ganglia and brainstem constitute a major therapeutic challenge and limit motor rehabilitation efficacy. They are often refractory to conservative treatment. Aberrant cerebral plasticity developed after deep brain lesions is thought to lead to abnormal cortical representation of the affected part of the body and then to pathological fixed postures. To assess the efficacy of motor cortex stimulation in patients with upper limb fixed dystonia. Ten patients were submitted to computer-assisted and electromyography-monitored implantation of intracranial epidural electrodes over the central cortical sulcus contralateral to the affected limb. Patients were followed up from 1 to 9 years (9 patients), except for patient 10, whose follow-up was limited to 4 months. Seven of 7 patients showed > 30% improvement in the Disability of Shoulder, Arm, and Hand Scale and an overall 70% increase in the score of the Short Form-36 Physical Activity subscale with significant and stable improvement of quality of life during stimulation. The partial recovery of hand dexterity observed in most of the treated patients additionally contributed to a significant improvement of their quality of life. Although the pathophysiology of fixed dystonia is unknown, our results suggest a major role of the motor cortex in this condition and reinforce the hypothesis that postlesional delayed cortical rearrangements might take place in these forms and be the target of effective therapeutic neuromodulation.