Neurological movement disorder substantially reduced by deep brain stimulation therapy

15 November 2006.

Minneapolis, USA. Research shows that pallidal deep-brain stimulation (DBS) can provide significant and sustained benefits to people with a disabling form of a neurological movement disorder called dystonia.

The treatment uses an implantable medical device to send mild electrical pulses to precisely-targeted areas of the brain involved in motor control. The results are published in the latest issue of The New England Journal of Medicine. The treatment was pioneered by Medtronic, which sponsored the study at ten medical centres in Germany, Norway and Austria.

All 40 patients who took part in this double-blind, randomized, controlled clinical study had "marked disability" owing to primary generalized or segmental dystonia, despite the best medical care. They all received an Activa neurostimulation system with electrodes positioned in the globus pallidus, a structure that forms part of the basal ganglia and which is involved in regulating voluntary movement at a subconscious level. In the study, half the patients began receiving stimulation immediately after implant of the system. The other half did not have stimulation switched on until three months after implant. Neither the patients nor the physicians who evaluated them knew who was receiving stimulation for the first three months of the study.

Three months after randomization, patients who received neurostimulation showed a significant reduction in the severity of their symptoms and in their degree of disability. The neurostimulation group experienced a 39.3 % improvement in the movement score (using the Burke-Fahn-Marsden Dystonia Rating Scale) compared to a 4.9% improvement in the non-stimulation group. Similarly, neurostimulation patients recorded a 37.5% reduction in the scale's disability scores, compared to an 8.3% reduction among non-stimulation patients.

Clinical evidence in support of neurostimulation for the treatment of movement disorders continues to mount. Numerous studies over the past decade have shown neurostimulation to be a viable treatment for symptoms of Parkinson's disease and disabling tremor. This latest study underlines the safety and efficacy of neurostimulation as a treatment for patients with debilitating forms of primary dystonia involving multiple parts or both sides of the body. The authority of many previous dystonia studies has been hampered by the difficulties of eliminating bias and by the lack of effective controls. The randomized, controlled and blinded design of this study makes the results all the more compelling.

As part of the study, all patients — regardless of their original group assignment — received neurostimulation therapy for at least six months. After three months, patients in the non-stimulation group had neurostimulation switched on, unblinding this extension phase of the study.

After the six-month extension phase, patients realized an average improvement in the motor score of 46%. This symptomatic benefits translated into significant improvements in all activities of daily living. Using the physical component of the SF-36 measure, quality of life was found to have improved by 31.5%.

Commenting upon the potential impact of these findings, "This study fulfils the rigid criteria of Class I evidence and, hence, the results will have implications on future dystonia treatment guidelines worldwide. Neurostimulation therapy should be implemented much earlier in the course of generalized or segmental dystonia as there are no alternatives in this population" added the leading researchers, Professor Reiner Benecke and Dr Jens Volkmann, from the Neurology Departments of, respectively, the University of Kiel and the University of Rostock in Germany.

Twenty-two adverse events were reported. In the randomised phase there were no reported adverse events with permanent sequelae. The adverse events in the extension phase were typically related to the stimulation and were resolved or improved by changing the stimulation measures. Four adverse events were considered permanent, requiring cessation of stimulation. No change in patients' cognitive status was observed, and mood was reported to have improved significantly during the study.

Activa therapy from Medtronic is available worldwide as a treatment for primary dystonia, the symptoms of Parkinson's disease and disabling tremor - the three most common movement disorders.

Dystonia is characterized by involuntary muscle contractions, which force certain parts of the body into sudden and sometimes permanent abnormal movements or postures. It can affect any part of the body - including the arms and legs, trunk, neck, eyelids, face, or vocal cords. Over 80,000 Europeans suffer from dystonia, the results of which often leave them in permanent debilitating pain or unable to live a normal life because of the contortions into which their muscles force them. Mental function is unaffected in dystonia patients frequently leaving them prisoners in their own bodies.

The study involved patients with primary generalized or segmental dystonia. "Primary" refers to the presence of dystonia in the absence of any other underlying disorder. "Generalized" means the symptoms involve several body areas on both sides of the body, whereas "segmental" indicates that two or more adjacent body areas are involved.

The study was supported by a research grant from Medtronic, and was conducted independently at ten academic medical centres in Germany, Norway, and Austria.

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