Deep-brain stimulation effects sustained in dystonia

By Eleanor McDermid, Senior medwireNews Reporter

Improvements in dystonia achieved with deep-brain stimulation (DBS) are usually sustained for at least 5 years, shows follow up of a randomized trial.

The trial was restricted to patients with primary dystonia (generalized or segmental), however. In a commentary accompanying the paper published in The Lancet Neurology, Michael Okun and Kelly Foote (University of Florida Center for Movement Disorders and Neurorestoration, Gainesville, USA) caution against overinterpreting the findings.

"It should be noted that most of the available data on dystonia DBS are unblinded, and the best results for this treatment have been reported in a select group of carefully screened patients," they say. "Patients with dystonia should be informed by their treating clinicians about how well they fit the profile of the patients typically included in the randomised trials of DBS."

They stress: "When outcome expectations are realistic and not inflated, the likelihood that patients' expectations will be met is increased."

In the original trial, which included 40 patients, blinded evaluations 3 months after surgery revealed 39.3% improvement in symptoms in patients receiving active DBS and a 4.9% deterioration in those given sham DBS. From then on, all patients were given 6 months of active DBS, and 38 agreed to long-term follow up (unblinded).

In an intention-to-treat analysis (including all 40 patients), the average Burke -Fahn -Marsden dystonia rating scale motor score was reduced by 20.8 points at 6 months, relative to baseline, by 26.5 points at 3 years, and by 25.1 points at 5 years. This corresponded to 47.9%, 61.1%, and 57.8% reductions versus baseline.

The research team, led by Jens Volkmann (Christian-Albrechts-University, Kiel, Germany), notes that the improvement seen between 6 months and 3 years was statistically significant.

Okun and Foote comment: "This scenario is unique when compared with other diseases treated with DBS, and will demand that individuals have patience while waiting to achieve full benefit from the therapy."

Four patients initially failed to respond to DBS, but two of these achieved at least a 50% improvement after more than 6 months and several reprogramming sessions. Another four patients had good responses at 6 months but lost the benefits by the 5-year follow up.

Between 6 months and 5 years there were 49 adverse events, the most common being dysarthria or worsening dysarthria (16 cases), and accidental deactivation of the internal pulse generator (five cases). There were 21 serious adverse events (requiring hospital admission or extension of stay) and almost all were directly related to the DBS device.

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