Deep Brain Stimulation for Dystonia Effective Long Term

Allison Gandey

April 24, 2009

April 24, 2009 — An implanted deep-brain-stimulation device is a safe and effective treatment for primary generalized dystonia, a new long-term study suggests. The work, published in the April issue of the Archives of Neurology, followed patients for at least 2 years after surgery, and the results are promising.

"We are seeing that deep brain stimulation works and that the benefits can be long lasting," senior author Michele Tagliati, MD, from the Mount Sinai School of Medicine, in New York, told Medscape Neurology & Neurosurgery.

While many questions remain, Dr. Tagliati says this study will help doctors address the 1 question most often asked by dystonia patients or their parents considering the procedure: "How long will the results last?"

The retrospective analysis included 30 dystonia patients. Most were followed for 3 years, but 5 were tracked for 7 years, and 1 patient for 8 years.

Participants received Medtronic's deep-brain-stimulation therapy. The company received humanitarian device exemption approval from the US Food and Drug Administration in April 2003.

Significant Improvement in Motor Function

All 30 patients experienced significant improvement in motor function. The Burke-Fahn-Marsden dystonia rating motor score improved a mean 79.6% (range, 40% – 100%) at 1 year and 82.5% (range, 49% – 100%) at 2 years.

The disability score improved a mean of 69.2% (range, 7% – 100%) at 1 year and 75.2% (range, 12.5% – 100%) at 2 years.

Overall clinical improvement was maintained at every successive examination and was still greater than 80% in the 5 patients who reached 7 years of follow-up.

"For many, this can mean the difference between being in a wheelchair or being able to walk and run again," Dr. Tagliati said. "While not all patients will experience such remarkable results, for some the improvements can be substantial."

In this study, none of the patients experienced an adverse neurologic event during surgery. But researchers observed hardware- and stimulation-related adverse events in 23% and 13% of patients.

Investigators saw a 4.9% complication rate per electrode-year, which they suggest is low.

Lower Stimulation Frequencies to Extend Battery Life

The researchers found that patients treated with lower stimulation frequencies and shorter pulse widths tended to benefit from longer battery life without experiencing a worse clinical outcome.

"These findings support other recent studies suggesting that the minimal effective stimulation pulse width and frequency for primary generalized dystonia may be lower than originally thought," they write.

Additional work is needed to determine the most efficient long-term stimulation settings for deep brain stimulation, Dr. Tagliati said. "This study is an important step, but it is by no means the last word, and there is still much to be understood."

This study was funded in part by a grant from the Bachmann-Strauss Dystonia and Parkinson Foundation. Dr. Tagliati and coauthor Dr. Ron Alterman, also from the Mount Sinai School of Medicine, report having received speaking honoraria and consulting fees from Medtronic that were unrelated to this work.

Arch Neurol. 2009;66:465-470. Abstract