Study Shows Deep-Brain Stimulation Effectively Treats Generalized Dystonia Long Term

Kathleen Louden

June 25, 2008

June 25, 2008 (Chicago, Illinois) — Twenty-six patients with genetically confirmed DYT1 dystonia had improvement in their motor signs with pallidal deep-brain stimulation (DBS) for at least 3 years and for as long as 10 years in 2 of the patients, a new study showed.

Results showing improvement at 1 year postoperatively did not significantly differ from outcomes at 3, 5, and 6 years after the start of treatment, said lead author Laura Cif, MD, PhD, from the Hospital Gui de Chauliac and the University of Montpellier School of Medicine, in France.

"Our results show there is a persistent efficacy of DBS in patients with DYT1 dystonia. The 10-year follow-up is a long time compared with other reports in the literature," Dr. Cif told Medscape Neurology & Neurosurgery.

She presented the results here at the 12th International Congress of Parkinson’s Disease and Movement Disorders, sponsored by the Movement Disorder Society.

Improved motor skills

Before surgery to implant the electrodes, the patients' mean motor score on the Burke-Fahn-Marsden Dystonia Rating Scale was 57.51 (with a score of 120 being most severe), according to the authors' poster presentation. There was a statistically significant decrease postoperatively to 15.15 (P < .0001) at 3 years and 16.25 (P < .0001) at 5 years.

The 26 consecutively recruited patients (16 females and 10 males) had a mean age at onset of disease of 8.1 years and a mean age at surgery of 21.1 years. One patient was an older adult. The mean number of body regions affected by dystonia before surgery was 6.2, indicating generalized disease, Dr. Cif said.

All patients initially had a bilateral single electrode lead implanted in the posterior lateral aspect of the internal globus pallidus, and no repositioning was required, Dr. Cif noted. If a second electrode pair was implanted later, she explained, it was placed in front of the original implant if the patient's lower limbs were primarily involved and behind the initial lead if the arms were affected. No patient had to discontinue stimulation, but 2 leads had to be replaced after they fractured, she told Medscape.

Motor and disability scores on the Dystonia Rating Scale were evaluated preoperatively, at 6 and 12 months postoperatively, and every year after that for up to 10 years. Two neurologists examined the patients, usually in a nonblinded fashion, Dr. Cif said.

Progression of dystonia

Despite long-term treatment with DBS, the dystonia slowly progressed, however, the authors found.

"Even if we have a significant improvement in these patients, there is some progression of the underlying disease, which we can see when we turn off the neurostimulator," Dr. Cif said in an interview. "Sometimes motor signs that were [initially] completely controlled under DBS recur."

Some patients had worsening of their disease about 4 years postoperatively, but she added that the loss of efficacy was not statistically significant for the whole patient population.

A subgroup of 8 patients, however, required implantation of a second pair of electrode leads (at a mean of 5 years after the first surgery) because of initial incomplete response (< 50%) or subsequent worsening of dystonia. This group, compared with the 18 patients who received only a single pair of electrodes, had significantly worse motor scores (P = .01) and disability scores (P = .025) at 5 years, results showed. In addition, only 4 of the 8 patients improved after receiving their second electrode pair.

"Not a cure"

Still, the results were encouraging to 1 attendee who reviewed the poster presentation. "DBS is not a cure, but a long-term therapy whose efficacy doesn't wane significantly is very exciting," said Benjamin Walter, MD, medical director of the DBS program at University Hospitals Case Medical Center, in Cleveland, Ohio.

A blinded, independent neurologic evaluation would have added to the validity of the study results, he commented. However, after viewing the authors' videotape of study patients moving before and after surgery, he said, "There's still dramatic improvement."

Neither Dr. Cif nor Dr. Walter reported any relevant financial disclosures.

12th International Congress of Parkinson’s Disease and Movement Disorders: Abstract 484. Presented June 24, 2008.

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