Pallidal deep brain stimulation improved symptoms in patients with primary dystonia. Those with a shorter disease duration may have a better outcome.
SEATTLE—Improvement following pallidal deep brain stimulation (DBS) for patients with primary dystonia may be predicted by age at surgery and duration of disease, according to Ioannis U. Isaias, MD. Patients with shorter disease duration may have a better outcome, while those older than 26 and with short disease duration may require more than a year to experience optimal benefit, Dr. Isaias reported at the 61st Annual Meeting of the American Academy of Neurology.
“The role of outcome predictors has actually been poorly defined,” stated Dr. Isaias, of the Department of Neurology at the Mount Sinai School of Medicine in New York City. A negative correlation between disease duration and DBS outcome after one year was previously reported. Dr. Isaias and colleagues investigated the role of clinical factors, such as disease duration and severity and DYT1 status, and demographic factors, such as gender, age at onset, and age at time of surgery, that might predict the outcome of DBS at one and three years.
Clinical records of 42 patients with medically refractory primary dystonia (31 DYT1+) and who underwent stereotactic pallidal DBS surgery among four international centers with three-year follow-up were assessed with use of the Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) at baseline, one year after DBS, and three years after DBS. Age, gender, duration of disease, and disease severity were correlated with BFMDRS score using Pearson coefficients and multiple regression analysis. A cluster analysis was conducted to identify participants who improved at one year and to further classify them by putative outcome predictive factors.
Disease Duration Versus Age at Surgery
“Pallidal DBS was largely successful, with an average improvement of 72% at one year and 77.4% at three years,” Dr. Isaias and colleagues reported. “Both disease duration and age at surgery significantly correlated with DBS outcome at one and three years, but only disease duration maintained a significant correlation after multiple regression analysis.” Clinical outcomes were not correlated with any other factors.
Patients who were 26 or younger showed approximately 28% more improvement, compared with patients who were 26 or older at the time of surgery. In addition, patients who had a shorter disease duration (17 years or less) showed 20% more improvement than those with a longer disease duration.
Based on these results, Dr. Isaias and his team classified a patient population consisting of three groups—those who were young at the time of surgery and with a short disease duration (n=50), those who were older at the time of surgery and had a short disease duration (n=11), and those who were older at the time of surgery and had a long disease duration (n=60).
Younger patients with the shortest duration of disease had the most improvement at one-year and three-year follow-ups. Dr. Isaias and coinvestigators commented that those who were older than 26 at the time of surgery and had a short disease duration may require more than one year to maximize outcome. Age at onset, severity of disease, and DYT1 status showed no predictive value. Most DYT1+ patients who were young at the time of surgery and had a short disease duration did not improve.
Dr. Isaias’s group concluded that patients with primary dystonia are “semi-candidates” for pallidal DBS. “We speculate that disease duration predicts how much clinical improvement may be expected after pallidal DBS, while age at surgery predicts how long it would take to achieve maximum improvement.”
—Laura Sassano