Dementia and Deep-Brain Stimulation in Parkinson’s

Dementia prevalence and incidence were not higher over time in Parkinson’s disease patients who had deep-brain stimulation (DBS) than in the general Parkinson’s population, a retrospective single-center study in France suggested.

Among Parkinson’s disease patients who had subthalamic nucleus DBS, dementia prevalence was 2.3% at 1 year, 8.5% at 5 years, and 29.8% at 10 years, reported Elena Moro, MD, of Grenoble Alpes University, and co-authors.

Dementia cumulative incidence at 1, 5, and 10 years was 2.3%, 10.9%, and 25.7%, respectively, the researchers noted in their study online in Neurology. The corresponding dementia incidence rate was 35.6 per 1,000 person-years.

“These rates are not higher than those reported in the general population of people with Parkinson’s,” Moro said. “The few studies that are available with similar disease duration have reported higher rates of dementia. Other studies of people with Parkinson’s who are taking medication for their symptoms show an incidence rate for dementia that varies from 50 to 100 per 1,000 person-years.”

This study shows long-term cognitive outcomes of the widest sample of Parkinson’s patients with longstanding subthalamic nucleus DBS reported so far, the investigators said.

“Previous studies concerning smaller numbers of patients and with shorter follow-up reported controversial results,” Moro told MedPage Today. “Our findings are more robust and support safety of DBS in the long-term.”

“Moreover, we found that preoperative clinical predictive factors of dementia after DBS were the same as in Parkinson’s patients without DBS,” she added.

Strong evidence shows that DBS of the subthalamic nucleus outperforms medical treatment in controlling motor complications in both short- and long-term follow-up in advanced Parkinson’s disease.

In their study, Moro and co-authors assessed 175 Parkinson’s patients who had bilateral subthalamic nucleus DBS between 1993 and 2007 at Centre Hospitalier Universitaire de Grenoble. Baseline average age was 56 and 63% were men; mean disease duration at baseline was 12 years.

All 175 patients were reassessed at 1 year; 142 (81.2%) were reassessed at 5 years, and 104 (59.4%) at 10 years. Fifty patients (28.6%) were lost at the 10-year follow-up, and 21 (12%) died. Mean follow-up time was 7.8 years; median time was 10 years. No patients dropped out due to explantation of the DBS system.

Male sex (HR 3.0, 95% CI 1.32-6.83, P=0.009), higher age (HR 1.07, 95% CI 1.02-1.13, P=0.007), hallucinations (HR 2.41, 95% CI 1.29-4.51, P=0.006), lower frontal score (HR 0.90, 95% CI 0.87-0.94, P<0.0001), and perioperative cerebral hemorrhage (HR 16.2, 95% CI 5.09-51.54, P<0.0001) were predictors of dementia.

“Although akinetic-rigid phenotype is widely recognized as a risk factor of dementia, in the present study it did not predict the development of dementia,” Moro and co-authors wrote. “This may be related to our strict preoperative selection, which allowed excluding from surgery patients with severe axial symptoms (not fully levodopa responsive) and cognitive issues.”

The study had several limitations, the main one being the lack of a control group, an issue in all long-term DBS studies, the researchers noted, adding that the high percentage of patients lost to follow-up also may have led to dementia incidence being underestimated.