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Deep brain stimulation remained effective in Parkinson's disease patients more than 15 years after the device was implanted, and patients continued to demonstrate significant improvement in motor symptoms, a retrospective study showed.

Parkinson's patients who had bilateral subthalamic nucleus deep brain stimulation for 15 years or longer spent 75% less time with dyskinesia and 58.7% less time in the off state than pre-surgery baseline (both P<0.001), reported Elena Moro, MD, PhD, of Grenoble Alpes University in France, and co-authors.

These patients also reduced their dopaminergic drugs by 50.6% (P<0.001), they wrote in . The Parkinson's Disease Quality of Life () questionnaire total score, emotional function domain score, and social function domain score improved by 13.8% (P=0.005), 13.6% (P=0.01) and 29.9% (P<0.001), respectively.

"Deep brain stimulation benefits seem to last for several years but not enough data have been available to show that these effects are still present more than 15 years after surgery," Moro said in a statement.

"Our study found that, despite the natural progression of Parkinson's disease and the worsening of some symptoms that become resistant to medications over the years, participants still maintained an overall improvement in quality of life," she added.

"These results (better motor outcomes with less medication) reinforce why subthalamic nucleus deep brain stimulation has revolutionized treatment for advanced Parkinson's disease," observed Kelvin Chou, MD, of the University of Michigan in Ann Arbor, and David Charles, MD, of Vanderbilt University in Nashville, in an .

Grenoble researchers were the first to report the therapeutic effects of bilateral subthalamic nucleus deep brain stimulation on bradykinesia and rigidity in patients with Parkinson's disease, Chou and Charles noted. The Grenoble group now has the largest number of patients who have lived with deep brain stimulation for 15 years or more.

When patients ask how long benefits of deep brain stimulation last, "we can now reassure them that, at least for subthalamic nucleus deep brain stimulation, improvement in motor complications lasts beyond 15 years and is often accompanied by improvement in quality of life," the editorialists wrote.

In their study, Moro and colleagues evaluated 51 patients with a mean of about 17 years followup after surgery. At surgery, all patients had idiopathic Parkinson's disease, disabling motor complications (motor fluctuations or levodopa-induced dyskinesia), and levodopa responsiveness in all Parkinson's cardinal motor symptoms, including tremor. On average, the group -- 33 men and 18 women -- was about 51 years old at baseline and had Parkinson's disease for 11.35 years.

In 39 patients with complete long-term data, subthalamic nucleus deep brain stimulation improved motor fluctuations and dyskinesia scores on the Unified Parkinson's Disease Rating Scale (). Compared with baseline, the time spent with dyskinesia was reduced by 75% (1.64 vs 0.41, P<0.001), and the time spent in the off state diminished by 58.7% (1.85 vs 0.74, P<0.001).

In 27 patients with full long-term followup data, both short-term and long-term PDQL scores improved. Total PDQL score improved by 26.7% at 1 year, while emotional function domain scores rose 21.7%, and social function domain scores increased 33.3%.

In the long-term, 19 patients (37.3%) were completely independent in their activities of daily living, 27 patients (52.9%) needed some help, and five (9.8%) were institutionalized. A total of 18 of 51 patients (35.3%) had dementia.

In contrast to medically managed Parkinson's patients who often lose weight, people in this study gained an average of 9 kg in the first year after surgery, which remained stable during the entire followup period. During long-term followup, five patients needed lead reimplantation due to intracranial infections, lead malfunctions, or lead suboptimal placement.

The study had several limitations, the researchers acknowledged. A high percentage of patients who received deep brain stimulation more than 15 years ago were lost at long-term followup, and the sample presented here may not be representative. Some people in the study did not have long-term motor or quality of life scores.

The editorialists also pointed out that the results are from a highly selected cohort that has been managed by experts in the field of movement disorders and deep brain stimulation. The average age at surgery was 51 and, as a group, these patients already had lived with Parkinson's for 11 years. In contrast, "the average age of onset for Parkinson's disease is between 65-70 years of age," Chou and Charles noted.

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