Deep brain stimulation with Boston Scientific’s Vercise system led to sustained “on” periods without troublesome dyskinesia and improvements in both motor and non-motor symptoms of Parkinson’s disease for at least one year, updated findings from the INTREPID trial show.
Use of the Vercise Deep Brain Stimulation system in patients enrolled in this ongoing study was also found to be safe.
The study, “Subthalamic nucleus deep brain stimulation with a multiple independent constant current-controlled device in Parkinson’s disease (INTREPID): a multicentre, double-blind, randomised, sham-controlled study,” was published in The Lancet Neurology.
Deep brain stimulation, or DBS, is a surgical procedure to implant a small, pacemaker-like device that delivers electrical impulses to specific areas of the brain. It is used to treat disabling neurological symptoms in people with advanced Parkinson’s, such as tremors, rigidity, stiffness, slowed movement, and walking problems.
Clinical trials have shown that this approach is effective at easing motor symptoms and improving quality of life, but results across these studies varied substantially. And none of these earlier trials used a sham control group while also blinding both patients and their doctors to the assigned treatment (double-blind design).
The INTREPID study (NCT01839396) is a well-controlled and blinded trial, designed to evaluate the safety and effectiveness of the Vercise DBS system in people whose Parkinson’s symptoms were not adequately controlled by levodopa medications.
This approved system targets the subthalamic nucleus (STN), a part of the brain that is overactive in patients. Unlike most other DBS devices, in which individual electrodes may have changes in their current over time, this device uses a multiple independent contact current-controlled (MICC) technology that allows it to deliver the desired current across each contact independent of changes that happen over time.
INTREPID enrolled patients at 23 U.S. clinical sites, ages 22 to 75 (mean age, 59.9), who had been diagnosed at least five years ago. All were unable to adequately control their motor symptoms despite optimal anti-parkinsonian therapy.
A total of 160 people were implanted with the DBS system, and given up to four weeks to allow for healing and the resolution of potential brain micro-lesions caused by electrode placement. They were then randomly assigned to either therapeutic stimulation (121 patients) or subtherapeutic electric impulses (39 patients; a control group) for three months.
After this time, all moved to the trial’s open-label phase and to active treatment (DBS) for up to five years. It is expected to conclude in August 2023.
INTREPID’s main goal was measures of change in the duration of “on” periods (or periods where symptoms are adequately controlled) without dyskinesia (uncontrolled, jerky movements) from the study’s beginning (baseline measures) to the end of the control group period (three months after randomization). Secondary measures included improvements in motor symptoms, quality of life, and treatment satisfaction. Safety and neuropsychological function were also assessed.
Improvements in motor function and life quality were evaluated using a Parkinson’s diary, the Unified Parkinson’s Disease Rating Scale (UPDRS), the 39-item Parkinson’s Disease Questionnaire (PDQ-39), Schwab and England Activities of Daily Living Scale, Short Form 36 Health Survey, Clinical Global Impression of Change Scale, and neuropsychological assessments.
Previously reported results showed that patients on the Vercise DBS system had motor symptom control for three hours more than did those in the control group, experienced a 49% improvement in motor symptoms, and had sustained improvements in their quality of life.
Researchers now reported additional data from the trial’s randomized part, as well as data on the 157 patients who completed one year of follow-up.
These results showed that those on active treatment also had better cognitive functioning at three months, with both total scores and domains such as initiation/perseveration and memory continuing to improve over time.
No changes in depression symptoms were evident in either group over one year of follow-up. Four patients, all in the active treatment group, developed suicidal thoughts, a well-described side effect of DBS treatment. One attempted suicide, but his mood improved after the electrodes were repositioned.
Researchers also found that device implantation alone (without its activation) was able to induce improvements in motor function and quality of life, possibly due to micro-lesions that changed the functioning of the subthalamic nucleus.
“But a contribution of a placebo effect cannot be excluded,” Günther Deuschl at Christian-Albrechts-University in Germany and Paul Krack with the University of Bern in Switzerland wrote in an accompanying editorial.
One-year data showed that motor symptoms had improved by 51% compared to scores before surgery to implant the device. These patients also experienced a total a six-hour gain in “on” time without dyskinesia, which “compared favourably to that of other randomised studies,” the team wrote.
Motors symptoms such as tremor, rigidity, bradykinesia, and gait, which had improved in the active treatment group after three months, continued to show increasing improvement over the one year of follow-up.
“In conclusion, this multicentre, prospective, double-blind, randomised controlled trial that evaluated a MICC DBS system in subthalamic nucleus showed evidence of significant improvements in motor function and quality of life, while maintaining an acceptable safety profile in patients with Parkinson’s disease,” the researchers wrote.
They also noted that at one year, about 41% of patients were using two or more electrodes to deliver current, which is a unique capability of MICC and the Vercise DBS systems.
“Future studies will be needed to fully assess the benefits of MICC technology on clinical outcomes,” they concluded.
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