What’s new in deep brain stimulation for Parkinson’s disease?

While there are now patients who began deep brain stimulation (DBS) for Parkinson’s disease more than two decades ago, new advances continue to improve the effectiveness of the treatment. Experts provided a review of the developments at the Canadian Neurological Sciences Federation annual congress held in Ottawa earlier this summer. Some of the advances will open the door for more patients to do well with DBS. The key is to initiate DBS at the right stage in the patient’s journey with Parkinson’s disease. The wait list for surgery can be up to a year in many centres and it’s important to refer early. Dr. Tejas Sankar, associate professor of surgery in the division of neurosurgery at the University of Alberta, advised physicians to consult with a movement disorder specialist about DBS for Parkinson’s disease. Waiting too long could mean a patient misses out on getting an improvement in their symptoms and quality of life. Criteria for surgeryBefore exploring new advances, it’s worth re-examining who responds best to DBS for Parkinson’s disease. This includes: Patients who have a levodopa response. The ideal candidate has a 40% improvement in Unified Parkinson’s Disease Rating Scale (UPDRS)-III between “off” condition and “on” condition, explained Dr. Renato Munhoz, a neurologist at University Health Network’s Krembil Brain Institute and associate professor at the University of Toronto. A study on the predictive utility of the levodopa challenge on clinical effectiveness of DBS was published in Movement Disorders Clinical Practice in 2023. The procedure isn’t recommended if the patient’s main disability is one that’s not responding to levodopa.Patients younger than 70-years-old. The response to DBS is not as good in older patients.Patients who have had Parkinson’s disease for more than four years. “We think of five years as a minimum,” Dr. Munhoz said. Genetic markers can also inform who will have good outcomes. Research published in 2023 suggested that patients with a glucocerebrosidase (GBA) mutation did poorly on cognitive function markers following subthalamic nucleus DBS.It’s also important to consider psychosocial factors to ensure surgery is done at a time when the patient’s mood and other psychological factors are still at a level where they can improve once motor function improves, Dr. Munhoz said. Awake DBS surgery Deep brain stimulation surgery is traditionally done while the patient is awake, so surgeons can use neurophysiology tools and watch for tremors to help guide the electrode implantation. Yet, with advanced imaging now available to guide electrode placement, some centres are looking at performing the surgery when the patient is under general anesthesia. The idea is to reduce the risk of post-operative delirium and other adverse events related to long surgeries. The GALAXY trial from the Netherlands compared general anesthesia versus local anesthesia for DBS of the subthalamic nucleus in patients with advanced Parkinson’s disease. Results published in JAMA in 2021 suggest there was no difference in the UPDRS motor examination between the two randomized groups. Another 2024 paper in the Journal of Neurology, Neurosurgery and Psychiatry reported that there were no differences in cognitive, mood and behavioural scores between the two groups. The surgeries where the patient was under general anesthesia were 26 minutes shorter, on average. A meta-analysis published in Neurosurgery in 2025 suggests that there was no significant difference between awake and asleep DBS surgery in terms of primary motor outcomes or levodopa equivalent daily dosage.While Dr. Sankar said he predicts that awake DBS surgery may soon become the norm, “I look at this with a bit of trepidation.” DBS surgery is not “another stereotaxic procedure,” he noted.Target areasNeurosurgeons continue to discuss what location or target for DBS is better: the subthalamic nucleus or the globus pallidus internus. “Why do you have to make that choice? Why not stimulate both and see what works?” Dr. Sankar said. A few centres, including one in Spain, are examining stimulation of both brain areas. Neurosurgeons are also questioning the route of the electrodes into the target areas. Some trajectories can have different effects, depending on the brain areas the electrodes pass through.Adaptive deep brain stimulationParkinson’s disease symptoms vary by patient, by the patient’s disease progression and even by the day for that patient. This is why the promise of a closed-loop system of DBS is welcome; it may allow patients to have personalized DBS therapy. Adaptive DBS measures the power of beta waves (with a frequency range between 13 and 30 Hz) and then programs the electrodes to dampen that activity, all in real time. There are two types of adaptive DBS being studied: single threshold, where a maximum level of local field potential power (between 8 and 30 Hz)—above which there are side effects—and minimum—below which there’s no effect on symptoms—are set, and the stimulation alters between the two. The second is dual threshold, where beta wave activity is kept within a specific range so the changes in stimulation are slower. The ADAPT-PD trial compared adaptive DBS (both single and dual threshold) with continuous DBS. Initial results published in Neurology suggest there was similar “on” time between the two groups, with a trend to improvement in the adaptive DBS compared to continuous DBS. A telling result was that 98% of the patients chose to stay on adaptive DBS. The adaptive DBS system for Parkinson’s disease was approved by the U.S. Food and Drug Administration in February. Adaptive DBS could come to Canada by the end of the year, Dr. Sankar said.New techniquesThere have been numerous advances in how the brain is stimulated. Pulse width was previously 60 microseconds, but “that proved to be too much for some,” Dr. Munhoz said. Longer stimulation can activate more distant, larger axons, which may produce more side effects, but well-placed electrodes and shorter pulse duration could provide more benefit. Results from the CUSTOMS-DBS, published in 2018, suggest that shorter pulse widths were equally effective and had a lower chance of side effects. The pulse can also be steered using multiple independent current control, where one or more cathodes can be controlled on their own to activate different targets using different amplitudes. There’s also contact steering. Electrodes have four or more levels of stimulation and its possible to design how those electrodes are stimulated, essentially steering the current. This is especially useful for stimulating small nuclei or for compensating for misplaced electrodes. Initial programming is an important part of deep brain stimulation where neurologists test to see how much stimulation is needed to get a benefit. Post-operation imaging tools can help identify if the electrodes are at the correct target and also can provide data to inform how to best program the stimulation. Research suggests these tools can reduce initial programming time. Neurosurgeons from the University of Toronto recently authored a review of some of the emerging techniques in DBS programming, published in the Canadian Journal of Neurological Sciences in Feb. 2025.DBS is an established therapy for Parkinson’s disease; it has among the strongest amount of evidence supporting it than any other treatment in neurosurgery, Dr. Sankar noted. These new advances only add to the evidence and understanding of the treatment.

What’s new in deep brain stimulation for Parkinson’s disease?

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