Rescue Procedures after Suboptimal Deep Brain Stimulation Outcomes in Common Movement Disorders

Utility of GPI+VIM dual-lead deep brain stimulation for Parkinson's disease patients with significant residual tremor on medication

OBJECTIVE

Randomized controlled trials have demonstrated that deep brain stimulation (DBS) of both the globus pallidus internus (GPI) and subthalamic nucleus (STN) for Parkinson's disease (PD) is superior to the best medical therapy. Tremor is particularly responsive to DBS, with reports of 70%-80% improvement. However, a small number of patients do not obtain the expected response with both STN and GPI targets. Indeed, the authors' patient population had a similar 81.2% tremor reduction with a 9.6% failure rate. In an analysis of these failures, they identified patients with preoperative on-medication tremor who subsequently received a GPI lead as a subpopulation at higher risk for inadequate tremor control. Thereafter, STN DBS was recommended for patients with on-medication tremor. However, for the patients with symptoms and comorbidities that favored GPI as the target, dual GPI and ventral intermediate nucleus of the thalamus (VIM) leads were proposed. This report details outcomes for those patients.

METHODS

This is a retrospective review of patients with PD who met the criteria for and underwent simultaneous GPI+VIM DBS surgery from 2015 to 2020 and had available follow-up data. The preoperative Unified Parkinson's Disease Rating Scale scores were obtained with the study participants on and off their medication. Postoperatively, the GPI lead was kept on at baseline and scores were obtained with and without VIM stimulation.

RESULTS

Thirteen PD patients with significant residual preoperative tremor on medication underwent simultaneous GPI+VIM DBS surgery (11 unilateral, 2 bilateral). A mean 90.6% (SD 15.0%) reduction in tremor scores was achieved with dual GPI+VIM stimulation compared to a 21.8% (SD 71.9%) reduction with GPI stimulation alone and a 30.9% (SD 37.8%) reduction with medication. Although rigidity and bradykinesia reductions were accomplished with just GPI stimulation, 13 of the 15 hemispheres required VIM stimulation to achieve excellent tremor control.

CONCLUSIONS

GPI+VIM stimulation was required to adequately control tremor in all but 2 patients in this series, substantiating the authors' hypothesis that, in their population, medication-resistant tremor does not completely respond to GPI stimulation. Dual stimulation of the GPI and VIM proved to be an effective option for the patients who had symptoms and comorbidities that favored GPI as a target and had medication-resistant tremor.

Methodological Considerations for Neuroimaging in Deep Brain Stimulation of the Subthalamic Nucleus in Parkinson's Disease Patients

Deep brain stimulation (DBS) of the subthalamic nucleus is a neurosurgical intervention for Parkinson's disease patients who no longer appropriately respond to drug treatments. A small fraction of patients will fail to respond to DBS, develop psychiatric and cognitive side-effects, or incur surgery-related complications such as infections and hemorrhagic events. In these cases, DBS may require recalibration, reimplantation, or removal. These negative responses to treatment can partly be attributed to suboptimal pre-operative planning procedures via direct targeting through low-field and low-resolution magnetic resonance imaging (MRI). One solution for increasing the success and efficacy of DBS is to optimize preoperative planning procedures via sophisticated neuroimaging techniques such as high-resolution MRI and higher field strengths to improve visualization of DBS targets and vasculature. We discuss targeting approaches, MRI acquisition, parameters, and post-acquisition analyses. Additionally, we highlight a number of approaches including the use of ultra-high field (UHF) MRI to overcome limitations of standard settings. There is a trade-off between spatial resolution, motion artifacts, and acquisition time, which could potentially be dissolved through the use of UHF-MRI. Image registration, correction, and post-processing techniques may require combined expertise of traditional radiologists, clinicians, and fundamental researchers. The optimization of pre-operative planning with MRI can therefore be best achieved through direct collaboration between researchers and clinicians.

Deep Brain Stimulation in Parkinson's Disease

Deep brain stimulation (DBS) has become an established therapeutic tool for treating patients with Parkinson's disease (PD) who have troublesome motor fluctuations and dyskinesias refractory to best medical therapy. In addition to its proven efficacy in patients with late PD, the EARLYSTIM trial not only demonstrated the efficacy of DBS in patients with early motor complications but also showed that it did not lose its therapeutic efficacy as the years passed by. However, like all other therapies for PD, DBS is not offered to patients either as a cure for this disease nor is it expected to stop the progression of the neurodegenerative process underlying PD; these important issues need to be highlighted to patients who are considering this therapy. This article aims to provide an introduction to residents or trainees starting a career in movement disorders of the technical aspects of this therapy and the evidence base for its use. For the latter objective, PUBMED was searched from 1946 to 2017 combining the search terms "deep brain stimulation" and "Parkinson's disease" looking for studies demonstrating the efficacy of this therapy in PD. Inclusion criteria included studies that involved more than 20 patients with a physician confirmed diagnosis of PD and a follow-up of greater than or equal to at least 12 months. The findings from those studies on motor symptoms, medication requirements, quality of life, and independence in activities of daily living in PD patients are summarized and presented in tabulated form in this paper at the end.

Deep Brain Stimulation Programming for Movement Disorders: Current Concepts and Evidence-Based Strategies

Deep brain stimulation (DBS) has become the treatment of choice for advanced stages of Parkinson's disease, medically intractable essential tremor, and complicated segmental and generalized dystonia. In addition to accurate electrode placement in the target area, effective programming of DBS devices is considered the most important factor for the individual outcome after DBS. Programming of the implanted pulse generator (IPG) is the only modifiable factor once DBS leads have been implanted and it becomes even more relevant in cases in which the electrodes are located at the border of the intended target structure and when side effects become challenging. At present, adjusting stimulation parameters depends to a large extent on personal experience. Based on a comprehensive literature search, we here summarize previous studies that examined the significance of distinct stimulation strategies for ameliorating disease signs and symptoms. We assess the effect of adjusting the stimulus amplitude (A), frequency (f), and pulse width (pw) on clinical symptoms and examine more recent techniques for modulating neuronal elements by electrical stimulation, such as interleaving (Medtronic®) or directional current steering (Boston Scientific®, Abbott®). We thus provide an evidence-based strategy for achieving the best clinical effect with different disorders and avoiding adverse effects in DBS of the subthalamic nucleus (STN), the ventro-intermedius nucleus (VIM), and the globus pallidus internus (GPi).

Cost-Effectiveness of Magnetic Resonance-Guided Focused Ultrasound for Essential Tremor

BACKGROUND

Radiofrequency thalamotomy and deep brain stimulation are current treatments for moderate to severe medication-refractory essential tremor. However, they are invasive and thus carry risks. Magnetic resonance-guided focused ultrasound is a new, less invasive surgical option. The objective of the present study was to determine the cost-effectiveness of magnetic resonance-guided focused ultrasound compared with standard treatments in Canada.

METHODS

We conducted a cost-utility analysis using a Markov cohort model. We compared magnetic resonance-guided focused ultrasound with no surgery in people ineligible for invasive neurosurgery and with radiofrequency thalamotomy and deep brain stimulation in people eligible for invasive neurosurgery. In the reference case analysis, we used a 5-year time horizon and a public payer perspective and discounted costs and benefits at 1.5% per year.

RESULTS

Compared with no surgery in people ineligible for invasive neurosurgery, magnetic resonance-guided focused ultrasound cost $21,438 more but yielded 0.47 additional quality-adjusted life years, producing an incremental cost-effectiveness ratio of $45,817 per quality-adjusted life year gained. In people eligible for invasive neurosurgery, magnetic resonance-guided focused ultrasound was slightly less effective but much less expensive compared with the current standard of care, deep brain stimulation. The results were sensitive to assumptions regarding the time horizon, cost of magnetic resonance-guided focused ultrasound, and probability of recurrence.

CONCLUSIONS

In people ineligible for invasive neurosurgery, the incremental cost-effectiveness ratio of magnetic resonance-guided focused ultrasound versus no surgery is comparable to many other tests and treatments that are widely adopted in high-income countries. In people eligible for invasive neurosurgery, magnetic resonance-guided focused ultrasound is also a reasonable option. © 2018 International Parkinson and Movement Disorder Society.

Magnetic Resonance-Guided Focused Ultrasound Neurosurgery for Essential Tremor: A Health Technology Assessment

BACKGROUND

The standard treatment option for medication-refractory essential tremor is invasive neurosurgery. A new, noninvasive alternative is magnetic resonance-guided focused ultrasound (MRgFUS) neurosurgery. We aimed to determine the effectiveness, safety, and cost-effectiveness of MRgFUS neurosurgery for the treatment of moderate to severe, medication-refractory essential tremor in Ontario. We also spoke with people with essential tremor to gain an understanding of their experiences and thoughts regarding treatment options, including MRgFUS neurosurgery.

METHODS

We performed a systematic review of the clinical literature published up to April 11, 2017, that examined MRgFUS neurosurgery alone or compared with other interventions for the treatment of moderate to severe, medication-refractory essential tremor. We assessed the risk of bias of each study and the quality of the body of evidence according to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) Working Group criteria. We performed a systematic review of the economic literature and created Markov cohort models to assess the cost-effectiveness of MRgFUS neurosurgery compared with other treatment options, including no surgery. We also estimated the budget impact of publicly funding MRgFUS neurosurgery in Ontario for the next 5 years. To contextualize the potential value of MRgFUS neurosurgery as a treatment option for essential tremor, we spoke with people with essential tremor and their families.

RESULTS

Nine studies met our inclusion criteria for the clinical evidence review. In noncomparative studies, MRgFUS neurosurgery was found to significantly improve tremor severity and quality of life and to significantly reduce functional disability (GRADE: very low). It was also found to be significantly more effective than a sham procedure (GRADE: high). We found no significant difference in improvements in tremor severity, functional disability, or quality of life between MRgFUS neurosurgery and deep brain stimulation (GRADE: very low). We found no significant difference in improvement in tremor severity compared with radiofrequency thalamotomy (GRADE: low). MRgFUS neurosurgery has a favourable safety profile.We estimated that MRgFUS neurosurgery has a mean cost of $23,507 and a mean quality-adjusted survival of 3.69 quality-adjusted life-years (QALYs). We also estimated that the mean costs and QALYs of radiofrequency thalamotomy and deep brain stimulation are $14,978 and 3.61 QALYs, and $57,535 and 3.94 QALYs, respectively. For people ineligible for invasive neurosurgery, we estimated the incremental cost-effectiveness ratio (ICER) of MRgFUS neurosurgery compared with no surgery as $43,075 per QALY gained. In people eligible for invasive neurosurgery, the ICER of MRgFUS neurosurgery compared with radiofrequency thalamotomy is $109,795 per QALY gained; when deep brain stimulation is compared with MRgFUS neurosurgery, the ICER is $134,259 per QALY gained. Of note however, radiofrequency thalamotomy is performed very infrequently in Ontario. We also estimated that the budget impact of publicly funding MRgFUS neurosurgery in Ontario at the current case load (i.e., 48 cases/year) would be about $1 million per year for the next 5 years.People with essential tremor who had undergone MRgFUS neurosurgery reported positive experiences with the procedure. The tremor reduction they experienced improved their ability to perform activities of daily living and improved their quality of life.

CONCLUSIONS

MRgFUS neurosurgery is an effective and generally safe treatment option for moderate to severe, medication-refractory essential tremor. It provides a treatment option for people ineligible for invasive neurosurgery and offers a noninvasive option for all people considering neurosurgery.For people ineligible for invasive neurosurgery, MRgFUS neurosurgery is cost-effective compared with no surgery. In people eligible for invasive neurosurgery, MRgFUS neurosurgery may be one of several reasonable options. Publicly funding MRgFUS neurosurgery for the treatment of moderate to severe, medication-refractory essential tremor in Ontario at the current case load would have a net budget impact of about $1 million per year for the next 5 years.People with essential tremor who had undergone MRgFUS neurosurgery reported positive experiences. They liked that it was a noninvasive procedure and reported a substantial reduction in tremor that resulted in an improvement in their quality of life.

The role of deep brain stimulation in Parkinson's disease: an overview and update on new developments

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by the loss of neuronal dopamine production in the brain. Oral therapies primarily augment the dopaminergic pathway. As the disease progresses, more continuous delivery of therapy is commonly needed. Deep brain stimulation (DBS) has become an effective therapy option for several different neurologic and psychiatric conditions, including PD. It currently has US Food and Drug Administration approval for PD and essential tremor, as well as a humanitarian device exception for dystonia and obsessive-compulsive disorder. For PD treatment, it is currently approved specifically for those patients suffering from complications of pharmacotherapy, including motor fluctuations or dyskinesias, and a disease process of at least 4 years of duration. Studies have demonstrated superiority of DBS and medical management compared to medical management alone in selected PD patients. Optimal patient selection criteria, choice of target, and programming methods for PD and the other indications for DBS are important topics that continue to be explored and remain works in progress. In addition, new hardware options, such as different types of leads, and different software options have recently become available, increasing the potential for greater efficacy and/or reduced side effects. This review gives an overview of therapeutic management in PD, specifically highlighting DBS and some of the recent changes with surgical therapy.