Improvement of Deep Brain Stimulation in Dyskinesia in Parkinson's Disease: A Meta-Analysis

Effectiveness of Deep Brain Stimulation in Improving Balance in Parkinson's Disease: A Systematic Review and Meta-Analysis

BACKGROUND

Balance dysfunction is a debilitating feature of advanced Parkinson's disease (PD), potentially improved by deep brain stimulation (DBS). This systematic review and meta-analysis pooled evidence from randomized controlled trials (RCTs) on DBS effectiveness in improving balance in PD.

METHODS

A systematic search was conducted to identify eligible RCTs investigating the effectiveness of DBS on improving balance in people with PD. Meta-analysis was performed using random effects models and reported as mean difference and 95% confidence intervals. Risk of bias was assessed using Cochrane's ROB-2 tool.

RESULTS

Seventeen RCTs were eligible (n = 333), utilizing a range of stimulation sites, parameters, reporting tools for balance outcomes, and control/comparator groups, making the identification of clear trends and recommendations difficult. Eleven studies were deemed as having some risk of bias, 4 having low risk of bias and 2 having high risk of bias. One small meta-analysis was conducted and found no significant difference in balance outcomes. Most studies reported no significant improvement in Timed Up-and-Go scores, Berg Balance Scale scores, frequency of falls, and balance-related items of the Movement Disorder Society's Unified Parkinson's Disease Rating Scales. Some studies reported improvements in the Tinetti balance test, posturography readings, and reduction in falls though these were not supported by other studies due to a lack of reporting on these items or conflicting findings.

CONCLUSIONS

Current research suggests that DBS results in no significant improvement in balance dysfunction for people with PD, though such assertions require larger RCTs with clear reporting methods using validated reporting tools.

Stereotactic Staged Asymmetric Bilateral Radiofrequency Lesioning for Parkinson's Disease

INTRODUCTION

Parkinson's disease (PD) is one of the most common neurodegenerative progressive disorders. Despite the dominance of neurostimulation technology, stereotactic lesioning operations play a significant role in the treatment of PD. The aim of the study was to evaluate the effectiveness and safety of staged bilateral asymmetric radiofrequency (RF) stereotactic lesioning in a highly selected group of PD patients.

MATERIAL AND METHODS

A retrospective review of 418 consecutive patients undergoing stereotactic ablation for advanced PD at our institution revealed 28 patients who underwent staged asymmetric bilateral ablation. In this subset, after initial RF thalamotomy, contralateral pallidotomy was performed in 16 (57.1%) patients (group Vim-GPi), and contralateral lesion of the subthalamic nucleus (STN) was performed in 12 (32.9%) patients (group Vim-STN). The mean duration of disease before the first surgery was 9.9 ± 0.8 years. The mean interval between the two operations was 3.5 ± 0.4 years (range, 1-10 years); in the Vim-GPi group, it was 3.1 ± 0.4 years; and in the Vim-STN group, it was 4.3 ± 0.1 years. After the second operation, the long-term follow-up lasted from 1 to 8 years (mean 4.8 ± 0.5 years). All patients were evaluated 1 year after the second operation.

RESULTS

One year after staged bilateral lesioning, the mean tremor score improved from baseline, prior to the first operation, from 19.8 to 3.8 (improvement of 81%), the overall mean rigidity score improved from 11.0 to 3.7 (improvement of 66%), and hypokinesia improved from 14.8 to 8.9 (improvement of 40%). One year after staged bilateral lesioning, the total UPDRS score improved in the Vim-GPi group by 47% in the OFF and 45.9% in the ON states. In the Vim-STN group, the total UPDRS score improved from baseline, prior to the first operation, by 44.8% in the OFF and 51.6% in the ON states. Overall, levodopa dose was reduced by 43.4%. Neurological complications were observed in 4 (14.3%) cases; among them, 1 (3.6%) patient had permanent events related to local ischemia after pallidotomy.

CONCLUSION

Staged asymmetric bilateral stereotactic RF lesioning can be a safe and effective method in highly selected patients with advanced PD, particularly where deep brain stimulation is not available or desirable. Careful identification and selection of patients for ablative surgery allow achieving optimal results in the treatment of PD with bilateral symptoms.

Controlled-Release Levodopa for the Treatment of Rapid Motor Fluctuations in Parkinson's Disease Subjects with Subthalamic Nucleus Deep Brain Stimulation

Objectives  We aimed to investigate the efficiency of controlled-release levodopa/benserazide (Madopar HBS) use during daytime in our pilot study on advanced-stage Parkinson's disease (PD) subjects with deep brain stimulation of the subthalamic nucleus (STN-DBS) therapy. Methods  We have evaluated all PD subjects with STN-DBS who had admitted to our outpatient polyclinic between February 2022 and March 2022. Among these patients, those who were taking levodopa therapy at least five times throughout the day and the efficiency of levodopa lasted less than 3 hours were detected. The standard levodopa therapy was switched to Madopar HBS in all patients who accepted the therapy chance and the clinical evaluation of the patients on Madopar HBS therapy was performed in the second month of the therapy. Results  Ultimately, the follow-up of all four patients in whom the levodopa therapy was changed to Madopar HBS yielded a significant reduction in the "off" periods and improvement in the PSQ-39 scores. Conclusion  We suggest the use of Madopar HBS in PD patients with STN-DBS surgery suffering from motor fluctuations, particularly in the subgroup with milder dyskinesias. Future study results of a large number of PD subjects with STN-DBS therapy are warranted to confirm our observations. The results of these studies may provide critical applications in clinical practice.

Basal ganglia functional connectivity network analysis does not support the 'noisy signal' hypothesis of Parkinson's disease

The 'noisy signal' hypothesis of basal ganglia dysfunction in Parkinson's disease (PD) suggests that major motor symptoms of the disorder are caused by the development of abnormal basal ganglia activity patterns resulting in the propagation of 'noisy' signals to target systems. While such abnormal activity patterns might be useful biomarkers for the development of therapeutic interventions, correlation between specific changes in activity and PD symptoms has been inconsistently demonstrated, and raises questions concerning the accuracy of the hypothesis. Here, we tested this hypothesis by considering three nodes of the basal ganglia network, the subthalamus, globus pallidus interna, and cortex during self-paced and cued movements in patients with PD. Interactions between these regions were analyzed using measures that assess both linear and non-linear relationships. Marked changes in the network are observed with dopamine state. Specifically, we detected functional disconnection of the basal ganglia from the cortex and higher network variability in untreated PD, but various patterns of directed functional connectivity with lower network variability in treated PD. When we examine the system output, significant correlation is observed between variability in the cortico-basal ganglia network and muscle activity variability but only in the treated state. Rather than supporting a role of the basal ganglia in the transmission of noisy signals in patients with PD, these findings suggest that cortico-basal ganglia network interactions by fault or design, in the treated Parkinsonian state, are actually associated with improved cortical network output variability.

In vivo probabilistic atlas of white matter tracts of the human subthalamic area combining track density imaging and optimized diffusion tractography

The human subthalamic area is a region of high anatomical complexity, tightly packed with tiny fiber bundles. Some of them, including the pallidothalamic, cerebello-thalamic, and mammillothalamic tracts, are relevant targets in functional neurosurgery for various brain diseases. Diffusion-weighted imaging-based tractography has been suggested as a useful tool to map white matter pathways in the human brain in vivo and non-invasively, though the reconstruction of these specific fiber bundles is challenging due to their small dimensions and complex anatomy. To the best of our knowledge, a population-based, in vivo probabilistic atlas of subthalamic white matter tracts is still missing. In the present work, we devised an optimized tractography protocol for reproducible reconstruction of the tracts of subthalamic area in a large data sample from the Human Connectome Project repository. First, we leveraged the super-resolution properties and high anatomical detail provided by short tracks track-density imaging (stTDI) to identify the white matter bundles of the subthalamic area on a group-level template. Tracts identification on the stTDI template was also aided by visualization of histological sections of human specimens. Then, we employed this anatomical information to drive tractography at the subject-level, optimizing tracking parameters to maximize between-subject and within-subject similarities as well as anatomical accuracy. Finally, we gathered subject level tracts reconstructed with optimized tractography into a large-scale, normative population atlas. We suggest that this atlas could be useful in both clinical anatomy and functional neurosurgery settings, to improve our understanding of the complex morphology of this important brain region.

Current Knowledge on the Background, Pathophysiology and Treatment of Levodopa-Induced Dyskinesia-Literature Review

Levodopa remains the primary drug for controlling motor symptoms in Parkinson’s disease through the whole course, but over time, complications develop in the form of dyskinesias, which gradually become more frequent and severe. These abnormal, involuntary, hyperkinetic movements are mainly characteristic of the ON phase and are triggered by excess exogenous levodopa. They may also occur during the OFF phase, or in both phases. Over the past 10 years, the issue of levodopa-induced dyskinesia has been the subject of research into both the substrate of this pathology and potential remedial strategies. The purpose of the present study was to review the results of recent research on the background and treatment of dyskinesia. To this end, databases were reviewed using a search strategy that included both relevant keywords related to the topic and appropriate filters to limit results to English language literature published since 2010. Based on the selected papers, the current state of knowledge on the morphological, functional, genetic and clinical features of levodopa-induced dyskinesia, as well as pharmacological, genetic treatment and other therapies such as deep brain stimulation, are described.

Globus Pallidus Internus (GPi) Deep Brain Stimulation for Parkinson's Disease: Expert Review and Commentary

INTRODUCTION

The globus pallidus internus (GPi) region has evolved as a potential target for deep brain stimulation (DBS) in Parkinson's disease (PD). DBS of the GPi (GPi DBS) is an established, safe and effective method for addressing many of the motor symptoms associated with advanced PD. It is important that clinicians fully understand this target when considering GPi DBS for individual patients.

METHODS

The literature on GPi DBS in PD has been comprehensively reviewed, including the anatomy, physiology and potential pitfalls that may be encountered during surgical targeting and post-operative management. Here, we review and address the implications of lead location on GPi DBS outcomes. Additionally, we provide a summary of randomized controlled clinical trials conducted on DBS in PD, together with expert commentary on potential applications of the GPi as target. Finally, we highlight future technologies that will likely impact GPi DBS, including closed-loop adaptive approaches (e.g. sensing-stimulating capabilities), advanced methods for image-based targeting and advances in DBS programming, including directional leads and pulse shaping.

RESULTS

There are important disease characteristics and factors to consider prior to selecting the GPi as the DBS target of PD surgery. Prior to and during implantation of the leads it is critical to consider the neuroanatomy, which can be defined through the combination of image-based targeting and intraoperative microelectrode recording strategies. There is an increasing body of literature on GPi DBS in patients with PD suggesting both short- and long-term benefits. Understanding the GPi target can be useful in choosing between the subthalamic (STN), GPi and ventralis intermedius nucleus as lead locations to address the motor symptoms and complications of PD.

CONCLUSION

GPi DBS can be effectively used in select cases of PD. As the ongoing DBS target debate continues (GPi vs. STN as DBS target), clinicians should keep in mind that GPi DBS has been shown to be an effective treatment strategy for a variety of symptoms, including bradykinesia, rigidity and tremor control. GPi DBS also has an important, direct anti-dyskinetic effect. GPi DBS is easier to program in the outpatient setting and will allow for more flexibility in medication adjustments (e.g. levodopa). Emerging technologies, including GPi closed-loop systems, advanced tractography-based targeting and enhanced programming strategies, will likely be future areas of GPi DBS expansion. We conclude that although the GPi as DBS target may not be appropriate for all PD patients, it has specific clinical advantages.

Effects of implantation of a deep brain stimulation device on patient weight in Parkinson's disease and essential tremor

OBJECTIVE

Deep brain stimulation (DBS) is a well-established therapy for treating neurological movement disorders. Some patients who have received DBS therapy have noticed significant weight gain. Further investigation into correlations between patient characteristics and weight gain following DBS device implantation, which the authors here have done, will provide physicians with useful clinical information.

METHODS

The authors performed a retrospective study of patients with Parkinson's disease (PD) and essential tremor (ET) who had received DBS therapy in the period from 2012 to 2017. Patient weights had been recorded preoperatively and at 3, 6, and 12 months postoperatively. These data were used to compare patient characteristics, including diagnosis, body mass index (BMI), sex, levodopa equivalent dose (LED), and change in Unified Parkinson's Disease Rating Scale (UPDRS) score. For PD patients, a quantile multivariate regression analysis was used to examine whether significant correlations existed between several of these patient characteristics, as well as age and weight gain following implantation.

RESULTS

PD patients had gained a significant amount of weight at 3 months (mean [SE] 2.66 [0.428] kg, p < 0.001), 6 months (3.64 [0.492] kg, p < 0.001), and 12 months (4.18 [0.540] kg, p < 0.001) after DBS placement. Patients who had undergone subthalamic nucleus (STN) DBS device placement gained, on average, more weight than the patients with globus pallidus internus (GPi) placement at both 6 months (mean 2.558 [1.020] kg, p = 0.01) and 12 months (2.358 [1.130] kg, p = 0.04). BMI in the STN cohort was greater than that in the GPi cohort at 6 months (mean difference [SE] 2.60 [1.127] kg/m2, p = 0.02) and at 12 months (2.36 [1.112] kg/m2, p = 0.04). A reduction in LED was negatively correlated with weight change at 6 months (r = -0.33, p < 0.001) and 12 months (r = -0.41, p < 0.001). There was no weight gain correlated with DBS therapy for ET.

CONCLUSIONS

PD patients experienced a significant change in weight over time after DBS therapy, whereas ET patients did not. PD patients with an STN target site experienced greater weight gain, on average, than those with a GPi target site. Furthermore, there was a significant increase in BMI at 6 and 12 months in patients with an STN target compared to that in patients with a GPi target. PD patients whose LED was reduced after DBS gained more weight at 6 and 12 months after surgery than the patients whose LED was kept at the same level or increased.

Measuring Subthalamic Nucleus Volume of Parkinson's Patients and Evaluating Its Relationship with Clinical Scales at Pre- and Postdeep Brain Stimulation Treatment: A Magnetic Resonance Imaging Study

This study investigated potential imaging biomarkers for predicting the efficacy of deep brain stimulation (DBS) of the subthalamic nucleus (STN) in patients with Parkinson's disease (PD). A total of 59 PD patients and 50 healthy control subjects underwent high-resolution 3-dimensional T1-weighted brain magnetic resonance imaging. Bilateral STN volumes were compared between the 2 groups, and a correlation analysis was performed to assess the relationship between bilateral STN volumes or intracranial volume (ICV) and pre- or postoperative clinical scale scores. The results showed that the left STN volume differed significantly between PD patients and controls. In patients, the left STN volume was negatively correlated with pre- and postoperative quality of life scores and positively correlated with Mini-mental State Examination (MMSE) and Montreal Cognitive Assessment scores; ICV was also positively correlated with the MMSE score. These findings indicate that changes in the left STN volume are a useful biomarker for evaluating the clinical outcome of PD patients following DBS.

Motor Thalamic Deep Brain Stimulation Alters Cortical Activity and Shows Therapeutic Utility for Treatment of Parkinson's Disease Symptoms in a Rat Model

Deep brain stimulation (DBS) in Parkinson's disease (PD) alters neuronal function and network communication to improve motor symptoms. The subthalamic nucleus (STN) is the most common DBS target for PD, but some patients experience adverse effects on memory and cognition. Previously, we reported that DBS of the ventral anterior (VA) and ventrolateral (VL) nuclei of the thalamus and at the interface between the two (VA|VL), collectively VA-VL, relieved forelimb akinesia in the hemiparkinsonian 6-hydroxydopamine (6-OHDA) rat model. To determine the mechanism(s) underlying VA-VL DBS efficacy, we examined how motor cortical neurons respond to VA-VL DBS using single-unit recording electrodes in anesthetized 6-OHDA lesioned rats. VA-VL DBS increased spike frequencies of primary (M1) and secondary (M2) motor cortical pyramidal cells and M2, but not M1, interneurons. To explore the translational merits of VA-VL DBS, we compared the therapeutic window, rate of stimulation-induced dyskinesia onset, and effects on memory between VA-VL and STN DBS. VA-VL and STN DBS had comparable therapeutic windows, induced dyskinesia at similar rates in hemiparkinsonian rats, and adversely affected performance in the novel object recognition (NOR) test in cognitively normal and mildly impaired sham animals. Interestingly, a subset of sham rats with VA-VL implants showed severe cognitive deficits with DBS off. VA-VL DBS improved NOR test performance in these animals. We conclude that VA-VL DBS may exert its therapeutic effects by increasing pyramidal cell activity in the motor cortex and interneuron activity in the M2, with plausible potential to improve memory in PD.

Pallidal versus subthalamic nucleus deep brain stimulation for levodopa-induced dyskinesia

OBJECTIVE

To compare the efficacy of subthalamic nucleus (STN) and globus pallidus internus (GPi) deep brain stimulation (DBS) on reducing levodopa-induced dyskinesia (LID) in Parkinson's disease, and to explore the potential underlying mechanisms.

METHODS

We retrospectively assessed clinical outcomes in 43 patients with preoperative LID who underwent DBS targeting the STN (20/43) or GPi (23/43). The primary clinical outcome was the change from baseline in the Unified Dyskinesia Rating Scale (UDysRS) and secondary outcomes included changes in the total daily levodopa equivalent dose, the drug-off Unified Parkinson Disease Rating Scale Part Ⅲ at the last follow-up (median, 18 months), adverse effects, and programming settings. Correlation analysis was used to find potential associated factors that could be used to predict the efficacy of DBS for dyskinesia management.

RESULTS

Compared to baseline, both the STN group and the GPi group showed significant improvement in LID with 60.73 ± 40.29% (mean ± standard deviation) and 93.78 ± 14.15% improvement, respectively, according to the UDysRS score. Furthermore, GPi-DBS provided greater clinical benefit in the improvement of dyskinesia (P < 0.05) compared to the STN. Compared to the GPi group, the levodopa equivalent dose reduction was greater in the STN group at the last follow-up (43.81% vs. 13.29%, P < 0.05). For the correlation analysis, the improvement in the UDysRS outcomes were significantly associated with a reduction in levodopa equivalent dose in the STN group (r = 0.543, P = 0.013), but not in the GPi group (r = -0.056, P = 0.801).

INTERPRETATION

Both STN and GPi-DBS have a beneficial effect on LID but GPi-DBS provided greater anti-dyskinetic effects. Dyskinesia suppression for STN-DBS may depend on the reduction of levodopa equivalent dose. Unlike the STN, GPi-DBS might exert a direct and independent anti-dyskinesia effect.