Stimulation of the globus pallidus internus in the treatment of Parkinson's disease: Long-term results of a monocentric cohort

Quality of Life after Deep Brain Stimulation in Parkinson's Disease: Does the Target Matter?

BACKGROUND

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) and globus pallidus internus (GPi) is an accepted therapy for Parkinson's disease (PD) with disabling motor complications. For elderly patients with poorer cognition and postural instability, GPi has been proposed as the preferable DBS target based on expert opinion, arguing GPi-DBS may be less complicated by depression, apathy, worsened verbal fluency, and executive dysfunction, resulting in greater improvement in quality of life (QoL). However, data supporting such patient-tailored approach are lacking.

OBJECTIVES

The aims were to analyze whether the DBS target influences QoL in a PD cohort and a matched subgroup of frail patients with poor cognitive status and reduced postural stability, and whether other factors affect the QoL outcomes.

METHODS

In this retrospective study, we analyzed a single-center cohort of 138 PD patients who received bilateral STN-DBS (117) or GPi-DBS (21) using the mentioned approach for target selection. All patients underwent standardized clinical evaluations of motor- and nonmotor signs as well as QoL before and 1 year after surgery.

RESULTS

DBS of both targets improved motor signs, dyskinesias, and pain. QoL improved without significant difference between the targets, but with a trend for greater improvement across all QoL domains in favor of the STN, even in an STN subgroup matched to the GPi group.

CONCLUSION

Our results contradict the prevailing belief that GPi-DBS is superior in frail PD patients with cognitive decline and postural instability, questioning the proposed patient-tailored approach of DBS target selection. Further studies are needed for a data-driven approach.

Economic Evaluations Comparing Deep Brain Stimulation to Best Medical Therapy for Movement Disorders: A Meta-Analysis

BACKGROUND

Movement disorders (Parkinson's disease, essential tremor, primary dystonia) are a debilitating group of conditions that are progressive in nature. The mainstay of treatment is best medical therapy; however, a number of surgical therapies are available, including deep brain stimulation. Economic evaluations are an important aspect of evidence to inform decision makers regarding funding allocated to these therapies.

OBJECTIVE

This systematic review and meta-analysis evaluated the cost effectiveness of including deep brain stimulation compared with best medical therapy for movement disorder indications in the adult population.

METHODS

Ovid Medical Literature Analysis and Retrieval System Online, Embase, and Cochrane Central Register of Controlled Trials were queried. Only economic evaluations reporting incremental cost-effectiveness ratios for including deep brain stimulation versus best medical therapy for movement disorders were included. Studies were reviewed in duplicate for inclusion and data abstraction. Data were harmonized using the Consumer Price Index and Purchasing Power Parity to standardize values to 2022 US dollars. For inclusion in meta-analyses, studies were required to have sufficient data available to calculate an estimate of the incremental net benefit. Meta-analyses of pooled incremental net benefit based on the time horizon were performed. The study was registered at PROSPERO (CRD42022335436).

RESULTS

There were 2190 studies reviewed, with 14 economic evaluations included following a title/abstract and full-text review. Only studies considering Parkinson's disease were available for the meta-analysis. Quality of the identified studies was low, with moderate transferability to the American Healthcare System, and certainty of evidence was low. However, studies with a longer time horizon (15 years to lifetime) were found to have significant positive incremental net benefit (indicating cost effectiveness) for including deep brain stimulation with a mean difference of US$40,504.81 (95% confidence interval 2422.42-78,587.19).

CONCLUSIONS

Deep brain stimulation was cost effective for Parkinson's disease when considered over the course of the patient's remaining life after implantation.

TRIAL REGISTRATION

Clinical Trial Registration: PROSPERO (CRD42022335436).

Deep brain stimulation (DBS) as a therapeutic approach in gait disorders: What does it bring to the table?

Gait deficits are found in various degenerative central nervous system conditions, and are particularly a hallmark of Parkinson's disease (PD). While there is no cure for such neurodegenerative disorders, Levodopa is considered as the standard medication in PD patients. Often times, the therapy of severe PD consists of deep brain stimulation (DBS) of the subthalamic nucleus. Earlier research exploring the effect of gait have reported contradictory results or insufficient efficacy. A change in gait includes various parameters, such as step length, cadence, Double-stance phase duration which may be positively affected by DBS. DBS could also be effective in correcting the levodopa-induced postural sway abnormalities. Moreover, during normal walking, interaction among the subthalamic nucleus and cortex -essential regions which exert a role in locomotion- are coupled. However, during the freezing of gait, the activity is desynchronized. The mechanisms underlying DBS-induced neurobehavioral improvements in such scenarios requires further study. The present review discusses DBS in the context of gait, the benefits associated with DBS compared to standard pharmacotherapy options, and provides insights into future research.

Identifying the therapeutic zone in globus pallidus deep brain stimulation for Parkinson's disease

OBJECTIVE

The globus pallidus internus (GPI) has been demonstrated to be an effective surgical target for deep brain stimulation (DBS) treatment in patients with medication-refractory Parkinson's disease (PD). The ability of neurosurgeons to define the area of greatest therapeutic benefit within the globus pallidus (GP) may improve clinical outcomes in these patients. The objective of this study was to determine the best DBS therapeutic implantation site within the GP for effective treatment in PD patients.

METHODS

The authors performed a retrospective review of 56 patients who underwent bilateral GP DBS implantation at their institution during the period from January 2015 to January 2020. Each implanted contact was anatomically localized. Patients were followed for stimulation programming for at least 6 months. The authors reviewed preoperative and 6-month postsurgery clinical outcomes based on data from the Unified Parkinson's Disease Rating Scale Part III (UPDRS III), dyskinesia scores, and levodopa equivalent daily dose (LEDD).

RESULTS

Of the 112 leads implanted, the therapeutic cathode was most frequently located in the lamina between the GPI external segment (GPIe) and the GP externus (GPE) (n = 40). Other common locations included the GPE (n = 24), the GPIe (n = 15), and the lamina between the GPI internal segment (GPIi) and the GPIe (n = 14). In the majority of patients (73%) a monopolar programming configuration was used. At 6 months postsurgery, UPDRS III off medications (OFF) and on stimulation (ON) scores significantly improved (z = -4.02, p < 0.001), as did postsurgery dyskinesia ON scores (z = -4.08, p < 0.001) and postsurgery LEDD (z = -4.7, p < 0.001).

CONCLUSIONS

Though the ventral GP (pallidotomy target) has been a commonly used target for GP DBS, a more dorsolateral target may be more effective for neuromodulation strategies. The assessment of therapeutic contact locations performed in this study showed that the lamina between GPI and GPE used in most patients is the optimal central stimulation target. This information should improve preoperative GP targeting.

Long-term motor outcomes of deep brain stimulation of the globus pallidus interna in Parkinson's disease patients: Five-year follow-up

BACKGROUND

Deep brain stimulation (DBS) of globus pallidus interna (GPi) is an established treatment for advanced Parkinson's disease (PD). However, in contrast to subthalamic nucleus (STN)-DBS, long-term outcomes of GPi-DBS have rarely been studied.

OBJECTIVE

We investigated the long-term motor outcomes in PD patients at 5 years after GPi-DBS.

METHODS

We retrospectively analyzed the clinical data for PD patients who underwent GPi-DBS. Longitudinal changes of UPDRS scores from baseline to 5 years after surgery were assessed.

RESULTS

Forty PD patients with a mean age of 59.5 ± 7.9 years at DBS surgery (mean duration of PD: 11.4 ± 3.4 years) were included at baseline and 25 patients were included in 5-year evaluation after DBS. Compared to baseline, sub-scores for tremor, levodopa-induced dyskinesia (LID), and motor fluctuation indicated improved states up to 5 years after surgery (p < 0.001). However, UPDRS Part 3 total score and sub-score for postural instability and gait disturbance (PIGD) gradually worsened over time until 5 years after surgery (p > 0.017 after Bonferroni correction). In a logistic regression model, only preoperative levodopa response was associated with the long-term benefits on UPDRS Part 3 total score and PIGD sub-score (OR = 1.20; 95% CI = 1.04-1.39; p = 0.015 and OR = 4.99; 95% CI = 1.39-17.89; p = 0.014, respectively).

CONCLUSIONS

GPi-DBS provides long-term beneficial effects against tremor, motor fluctuation and LID, but PIGD symptoms gradually worsen. This selective long-term benefit has implications for the optimal application of DBS in PD patients.

How Does Deep Brain Stimulation Change the Course of Parkinson's Disease?

A robust body of evidence from randomized controlled trials has established the efficacy of deep brain stimulation (DBS) in reducing off time and dyskinesias in levodopa‐treated patients with Parkinson's disease (PD). These effects go along with improvements in on period motor function, activities of daily living, and quality of life. In addition, subthalamic DBS is effective in controlling drug‐refractory PD tremor. Here, we review the available data from long‐term observational and controlled follow‐up studies in DBS‐treated patients to re‐examine the persistence of motor and quality of life benefits and evaluate the effects on disease progression, major disability milestones, and survival. Although there is consistent evidence from observational follow‐up studies in DBS‐treated patients over 5–10 years and beyond showing sustained improvement of motor control, the long‐term impact of DBS on overall progression of disability in PD is less clear. Whether DBS reduces or delays the development of later motor and non‐motor disability milestones in comparison to best medical management strategies is difficult to answer by uncontrolled observational follow‐up, but there are signals from controlled long‐term observational studies suggesting that subthalamic DBS may delay some of the late‐stage disability milestones including psychosis, falls, and institutionalization, and also slightly prolongs survival compared with matched medically managed patients. These observations could be attributable to the sustained improvements in motor function and reduction in medication‐induced side effects, whereas there is no clinical evidence of direct effects of DBS on the underlying disease progression. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society

Voice handicap Index in Parkinson's patients: Subthalamic versus globus pallidus deep brain stimulation

PURPOSE

Subthalamic nucleus (STN) and globus pallidus interna (GPI) are the two most common sites for deep brain stimulation (DBS) in people with Parkinson's disease (PWP). Voice impairments are a common symptom of Parkinson's disease and information about voice outcomes with DBS is limited. Most studies in speech-language pathology have focused on STN-DBS and few have examined the effects of GPI-DBS. This was an initial effort to examine the impact of DBS location on Vocal Handicap Index (VHI) scores, which assess the impact of a voice disorder on an individual.

METHOD

Twenty-four gender-matched PWP (12 STN-DBS and 12 GPI-DBS) completed the VHI post-DBS implantation. Two-tailed independent samples t-tests were used to compare each VHI scale score (physical, functional, emotional, total) and patient factors between the two groups.

RESULTS

No significant differences in total or subscale VHI scores were identified between the two DBS groups. A trend toward greater impairment in PWP with GPI-DBS was noted. An association between higher VHI scores and DBS settings was found.

CONCLUSIONS

Studies directly comparing speech outcomes for different DBS targets are lacking. The current findings provide new insights concerning voice outcomes following DBS by adding to the limited literature directly comparing speech outcomes in multiple DBS targets. Limitations and directions for future research are discussed.

Long-term clinical outcomes of bilateral GPi deep brain stimulation in advanced Parkinson's disease: 5 years and beyond

OBJECTIVE

Few studies have reported long-term outcomes of globus pallidus internus (GPi) deep brain stimulation (DBS) in Parkinson's disease (PD). The authors aimed to investigate long-term outcomes of bilateral GPi DBS for 5 years and beyond for PD patients.

METHODS

The authors retrospectively analyzed the clinical outcomes in 65 PD patients treated with bilateral GPi DBS at a single center. The outcome measures of motor symptoms and health-related quality of life (HRQoL) included the Unified Parkinson's Disease Rating Scale (UPDRS) and the Parkinson's Disease Questionnaire (PDQ-39). Scores at baseline were compared with those at 1, 3, 5, and 6-8 years after implantation using Wilcoxon signed-rank tests with α correction.

RESULTS

GPi DBS significantly improved the off-medication UPDRS III total scores, UPDRS IV, and dyskinesia score at 1 year when compared with baseline (all p < 0.001). The off- and on-medication tremor scores, UPDRS IV, and dyskinesia scores showed moderate and sustained improvement (the ranges of the mean percentage improvement at each time point were 61%-75%, 30%-80%, 29%-40%, and 40%-65%, respectively) despite lacking statistical significance at long-term follow-up with diminishing sample sizes. The off-medication UPDRS III total scores did not show significant improvement at 5 years or later, primarily because of worsening in rigidity, akinesia, speech, gait, and postural stability scores. The on-medication UPDRS III total scores also worsened over time, with a significant worsening at 6-8 years when compared with baseline (p = 0.008). The HRQoL analyses based on the PDQ-39 revealed significant improvement in the activities of daily living and discomfort domains at 1 year (p = 0.003 and 0.006, respectively); however, all the domains showed gradual worsening at the later time points without reaching statistical significance. At 3 years, the communication domain showed significant worsening compared with baseline scores (p = 0.002).

CONCLUSIONS

GPi DBS in PD patients in this single-center cohort was associated with sustained long-term benefits in the off- and on-medication tremor score and motor complications. HRQoL and the cardinal motor symptoms other than tremor may worsen gradually in the long term. When counseling patients, it is important to recognize that benefits in tremor and dyskinesia are expected to be most persistent following bilateral GPi DBS implantation.

An Update on Medical and Surgical Treatments of Parkinson's Disease

Parkinson’s disease (PD) is characterized by degeneration of dopaminergic neurons in the substantia nigra pars compacta and other neuronal populations. The worldwide prevalence of PD is over 7 million and has been increasing more rapidly than many other neurodegenerative disorders. PD symptoms can be broadly divided into motor (slowness, stiffness, tremor) and non-motor symptoms (such as depression, dementia, psychosis, orthostatic hypotension). Patients can also have prodromal symptoms of rapid eye movement sleep behavior disorder, hyposmia, and constipation. The diagnosis of PD is mainly clinical, but dopamine transporter single-photon emission computed tomography can improve the accuracy of the diagnosis. Dopamine based therapies are used for the treatment of motor symptoms. Non-motor symptoms are treated with other medications such as selective serotonin reuptake inhibitors (depression/anxiety), acetylcholinesterase inhibitors (dementia), and atypical antipsychotics (psychosis). Patients with motor fluctuations or uncontrolled tremor, benefit from deep brain stimulation. Levodopa-carbidopa intestinal gel is an alternative to deep brain stimulation for uncontrolled motor fluctuations. Rehabilitative therapies such as physical, occupational, and speech therapy are important during all stages of the disease. Management of PD is complex but there have been significant advancements in the treatment of motor and non-motor symptoms over the past few years. This review discusses the updates in the medical and surgical management of PD.

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.

Therapeutic Strategies to Treat or Prevent Off Episodes in Adults with Parkinson's Disease

Parkinson's disease is a chronic, neurodegenerative disease, which manifests with a mixture of motor, cognitive and behavioural symptoms. Levodopa is the most effective antiparkinsonian treatment to date, although chronic use engenders a mixture of complications in a substantial proportion of patients. Amongst these is the occurrence of episodes of worsening symptoms-'off' phenomena. These episodes can manifest with either motor or non-motor symptoms or a combination of these features and have been found to have profound impacts on patients' quality of life. Although preventative measures are poorly evidenced, avoiding excessive total daily levodopa intake in selected populations that are deemed to be of a higher risk for developing these episodes warrants further exploration. Methods to improve levodopa bioavailability and delivery to the brain are currently available and are of value in addressing these episodes once they have become established. These include modifications to levodopa formulations as well as the use of complimentary agents that improve levodopa bioavailability. The deployment of device-assisted approaches is a further dimension that can be considered in addressing these debilitating episodes. This review summarises the clinical manifestations of 'off' phenomena and the current approaches to treat them. Although we briefly discuss clinical advances on the horizon, the predominant focus is on existing, established treatments.

Deep brain stimulation of the internal globus pallidus does not affect the limbic circuit in patients with Parkinson's disease: a PET study

INTRODUCTION

Internal globus pallidus (GPi) deep brain stimulation (DBS) is a safe and effective alternative treatment in Parkinson's disease (PD) for patients with cognitive impairment. However, no study has yet investigated metabolic changes within a large series of patients undergoing GPi stimulation.

OBJECTIVE

We assessed motor, cognitive and psychiatric changes, as well as modifications in brain glucose metabolism measured with FDG-PET, before and after bilateral GPi-DBS.

METHODS

In the same week, 32 patients with PD underwent a motor, cognitive and psychiatric assessment and a resting-state FDG-PET scan, 4 months before and 4 months after GPi-DBS surgery. For the voxelwise metabolic change assessment, the p value was controlled for multiple comparisons using the family wise error rate.

RESULTS

After GPi-DBS surgery, patients showed a significant overall improvement in motor status. No cognitive or psychiatric changes were observed after surgery. Nor were any clusters with significantly relative metabolic changes found in the limbic circuit after surgery. Clusters with significantly relative metabolic changes were observed in the left and right Brodmann area (BA) 6, the right BA 9, the right and left BA 39 and the left BA 17.

CONCLUSION

The present study confirmed that GPi-DBS is an effective treatment in patients with advanced PD, owing to metabolic changes in the areas involved in motor execution. The absence of relative metabolic decrease in the limbic circuit and the few changes affecting the associative circuit could explain why GPi-DBS is cognitively safe.

Parkinson's disease motor subtypes and bilateral GPi deep brain stimulation: One-year outcomes

OBJECTIVE

We aimed to explore the differences in motor symptoms and quality of life (QOL) outcomes following bilateral globus pallidus internus deep brain stimulation (GPi DBS), across well-defined motor subtypes of Parkinson's disease (PD), to improve clinical decision making.

METHODS

This single-center retrospective study investigated bilateral GPi DBS outcomes in 65 PD patients. Outcome measures included the Unified Parkinson's Disease Rating Scale (UPDRS) and Parkinson's Disease Questionnaire (PDQ-39) before and one year after surgery. Outcomes were compared between the tremor-dominant (TD) and postural instability and gait difficulty (PIGD) subtypes and between the TD and akinetic-rigid (AR) subtypes.

RESULTS

For the entire cohort, motor function (UPDRS III) in the Off-medication state, motor complications (UPDRS IV), activities of daily living (ADL, UPDRS II), and the ADL and discomfort domains of PDQ-39 significantly improved one year following GPi implantation compared to baseline (effect size = 1.32, 1.15, 0.25, 0.45, and 0.34, respectively). GPi DBS improved the Off-medication UPDRS III scores regardless of the motor subtypes. However, compared to the PIGD and AR patients, the TD patients showed greater improvement in overall UPDRS III postoperatively primarily due to greater tremor improvement in the Off-medication state. The outcomes in akinesia, rigidity, axial symptoms and QOL were similar among all subtypes.

CONCLUSION

Bilateral GPi DBS was effective for advanced PD patients regardless of motor subtypes. Greater tremor improvement in the TD patients accounted for greater Off-medication motor improvement. Longer-term GPi DBS outcomes across different motor subtypes and brain targets should be further studied.

Characteristics of oscillatory pallidal neurons in patients with Parkinson's disease

BACKGROUND

Excessive neuronal activity in the globus pallidus internus (GPi) is believed to promote parkinsonian akinesia/bradykinesia, but not tremor. Parkinsonian tremor is thought to result from dysfunction in the basal ganglia and cerebello-thalamo-cortical circuits. Whether the GPi is involved in tremorgenesis has not been fully elucidated. This study was designed to quantify the characteristics of oscillatory GPi neurons in patients with Parkinson's disease.

METHODS

Nine patients undergoing surgery were studied. Microelectrode recordings in the GPi and electromyographic (EMG) activity in the limbs were recorded and the mean spontaneous firing rates (MSFRs) were calculated. Spectral analysis was used to assess neuronal oscillatory patterns. Coherence analysis was applied to explore the relationship between oscillatory neurons and EMG.

RESULTS

Of 79 GPi neurons, 50.6% oscillated at the tremor frequency; 25.3% oscillated at β frequency, and 24.1% did not oscillate. The MSFR of all neurons was 81.5 ± 7.4 spikes/s. Among neurons oscillating at tremor frequency, 40% were coherent with the tremor. In four neurons, the pattern changed from tremor frequency to β frequency or vice versa. It appeared that the tremor began before the GPi fired bursts.

CONCLUSION

Some neuronal activity in the GPi correlates with tremor and this correlation might be due to either feedback, maintenance, or initiation. Since there were examples of EMG tremor prior to GPi activity, initiation seems least likely. The data further support the prediction of the classic pathophysiology model of Parkinson's disease.

From medications to surgery: advances in the treatment of motor complications in Parkinson's disease

Motor complications are responsible for the large burden of disability and poor quality of life in Parkinson’s disease (PD). The pulsatile nature of stimulation with oral dopaminergic therapies due to relatively short pharmacokinetic profiles and dysfunctional gastrointestinal absorption have been attributed to the development of PD motor complications. In this review, we will provide an overview of the pharmacologic and surgical therapies currently available and under investigation for the treatment of motor fluctuations and dyskinesia.