Dementia and subthalamic deep brain stimulation in Parkinson disease

Preoperative cognitive profile predictive of cognitive decline after subthalamic deep brain stimulation in Parkinson's disease

Cognitive decline represents a severe non-motor symptom of Parkinson's disease (PD) that can significantly reduce the benefits of subthalamic deep brain stimulation (STN DBS). Here, we aimed to describe post-surgery cognitive decline and identify pre-surgery cognitive profile associated with faster decline in STN DBS-treated PD patients. A retrospective observational study of 126 PD patients treated by STN DBS combined with oral dopaminergic therapy followed for 3.54 years on average (SD = 2.32) with repeated assessments of cognition was conducted. Pre-surgery cognitive profile was obtained via a comprehensive neuropsychological examination and data analysed using exploratory factor analysis and Bayesian generalized linear mixed models. On the whole, we observed a mild annual cognitive decline of 0.90 points from a total of 144 points in the Mattis Dementia Rating Scale (95% posterior probability interval [-1.19, -0.62]) with high inter-individual variability. However, true score changes did not reach previously reported reliable change cut-offs. Executive deficit was the only pre-surgery cognitive variable to reliably predict the rate of post-surgery cognitive decline. On the other hand, exploratory analysis of electrode localization did not yield any statistically clear results. Overall, our data and models imply mild gradual average annual post-surgery cognitive decline with high inter-individual variability in STN DBS-treated PD patients. Nonetheless, patients with worse long-term cognitive prognosis can be reliably identified via pre-surgery examination of executive functions. To further increase the utility of our results, we demonstrate how our models can help with disentangling true score changes from measurement error in future studies of post-surgery cognitive changes.

Clinical neurophysiology in the treatment of movement disorders: IFCN handbook chapter

In this review, different aspects of the use of clinical neurophysiology techniques for the treatment of movement disorders are addressed. First of all, these techniques can be used to guide neuromodulation techniques or to perform therapeutic neuromodulation as such. Neuromodulation includes invasive techniques based on the surgical implantation of electrodes and a pulse generator, such as deep brain stimulation (DBS) or spinal cord stimulation (SCS) on the one hand, and non-invasive techniques aimed at modulating or even lesioning neural structures by transcranial application. Movement disorders are one of the main areas of indication for the various neuromodulation techniques. This review focuses on the following techniques: DBS, repetitive transcranial magnetic stimulation (rTMS), low-intensity transcranial electrical stimulation, including transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS), and focused ultrasound (FUS), including high-intensity magnetic resonance-guided FUS (MRgFUS), and pulsed mode low-intensity transcranial FUS stimulation (TUS). The main clinical conditions in which neuromodulation has proven its efficacy are Parkinson's disease, dystonia, and essential tremor, mainly using DBS or MRgFUS. There is also some evidence for Tourette syndrome (DBS), Huntington's disease (DBS), cerebellar ataxia (tDCS), and axial signs (SCS) and depression (rTMS) in PD. The development of non-invasive transcranial neuromodulation techniques is limited by the short-term clinical impact of these techniques, especially rTMS, in the context of very chronic diseases. However, at-home use (tDCS) or current advances in the design of closed-loop stimulation (tACS) may open new perspectives for the application of these techniques in patients, favored by their easier use and lower rate of adverse effects compared to invasive or lesioning methods. Finally, this review summarizes the evidence for keeping the use of electromyography to optimize the identification of muscles to be treated with botulinum toxin injection, which is indicated and widely performed for the treatment of various movement disorders.

Developments in the prediction of cognitive changes following deep brain stimulation in persons with Parkinson's disease

INTRODUCTION

Deep brain stimulation (DBS) is an effective treatment for Parkinson's disease (PD) motor symptoms that improves function and quality of life in appropriately selected patients. Because mild to moderate cognitive declines can follow DBS and impact quality of life in a minority of patients, an important consideration involves the cognitive deficit and its prediction.

AREAS COVERED

The author briefly summarizes cognitive outcomes from DBS and reviews in more detail the risks/predictors of post-DBS cognitive dysfunction by mainly focusing on work published between 2018 and 2024 and using comprehensive neuropsychological (NP) evaluations. Most publications concern bilateral subthalamic nucleus (STN) DBS. Comment is offered on challenges and potential avenues forward.

EXPERT OPINION

STN DBS is relatively safe cognitively but declines occur especially in verbal fluency and executive function/working memory. Numerous predictors and risk factors for cognitive outcomes have been identified (age and pre-operative neuropsychological status appear the most robust) but precise risk estimates cannot yet be confidently offered. Future studies should employ study center consortia, follow uniform reporting criteria (to be developed), capitalize on advances in stimulation, biomarkers, and artificial intelligence, and address DBS in diverse groups. Advances offer an avenue to investigate the amelioration of cognitive deficits in PD using neuromodulation.

Differential Cognitive Effects of Unilateral Subthalamic Nucleus Deep Brain Stimulation for Parkinson's Disease

OBJECTIVE

The aim of this study was to investigate the cognitive effects of unilateral directional versus ring subthalamic nucleus deep brain stimulation (STN DBS) in patients with advanced Parkinson's disease.

METHODS

We examined 31 participants who underwent unilateral STN DBS (left n = 17; right n = 14) as part of an National Institutes of Health (NIH)-sponsored randomized, double-blind, crossover study contrasting directional versus ring stimulation. All participants received unilateral DBS implants in the hemisphere more severely affected by motor parkinsonism. Measures of cognition included verbal fluency, auditory-verbal memory, and response inhibition. We used mixed linear models to contrast the effects of directional versus ring stimulation and implant hemisphere on longitudinal cognitive function.

RESULTS

Crossover analyses showed no evidence for group-level changes in cognitive performance related to directional versus ring stimulation. Implant hemisphere, however, impacted cognition in several ways. Left STN participants had lower baseline verbal fluency than patients with right implants (t [20.66 = -2.50, p = 0.02]). Verbal fluency declined after left (p = 0.013) but increased after right STN DBS (p < 0.001), and response inhibition was faster following right STN DBS (p = 0.031). Regardless of hemisphere, delayed recall declined modestly over time versus baseline (p = 0.001), and immediate recall was unchanged.

INTERPRETATION

Directional versus ring STN DBS did not differentially affect cognition. Similar to prior bilateral DBS studies, unilateral left stimulation worsened verbal fluency performance. In contrast, unilateral right STN surgery increased performance on verbal fluency and response inhibition tasks. Our findings raise the hypothesis that unilateral right STN DBS in selected patients with predominant right brain motor parkinsonism could mitigate declines in verbal fluency associated with the bilateral intervention. ANN NEUROL 2024;95:1205-1219.

How to Use the New European Academy of Neurology/Movement Disorder Society European Section Guideline for Invasive Therapies in Parkinson's Disease

BACKGROUND

The decision to choose invasive treatments for Parkinson's disease (PD) is complex and needs careful consideration.

OBJECTIVES

Although the recommendations of the European Academy of Neurology/Movement Disorder Society European Section guideline for invasive therapies of PD are useful, the different clinical profiles of people with PD who seek advice for possible invasive therapy need further attention.

METHODS AND RESULTS

Here we describe 8 clinical standard situations of people with PD unsatisfied with their current oral treatment where invasive therapies may be considered. These are PD patients presenting with the following symptoms: (1) severe motor fluctuations, (2) beginning of levodopa-responsive fluctuations, severe tremor at (3) young or (4) advanced age, (5) impulse control disorders and related behavioral disorders, (6) hallucinations and psychosis, (7) minimal cognitive impairment or mild dementia, and (8) patients in need of palliative care. For some of these conditions, evidence at lower level or simple clinical considerations exist.

CONCLUSIONS

There are no one-fits-all answers, but physician and patient should discuss each option carefully considering symptom profile, psychosocial context, availability of therapy alternatives, and many other factors. The current paper outlines our proposed approach to these circumstances.

Gender discrepancies and differences in motor and non-motor symptoms, cognition, and psychological outcomes in the treatment of Parkinson's disease with subthalamic deep brain stimulation

Available data suggest that there may be gender differences in the effect of STN-DBS in the treatment of Parkinson's disease (PD). The aim of this study was to review data on gender discrepancies and gender differences in clinical outcomes in PD patients treated with deep brain stimulation of the subthalamic nucleus (STN-DBS). Included were original studies that specifically examined gender discrepancies or gender differences in PD patients with STN-DBS. Men receive more DBS than women, for various indications. The decision-making process for DBS in women compared to men is more influenced by personal preferences and external factors. Motor symptoms improve in both genders, but bradykinesia improves more in men. The postoperative reduction of the levodopa equivalent daily dose seems to be more pronounced in men. Men show more cognitive deterioration and less improvement than women after STN-DBS. Women show more depressive symptoms before surgery, but they improve similarly to men. Men show more improvement in impulsivity and less decrease in impulsive behaviour symptoms than women. Anxiety and personality traits remain unchanged in both genders. Voice quality improves more in men and deteriorates less often than in women. Men gain fat-free mass and fat mass, but women only gain fat mass. Regarding sexual function the evidence is inconsistent. More urinary symptoms improve in women than in men. Pain and restless leg syndrome seems to improve more in men. Regarding quality of life, the evidence seems to be inconsistent, and activities of daily living seems to improve in both genders. Better prospective controlled studies, focusing directly on gender differences in PD patients treated with STN-DBS, are needed to better explain gender differences in STN-DBS for PD.

Longitudinal Neuropsychological Assessment of Symptomatic Edema after Subthalamic Nucleus Deep Brain Stimulation Surgery: A Case Series Study

Severe non-infectious or non-haemorrhagic brain edema surrounding the electrode represents a rare complication of subthalamic nucleus deep brain stimulation (STN-DBS) surgery. The aim of this study is to report three patients with advanced Parkinson's Disease (PD) who developed symptomatic brain edema after STN-DBS surgery treated with intravenous steroids with a specific profile of reversible cognitive alterations. Patients were both assessed with a comprehensive neuropsychological battery including attention, memory, visuo-spatial and executive tasks. They were also briefly assessed for emotional and behavioural alterations, and for possible limitations in the activities of daily living. Normative data for an Italian population were available for all neuropsychological tests. The patients were firstly assessed before the surgery (baseline) as soon as they became symptomatic for the post-surgery edema and a few more times in follow-up up to ten months. In all patients we observed the resolution of cognitive deficits within six months after surgery with the corresponding reabsorption of edema at brain CT scans. The appearance of post-DBS edema is a fairly frequent and clinically benign event. However, in some rare cases it can be very marked and lead to important clinical-albeit transient-disturbances. These events can compromise, at least from a psychological point of view, the delicate path of patients who undergo DBS and can prolong the post-operative hospital stay. In this setting it could be helpful to perform a brain CT scan in 2-3 days with the aim of detecting the early appearance of edema and treating it before it can constitute a relevant clinical problem.

Long-term effects of bilateral subthalamic nucleus deep brain stimulation on gait disorders in Parkinson's disease: a clinical-instrumental study

OBJECTIVE

To assess the long-term effects of bilateral subthalamic nucleus deep brain stimulation (STN-DBS) on gait in a cohort of advanced Parkinson's Disease (PD) patients.

METHODS

This observational study included consecutive PD patients treated with bilateral STN-DBS. Different stimulation and drug treatment conditions were assessed: on-stimulation/off-medication, off-stimulation/off-medication, and on-stimulation/on-medication. Each patient performed the instrumented Timed Up and Go test (iTUG). The instrumental evaluation of walking ability was carried out with a wearable inertial sensor containing a three-dimensional (3D) accelerometer, gyroscope, and magnetometer. This device could provide 3D linear acceleration, angular velocity, and magnetic field vector. Disease motor severity was evaluated with the total score and subscores of the Unified Parkinson Disease Rating Scale part III.

RESULTS

Twenty-five PD patients with a 5-years median follow-up after surgery (range 3-7) were included (18 men; mean disease duration at surgery 10.44 ± 4.62 years; mean age at surgery 58.40 ± 5.73 years). Both stimulation and medication reduced the total duration of the iTUG and most of its different phases, suggesting a long-term beneficial effect on gait after surgery. However, comparing the two treatments, dopaminergic therapy had a more marked effect in all test phases. STN-DBS alone reduced total iTUG duration, sit-to-stand, and second turn phases duration, while it had a lower effect on stand-to-sit, first turn, forward walking, and walking backward phases duration.

CONCLUSIONS

This study highlighted that in the long-term after surgery, STN-DBS may contribute to gait and postural control improvement when used together with dopamine replacement therapy, which still shows a substantial beneficial effect.

Long-term neuropsychological outcomes of deep brain stimulation in early-stage Parkinson's disease

INTRODUCTION

The pilot trial of deep brain stimulation (DBS) in early-stage Parkinson's disease (PD) randomized 30 patients (medication duration 0.5-4 years; without dyskinesia or motor fluctuations) to receive optimal drug therapy alone (early ODT) or subthalamic nucleus (STN) DBS plus ODT (early DBS + ODT). This study reports long-term neuropsychological outcomes from the early DBS pilot trial.

METHODS

This is an extension of an earlier study that examined two-year neuropsychological outcomes in the pilot trial. The primary analysis was conducted on the five-year cohort (n = 28), and a secondary analysis was conducted on the 11-year cohort (n = 12). Linear mixed effects models for each analysis compared overall trend in outcomes for randomization groups. All subjects who completed the 11-year assessment were also pooled to evaluate long-term change from baseline.

RESULTS

There were no significant differences between groups in either the five- or 11-year analyses. Across all PD patients who completed the 11-year visit, there was significant decline in Stroop Color and Color-Word and Purdue Pegboard from baseline to 11 years.

CONCLUSIONS

Previous significant differences between the groups in phonemic verbal fluency and cognitive processing speed showing more decline for early DBS + ODT subjects one year after baseline diminished as PD progressed. No cognitive domains were worse for early DBS + ODT subjects compared to standard of care subjects. There were shared declines across all subjects on cognitive processing speed and motor control, likely reflecting disease progression. More study is needed to understand the long-term neuropsychological outcomes associated with early DBS in PD.

Differential cognitive effects of unilateral left and right subthalamic nucleus deep brain stimulation for Parkinson disease

Objective

To investigate hemispheric effects of directional versus ring subthalamic nucleus (STN) deep brain stimulation (DBS) surgery on cognitive function in patients with advanced Parkinson's disease (PD).

Methods

We examined 31 PD patients (Left STN n = 17; Right STN n = 14) who underwent unilateral subthalamic nucleus (STN) DBS as part of a NIH-sponsored randomized, cross-over, double-blind (ring vs directional) clinical trial. Outcome measures were tests of verbal fluency, auditory-verbal memory, and response inhibition. First, all participants were pooled together to study the effects of directional versus ring stimulation. Then, we stratified the groups by surgery hemisphere and studied the longitudinal changes in cognition post-unilateral STN DBS.

Results

Relative to pre-DBS cognitive baseline performances, there were no group changes in cognition following unilateral DBS for either directional or ring stimulation. However, assessment of unilateral DBS by hemisphere revealed a different pattern. The left STN DBS group had lower verbal fluency than the right STN group (t(20.66 = -2.50, p = 0.02). Over a period of eight months post-DBS, verbal fluency declined in the left STN DBS group (p = 0.013) and improved in the right STN DBS group over time (p < .001). Similarly, response inhibition improved following right STN DBS (p = 0.031). Immediate recall did not significantly differ over time, nor was it affected by implant hemisphere, but delayed recall equivalently declined over time for both left and right STN DBS groups (left STN DBS p = 0.001, right STN DBS differ from left STN DBS p = 0.794).

Conclusions

Directional and ring DBS did not differentially or adversely affect cognition over time. Regarding hemisphere effects, verbal fluency decline was observed in those who received left STN DBS, along with the left and right STN DBS declines in delayed memory. The left STN DBS verbal fluency decrement is consistent with prior bilateral DBS research, likely reflecting disruption of the basal-ganglia-thalamocortical network connecting STN and inferior frontal gyrus. Interestingly, we found an improvement in verbal fluency and response inhibition following right STN DBS. It is possible that unilateral STN DBS, particularly in the right hemisphere, may mitigate cognitive decline.

Developments in the mechanistic understanding and clinical application of deep brain stimulation for Parkinson's disease

INTRODUCTION. Deep brain stimulation (DBS) is a life-changing treatment for patients with Parkinson's disease (PD) and gives the unique opportunity to directly explore how basal ganglia work. Despite the rapid technological innovation of the last years, the untapped potential of DBS is still high.

AREAS COVERED. This review summarizes the developments in the mechanistic understanding of DBS and the potential clinical applications of cutting-edge technological advances. Rather than a univocal local mechanism, DBS exerts its therapeutic effects through several multimodal mechanisms and involving both local and network-wide structures, although crucial questions remain unexplained. Nonetheless, new insights in mechanistic understanding of DBS in PD have provided solid bases for advances in preoperative selection phase, prediction of motor and non-motor outcomes, leads placement and postoperative stimulation programming.

EXPERT OPINION. DBS has not only strong evidence of clinical effectiveness in PD treatment, but technological advancements are revamping its role of neuromodulation of brain circuits and key to better understanding PD pathophysiology. In the next few years, the worldwide use of new technologies in clinical practice will provide large data to elucidate their role and to expand their applications for PD patients, providing useful insights to personalize DBS treatment and follow-up.

Advances in DBS Technology and Novel Applications: Focus on Movement Disorders

PURPOSE OF REVIEW

Deep brain stimulation (DBS) is an established treatment in several movement disorders, including Parkinson's disease, dystonia, tremor, and Tourette syndrome. In this review, we will review and discuss the most recent findings including but not limited to clinical evidence.

RECENT FINDINGS

New DBS technologies include novel hardware design (electrodes, cables, implanted pulse generators) enabling new stimulation patterns and adaptive DBS which delivers potential stimulation tailored to moment-to-moment changes in the patient's condition. Better understanding of movement disorders pathophysiology and functional anatomy has been pivotal for studying the effects of DBS on the mesencephalic locomotor region, the nucleus basalis of Meynert, the substantia nigra, and the spinal cord. Eventually, neurosurgical practice has improved with more accurate target visualization or combined targeting. A rising research domain emphasizes bridging neuromodulation and neuroprotection. Recent advances in DBS therapy bring more possibilities to effectively treat people with movement disorders. Future research would focus on improving adaptive DBS, leading more clinical trials on novel targets, and exploring neuromodulation effects on neuroprotection.

Does Motor Symptoms Asymmetry Predict Motor Outcome of Subthalamic Deep Brain Stimulation in Parkinson's Disease Patients?

Background

In Parkinson's disease (PD), the side of motor symptoms onset may influence disease progression, with a faster motor symptom progression in patients with left side lateralization. Moreover, worse neuropsychological outcomes after subthalamic nucleus deep brain stimulation (STN-DBS) have been described in patients with predominantly left-sided motor symptoms. The objective of this study was to evaluate if the body side of motor symptoms onset may predict motor outcome of bilateral STN-DBS.

Methods

This retrospective study included all consecutive PD patients treated with bilateral STN-DBS at Grenoble University Hospital from 1993 to 2015. Demographic, clinical and neuroimaging data were collected before (baseline condition) and 1 year after surgery (follow-up condition). The predictive factors of motor outcome at one-year follow-up, measured by the percentage change in the MDS-UPDRS-III score, were evaluated through univariate and multivariate linear regression analysis.

Results

A total of 233 patients were included with one-year follow-up after surgery [143 males (61.40%); 121 (51.90 %) right body onset; 112 (48.10%) left body onset; mean age at surgery, 55.31 ± 8.44 years; mean disease duration, 11.61 ± 3.87]. Multivariate linear regression analysis showed that the left side of motor symptoms onset did not predict motor outcome (β = 0.093, 95% CI = −1.967 to 11.497, p = 0.164).

Conclusions

In this retrospective study, the body side of motor symptoms onset did not significantly influence the one-year motor outcome in a large cohort of PD patients treated with bilateral STN-DBS.

Low-frequency oscillations link frontal and parietal cortex with subthalamic nucleus in conflicts

Low-frequency oscillations (LFOs, 28 Hz) in the subthalamic nucleus(STN) are known to reflect cognitive conflict. However, it is unclear if LFOs mediate communication and functional interactions among regions implicated in conflict processing, such as the motor cortex (M1), premotor cortex (PMC), and superior parietal lobule (SPL). To investigate the potential contribution of LFOs to cognitive conflict mediation, we recorded M1, PMC, and SPL activities by right subdural electrocorticography (ECoG) simultaneously with bilateral STN local field potentials (LFPs) by deep brain stimulation electrodes in 13 patients with Parkinson's disease who performed the arrow version of the Eriksen flanker task. Elevated cue-related LFO activity was observed across patients during task trials, with the earliest onset in PMC and SPL. At cue onset, LFO power exhibited a significantly greater increase or a trend of a greater increase in the PMC, M1, and STN, and less increase in the SPL during high-conflict (incongruent) trials than in low-conflict (congruent) trials. The local LFO power increases in PMC, SPL, and right STN were correlated with response time, supporting the notion that these structures are critical hubs for cognitive conflict processing. This power increase was accompanied by increased functional connectivity between the PMC and right STN, which was correlated with response time across subjects. Finally, ipsilateral PMC-STN Granger causality was enhanced during high-conflict trials, with direction from STN to PMC. Our study indicates that LFOs link the frontal and parietal cortex with STN during conflicts, and the ipsilateral PMC-STN connection is specifically involved in this cognitive conflict processing.

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

Deep brain stimulation in Parkinson's disease: state of the art and future perspectives

For more than 30 years, Deep Brain Stimulation (DBS) has been a therapeutic option for Parkinson's disease (PD) treatment. However, this therapy is still underutilized mainly due to misinformation regarding risks and clinical outcomes. DBS can ameliorate several motor and non-motor symptoms, improving patients' quality of life. Furthermore, most of the improvement after DBS is long-lasting and present even in advanced PD. Adequate patient selection, precise electric leads placement, and correct DBS programming are paramount for good surgical outcomes. Nonetheless, DBS still has many limitations: axial symptoms and signs, such as speech, balance and gait, do not improve to the same extent as appendicular symptoms and can even be worsened as a direct or indirect consequence of surgery and stimulation. In addition, there are still unanswered questions regarding patient's selection, surgical planning and programming techniques, such as the role of surgicogenomics, more precise imaging-based lead placement, new brain targets, advanced programming strategies and hardware features. The net effect of these innovations should not only be to refine the beneficial effect we currently observe on selected symptoms and signs but also to improve treatment resistant facets of PD, such as axial and non-motor features. In this review, we discuss the current state of the art regarding DBS selection, implant, and programming, and explore new advances in the DBS field.

Motor symptom asymmetry predicts non-motor outcome and quality of life following STN DBS in Parkinson's disease

Risk factors for long-term non-motor symptoms and quality of life following subthalamic nucleus deep brain stimulation (STN DBS) have not yet been fully identified. In the present study, we investigated the impact of motor symptom asymmetry in Parkinson's disease. Data were extracted for 52 patients with Parkinson's disease (half with predominantly left-sided motor symptoms and half with predominantly right-sided ones) who underwent bilateral STN and a matched healthy control group. Performances for cognitive tests, apathy and depression symptoms, as well as quality-of-life questionnaires at 12 months post-DBS were compared with a pre-DBS baseline. Results indicated a deterioration in cognitive performance post-DBS in patients with predominantly left-sided motor symptoms. Performances of patients with predominantly right-sided motor symptoms were maintained, except for a verbal executive task. These differential effects had an impact on patients' quality of life. The results highlight the existence of two distinct cognitive profiles of Parkinson's disease, depending on motor symptom asymmetry. This asymmetry is a potential risk factor for non-motor adverse effects following STN DBS.

Target Selection for Magnetic Resonance-Guided Focused Ultrasound in the Treatment of Parkinson's Disease

Parkinson's disease (PD) is a common, progressive, and incurable neurodegenerative disease. Pharmacological treatment is the first-line therapy for PD, including carbidopa-levodopa, dopamine agonists. However, some patients respond poorly to medication. For these patients, functional neurosurgical treatment is an important option. Magnetic resonance-guided focused ultrasound (MRgFUS) is a novel, minimally invasive surgical option for patients refractory to drugs. Currently, several important anatomical structures can be targeted by MRgFUS in the treatment of PD. However, there is no uniform standard for target selection. This review summarizes the clinical studies on MRgFUS for PD, focusing on the relationship between different treatment targets and the relieved symptoms, to help clinicians determine the ideal therapeutic target for individual patients. EVIDENCE LEVEL: 5 TECHNICAL EFFICACY: Stage 4.

Short and Long-Term Cognitive Effects of Subthalamic Deep Brain Stimulation in Parkinson's Disease and Identification of Relevant Factors

BACKGROUND

Subthalamic nucleus deep brain stimulation (STN-DBS) successfully controls the motor symptoms of Parkinson's disease (PD) but has associated cognitive side-effects.

OBJECTIVE

Establish the short- and long-term cognitive effects of STN-DBS in PD.

METHODS

Both the short-term and long-term effects of STN-DBS on cognition were examined through evaluation of the controlled studies that compared patients with STN-DBS to unoperated PD patients, thus controlling for illness progression. We also reviewed the literature to identify the factors that influence cognitive outcome of STN-DBS in PD.

RESULTS

The meta-analysis of the short-term cognitive effects of STN-DBS revealed moderate effect sizes for semantic and phonemic verbal fluency and small effect sizes for psychomotor speed and language, indicating greater decline in the STN-DBS operated than the unoperated patients in these cognitive domains. The longer-term STN-DBS results from controlled studies indicated rates of cognitive decline/dementia up to 32%; which are no different from the rates from the natural progression of PD. Greater executive dysfunction and poorer memory pre-operatively, older age, higher pre-operative doses of levodopa, and greater axial involvement are some of the factors associated with worse cognition after STN-DBS in PD.

CONCLUSION

This evidence can be used to inform patients and their families about the short-term and long-term risks of cognitive decline following STN-DBS surgery and aid the team in selection of suitable candidates for surgery.

Heterogeneity of PD-MCI in Candidates to Subthalamic Deep Brain Stimulation: Associated Cortical and Subcortical Modifications

BACKGROUND

Parkinson's disease mild cognitive impairment (PD-MCI) is frequent and heterogenous. There is no consensus about its influence on subthalamic deep brain stimulation (STN-DBS) outcomes.

OBJECTIVE

To determine the prevalence of PD-MCI and its subtypes in candidates to STN-DBS. Secondarily, we sought to identify MRI structural markers associated with cognitive impairment in these subgroups.

METHODS

Baseline data from the French multicentric PREDISTIM cohort were used. Candidates to STN-DBS were classified according to their cognitive performance in normal cognition (PD-NC) or PD-MCI. The latter included frontostriatal (PD-FS) and posterior cortical (PD-PC) subtypes. Between-group comparisons were performed on demographical and clinical variables as well as on T1-weighted MRI sequences at the cortical and subcortical levels.

RESULTS

320 patients were included: 167 (52%) PD-NC and 153 (48%) PD-MCI patients. The latter group included 123 (80%) PD-FS and 30 (20%) PD-PC patients. There was no between-group difference regarding demographic and clinical variables. PD-PC patients had significantly lower global efficiency than PD-FS patients and significantly worse performance on visuospatial functions, episodic memory, and language. Compared to PD-NC, PD-MCI patients had cortical thinning and radiomic-based changes in the left caudate nucleus and hippocampus. There were no significant differences between the PD-MCI subtypes.

CONCLUSION

Among the candidates to STN-DBS, a significant proportion has PD-MCI which is associated with cortical and subcortical alterations. Some PD-MCI patients have posterior cortical deficits, a subtype known to be at higher risk of dementia.

Nucleus basalis of Meynert predicts cognition after deep brain stimulation in Parkinson's disease

INTRODUCTION

Subthalamic DBS in Parkinson's disease has been associated with cognitive decline in few cases. Volume reduction of the nucleus basalis of Meynert (NBM) seems to precede cognitive impairment in Parkinson's disease. In this retrospective study, we evaluated NBM volume as a predictor of cognitive outcome 1 year after subthalamic DBS.

METHODS

NBM volumes were calculated from preoperative MRIs using voxel-based morphometry. Cognitive outcome was defined as the relative change of MMSE or DemTect scores from pre-to 1 year postoperatively. A multiple linear regression analysis adjusted for the number of cognitive domains affected in the preoperative neuropsychological testing and UPDRS III was conducted. To account for other variables and potential non-linear effects, an additional machine learning analysis using random forests was applied.

RESULTS

55 patients with Parkinson's disease (39 male, age 61.4 ± 7.5 years, disease duration 10.8 ± 4.7 years) who received bilateral subthalamic DBS electrodes at our center were included. Although overall cognition did not change significantly, individual change in cognitive abilities was variable. Cognitive outcome could be predicted based on NBM size (B = 208.98, p = 0.022*) in the regression model (F(3,49) = 2.869; R² of 0.149; p = 0.046*). Using random forests with more variables, cognitive outcome could also be predicted (average root mean squared error between predicted and true cognitive change 11.28 ± 9.51, p = 0.039*). Also in this model, NBM volume was the most predictive variable.

CONCLUSION

NBM volume can be used as a simple non-invasive predictor for cognitive outcome after DBS in Parkinson's disease, especially when combined with other clinical parameters that are prognostically relevant.

Short- and long-term motor outcome of STN-DBS in Parkinson's Disease: focus on sex differences

INTRODUCTION

Subthalamic nucleus deep brain stimulation (STN-DBS) is an established treatment for patients with Parkinson's disease (PD) with motor complications; the contribution of sex in determining the outcome is still not understood.

METHODS

We included 107 patients (71 males) with PD consecutively implanted with STN-DBS at our center. We reviewed patient charts from our database and retrospectively collected demographical and clinical data at baseline and at three follow-up visits (1, 5 and 10 years).

RESULTS

We found a long-lasting effect of DBS on motor complications, despite a progressive worsening of motor performances in the ON medication condition. Bradykinesia and non-dopaminergic features seem to be the major determinant of this progression. Conversely to males, females showed a trend towards worsening in bradykinesia already at 1-year follow-up and poorer scores in non-dopaminergic features at 10-year follow-up. Levodopa Equivalent Daily Dose (LEDD) was significantly reduced after surgery compared to baseline values; however, while in males LEDD remained significantly lower than baseline even 10 years after surgery, in females LEDD returned at baseline values. Males showed a sustained effect on dyskinesias, but this benefit was less clear in females; the total electrical energy delivered was consistently lower in females compared to males. The profile of adverse events did not appear to be influenced by sex.

CONCLUSION

Our data suggest that there are no major differences on the motor effect of STN-DBS between males and females. However, there may be some slight differences that should be specifically investigated in the future and that may influence therapeutic decisions in the chronic follow-up.

Eight-year follow-up outcome of subthalamic deep brain stimulation for Parkinson's disease: Maintenance of therapeutic efficacy with a relatively low levodopa dosage and stimulation intensity

AIMS

This follow-up study aimed to examine the 8-year efficacy and safety of subthalamic nucleus (STN) deep brain stimulation (DBS) for patients with Parkinson's disease (PD) in southern China.

METHODS

The follow-up data of 10 patients with PD undergoing STN-DBS were analyzed. Motor symptoms were assessed before and 1, 3, 5, and 8 years after the surgery with stimulation-on in both off-medication (off-med) and on-medication (on-med) status using the Unified Parkinson's disease Rating Scale Part III. The quality of life was assessed using the 39-item Parkinson's Disease Questionnaire. The sleep, cognition, and emotion were evaluated using a series of nonmotor scales. Levodopa equivalent daily dose (LEDD) and stimulation parameters were recorded at each follow-up.

RESULTS

The motor symptoms were improved by 50.9%, 37.7%, 36.7%, and 37.3% in 1, 3, 5, and 8 years, respectively, in the off-med / stimulation-on status compared with the baseline. The quality of life improved by 39.7% and 56.1% in 1 and 3 years, respectively, but declined to the preoperative level thereafter. The sleep, cognition, and emotion were mostly unchanged. LEDD reduced from 708.1 ± 172.5 mg to 330 ± 207.8 mg in 8 years. The stimulation parameters, including amplitude, pulse width, and frequency, were 2.77 ± 0.49 V, 71.3 ± 12.8 μs, and 121.5 ± 21 Hz, respectively, in 8 years.

CONCLUSION

Long-term therapeutic efficacy of STN-DBS could be achieved even with relatively low stimulation intensity and medication dosage for PD patients in southern China. Motor improvement and medication reduction were maintained through the 8-year follow-up, but improvement in quality of life lasted for only 3 years. No definite changes was found in nonmotor symptoms after STN-DBS.

The severity progression of non-motor symptoms in Parkinson's disease: a 6-year longitudinal study in Taiwanese patients

Nonmotor symptoms (NMSs) cause major burden in patients with Parkinson's disease (PD). Previous NMSs progression studies mostly focused on the prevalence. We conducted a longitudinal study to identify the progression pattern by the severity. PD patients recruited from the outpatient clinics of a tertiary medical center were evaluated by the Unified Parkinson's Disease Rating Scale and Non-Motor Symptoms Scale (NMSS). A retrospective study with three-step analysis was performed. Step 1, the NMSs severity was compared among patients stratified by disease duration every 2 years up to 10 years. Step 2, patients with repeated tests in 2 years were categorized into 4 groups by the diseased duration of every 5 years. Step 3, the NMSS score changes in 6 years follow-up were determined, and the dosage of anti-PD drugs was compared to the NMSs severity changes. 676 patients completed the step 1 analysis, which showed a trend of NMSs worsening but not significant until the disease duration longer than 4-6 years. Furthermore, the severity did not change between repeated evaluations in 2 years in all patients. The progression became apparent after 6 years. Individual symptoms had different progression patterns and the increment of medications was independent to NMSs evolution. We demonstrated the NMSs severity progression in Taiwanese PD patients and the independence of the medications and NMSs progression.

Long-term Outcomes (15 Years) After Subthalamic Nucleus Deep Brain Stimulation in Patients With Parkinson Disease

OBJECTIVE

To evaluate the effects of deep brain stimulation of the subthalamic nucleus (STN-DBS) on motor complications in patients with Parkinson disease (PD) beyond 15 years after surgery.

METHODS

Data on motor complications, quality of life (QoL), activities of daily living, Unified Parkinson's Disease Rating Scale motor scores, dopaminergic treatment, stimulation measures, and side effects of STN-DBS were retrospectively retrieved and compared before surgery, at 1 year, and beyond 15 years after bilateral STN-DBS.

RESULTS

Fifty-one patients with 17.06 ± 2.18 years STN-DBS follow-up were recruited. Compared to baseline, the time spent with dyskinesia and the time spent in the "off" state were reduced by 75% (p < 0.001) and by 58.7% (p < 0.001), respectively. Moreover, dopaminergic drugs were reduced by 50.6% (p < 0.001). Parkinson's Disease Quality of Life Questionnaire total score and the emotional function and social function domains improved 13.8% (p = 0.005), 13.6% (p = 0.01), and 29.9% (p < 0.001), respectively. Few and mostly manageable device-related adverse events were observed during the follow-up.

CONCLUSIONS

STN-DBS is effective beyond 15 years from the intervention, notably with significant improvement in motor complications and stable reduction of dopaminergic drugs. Furthermore, despite the natural continuous progression of PD with worsening of levodopa-resistant motor and nonmotor symptoms over the years, patients undergoing STN-DBS could maintain an improvement in QoL.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence that, for patients with PD, STN-DBS remains effective at treating motor complications 15 years after surgery.

Characterizing Complications of Deep Brain Stimulation Devices for the Treatment of Parkinsonian Symptoms Without Tremor: A Federal MAUDE Database Analysis

Introduction Deep brain stimulation (DBS) is a modality of treatment for medication refractory Parkinson's disease (PD) in patients with debilitating motor symptoms. While potentially life-changing for individuals with Parkinson's disease, characterization of adverse events for these DBS devices have not yet been systematically organized. Therefore, the goal of this study was to characterize reported complications of DBS devices reported to the Food & Drug Administration over the last 10 years. Methods The Manufacturer and User Facility Device Experience (MAUDE) database was utilized to retrieve entries reported under "Stimulator, Electrical, Implanted, For Parkinsonian Symptoms" between July 31, 2010 and August 1, 2020. After removing duplicate entries, each unique adverse event reported was sorted into complication categories based on the entries' provided narrative description. A final tabulation of complications was generated. Results The search query revealed 221 unique adverse events. The most common DBS devices were the Vercise Gevia, Vercise Cartesia and Vercise PC produced by Boston Scientific (Brian Walker, Boston Scientific, Marlborough, MA, USA). The most commonly reported complications were infection (16.2%) follow by lead migrations (8.6%). Other common causes of complications were circuit-related impedance (6.5%), cerebral bleeds (6.3%), device failure (6.3%) and device-related trauma (4.5%). Over a third (40%) of all devices reported with adverse events required returning to the operating room for explant or revision. Conclusion The most common complications of DBS systems are infections followed by lead migrations. Further research is needed to minimize infection rates associated with DBS systems and to reduce intrinsic device malfunctions for patients in the future.

Predictors of Long-Term Outcome of Subthalamic Stimulation in Parkinson Disease

OBJECTIVE

This study was undertaken to identify preoperative predictive factors of long-term motor outcome in a large cohort of consecutive Parkinson disease (PD) patients with bilateral subthalamic nucleus deep brain stimulation (STN-DBS).

METHODS

All consecutive PD patients who underwent bilateral STN-DBS at the Grenoble University Hospital (France) from 1993 to 2015 were evaluated before surgery, at 1 year (short-term), and in the long term after surgery. All available demographic variables, neuroimaging data, and clinical characteristics were collected. Preoperative predictors of long-term motor outcome were investigated by performing survival and univariate/multivariate Cox regression analyses. Loss of motor benefit from stimulation in the long term was defined as a reduction of less than 25% in the Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS) part III scores compared to the baseline off-medication scores. As a secondary objective, potential predictors of short-term motor outcome after STN-DBS were assessed by performing univariate and multivariate linear regression analyses.

RESULTS

In the long-term analyses (mean follow-up = 8.4 ± 6.26 years, median = 10 years, range = 1-17 years), 138 patients were included. Preoperative higher frontal score and off-medication MDS-UPDRS part III scores predicted a better long-term motor response to stimulation, whereas the presence of vascular changes on neuroimaging predicted a worse motor outcome. In 357 patients with available 1-year follow-up, preoperative levodopa response, tremor dominant phenotype, baseline frontal score, and off-medication MDS-UPDRS part III scores predicted the short-term motor outcome.

INTERPRETATION

Frontal lobe dysfunction, disease severity in the off-medication condition, and the presence of vascular changes on neuroimaging represent the main preoperative clinical predictors of long-term motor STN-DBS effects. ANN NEUROL 2021;89:587-597.