A Review of Cognitive Outcomes Across Movement Disorder Patients Undergoing Deep Brain Stimulation

Motor and Non-motor Outcomes of Deep Brain Stimulation across the Genetic Panorama of Parkinson's Disease: A Multi-Scale Meta-Analysis

BACKGROUND

In the era of modern medicine, where high-throughput sequencing techniques are readily available, it is desirable to elucidate the role of genetic background in patients with Parkinson's Disease (PD) undergoing Deep Brain Stimulation (DBS). Genetic stratification of PD patients undergoing DBS may assist in patient selection and prediction of clinical outcomes and complement existing selection procedures such as levodopa challenge testing.

OBJECTIVE

To capture a broad spectrum of motor and non-motor DBS outcomes in genetic PD patients with data from the recently updated literature.

METHODS

A multi-scale meta-analysis with 380 genetic PD cases was conducted using the Cochrane Review Manager, JASP software and R.

RESULTS

This meta-analysis revealed that overall, patients with genetic PD are good candidates for DBS but the outcomes might differ depending on the presence of specific mutations. PRKN carriers benefited the most regarding motor function, daily dose medication and motor complications. However, GBA carriers appeared to be more prone to cognitive decline after subthalamic nucleus DBS accompanied by a low quality of life with variable severity depending on genetic variants and concomitant alterations in other genes. Apart from GBA, cognitive worsening was also observed in SNCA carriers. Pre-operative levodopa responsiveness and a younger age of onset are associated with a favorable motor outcome.

CONCLUSION

A personalized approach with a variant-based risk stratification within the emerging field of surgicogenomics is needed. Integration of polygenic risk scores in clinical-decision making should be encouraged.

Cognitive and psychiatric outcomes in the GALAXY trial: effect of anaesthesia in deep brain stimulation

BACKGROUND

This study aims: (1) To compare cognitive and psychiatric outcomes after bilateral awake versus asleep subthalamic nucleus (STN) deep brain stimulation (DBS) surgery for Parkinson's disease (PD). (2) To explore the occurrence of psychiatric diagnoses, cognitive impairment and quality of life after surgery in our whole sample. (3) To validate whether we can predict postoperative cognitive decline.

METHODS

110 patients with PD were randomised to receive awake (n=56) or asleep (n=54) STN DBS surgery. At baseline and 6-month follow-up, all patients underwent standardised assessments testing several cognitive domains, psychiatric symptoms and quality of life.

RESULTS

There were no differences on neuropsychological composite scores and psychiatric symptoms between the groups, but we found small differences on individual tests and cognitive domains. The asleep group performed better on the Rey Auditory Verbal Learning Test delayed memory test (f=4.2, p=0.04), while the awake group improved on the Rivermead Behavioural Memory Test delayed memory test. (f=4.4, p=0.04). The Stroop III score was worse for the awake group (f=5.5, p=0.02). Worse scores were present for Stroop I (Stroop word card) (f=6.3, p=0.01), Stroop II (Stroop color card) (f=46.4, p<0.001), Stroop III (Stroop color-word card) (f=10.8, p=0.001) and Trailmaking B/A (f=4.5, p=0.04). Improvements were seen on quality of life: Parkinson's Disease Questionnaire-39 (f=24.8, p<0.001), and psychiatric scales: Hamilton Depression Rating Scale (f=6.2, p=0.01), and Hamilton Anxiety Rating Scale (f=5.5, p=0.02).

CONCLUSIONS

This study suggests that the choice between awake and asleep STN DBS does not affect cognitive, mood and behavioural adverse effects, despite a minor difference in memory. STN DBS has a beneficial effect on quality of life, mood and anxiety symptoms.

TRIAL REGISTRATION NUMBER

NTR5809.

Cognitive outcomes in patients with essential tremor treated with deep brain stimulation: a systematic review

Introduction

Essential tremor (ET) is a common neurological disease. Deep brain stimulation (DBS) to the thalamic ventral intermediate nucleus (VIM) or the adjacent structures, such as caudal zona incerta/ posterior subthalamic area (cZi/PSA), can be effective in treating medication refractory tremor. However, it is not clear whether DBS can cause cognitive changes, in which domain, and to what extent if so.

Methods

We systematically searched PubMed and the Web of Science for available publications reporting on cognitive outcomes in patients with ET who underwent DBS following the PICO (population, intervention, comparators, and outcomes) concept. The PRISMA guideline for systematic reviews was applied.

Results

Twenty relevant articles were finally identified and included for review, thirteen of which were prospective (one also randomized) studies and seven were retrospective. Cognitive outcomes included attention, memory, executive function, language, visuospatial function, and mood-related variables. VIM and cZi/PSA DBS were generally well tolerated, although verbal fluency and language production were affected in some patients. Additionally, left-sided VIM DBS was associated with negative effects on verbal abstraction, word recall, and verbal memory performance in some patients.

Conclusion

Significant cognitive decline after VIM or cZi/PSA DBS in ET patients appears to be rare. Future prospective randomized controlled trials are needed to meticulously study the effect of the location, laterality, and stimulation parameters of the active contacts on cognitive outcomes while considering possible medication change post-DBS, timing, standard neuropsychological battery, practice effects, the timing of assessment, and effect size as potential confounders.

Alternative patterns of deep brain stimulation in neurologic and neuropsychiatric disorders

Deep brain stimulation (DBS) is a widely used clinical therapy that modulates neuronal firing in subcortical structures, eliciting downstream network effects. Its effectiveness is determined by electrode geometry and location as well as adjustable stimulation parameters including pulse width, interstimulus interval, frequency, and amplitude. These parameters are often determined empirically during clinical or intraoperative programming and can be altered to an almost unlimited number of combinations. Conventional high-frequency stimulation uses a continuous high-frequency square-wave pulse (typically 130-160 Hz), but other stimulation patterns may prove efficacious, such as continuous or bursting theta-frequencies, variable frequencies, and coordinated reset stimulation. Here we summarize the current landscape and potential clinical applications for novel stimulation patterns.

Neurologists' preferences for device-aided therapy for advanced Parkinson's disease in Japan

OBJECTIVE

This study measures the relative preference for attributes of device-aided therapies (DATs) for advanced Parkinson's Disease (PD) from the perspective of Japanese neurologists.

METHODS

Attributes and levels were elicited based on literature and interviews with certified neurologists experienced with DATs. An online survey including a discrete choice experiment (DCE) was developed, pilot tested, and distributed through an online panel to neurologists treating advanced PD patients. Participants were asked to choose treatments among several choice sets of two hypothetical DATs described only by the attributes, or no DAT (continuing oral treatment). A conditional logit model using the Bayesian framework was developed to estimate the marginal utilities of attributes' levels, and the relative utility of treatments available to Japanese advanced PD patients or being developed in Japan was assessed.

RESULTS

The DCE survey completed by 308 neurologists showed that the attributes with the greatest influence on DAT selection were surgery requirement (relative importance of 28%), average increase in the duration of daily "on" time without dyskinesia which affects daily activities (15%), average change in cognitive function related to treatment introduction (15%), device management frequency (14%), average number of pills of oral PD medication after treatment introduction (13%), average influence of treatment on symptoms of depression (12%), and type of device (large/small) (3%). All attributes significantly influenced respondents' choices, except for external device type. Experience with DATs did not influence the directions of preferences. Out of treatment profiles representing DATs, continuous subcutaneous infusion of levodopa-carbidopa had a higher preference score than levodopa-carbidopa intestinal gel infusion and deep brain stimulation.

CONCLUSIONS

Our findings suggest that Japanese neurologists would prefer a DAT without surgery requirement. Other factors related to efficacy, safety, and administration mode have a significant, but a smaller influence on prescription choices.

Should we offer deep brain stimulation to Parkinson's disease patients with GBA mutations?

Parkinson's disease (PD) patients who are carriers of glucosylceramidase β1 (GBA1) gene mutations typically have an earlier age at onset and a more aggressive disease course, with a higher burden of neuropsychological issues. The use of deep brain stimulation (DBS) in PD patients with disabling motor fluctuations and absence of dementia is a widespread therapeutic option, often with good results in terms of improvement in activities of daily living and quality of life. Although all PD patients, when fulfilling the common selection criteria for DBS, can benefit from this intervention, some studies have raised attention toward the fact that PD patients who are carriers of GBA1 variants may have a worse DBS outcome possibly due to an accelerated progression of cognitive decline. From this viewpoint, we summarize the current literature, highlighting the knowledge gaps and proposing suggestions for further research as well as for clinical practice in this timeframe of uncertainty related to using DBS in PD patients who are carriers of GBA1 variants.

Effects of deep brain stimulation target on the activation and suppression of action impulses

OBJECTIVE

Deep brain stimulation (DBS) is an effective treatment to improve motor symptoms in Parkinson's disease (PD). The Globus Pallidus (GPi) and the Subthalamic Nucleus (STN) are the most targeted brain regions for stimulation and produce similar improvements in PD motor symptoms. However, our understanding of stimulation effects across targets on inhibitory action control processes is limited. We compared the effects of STN (n = 20) and GPi (n = 13) DBS on inhibitory control in PD patients.

METHODS

We recruited PD patients undergoing DBS at the Vanderbilt Movement Disorders Clinic and measured their performance on an inhibitory action control task (Simon task) before surgery (optimally treated medication state) and after surgery in their optimally treated state (medication plus their DBS device turned on).

RESULTS

DBS to both STN and GPi targets induced an increase in fast impulsive errors while simultaneously producing more proficient reactive suppression of interference from action impulses.

CONCLUSIONS

Stimulation in GPi produced similar effects as STN DBS, indicating that stimulation to either target increases the initial susceptibility to act on strong action impulses while concomitantly improving the ability to suppress ongoing interference from activated impulses.

SIGNIFICANCE

Action impulse control processes are similarly impacted by stimulating dissociable nodes in frontal-basal ganglia circuitry.

Parkinson’s disease with mild cognitive impairment may has a lower risk of cognitive decline after subthalamic nucleus deep brain stimulation: A retrospective cohort study

Background

The cognitive outcomes induced by subthalamic nucleus deep brain stimulation (STN-DBS) remain unclear, especially in PD patients with mild cognitive impairment (MCI). This study explored the cognitive effects of STN-DBS in PD patients with MCI.

Methods

This was a retrospective cohort study that included 126 PD patients who underwent STN-DBS; all patients completed cognitive and motor assessments before and at least 6 months after surgery. Cognitive changes were mainly evaluated by the Montreal cognitive assessment (MoCA) scale and the seven specific MoCA domains, including visuospatial/executive function, naming, attention, language, abstract, delayed recall, and orientation. Motor improvement was evaluated by the UPDRS-III. Cognitive changes and motor improvements were compared between PD-MCI and normal cognitive (NC) patients. Logistic regression analyses were performed to explore predictors of post-operative cognitive change.

Results

At the time of surgery, 61.90% of the included PD patients had MCI. Compared with the PD-MCI group, the PD-NC group had a significantly higher proportion of cases with post-operative cognitive decline during follow-up of up to 36 months (mean 17.34 ± 10.61 months), mainly including in global cognitive function, visuospatial/executive function and attention. Covariate-adjusted binary logistic regression analyses showed that pre-operative global cognitive status was an independent variable for post-operative cognitive decline. We also found that pre-operative cognitive specific function could predict its own decline after STN-DBS, except for the naming and orientation domains.

Conclusion

PD-MCI patients are at a lower risk of cognitive decline after STN-DBS compared with PD-NC patients.

Developing Predictor Models of Postoperative Verbal Fluency After Deep Brain Stimulation Using Preoperative Neuropsychological Assessment

BACKGROUND

Deep brain stimulation (DBS) for Parkinson disease provides significant improvement of motor symptoms but can also produce neurocognitive side effects. A decline in verbal fluency (VF) is among the most frequently reported side effects. Preoperative factors that could predict VF decline have yet to be identified.

OBJECTIVE

To develop predictive models of DBS postoperative VF decline using a machine learning approach.

METHODS

We used a prospective database of patients who underwent neuropsychological and VF assessment before both subthalamic nucleus (n = 47, bilateral = 44) and globus pallidus interna (n = 43, bilateral = 39) DBS. We used a neurobehavioral rating profile as features for modeling postoperative VF. We constructed separate models for action, semantic, and letter VF. We used a leave-one-out scheme to test the accuracy of the predictive models using median absolute error and correlation with actual postoperative scores.

RESULTS

The predictive models were able to predict the 3 types of VF with high accuracy ranging from a median absolute error of 0.92 to 1.36. Across all three models, higher preoperative fluency, digit span, education, and Mini-Mental State Examination were predictive of higher postoperative fluency scores. By contrast, higher frontal system deficits, age, Questionnaire for Impulsive-Compulsive Disorders in Parkinson's disease scored by the patient, disease duration, and Behavioral Inhibition/Behavioral Activation Scale scores were predictive of lower postoperative fluency scores.

CONCLUSION

Postoperative VF can be accurately predicted using preoperative neurobehavioral rating scores above and beyond preoperative VF score and relies on performance over different aspects of executive function.

Essential tremor impairs the ability to suppress involuntary action impulses

Essential tremor (ET) is a movement disorder characterized primarily by action tremor which affects the regulation of movements. Disruptions in cerebello-thalamocortical networks could interfere with cognitive control over actions in ET, for example, the ability to suppress a strong automatic impulse over a more appropriate action (conflict control). The current study investigated whether ET impacts conflict control proficiency. Forty-one ET patients and 29 age-matched healthy controls (HCs) performed a conflict control task (Simon task). Participants were instructed to give a left or right response to a spatially lateralized arrow (direction of the arrow). When the action signaled by the spatial location and direction of the arrow were non-corresponding (induced conflict), the inappropriate action impulse required suppression. Overall, ET patients responded slower and less accurately compared to HCs. ET patients were especially less accurate on non-corresponding conflict (Nc) versus corresponding (Cs) trials. A focused analysis on fast impulsive response rates (based on the accuracy rate at the fastest reaction times on Nc trials) showed that ET patients made more fast errors compared to HCs. Results suggest impaired conflict control in ET compared to HCs. The increased impulsive errors seen in the ET population may be a symptom of deficiencies in the cerebello-thalamocortical networks, or, be caused by indirect effects on the cortico-striatal pathways. Future studies into the functional networks impacted by ET (cortico-striatal and cerebello-thalamocortical pathways) could advance our understanding of inhibitory control in general and the cognitive deficits in ET.

Novel targets in deep brain stimulation for movement disorders

The neurosurgical treatment of movement disorders, primarily via deep brain stimulation (DBS), is a rapidly expanding and evolving field. Although conventional targets including the subthalamic nucleus (STN) and internal segment of the globus pallidus (GPi) for Parkinson's disease and ventral intermediate nucleus of the thalams (VIM) for tremor provide substantial benefit in terms of both motor symptoms and quality of life, other targets for DBS have been explored in an effort to maximize clinical benefit and also avoid undesired adverse effects associated with stimulation. These novel targets primarily include the rostral zona incerta (rZI), caudal zona incerta (cZI)/posterior subthalamic area (PSA), prelemniscal radiation (Raprl), pedunculopontine nucleus (PPN), substantia nigra pars reticulata (SNr), centromedian/parafascicular (CM/PF) nucleus of the thalamus, nucleus basalis of Meynert (NBM), dentato-rubro-thalamic tract (DRTT), dentate nucleus of the cerebellum, external segment of the globus pallidus (GPe), and ventral oralis (VO) complex of the thalamus. However, reports of outcomes utilizing these targets are scattered and disparate. In order to provide a comprehensive resource for researchers and clinicians alike, we have summarized the existing literature surrounding these novel targets, including rationale for their use, neurosurgical techniques where relevant, outcomes and adverse effects of stimulation, and future directions for research.

Cognitive outcome following bilateral subthalamic nucleus deep brain stimulation for Parkinson's disease-a comparative observational study in Indian patients

BACKGROUND

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) improves motor symptoms and motor complications of Parkinson's disease (PD). The intervention is expected to result in some cognitive changes, the nature of which is not uniform across the studies which have reported them. PD itself is associated with progressive cognitive decline and hence longitudinal follow-up studies with medically managed control group of patients are needed to explore the cognitive deficits attributable to DBS.

METHODS

We conducted a prospective comparative observational study to assess the effects of bilateral STN DBS on cognition. Cognitive functions were assessed at baseline and after a minimum of two years after surgery, and compared with baseline and follow-up assessments in patients on medical management alone.

RESULTS

Thirty-four patients with PD who underwent bilateral STN DBS and thirty-four medically managed patients participated in the study. At a mean follow-up of around 33 months, we found a significant decline in verbal fluency scores in the DBS group compared to those on medical management alone (1.15 ± 1.23 vs 0.59 ± 0.93, p = 0.034) and a trend for decline was noted in digit span test. There was no difference in the performance in tests addressing other cognitive domains, or tests of global cognitive function. No patient developed dementia. Motor functions and activities of daily living (ADL) were significantly better in the surgical group.

CONCLUSION

STN DBS results in minor deficits in executive functions, particularly verbal fluency. These may be inconsequential, considering the marked improvement in motor functions and ADL.

Deep Brain Stimulation in Parkinson Disease: A Meta-analysis of the Long-term Neuropsychological Outcomes

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) or globus pallidum internus (GPi) improves motor functions in patients with Parkinson's disease (PD) but may cause a decline in specific cognitive domains. The aim of this systematic review and meta-analysis was to assess the long-term (1-3 years) effects of STN or GPi DBS on four cognitive functions: (i) memory (delayed recall, working memory, immediate recall), (ii) executive functions including inhibition control (Color-Word Stroop test) and flexibility (phonemic verbal fluency), (iii) language (semantic verbal fluency), and (iv) mood (anxiety and depression). Medline and Web of Science were searched, and studies published before July 2021 investigating long-term changes in PD patients following DBS were included. Random-effects model meta-analyses were performed using the R software to estimate the standardized mean difference (SMD) computed as Hedges' g with 95% CI. 2522 publications were identified, 48 of which satisfied the inclusion criteria. Fourteen meta-analyses were performed including 2039 adults with a clinical diagnosis of PD undergoing DBS surgery and 271 PD controls. Our findings add new information to the existing literature by demonstrating that, at a long follow-up interval (1-3 years), both positive effects, such as a mild improvement in anxiety and depression (STN, Hedges' g = 0,34, p = 0,02), and negative effects, such as a decrease of long-term memory (Hedges' g = -0,40, p = 0,02), verbal fluency such as phonemic fluency (Hedges' g = -0,56, p < 0,0001), and specific subdomains of executive functions such as Color-Word Stroop test (Hedges' g = -0,45, p = 0,003) were observed. The level of evidence as qualified with GRADE varied from low for the pre- verses post-analysis to medium when compared to a control group.

Reliable cognitive change following unilateral deep brain stimulation in essential tremor

Objective: This retrospective analysis assessed regression-based reliable change (RC) of cognition in a sample of essential tremor (ET) patients who underwent unilateral deep brain stimulation of the ventral intermediate nucleus of the thalamus (VIM-DBS).Method: Thirty patients (mean age at pre-evaluation = 70.4 ± 6.3 years) underwent neuropsychological evaluation pre- and post-unilateral VIM-DBS placement (mean time between pre and post-evaluation = 13.1 ± 4.0 months). Paired samples t-tests and RC analyses were employed.Results: No significant within-group differences were observed when cognitive scores were compared between evaluations. The vast majority of patients demonstrated stability across pre-and post-surgical evaluations (i.e. 29 out of 30); however, those with high-risk co-morbid medical conditions may be vulnerable to post-surgical cognitive decline as indicated by RC measures.Conclusions: The use of regression-based RC indices to assess individual cognitive changes between pre and post-surgical evaluations control for systematic and measurement errors that can occur over repeated evaluations, and may be able to identify cognitive changes that evade detection in traditional within-group comparisons.

Delayed Recovery After Deep Brain Stimulation Surgery for Parkinson's Disease Under General Anesthesia-Cases Report

Objective

Parkinson's disease (PD) is a neurodegenerative syndrome, and deep-brain stimulation (DBS) is an effective therapy for carefully screened patients with PD. However, delayed recovery after anesthesia, which occurs after taking prolonged general anesthesia for such patients, has been reported less frequently in literature. This report explores the possible causes of postoperative awakening delay in patients undergoing DBS surgery due to general anesthesia and provides a reference for anesthesia management of similar operations in the future.

Case Presentation

Three patients with PD elective underwent DBS surgery. The first patients demonstrated walking disability, gait deficits, unstable posture, limb stiffness, and imbalance. The second demonstrated left limb static tremor, stiffness, and bradykinesia. The third demonstrated bradykinesia, rigidity, walking deficits, and decreased facial expression. These included two males and one female with a mean patient age of 60.7 ± 6.7year, weight of 63.7 ± 11 kg, the height of 163.3 ± 7.6 cm, and preoperative American Society of Anesthesiology rating of 2.3 ± 0.6. The preoperative Glasgow Coma Scale mean score was 15. All patients completed the operation under general anesthesia (the mean anesthesia time was 5.3 ± 1.1 h). The mean operation time was 252 ± 60 min. The mean bleeding volume was 50 ml, and the urine volume was 867 ± 569 ml. However, all the patients showed unconsciousness after 95 ± 22 min after stopping the anesthetic, and the respiratory function was in good condition, but they could not cooperate with anesthesiologists and had no response to the anesthesiologist's instructions. The mean hospital stay was 17 ± 7 days. All patients were discharged uneventfully. The average number of days patients followed up postoperatively was 171 ± 28.5 days. Motor and speech were improved significantly postoperatively in three patients compared with preoperatively. Taking anti-Parkinson medication was markedly reduced. There were no complications during postoperative follow-up.

Conclusions

To prevent delayed recovery occurring after DBS surgery in Parkinson's disease, it is recommended to take scalp nerve block + general anesthesia to complete the procedure while avoiding general anesthesia.

Subcortical Iron Accumulation Pattern May Predict Neuropsychological Outcomes After Subthalamic Nucleus Deep Brain Stimulation: A Pilot Study

BACKGROUND:

Neuropsychological outcomes after deep brain stimulation (DBS) are variable and may arise from the heterogeneous neuropathological processes in Parkinson’s disease (PD).

OBJECTIVE:

To explore if brain iron accumulation patterns and its region-specific alterations relate to neuropsychological outcomes post-DBS.

METHODS:

Thirty-two PD subjects were identified from our database with susceptibility MRI prior to bilateral subthalamic nucleus (STN) DBS between 2011–2016. Demographic (age, sex, education), clinical information (disease duration, neuropsychological scores), and R2* (susceptibility MRI measure reflecting iron) in 11 subcortical regions of interest were obtained. Neuropsychological outcomes were defined as changes in psychomotor speed, executive function, attention, memory, and depression by subtracting pre- and post-DBS scores. A penalized logistic analysis was used to identify the best pre-DBS clinical and R2* predictors for each neuropsychological domain. Pearson’s partial correlations explored R2* associations with neuropsychological outcomes.

RESULTS:

Combined clinical and MRI metrics were associated better with neuropsychological outcomes (R²≥0.373, p-value≤0.008) than either alone. Adding R2* metrics increased prediction of executive function (R²=0.455, p=0.008) and attention (R²=0.182, p=0.018) outcomes over clinical metrics alone. Specifically, R2* in the substantia nigra, caudate, STN, and hippocampus improved prediction of executive function, and in the putamen for attention. Interestingly, higher caudate R2* correlated with better executive function (p=0.043), whereas higher putamen R2* associated with worsening attention (p=0.018).

CONCLUSIONS:

Brain iron accumulation patterns, captured by susceptibility MRI, may add value to clinical evaluation in predicting neuropsychological outcomes post-DBS in PD. Further studies are warranted to validate these findings and understand the region-specific relationships between iron and DBS outcomes.

Neuropsychological outcomes after thalamic deep brain stimulation for essential tremor

INTRODUCTION

Non-motor DBS outcomes have received little attention in ET relative to PD. This study examines neuropsychological outcomes in ET following thalamic VIM DBS.

METHODS

Fifty patients completed neuropsychological evaluations preoperatively and approximately seven months postoperatively. Cognition and mood changes were analyzed at the group level and individual level. Additional associations with treatment, disease, and demographic characteristics were assessed.

RESULTS

Significant cognitive decline was not observed at the group level. At the individual level, 46% of patients demonstrated at least subtle overall cognitive decline (≥1SD on at least one test within at least two domains). Mild decline (≥1SD) was seen in 10%-29.17% of patients on individual tests across all cognitive domains, with highest rates in verbal memory. Substantial cognitive decline (≥2SD) occurred in less than 9% of the sample across all tests. Factors related to cognitive decline included higher DBS parameter settings, older age of ET onset, intracranial complications, and inability to reduce ET medications postoperatively. Depression and anxiety did not change when accounting for questionnaire items that could be falsely elevated by tremor.

CONCLUSION

Substantial cognitive decline after VIM DBS is rare in patients with ET. However, subtle decrements can occur across cognitive domains and particularly in verbal memory. DBS parameter settings may relate to cognitive decline. Further research is needed to better understand possible associations with electrode lateralization and other variables that could also relate to disease progression and test-retest effects. Symptoms of depression and anxiety remain stable.

Effect of deep brain stimulation on brain network and white matter integrity in Parkinson's disease

Aims

The effects of subthalamic nucleus (STN)‐deep brain stimulation (DBS) on brain topological metrics, functional connectivity (FC), and white matter integrity were studied in levodopa‐treated Parkinson’s disease (PD) patients before and after DBS.

Methods

Clinical assessment, resting‐state functional MRI (rs‐fMRI), and diffusion tensor imaging (DTI) were performed pre‐ and post‐DBS in 15 PD patients, using a within‐subject design. The rs‐fMRI identified brain network topological metric and FC changes using graph‐theory‐ and seed‐based methods. White matter integrity was determined by DTI and tract‐based spatial statistics.

Results

Unified Parkinson's Disease Rating Scale III (UPDRS‐ III) scores were significantly improved by 35.3% (p < 0.01) after DBS in PD patients, compared with pre‐DBS patients without medication. Post‐DBS PD patients showed a significant decrease in the graph‐theory‐based degree and cost in the middle temporal gyrus and temporo‐occipital part‐Right. Changes in FC were seen in four brain regions, and a decrease in white matter integrity was seen in the left anterior corona radiata. The topological metrics changes were correlated with Beck Depression Inventory II (BDI‐II) and the FC changes with UPDRS‐III scores.

Conclusion

STN‐DBS modulated graph‐theoretical metrics, FC, and white matter integrity. Brain connectivity changes observed with multi‐modal imaging were also associated with postoperative clinical improvement. These findings suggest that the effects of STN‐DBS are caused by brain network alterations.

Cognitive Outcome After Deep Brain Stimulation for Refractory Obsessive-Compulsive Disorder: A Systematic Review

INTRODUCTION

Deep brain stimulation (DBS) is an effective treatment for refractory obsessive-compulsive disorder (OCD). Neuropsychological assessment contributes to DBS treatment in several ways: it monitors the cognitive safety of the treatment, identifies beneficial or detrimental cognitive side effects and it could aid to explain variability in treatment outcome, and possibly the treatment's working mechanism(s).

BACKGROUND

This systematic review assessed the cognitive safety of DBS for OCD and explored whether changes in cognitive function may help explain its working mechanism(s).

MATERIALS AND METHODS

EMBASE, PubMed/Medline, Psycinfo, and the Cochrane Library were systematically searched for studies reporting cognitive outcomes following DBS for OCD. Searches were completed in November 2020. Included studies were appraised for study design and quality according to National Heart, Lung and Blood Institute (NHLBI) quality assessment tools.

RESULTS

Five randomized controlled trials and ten observational studies comprising a total of 178 patients were analyzed collectively. Variable outcomes of DBS were observed in the domains of attention, memory, executive functioning, and in particular cognitive flexibility.

CONCLUSION

Although individual studies generally do not report cognitive deterioration after DBS for OCD, the variability of study designs and the multitude of cognitive measures used, precluded a meta-analysis to confirm its safety, and recognition of a cognitive pattern through which the efficacy of DBS for OCD might be explained. In future, prospective studies should preferably include a standardized neuropsychological assessment battery specifically addressing executive functioning and have a longer-term follow-up in order to demonstrate the cognitive safety of the procedure. Such prospective and more uniform data collection may also contribute to our understanding of the working mechanisms of DBS in OCD.

Preoperative Electroencephalography-Based Machine Learning Predicts Cognitive Deterioration after Subthalamic Deep Brain Stimulation

Background

Subthalamic deep brain stimulation (STN DBS) may relieve refractory motor complications in Parkinson's disease (PD) patients. Despite careful screening, it remains difficult to determine severity of alpha‐synucleinopathy involvement which influences the risk of postoperative complications including cognitive deterioration. Quantitative electroencephalography (qEEG) reflects cognitive dysfunction in PD and may provide biomarkers of postoperative cognitive decline.

Objective

To develop an automated machine learning model based on preoperative EEG data to predict cognitive deterioration 1 year after STN DBS.

Methods

Sixty DBS candidates were included; 42 patients had available preoperative EEGs to compute a fully automated machine learning model. Movement Disorder Society criteria classified patients as cognitively stable or deteriorated at 1‐year follow‐up. A total of 16,674 EEG‐features were extracted per patient; a Boruta algorithm selected EEG‐features to reflect representative neurophysiological signatures for each class. A random forest classifier with 10‐fold cross‐validation with Bayesian optimization provided class‐differentiation.

Results

Tweny‐five patients were classified as cognitively stable and 17 patients demonstrated cognitive decline. The model differentiated classes with a mean (SD) accuracy of 0.88 (0.05), with a positive predictive value of 91.4% (95% CI 82.9, 95.9) and negative predictive value of 85.0% (95% CI 81.9, 91.4). Predicted probabilities between classes were highly differential (hazard ratio 11.14 [95% CI 7.25, 17.12]); the risk of cognitive decline in patients with high probabilities of being prognosticated as cognitively stable (>0.5) was very limited.

Conclusions

Preoperative EEGs can predict cognitive deterioration after STN DBS with high accuracy. Cortical neurophysiological alterations may indicate future cognitive decline and can be used as biomarkers during the DBS screening. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society

Dietary nutrition for neurological disease therapy: Current status and future directions

Adequate food intake and relative abundance of dietary nutrients have undisputed effects on the brain function. There is now substantial evidence that dietary nutrition aids in the prevention and remediation of neurologic symptoms in diverse pathological conditions. The newly described influences of dietary factors on the alterations of mitochondrial dysfunction, epigenetic modification and neuroinflammation are important mechanisms that are responsible for the action of nutrients on the brain health. In this review, we discuss the state of evidence supporting that distinct dietary interventions including dietary supplement and dietary restriction have the ability to tackle neurological disorders using Alzheimer's disease, Parkinson's disease, stroke, epilepsy, traumatic brain injury, amyotrophic lateral sclerosis, Huntington's disease and multiple sclerosis as examples. Additionally, it is also highlighting that diverse potential mechanisms such as metabolic control, epigenetic modification, neuroinflammation and gut-brain axis are of utmost importance for nutrient supply to the risk of neurologic condition and therapeutic response. Finally, we also highlight the novel concept that dietary nutrient intervention reshapes metabolism-epigenetics-immunity cycle to remediate brain dysfunction. Targeting metabolism-epigenetics-immunity network will delineate a new blueprint for combating neurological weaknesses.

Global Variability in Deep Brain Stimulation Practices for Parkinson's Disease

Introduction

Deep brain stimulation (DBS) has become a standard treatment option for select patients with Parkinson’s disease (PD). The selection process and surgical procedures employed have, to date, not been standardized.

Methods

A comprehensive 58-question web-based survey was developed with a focus on DBS referral practices and peri-operative management. The survey was distributed to the Parkinson’s Foundation Centers of Excellence, members of the International Parkinson’s Disease and Movement Disorders Society, and the Parkinson Study Group (Functional Neurosurgery Working Group) between December 2015 and May 2016.

Results

There were 207 individual respondents (20% response rate) drawn from 59 countries and 6 continents, of whom 64% received formal training in DBS. Thirteen percent of centers reported that DBS could proceed despite a confidence level of < 50% for PD diagnosis. A case-based approach to DBS candidacy was applied in 51.3% of centers without a cut-off for levodopa-responsiveness. Surprisingly, 33% of centers regularly used imaging for diagnostic confirmation of idiopathic PD. Thirty-one percent of centers reported that neuropsychological evaluation did not affect DBS target selection. Approximately half of the respondents reported determination of DBS candidacy based on a multidisciplinary committee evaluation and 1/3^rd reported that a committee was used for target selection. Eight percent of respondents felt that psychosocial factors should not impact DBS candidacy nor site selection. Involvement of allied health professionals in the preoperative process was sparse. There was high variability in preoperative education about DBS outcome expectations. Approximately half of the respondents did not utilize a “default brain target,” though STN was used more commonly than GPi. Specific DBS procedure techniques applied, as well as follow-up timelines, were highly variable.

Conclusion

Results revealed high variability on the best approaches for DBS candidate selection, brain target selection, procedure type, and postoperative practices. Cognitive and mood assessments were underutilized. There was low reliance on multidisciplinary teams or psychosocial factors to impact the decision-making process. There were small but significant differences in practice across global regions, especially regarding multidisciplinary teams. The wide variability of responses across multiple facets of DBS care highlights the need for prospective studies to inform evidence-based guidelines.

Functional and Cognitive Improvement After an Intensive Inpatient Multidisciplinary Rehabilitation Program in Mild to Severe Parkinson's Disease: A Retrospective and Observational Study

Parkinson's disease (PD) is a neurodegenerative disorder characterized by motor (resting tremor, rigidity, bradykinesia, postural instability, and gait disturbances) and nonmotor symptoms (cognitive, neuropsychiatric, and autonomic problems). In recent years, several studies demonstrated that neurorehabilitation therapy is an effective treatment in addition to pharmacological personalized interventions in persons with PD (PwPD). The main aim of this study was to explore the short-term changes in functional, cognitive, and geriatric domains after a multidimensional rehabilitation program in PwPD (as primary condition) in mild-moderate (M-Ms) to severe (Ss) stages. Our second aim was to compare the effects of multidimensional rehabilitation in M-Ms versus Ss of PD. Twenty-four PwPD in M-Ms to Ss [age (mean ± SD) = 76.25 ± 9.42 years; male/female = 10/14; Hoehn and Yahr (median; IQR) = 4.00; 1.75] were included in a retrospective, observational study. Motor, cognitive, functional, and neuropsychiatric aspects were collected in admission (T0) and in discharge (T1). PwPD were involved in a person-tailored (to individual's needs), inpatient, intensive (5-7 days per week), multidisciplinary (combining cognitive, physical, occupational, and speech therapies), comprehensive, and rehabilitative program. According to Movement Disorders Society Unified Parkinson's Disease Rating Scale III cutoff, PwPD were classified in M-Ms or Ss (M-Ms ≤59; Ss >59); 87.50% of our sample reported significant reduction of functional disability at Barthel Index (p < 0.001). A significant improvement in Token test (p = 0.021), semantic fluency (p = 0.036), Rey's Figure-Copy (p < 0.001), and Raven's Colored Progressive Matrices (p = 0.004) was observed. The pain intensity perception (p < 0.001) and the risk of developing pressure ulcers (p < 0.001) as assessed, respectively, by the Numeric Rating Scale and by the Norton Scale were improved. With regard to the second aim, in M-Ms group, we found a positive correlation between the number of neuromotor sessions and the change in functional disability and language comprehension; in the Ss group, on the other hand, despite a higher number of hospitalization days, the total number of completed sessions was positively associated with the change in visuoconstructional abilities. Our findings suggest that an intensive, inpatient, and multidisciplinary rehabilitation program may improve functional abilities, some strategic cognitive functions, and geriatric aspects in PwPD with mild-moderate motor impairment.

A retrospective comparison of cognitive performance in individuals with advanced Parkinson's Disease in Hong Kong and Canada

A deeper understanding of the cross-cultural applicability of cognitive tests across countries and cultures is needed to better equip neuropsychologists for the assessment of patients from diverse backgrounds. Our study compared cognitive test scores in patients with advanced Parkinson's disease (PD) at the Prince of Wales Hospital (n = 63; Hong Kong) and the Foothills Medical Center (n = 20; Calgary, Canada). The groups did not differ in age or sex (p > .05), but Western patients had significantly more years of education (M = 14.2, SD = 2.7) than Asian patients (M = 10.33, SD = 4.4). Cognitive tests administered to both groups included: digit span, verbal fluency (animals), the Boston Naming Test, and verbal memory (California Verbal Learning Test or Chinese Auditory Verbal Learning Test). Testing was completed before and 12 months after deep brain stimulation surgery. Results showed cognitive performance was similar across time, but significant group differences were found on digit span forward (longer among patients from Hong Kong; F(1, 75) = 44.155, p < .001) and the Boston Naming Test (higher percent spontaneous correct among patients from Canada; F(1, 62) = 7.218, p = .009, η² = 0.104), after controlling for age, sex, and years of education. In conclusion, our findings provide preliminary support for the similarity of Chinese versions of tests originally developed for Western populations. Also, we caution that some aspects of testing may be susceptible to cultural bias and therefore warrant attention in clinical practice and refinement in future test development for Asian patients.

Deep brain stimulation effects on verbal fluency dissociated by target and active contact location

OBJECTIVE

Deep brain stimulation (DBS) improves motor symptoms in Parkinson's disease (PD), but it can also disrupt verbal fluency with significant costs to quality of life. The current study investigated how variability of bilateral active electrode coordinates along the superior/inferior, anterior/posterior, and lateral/medial axes in the subthalamic nucleus (STN) or the globus pallidus interna (GPi) contribute to changes in verbal fluency. We predicted that electrode location in the left hemisphere would be linked to changes in fluency, especially in the STN.

METHODS

Forty PD participants treated with bilateral DBS targeting STN (n = 23) or GPi (n = 17) completed verbal fluency testing in their optimally treated state before and after DBS therapy. Normalized atlas coordinates from left and right active electrode positions along superior/inferior, anterior/posterior, and lateral/medial axes were used to predict changes in fluency postoperatively, separately for patients with STN and GPi targets.

RESULTS

Consistent with prior studies, fluency significantly declined pre- to postsurgery (in both DBS targets). In STN-DBS patients, electrode position along the inferior to superior axis in the left STN was a significant predictor of fluency changes; relatively more superior left active electrode was associated with the largest fluency declines in STN. Electrode coordinates in right STN or GPi (left or right) did not predict fluency changes.

INTERPRETATION

We discuss these findings in light of putative mechanisms and potential clinical impact.

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.

Predicting Neurocognitive Change after Bilateral Deep Brain Stimulation of Subthalamic Nucleus for Parkinson's Disease

OBJECTIVE

Deep brain stimulation (DBS) of the bilateral subthalamic nucleus (STN) is a standard surgical treatment option in patients with advanced Parkinson's disease. Adverse effects on cognitive function have been reported, impacting the quality of life of patients and caregivers. We aimed to investigate a quantitative predictive preexisting cognitive factor for predicting postoperative cognitive changes.

METHODS

Thirty-five patients underwent STN-DBS. A battery of neuropsychological tests were used to examine executive function, processing speed, and visuospatial function both preoperatively and 1 year postoperatively. A multiple logistic regression analysis was performed to investigate the relationships between preoperative factors and cognitive outcomes. The predictive value of the preoperative factors for global cognitive decline during long-term follow-up were evaluated.

RESULTS

The patients exhibited significant changes in processing speed and visuospatial function after surgery. Using reliable change index values, lower preoperative scores on the Similarities and Object Assembly subtests of the Wechsler Adult Intelligence Scale III were associated with decreases in visuospatial function at 1 year after DBS. The odds ratios were 10.2 for Similarities and 9.53 for Object Assembly. The proportion of Mini Mental State Examination-maintained patients with low scores on the Similarities subtest was significantly lower than that of patients with high scores at 3 and 5 years. No factors were found to be related to decreases in processing speed.

CONCLUSIONS

Preoperative evaluation of the Similarities and Object Assembly subtests may be useful to identify patients who are at a greater risk of experiencing decreases in visuospatial functioning after STN-DBS. Furthermore, a low score on the Similarities subtest may predict future global cognitive deterioration.

"Benign" tremor? A serial case report of 2.5 year progression from mild cognitive impairment to amnestic dementia following deep brain stimulator placement for essential tremor

Essential tremor (ET) is a prevalent neurological disorder with associated neuropsychological sequalae. Although cognitive deficits associated with ET are traditionally conceptualized as attention, processing speed, and executive impairments attributed to underlying frontal-subcortical dysfunction, emerging literature highlights the elevated frequency of progressive amnestic memory impairments in patients with ET. This case study centers around a 75-year-old woman with a 15-year history of ET who underwent deep brain stimulation (DBS) as well as three neuropsychological evaluations, one pre-surgically and two post-surgically at one and two-years post successful DBS surgery. Neuropsychological evaluation results revealed circumscribed mild and variable memory deficits pre-surgically and one-year post-surgically, However, two-years post-DBS, reliable change indices revealed significant declines in verbal/visual memory, consistent with an amnestic presentation, in addition to executive functions, aspects of higher-level language abilities, and overall IQ. This case study adds to a growing literature identifying a subset of ET patients with a neurodegenerative cognitive trajectory characterized by progressive, amnestic memory impairment. The case also highlights the importance of serial monitoring of cognition beyond the pre-surgical DBS workup to monitor for clinically significant decline(s).

The association between surgical characteristics and cognitive decline following deep brain stimulation of the subthalamic nucleus in Parkinson's disease

OBJECTIVE

Despite optimal improvement in motor functioning, both short- and long-term studies have reported small but consistent changes in cognitive functioning following STN-DBS in Parkinson's disease (PD). The aim of the present study was to explore whether surgical characteristics were associated with cognitive decline one year following STN-DBS.

METHODS

We retrospectively analyzed 49 PD patients who underwent bilateral STN-DBS. Cognitive change scores were related to the number of microelectrode recording (MER) trajectories, the STN length as measured by MER, and cortical entry points. Regression analyses were corrected for age at surgery, disease duration, education and preoperative levodopa responsiveness. Patients were then divided into a cognitive and non-cognitive decline group for each neuropsychological test and compared regarding demographic and surgical characteristics.

RESULTS

One year postoperatively, significant declines were found in verbal fluency, Stroop Color-Word test and Trail Making Test B (TMT-B). Only changes in TMT-B were associated with the coronal entry point in the right hemisphere. The number of MER trajectories and STN length were not associated with cognitive change scores. When comparing the cognitive decline and non-cognitive decline groups, no significant differences were found in surgical characteristics.

CONCLUSIONS

The electrode passage through the right prefrontal lobe may contribute to subtle changes in executive function. However, only few patients showed clinically relevant cognitive decline. The use of multiple MER trajectories and a longer STN length were not associated with cognitive decline one year following surgery. From a cognitive point of view, DBS may be considered a relatively safe procedure.

On the Use of TMS to Investigate the Pathophysiology of Neurodegenerative Diseases

Neurodegenerative diseases are a collection of disorders that result in the progressive degeneration and death of neurons. They are clinically heterogenous and can present as deficits in movement, cognition, executive function, memory, visuospatial awareness and language. Transcranial magnetic stimulation (TMS) is a non-invasive brain stimulation tool that allows for the assessment of cortical function in vivo. We review how TMS has been used for the investigation of three neurodegenerative diseases that differ in their neuroanatomical axes: (1) Motor cortex-corticospinal tract (motor neuron diseases), (2) Non-motor cortical areas (dementias), and (3) Subcortical structures (parkinsonisms). We also make four recommendations that we hope will benefit the use of TMS in neurodegenerative diseases. Firstly, TMS has traditionally been limited by the lack of an objective output and so has been confined to stimulation of the motor cortex; this limitation can be overcome by the use of concurrent neuroimaging methods such as EEG. Given that neurodegenerative diseases progress over time, TMS measures should aim to track longitudinal changes, especially when the aim of the study is to look at disease progression and symptomatology. The lack of gold-standard diagnostic confirmation undermines the validity of findings in clinical populations. Consequently, diagnostic certainty should be maximized through a variety of methods including multiple, independent clinical assessments, imaging and fluids biomarkers, and post-mortem pathological confirmation where possible. There is great interest in understanding the mechanisms by which symptoms arise in neurodegenerative disorders. However, TMS assessments in patients are usually carried out during resting conditions, when the brain network engaged during these symptoms is not expressed. Rather, a context-appropriate form of TMS would be more suitable in probing the physiology driving clinical symptoms. In all, we hope that the recommendations made here will help to further understand the pathophysiology of neurodegenerative diseases.

Deep brain stimulation and recordings: Insights into the contributions of subthalamic nucleus in cognition

Recent progress in targeted interrogation of basal ganglia structures and networks with deep brain stimulation in humans has provided insights into the complex functions the subthalamic nucleus (STN). Beyond the traditional role of the STN in modulating motor function, recognition of its role in cognition was initially fueled by side effects seen with STN DBS and later revealed with behavioral and electrophysiological studies. Anatomical, clinical, and electrophysiological data converge on the view that the STN is a pivotal node linking cognitive and motor processes. The goal of this review is to synthesize the literature to date that used DBS to examine the contributions of the STN to motor and non-motor cognitive functions and control. Multiple modalities of research have provided us with an enhanced understanding of the STN and reveal that it is critically involved in motor and non-motor inhibition, decision-making, motivation and emotion. Understanding the role of the STN in cognition can enhance the therapeutic efficacy and selectivity not only for existing applications of DBS, but also in the development of therapeutic strategies to stimulate aberrant circuits to treat non-motor symptoms of Parkinson's disease and other disorders.

The effect of STN DBS on modulating brain oscillations: consequences for motor and cognitive behavior

In this review, we highlight Professor John Rothwell's contribution towards understanding basal ganglia function and dysfunction, as well as the effects of subthalamic nucleus deep brain stimulation (STN DBS). The first section summarizes the rate and oscillatory models of basal ganglia dysfunction with a focus on the oscillation model. The second section summarizes the motor, gait, and cognitive mechanisms of action of STN DBS. In the final section, we summarize the effects of STN DBS on motor and cognitive tasks. The studies reviewed in this section support the conclusion that high-frequency STN DBS improves the motor symptoms of Parkinson's disease. With respect to cognition, STN DBS can be detrimental to performance especially when the task is cognitively demanding. Consolidating findings from many studies, we find that while motor network oscillatory activity is primarily correlated to the beta-band, cognitive network oscillatory activity is not confined to one band but is subserved by activity in multiple frequency bands. Because of these findings, we propose a modified motor and associative/cognitive oscillatory model that can explain the consistent positive motor benefits and the negative and null cognitive effects of STN DBS. This is clinically relevant because STN DBS should enhance oscillatory activity that is related to both motor and cognitive networks to improve both motor and cognitive performance.

Advantages and Recent Developments of Autologous Cell Therapy for Parkinson's Disease Patients

Parkinson’s Disease (PD) is a progressive degenerative disease characterized by tremor, bradykinesia, rigidity and postural instability. There are approximately 7–10 million PD patients worldwide. Currently, there are no biomarkers available or pharmaceuticals that can halt the dopaminergic neuron degeneration. At the time of diagnosis about 60% of the midbrain dopamine (mDA) neurons have already degenerated, resulting in a depletion of roughly 70% of striatal dopamine (DA) levels and synapses. Symptomatic treatment (e.g., with L-dopa) can initially restore DA levels and motor function, but with time often lead to side-effects like dyskinesia. Deep-brain-stimulation can alleviate these side-effects and some of the motor symptoms but requires repeat procedures and adds limitations for the patients. Restoration of dopaminergic synapses using neuronal cell replacement therapy has shown benefit in clinical studies using cells from fetal ventral midbrain. This approach, if done correctly, increases DA levels and restores synapses, allowing biofeedback regulation between the grafted cells and the host brain. Drawbacks are that it is not scalable for a large patient population and the patients require immunosuppression. Stem cells differentiated in vitro to mDA neurons or progenitors have shown promise in animal studies and is a scalable approach that allows for cryopreservation of transplantable cells and rigorous quality control prior to transplantation. However, all allogeneic grafts require immunosuppression. HLA-donor-matching, reduces, but does not completely eliminate, the need for immunosuppression, and is currently investigated in a clinical trial for PD in Japan. Since immune compatibility is very important in all areas of transplantation, these approaches may ultimately be of less benefit to the patients than an autologous approach. By using the patient’s own somatic cells, reprogrammed to induced pluripotent stem cells (iPSCs) and differentiated to mDA neurons immunosuppression is not required, and may also present with several biological and functional advantages in the patients, as described in this article. The proof-of-principle of autologous iPSC mDA restoration of function has been shown in parkinsonian non-human primates (NHPs), and this can now be investigated in clinical trials in addition to the allogeneic and HLA-matched approaches. In this review, we focus on the autologous approach of cell therapy for PD.

Electromyography Biomarkers for Quantifying the Intraoperative Efficacy of Deep Brain Stimulation in Parkinson's Patients With Resting Tremor

Introduction: Deep brain stimulation (DBS) is an effective therapy for resting tremor in Parkinson's disease (PD). However, quick and objective biomarkers for quantifying the efficacy of DBS intraoperatively are lacking. Therefore, we aimed to study how DBS modulates the intraoperative neuromuscular pattern of resting tremor in PD patients and to find predictive surface electromyography (sEMG) biomarkers for quantifying the intraoperative efficacy of DBS. Methods: Intraoperative sEMG of 39 PD patients with resting tremor was measured with the DBS on and off, respectively, during the intraoperative DBS testing stage. Twelve signal features (time and frequency domains) were extracted from the intraoperative sEMG data. These sEMG features were associated with the clinical outcome to evaluate the efficacy of intraoperative DBS. Also, an sEMG-based prediction model was established to predict the clinical improvement rate (IR) of resting tremor with DBS therapy. Results: A typical resting tremor with a peak frequency of 4.93 ± 0.98 Hz (mean ± SD) was measured. Compared to the baseline, DBS modulated significant neuromuscular pattern changes in most features except for the peak frequency, by decreasing the motor unit firing rate, amplitude, or power and by changing the regularity pattern. Three sEMG features were detected with significant associations with the clinical improvement rate (IR) of the tremor scale: peak frequency power (R = 0.37, p = 0.03), weighted root mean square (R = 0.42, p = 0.01), and modified mean amplitude power (R = 0.48, p = 0.003). These were adopted to train a Gaussian process regression model with a leave-one-out cross-validation procedure. The prediction values from the trained sEMG prediction model (1,000 permutations, p = 0.003) showed a good correlation (r = 0.47, p = 0.0043) with the true IR of the tremor scale. Conclusion: DBS acutely modulated the intraoperative resting tremor, mainly by suppressing the amplitude and motor unit firing rate and by changing the regularity pattern, but not by modifying the frequency pattern. Three features showed strong robustness and could be used as quick intraoperative biomarkers to quantify and predict the efficacy of DBS in PD patients with resting tremor.

Tourette's disorder in children and adolescents

Tourette's disorder (TD) is one of the five American Psychiatric Association's 2013 Diagnostic and Statistical Manual of Mental Disorders (DSM-5) classifications of tic disorders. Eponymously linked with the noted 19th century French physician, Gilles de la Tourette [1857-1904], this disorder is identified in 0.3% to 0.7% of the population. It is characterized as a familial neuropsychiatric condition with multiple motor tics and vocal tics (one or more) present for more than 1 year with varying severity. The underlying pathophysiology involves dysfunctional activity of the basal ganglia and circuitry of the frontal cortex as well as dorsolateral striatum deficits. Contributory factors include genetic features interacting with milieu influences. A number of comorbid disorders are seen including obsessive-compulsive disorder (OCD) and attention-deficit/hyperactivity disorder (ADHD). Concepts of management are considered including behavioral therapy and pharmacologic approaches with alpha-adrenoceptor agonists, atypical antipsychotics (AAs), haloperidol, pimozide and others. Other management includes botulinum injections and deep brain stimulation in adults.

Subcortical Intermittent Theta-Burst Stimulation (iTBS) Increases Theta-Power in Dorsolateral Prefrontal Cortex (DLPFC)

Introduction

Cognitive symptoms from Parkinson’s disease cause severe disability and significantly limit quality of life. Little is known about mechanisms of cognitive impairment in PD, although aberrant oscillatory activity in basal ganglia-thalamo-prefrontal cortical circuits likely plays an important role. While continuous high-frequency deep brain stimulation (DBS) improves motor symptoms, it is generally ineffective for cognitive symptoms. Although we lack robust treatment options for these symptoms, recent studies with transcranial magnetic stimulation (TMS), applying intermittent theta-burst stimulation (iTBS) to dorsolateral prefrontal cortex (DLPFC), suggest beneficial effects for certain aspects of cognition, such as memory or inhibitory control. While TMS is non-invasive, its results are transient and require repeated application. Subcortical DBS targets have strong reciprocal connections with prefrontal cortex, such that iTBS through the permanently implanted lead might represent a more durable solution. Here we demonstrate safety and feasibility for delivering iTBS from the DBS electrode and explore changes in DLPFC electrophysiology.

Methods

We enrolled seven participants with medically refractory Parkinson’s disease who underwent DBS surgery targeting either the subthalamic nucleus (STN) or globus pallidus interna (GPi). We temporarily placed an electrocorticography strip over DLPFC through the DBS burr hole. After placement of the DBS electrode into either GPi (n = 3) or STN (n = 4), awake subjects rested quietly during iTBS (three 50-Hz pulses delivered at 5 Hz for 2 s, followed by 8 s of rest). We contrasted power spectra in DLPFC local field potentials during iTBS versus at rest, as well as between iTBS and conventional high-frequency stimulation (HFS).

Results

Dominant frequencies in DLPFC at rest varied among subjects and along the subdural strip electrode, though they were generally localized in theta (3–8 Hz) and/or beta (10–30 Hz) ranges. Both iTBS and HFS were well-tolerated and imperceptible. iTBS increased theta-frequency activity more than HFS. Further, GPi stimulation resulted in significantly greater theta-power versus STN stimulation in our sample.

Conclusion

Acute subcortical iTBS from the DBS electrode was safe and well-tolerated. This novel stimulation pattern delivered from the GPi may increase theta-frequency power in ipsilateral DLPFC. Future studies will confirm these changes in DLPFC activity during iTBS and evaluate whether they are associated with improvements in cognitive or behavioral symptoms from PD.