Deep brain stimulation: Preoperative issues

Clinical and Brain Morphometry Predictors of Deep Brain Stimulation Outcome in Parkinson's Disease

Subthalamic deep brain stimulation (STN-DBS) is known to improve motor function in advanced Parkinson's disease (PD) and to enable a reduction of anti-parkinsonian medication. While the levodopa challenge test and disease duration are considered good predictors of STN-DBS outcome, other clinical and neuroanatomical predictors are less established. This study aimed to evaluate, in addition to clinical predictors, the effect of patients' individual brain topography on DBS outcome. The medical records of 35 PD patients were used to analyze DBS outcomes measured with the following scales: Part III of the Unified Parkinson's Disease Rating Scale (UPDRS-III) off medication at baseline, and at 6-months during medication off and stimulation on, use of anti-parkinsonian medication (LED), Abnormal Involuntary Movement Scale (AIMS) and Non-Motor Symptoms Questionnaire (NMS-Quest). Furthermore, preoperative brain MRI images were utilized to analyze the brain morphology in relation to STN-DBS outcome. With STN-DBS, a 44% reduction in the UPDRS-III score and a 43% decrease in the LED were observed (p<0.001). Dyskinesia and non-motor symptoms decreased significantly [median reductions of 78,6% (IQR 45,5%) and 18,4% (IQR 32,2%) respectively, p=0.001 - 0.047]. Along with the levodopa challenge test, patients' age correlated with the observed DBS outcome measured as UPDRS-III improvement (ρ= -0.466 - -0.521, p<0.005). Patients with greater LED decline had lower grey matter volumes in left superior medial frontal gyrus, in supplementary motor area and cingulum bilaterally. Additionally, patients with greater UPDRS-III score improvement had lower grey matter volume in similar grey matter areas. These findings remained significant when adjusted for sex, age, baseline LED and UPDRS scores respectively and for total intracranial volume (p=0.0041- 0.001). However, only the LED decrease finding remained significant when the analyses were further controlled for stimulation amplitude. It appears that along with the clinical predictors of STN-DBS outcome, individual patient topographic differences may influence DBS outcome. Clinical Trial Registration Number: NCT06095245, registration date October 23, 2023, retrospectively registered.

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.

Interpretable video-based tracking and quantification of parkinsonism clinical motor states

Quantification of motor symptom progression in Parkinson's disease (PD) patients is crucial for assessing disease progression and for optimizing therapeutic interventions, such as dopaminergic medications and deep brain stimulation. Cumulative and heuristic clinical experience has identified various clinical signs associated with PD severity, but these are neither objectively quantifiable nor robustly validated. Video-based objective symptom quantification enabled by machine learning (ML) introduces a potential solution. However, video-based diagnostic tools often have implementation challenges due to expensive and inaccessible technology, and typical "black-box" ML implementations are not tailored to be clinically interpretable. Here, we address these needs by releasing a comprehensive kinematic dataset and developing an interpretable video-based framework that predicts high versus low PD motor symptom severity according to MDS-UPDRS Part III metrics. This data driven approach validated and robustly quantified canonical movement features and identified new clinical insights, not previously appreciated as related to clinical severity, including pinkie finger movements and lower limb and axial features of gait. Our framework is enabled by retrospective, single-view, seconds-long videos recorded on consumer-grade devices such as smartphones, tablets, and digital cameras, thereby eliminating the requirement for specialized equipment. Following interpretable ML principles, our framework enforces robustness and interpretability by integrating (1) automatic, data-driven kinematic metric evaluation guided by pre-defined digital features of movement, (2) combination of bi-domain (body and hand) kinematic features, and (3) sparsity-inducing and stability-driven ML analysis with simple-to-interpret models. These elements ensure that the proposed framework quantifies clinically meaningful motor features useful for both ML predictions and clinical analysis.

Predictors of short-term anxiety outcome in subthalamic stimulation for Parkinson's disease

The effects of subthalamic nucleus deep brain stimulation (STN-DBS) on anxiety in Parkinson's disease (PD) are understudied. We identified clinical predictors of STN-DBS effects on anxiety in this study. In this prospective, open-label, multicentre study, we assessed patients with anxiety undergoing STN-DBS for PD preoperatively and at 6-month follow-up postoperatively. We assessed the Hospital Anxiety and Depression Scale (HADS-anxiety and depression subscales), Unified PD Rating Scale-motor examination, Scales for Outcomes in PD-motor (SCOPA-M)-activities of daily living (ADL) and -motor complications, Non-Motor Symptom Scale (NMSS), PDQuestionnaire-8 (PDQ-8), and levodopa-equivalent daily dose. We tested changes at follow-up with Wilcoxon signed-rank test and corrected for multiple comparisons (Bonferroni method). We identified patients with a clinically relevant anxiety improvement of anxiety based on a designated threshold of ½ standard deviation of baseline HADS-anxiety. Moreover, we investigated predictors of HADS-anxiety changes with correlations and linear regressions. We included 50 patients with clinically relevant baseline anxiety (i.e., HADS-anxiety ≥ 8) aged 63.1 years ± 8.3 with 10.4 years ± 4.5 PD duration. HADS-anxiety improved significantly at 6-month follow-up as 80% of our cohort experienced clinically relevant anxiety improvement. In predictor analyses, worse baseline SCOPA-ADL and NMSS-urinary domain were associated with greater HADS-anxiety improvements. HADS-anxiety and PDQ-8 changes correlated moderately. Worse preoperative ADL and urinary symptoms predicted favourable postoperative anxiety outcome, which in turn was directly proportionate to greater QoL improvement. This study highlights the importance of detailed anxiety assessments alongside other non-motor and motor symptoms when advising and monitoring patients undergoing STN-DBS for PD.

Fundamentals of deep brain stimulation for Parkinson's disease in clinical practice: part 1

Deep brain stimulation (DBS) is recognized as an established therapy for Parkinson's disease (PD) and other movement disorders in the light of the developments seen over the past three decades. Long-term efficacy is established for PD with documented improvement in the cardinal motor symptoms of PD and levodopa-induced complications, such as motor fluctuations and dyskinesias. Timing of patient selection is crucial to obtain optimal benefits from DBS therapy, before PD complications become irreversible. The objective of this first part review is to examine the fundamental concepts of DBS for PD in clinical practice, discussing the historical aspects, patient selection, potential effects of DBS on motor and non-motor symptoms, and the practical management of patients after surgery.

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.

Preoperative motor deficits and depressive symptoms predict quality of life in patients with Parkinson's disease at different time points after surgery for subthalamic stimulation: a retrospective study

BACKGROUND

While subthalamic nucleus deep brain stimulation (STN-DBS) improves the quality of life (QoL) of patients with Parkinson's disease (PD), the clinical parameters that predict this improvement remain debated. This retrospective study explored whether preoperative motor, cognitive, and affective parameters predict QoL or its components at 6 and 12 months after STN-DBS surgery.

METHODS

QoL was assessed with the Parkinson's Disease Questionnaire-39 (PDQ-39) before (baseline), at 6 months (N = 90) and 12 months (N = 63) after STN-DBS surgery. Changes in the PDQ-39 and its subdomains were analysed with Wilcoxon signed-rank tests. In total, seven motor, cognitive, and affective parameters recorded at baseline were used in multiple linear regressions to predict QoL and its subdomains.

RESULTS

QoL had improved significantly at six months post STN-DBS surgery. After 12 months, this effect remained significant but was less pronounced. At both time points, significant improvements in mobility, activities of daily living, stigma, and bodily discomfort were present. Correlation and linear regression analyses showed that preoperative QoL status and changes in QoL at 6 and 12 months after surgery were driven by preoperative dopaminergic medication, as well as motor (UPDRS-III medOFF and PIGD-subscore medOFF) and affective (HADS anxiety and depression) symptoms. In contrast, preoperative cognitive performance did not predict QoL at any time point.

CONCLUSION

Data show that preoperative motor and affective symptoms drive both QoL baseline status and changes in QoL after STN-DBS surgery. Thus, these clinical parameters need to be assessed appropriately to provide comprehensive presurgical advice to patients suffering from PD.

Levodopa improved different motor symptoms in patients with Parkinson's disease by reducing the functional connectivity of specific thalamic subregions

BACKGROUND

The thalamus is an important relay station for the motor circuit of human. Levodopa can reverse the clinical manifestations by modulating the function of motor circuits, but its detailed mechanisms are still not fully understood. We aimed to explore (1) the mechanism by which levodopa modulates the functional connectivity (FC) in the subregions of the thalamus; (2) the relationship between the changed FC and the improvement of motor symptoms in Parkinson's disease (PD) patients.

METHODS

Resting-state functional MRI was used to scan 36 PD patients and 37 healthy controls. The FC between the subregions in the thalamus and the whole brain was measured and compared under different medication states of PD patients. The correlation between the improvement of motor symptoms and changes in FC in the thalamus subregions was examined.

RESULTS

The PD on state exhibited decreased FC between the right pre-motor thalamus and the right postcentral gyrus, as well as the right lateral pre-frontal thalamus and the right postcentral gyrus. These decreases were positively correlated with the improvement of resting tremor. The PD on state also exhibited decreased FC between the left lateral pre-frontal thalamus and right paracentral lobule, which was positively correlated with the improvement of bradykinesia.

CONCLUSIONS

This study demonstrates that levodopa treats PD by decreasing the FC between the thalamus subregions and pre/post-central cortex. Our results provide a basis for further exploration of the functional activity of thalamic subregions and offer new insights into the precision treatment in PD patients.

Neuroimaging and serum biomarkers of neurodegeneration and neuroplasticity in Parkinson's disease patients treated by intermittent theta-burst stimulation over the bilateral primary motor area: a randomized, double-blind, sham-controlled, crossover trial study

Background and objectives

Intermittent theta-burst stimulation (iTBS) is a patterned form of excitatory transcranial magnetic stimulation that has yielded encouraging results as an adjunctive therapeutic option to alleviate the emergence of clinical deficits in Parkinson's disease (PD) patients. Although it has been demonstrated that iTBS influences dopamine-dependent corticostriatal plasticity, little research has examined the neurobiological mechanisms underlying iTBS-induced clinical enhancement. Here, our primary goal is to verify whether iTBS bilaterally delivered over the primary motor cortex (M1) is effective as an add-on treatment at reducing scores for both motor functional impairment and nonmotor symptoms in PD. We hypothesize that these clinical improvements following bilateral M1-iTBS could be driven by endogenous dopamine release, which may rebalance cortical excitability and restore compensatory striatal volume changes, resulting in increased striato-cortico-cerebellar functional connectivity and positively impacting neuroglia and neuroplasticity.

Methods

A total of 24 PD patients will be assessed in a randomized, double-blind, sham-controlled crossover study involving the application of iTBS over the bilateral M1 (M1 iTBS). Patients on medication will be randomly assigned to receive real iTBS or control (sham) stimulation and will undergo 5 consecutive sessions (5 days) of iTBS over the bilateral M1 separated by a 3-month washout period. Motor evaluation will be performed at different follow-up visits along with a comprehensive neurocognitive assessment; evaluation of M1 excitability; combined structural magnetic resonance imaging (MRI), resting-state electroencephalography and functional MRI; and serum biomarker quantification of neuroaxonal damage, astrocytic reactivity, and neural plasticity prior to and after iTBS.

Discussion

The findings of this study will help to clarify the efficiency of M1 iTBS for the treatment of PD and further provide specific neurobiological insights into improvements in motor and nonmotor symptoms in these patients. This novel project aims to yield more detailed structural and functional brain evaluations than previous studies while using a noninvasive approach, with the potential to identify prognostic neuroprotective biomarkers and elucidate the structural and functional mechanisms of M1 iTBS-induced plasticity in the cortico-basal ganglia circuitry. Our approach may significantly optimize neuromodulation paradigms to ensure state-of-the-art and scalable rehabilitative treatment to alleviate motor and nonmotor symptoms of PD.

Predicting Motor Outcome and Quality of Life After Subthalamic Deep Brain Stimulation for Parkinson's Disease: The Role of Standard Screening Measures and Wearable-Data

BACKGROUND

Standardized screening for subthalamic deep brain stimulation (STN DBS) in Parkinson's disease (PD) patients is crucial to determine eligibility, but its utility to predict postoperative outcomes in eligible patients is inconclusive. It is unknown whether wearable data can contribute to this aim.

OBJECTIVE

To evaluate the utility of universal components incorporated in the DBS screening, complemented by a wearable sensor, to predict motor outcomes and Quality of life (QoL) one year after STN DBS surgery.

METHODS

Consecutive patients were included in the OPTIMIST cohort study from two DBS centers. Standardized assessments included a preoperative Levodopa Challenge Test (LCT), and questionnaires on QoL and non-motor symptoms including cognition, psychiatric symptoms, impulsiveness, autonomic symptoms, and sleeping problems. Moreover, an ambulatory wearable sensor (Parkinson Kinetigraph (PKG)) was used. Postoperative assessments were similar and also included a Stimulation Challenge Test to determine DBS effects on motor function.

RESULTS

Eighty-three patients were included (median (interquartile range) age 63 (56-68) years, 36% female). Med-OFF (Stim-OFF) motor severity deteriorated indicating disease progression, but patients significantly improved in terms of Med-ON (Stim-ON) motor function, motor fluctuations, QoL, and most non-motor domains. Motor outcomes were not predicted by preoperative tests, including covariates of either LCT or PKG. Postoperative QoL was predicted by better preoperative QoL, lower age, and more preoperative impulsiveness scores in multivariate models.

CONCLUSION

Data from the DBS screening including wearable data do not predict postoperative motor outcome at one year. Post-DBS QoL appears primarily driven by non-motor symptoms, rather than by motor improvement.

Emotional symptoms and cognitive function outcomes of subthalamic stimulation in Parkinson's disease depend on location of active contacts and the volume of tissue activated

BACKGROUND

Subthalamic nucleus (STN) deep brain stimulation (DBS) is an effective treatment for Parkinson's disease (PD), that can improve patients' motor and non-motor symptoms. However, there are differences in the improvement of patients' emotional symptoms and cognitive function.

OBJECTIVE

To investigate the impact of active contact location and the volume of tissue activated (VTA) on patients' emotional symptoms and cognitive function in STN-DBS in PD.

METHODS

A total of 185 PD patients were included in this study. We evaluated them using the Movement Disorder Society-Unified Parkinson's Disease Rating Scale, Hamilton Anxiety Scale (HAM-A), Hamilton Depression Scale (HAM-D), Montreal Cognitive Assessment (MoCA), and Mini-Mental State Examination (MMSE) scales at the preoperative, 1- and 12-month postoperative time points. Leads were positioned in standard space using the Lead-DBS toolbox, and VTA was calculated for analysis.

RESULTS

When the lead active contact was closer to the ventral side of the STN, the patients' HAM-A improvement rate was higher, and when the active contact was closer to the anterior and dorsal sides of the STN, the patients' MoCA improvement rate was higher. Stimulation of the sensorimotor zone was more favorable to the improvement of HAM-A and HAM-D in patients. And, the stimulation of the associative zone was more favorable to the improvement of MoCA in patients.

CONCLUSION

Our results provide evidence that the 12-month outcomes of cognitive function and emotional symptoms in PD patients with STN-DBS were closely related to the specific location of the active contacts in the STN and influenced by the VTA.

Patients with Cognitive Impairment in Parkinson's Disease Benefit from Deep Brain Stimulation: A Case-Control Study

Background

Deep brain stimulation (DBS) for Parkinson's disease (PD) is generally contraindicated in persons with dementia but it is frequently performed in people with mild cognitive impairment or normal cognition, and current clinical guidelines are primarily based on these cohorts.

Objectives

To determine if moderately cognitive impaired individuals including those with mild dementia could meaningfully benefit from DBS in terms of motor and non-motor outcomes.

Methods

In this retrospective case-control study, we identified a cohort of 40 patients with PD who exhibited moderate (two or more standard deviations below normative scores) cognitive impairment (CI) during presurgical workup and compared their 1-year clinical outcomes to a cohort of 40 matched patients with normal cognition (NC). The surgery targeted subthalamus, pallidus or motor thalamus, in a unilateral, bilateral or staged approach.

Results

At preoperative baseline, the CI cohort had higher Unified Parkinson's Disease Rating Scale (UPDRS) subscores, but similar levodopa responsiveness compared to the NC cohort. The NC and CI cohorts demonstrated comparable degrees of postoperative improvement in the OFF-medication motor scores, motor fluctuations, and medication reduction. There was no difference in adverse event rates between the two cohorts. Outcomes in the CI cohort did not depend on the target, surgical staging, or impaired cognitive domain.

Conclusions

Moderately cognitively impaired patients with PD can experience meaningful motor benefit and medication reduction with DBS.

Deep brain stimulation in Early Onset Parkinson's disease

INTRODUCTION

Subthalamic Deep Brain Stimulation (STN-DBS) is a safe and well-established therapy for the management of motor symptoms refractory to best medical treatment in patients with Parkinson's disease (PD). Early intervention is discussed especially for Early-onset PD (EOPD) patients that present with an age of onset ≤ 45-50 years and see themselves often confronted with high psychosocial demands.

METHODS

We retrospectively assessed the effect of STN-DBS at 12 months follow-up (12-MFU) in 46 EOPD-patients. Effects of stimulation were evaluated by comparison of disease-specific scores for motor and non-motor symptoms including impulsiveness, apathy, mood, quality of life (QoL), cognition before surgery and in the stimulation ON-state without medication. Further, change in levodopa equivalent dosage (LEDD) after surgery, DBS parameter, lead localization, adverse and serious adverse events as well as and possible additional clinical features were assessed.

RESULTS

PD-associated gene mutations were found in 15% of our EOPD-cohort. At 12-MFU, mean motor scores had improved by 52.4 ± 17.6% in the STIM-ON/MED-OFF state compared to the MED-OFF state at baseline (p = 0.00; n = 42). These improvements were accompanied by a significant 59% LEDD reduction (p < 0.001), a significant 6.6 ± 16.1 points reduction of impulsivity (p = 0.02; n = 35) and a significant 30 ± 50% improvement of QoL (p = 0.01). At 12-MFU, 9 patients still worked full- and 6 part-time. Additionally documented motor and/or neuropsychiatric features decreased from n = 41 at baseline to n = 14 at 12-MFU.

CONCLUSION

The present study-results demonstrate that EOPD patients with and without known genetic background benefit from STN-DBS with significant improvement in motor as well as non-motor symptoms. In line with this, patients experienced a meaningful reduction of additional neuropsychiatric features. Physicians as well as patients have an utmost interest in possible predictors for the putative DBS outcome in a cohort with such a highly complex clinical profile. Longitudinal monitoring of DBS-EOPD-patients over long-term intervals with standardized comprehensive clinical assessment, accurate phenotypic characterization and documentation of clinical outcomes might help to gain insights into disease etiology, to contextualize genomic information and to identify predictors of optimal DBS candidates as well as those in danger of deterioration and/or non-response in the future.

Clinical factors and dopamine transporter availability for the prediction of outcomes after globus pallidus deep brain stimulation in Parkinson's disease

We aimed to investigate the predictive value of preoperative clinical factors and dopamine transporter imaging for outcomes after globus pallidus interna (GPi) deep brain stimulation (DBS) in patients with advanced Parkinson’s disease (PD). Thirty-one patients with PD who received bilateral GPi DBS were included. The patients underwent preoperative [¹⁸F] FP-CIT positron emission tomography before DBS surgery. The Unified Parkinson’s Disease Rating Scale (UPDRS) were used to assess outcomes 12 months after DBS. Univariate and multivariate linear regression analysis were performed to investigate the association between clinical variables including sex, age at onset of PD, disease duration, cognitive status, preoperative motor severity, levodopa responsiveness, daily dose of dopaminergic medication, and dopamine transporter availability in the striatum and outcomes after GPi DBS. Younger age at onset of PD was associated with greater DBS motor responsiveness and lower postoperative UPDRS III score. Greater levodopa responsiveness, lower preoperative UPDRS III score and lower striatal dopamine transporter availability were associated with lower postoperative UPDRS III score. Younger age at onset was also associated with greater decrease in UPDRS IV score and dyskinesia score after GPi DBS. Our results provide useful information to select DBS candidates and predict therapeutic outcomes after GPi DBS in advanced PD.

Lead location as a determinant of motor benefit in subthalamic nucleus deep brain stimulation for Parkinson’s disease

Background

Subthalamic nucleus (STN) deep brain stimulation (DBS) is regarded as an effective treatment for patients with advanced Parkinson’s disease (PD). Clinical benefit, however, varies significantly across patients. Lead location has been hypothesized to play a critical role in determining motor outcome and may account for much of the observed variability reported among patients.

Objective

To retrospectively evaluate the relationship of lead location to motor outcomes in patients who had been implanted previously at another center by employing a novel visualization technology that more precisely determines the location of the DBS lead and its contacts with respect to each patient’s individually defined STN.

Methods

Anatomical models were generated using novel imaging in 40 PD patients who had undergone bilateral STN DBS (80 electrodes) at another center. Patient-specific models of each STN were evaluated to determine DBS electrode contact locations with respect to anterior to posterior and medial to lateral regions of the individualized STNs and compared to the change in the contralateral hemi-body Unified Parkinson’s Disease Rating Scale Part III (UPDRS-III) motor score.

Results

The greatest improvement in hemi-body motor function was found when active contacts were located within the posterolateral portion of the STN (71.5%). Motor benefit was 52 and 36% for central and anterior segments, respectively. Active contacts within the posterolateral portion also demonstrated the greatest reduction in levodopa dosage (77%).

Conclusion

The degree of motor benefit was dependent on the location of the stimulating contact within the STN. Although other factors may play a role, we provide further evidence in support of the hypothesis that lead location is a critical factor in determining clinical outcomes in STN DBS.

A Review on Response to Device-Aided Therapies Used in Monogenic Parkinsonism and GBA Variants Carriers: A Need for Guidelines and Comparative Studies

Parkinson's disease (PD) is in some cases predisposed-or-caused by genetic variants, contributing to the expression of different phenotypes. Regardless of etiology, as the disease progresses, motor fluctuations and/or levodopa-induced dyskinesias limit the benefit of pharmacotherapy. Device-aided therapies are good alternatives in advanced disease, including deep brain stimulation (DBS), levodopa-carbidopa intestinal gel, and continuous subcutaneous infusion of apomorphine. Candidate selection and timing are critical for the success of such therapies. Genetic screening in DBS cohorts has shown a higher proportion of mutation carriers than in general cohorts, suggesting that genetic factors may influence candidacy for advanced therapies. The response of monogenic PD to device therapies is not well established, and the contribution of genetic information to decision-making is still a matter of debate. The limited evidence regarding gene-dependent response to device-aided therapies is reviewed here. An accurate understanding of the adequacy and responses of different mutation carriers to device-aided therapies requires the development of specific studies with long-term monitoring.

Association of Preoperative Visual Hallucinations With Cognitive Decline After Deep Brain Stimulation for Parkinson's Disease

OBJECTIVE

Deep brain stimulation (DBS) is effective for the motor symptoms of Parkinson's disease (PD). Although most patients benefit with minimal cognitive side effects, cognitive decline is a risk, and there is little available evidence to guide preoperative risk assessment. Visual illusions or visual hallucinations (VHs) and impulse-control behaviors (ICBs) are relatively common complications of PD and its treatment and may be a marker of more advanced disease, but their relationship with postoperative cognition has not been established. The authors aimed to determine whether any preoperative history of VHs or ICBs is associated with cognitive change after DBS.

METHODS

Retrospective chart review identified 54 patients with PD who received DBS of the subthalamic nucleus or globus pallidus internus and who completed both pre- and postoperative neuropsychological testing. Linear regression models were used to assess whether any preoperative history of VHs or ICBs was associated with changes in attention, executive function, language, memory, or visuospatial cognitive domains while controlling for surgical target and duration between evaluations.

RESULTS

The investigators found that a history of VHs was associated with declines in attention (b=-4.04, p=0.041) and executive function (b=-4.24, p=0.021). A history of ICBs was not associated with any significant changes.

CONCLUSIONS

These results suggest that a history of VHs may increase risk of cognitive decline after DBS; thus, specific preoperative counseling and targeted remediation strategies for these patients may be indicated. In contrast, a history of ICBs does not appear to be associated with increased cognitive risk.

Gender gap in deep brain stimulation for Parkinson's disease

Previous studies have shown less access to deep brain stimulation (DBS) for Parkinson’s disease (PD) in women compared to men raising concerns about a potential gender gap resulting from nonclinical factors or gender differences in clinical efficacy for postoperative quality of life (QoL), motor, and nonmotor symptoms (NMS) outcomes. This was a cross-sectional and a longitudinal, prospective, observational, controlled, quasi-experimental, international multicenter study. A total sample size of 505 consisted of 316 consecutively referred patients for DBS indication evaluation at the University Hospital Cologne (01/2015–09/2020) and 189 consecutively treated patients at DBS centers in the University Hospitals Cologne and Marburg, Salford’s Royal Hospital Manchester, and King’s College Hospital London. In the cross-sectional cohort, we examined gender proportions at referral, indication evaluations, and DBS surgery. In the longitudinal cohort, clinical assessments at preoperative baseline and 6-month follow-up after surgery included the PD Questionnaire-8, NMSScale, Scales for Outcomes in PD-motor scale, and levodopa-equivalent daily dose. Propensity score matching resulted in a pseudo-randomized sub-cohort balancing baseline demographic and clinical characteristics between women with PD and male controls. 316 patients were referred for DBS. 219 indication evaluations were positive (women n = 102, respectively n = 82). Women with PD were disproportionally underrepresented in referrals compared to the general PD population (relative risk [RR], 0.72; 95%CI, 0.56–0.91; P = 0.002), but more likely to be approved for DBS than men (RR, 1.17; 95%CI, 1.03–1.34; P = 0.029). Nonetheless, their total relative risk of undergoing DBS treatment was 0.74 (95%CI, 0.48–1.12) compared to men with PD. At baseline, women had longer disease duration and worse dyskinesia. Exploring QoL domains, women reported worse mobility and bodily discomfort. At follow-up, all main outcomes improved equally in both genders. Our study provides evidence of a gender gap in DBS for PD. Women and men with PD have distinct preoperative nonmotor and motor profiles. We advocate that more focus should be directed toward the implementation of gender equity as both genders benefit from DBS with equal clinical efficacy. This study provides Class II evidence of beneficial effects of DBS in women with PD compared to male controls.

Therapeutic Devices for Motor Symptoms in Parkinson’s Disease: Current Progress and a Systematic Review of Recent Randomized Controlled Trials

Background

Pharmacotherapy is the first-line treatment option for Parkinson’s disease, and levodopa is considered the most effective drug for managing motor symptoms. However, side effects such as motor fluctuation and dyskinesia have been associated with levodopa treatment. For these conditions, alternative therapies, including invasive and non-invasive medical devices, may be helpful. This review sheds light on current progress in the development of devices to alleviate motor symptoms in Parkinson’s disease.

Methods

We first conducted a narrative literature review to obtain an overview of current invasive and non-invasive medical devices and thereafter performed a systematic review of recent randomized controlled trials (RCTs) of these devices.

Results

Our review revealed different characteristics of each device and their effectiveness for motor symptoms. Although invasive medical devices are usually highly effective, surgical procedures can be burdensome for patients and have serious side effects. In contrast, non-pharmacological/non-surgical devices have fewer complications. RCTs of non-invasive devices, especially non-invasive brain stimulation and mechanical peripheral stimulation devices, have proven effectiveness on motor symptoms. Nearly no non-invasive devices have yet received Food and Drug Administration certification or a CE mark.

Conclusion

Invasive and non-invasive medical devices have unique characteristics, and several RCTs have been conducted for each device. Invasive devices are more effective, while non-invasive devices are less effective and have lower hurdles and risks. It is important to understand the characteristics of each device and capitalize on these.

Methodological Considerations for Setting Up Deep Brain Stimulation Studies for New Indications

Deep brain stimulation (DBS) is a neurosurgical treatment with a growing range of indications. The number of clinical studies is expanding because of DBS for new indications and efforts to improve DBS for existing indications. To date, various methods have been used to perform DBS studies. Designing a clinical intervention study with active implantable medical devices has specific challenges while expanding patient treatment. This paper provides an overview of the key aspects that are essential for setting up a DBS study.

Automatic detection of neuromelanin and iron in the midbrain nuclei using a magnetic resonance imaging ‐based brain template

Parkinson disease (PD) is a chronic progressive neurodegenerative disorder characterized pathologically by early loss of neuromelanin (NM) in the substantia nigra pars compacta (SNpc) and increased iron deposition in the substantia nigra (SN). Degeneration of the SN presents as a 50 to 70% loss of pigmented neurons in the ventral lateral tier of the SNpc at the onset of symptoms. Also, using magnetic resonance imaging (MRI), iron deposition and volume changes of the red nucleus (RN), and subthalamic nucleus (STN) have been reported to be associated with disease status and rate of progression. Further, the STN serves as an important target for deep brain stimulation treatment in advanced PD patients. Therefore, an accurate in‐vivo delineation of the SN, its subregions and other midbrain structures such as the RN and STN could be useful to better study iron and NM changes in PD. Our goal was to use an MRI template to create an automatic midbrain deep gray matter nuclei segmentation approach based on iron and NM contrast derived from a single, multiecho magnetization transfer contrast gradient echo (MTC‐GRE) imaging sequence. The short echo TE = 7.5 ms data from a 3D MTC‐GRE sequence was used to find the NM‐rich region, while the second echo TE = 15 ms was used to calculate the quantitative susceptibility map for 87 healthy subjects (mean age ± SD: 63.4 ± 6.2 years old, range: 45–81 years). From these data, we created both NM and iron templates and calculated the boundaries of each midbrain nucleus in template space, mapped these boundaries back to the original space and then fine‐tuned the boundaries in the original space using a dynamic programming algorithm to match the details of each individual's NM and iron features. A dual mapping approach was used to improve the performance of the morphological mapping of the midbrain of any given individual to the template space. A threshold approach was used in the NM‐rich region and susceptibility maps to optimize the DICE similarity coefficients and the volume ratios. The results for the NM of the SN as well as the iron containing SN, STN, and RN all indicate a strong agreement with manually drawn structures. The DICE similarity coefficients and volume ratios for these structures were 0.85, 0.87, 0.75, and 0.92 and 0.93, 0.95, 0.89, 1.05, respectively, before applying any threshold on the data. Using this fully automatic template‐based deep gray matter mapping approach, it is possible to accurately measure the tissue properties such as volumes, iron content, and NM content of the midbrain nuclei.

Subthalamic Nucleus Stimulation in Parkinson's Disease: 5-Year Extension Study of a Randomized Trial

Background

In Parkinson's disease (PD) long-term motor outcomes of subthalamic nucleus deep brain stimulation (STN-DBS) are well documented, while comprehensive reports on non-motor outcomes are fewer and less consistent.

Objective

To report motor and non-motor symptoms after 5-years of STN-DBS.

Methods

We performed an open 5-year extension study of a randomized trial that compared intraoperative verification versus mapping of STN using microelectrode recordings. Changes from preoperative to 5-years of STN-DBS were evaluated for motor and non-motor symptoms (MDS-UPDRS I-IV), sleep disturbances (PDSS), autonomic symptoms (Scopa-Aut), quality of life (PDQ-39) and cognition through a neuropsychological test battery. We evaluated whether any differences between the two randomization groups were still present, and assessed preoperative predictors of physical dependence after 5 years of treatment using logistic regression.

Results

We found lasting improvement of off-medication motor symptoms (total MDS-UPDRS III, bradykinetic-rigid symptoms and tremor), on-medication tremor, motor fluctuations, and sleep disturbances, but reduced performance across all cognitive domains, except verbal memory. Reduction of verbal fluency and executive function was most pronounced the first year and may thus be more directly related to the surgery than worsening in other domains. The group mapped with multiple microelectrode recordings had more improvement of bradykinetic-rigid symptoms and of PDQ-39 bodily discomfort sub-score, but also more reduction in word fluency. Older age was the most important factor associated with physical dependence after 5 years.

Conclusion

STN-DBS offers good long-term effects, including improved sleep, despite disease progression. STN-DBS surgery may negatively impact verbal fluency and executive function.

Hyperostosis in Combination With Low Skull Density Ratio: A Potential Contraindication for Magnetic Resonance Imaging-Guided Focused Ultrasound Thalamotomy

Since its approval in treating a number of movement disorders, magnetic resonance imaging–guided focused ultrasound (MRgFUS) has been adopted rapidly as one of the standard treatment modalities internationally. However, the efficiency of the energy delivered by the ultrasonic waves is largely determined by the highly variable bone morphology and density characteristics of the skull. One of the widely accepted indices used to facilitate patient selection is the skull density ratio (SDR). Earlier literature suggested that an SDR of less than 0.4 would be unfavorable for MRgFUS treatment. Some prior studies have excluded patients with hyperostosis. However, there is little published data regarding the impact of other skull features such as hyperostosis on treatment success. We present the case of a 66-year-old man with medically refractory essential tremor who had an SDR of 0.38 and extensive hyperostosis frontalis interna and underwent attempted MRgFUS thalamotomy treatment. However, intraoperatively the treatment was unsuccessful in generating sufficiently elevated temperature to create a lesion of the usual desired volume, and as expected, there was minimal clinical improvement. For comparison, we also summarize a case series of 4 other patients with an SDR of less than 0.4 who had successful outcomes. We believe that SDR should not be used as the only means of selecting patients for MRgFUS. Instead, important factors such as hyperostosis should be taken into consideration for patient selection and pretreatment counseling.

A Randomized, Double-Blinded Crossover Trial of Short Versus Conventional Pulse Width Subthalamic Deep Brain Stimulation in Parkinson's Disease

BACKGROUND

Subthalamic nucleus deep brain stimulation (STN-DBS) is a well-established treatment for patients with Parkinson's disease. Previous acute challenge studies suggested that short pulse widths might increase the therapeutic window while maintaining motor symptom control with a decrease in energy consumption. However, only little is known about the effect of short pulse width stimulation beyond the setting of an acute challenge.

OBJECTIVE

To compare 4 weeks of STN-DBS with conventional pulse width stimulation (60 μs) to 4 weeks of STN-DBS with short pulse width stimulation (30 μs) regarding motor symptom control.

METHODS

This study was a monocentric, double-blinded, randomized crossover non-inferiority trial investigating whether short pulse width stimulation with 30 μs maintains equal motor control as conventional 60 μs stimulation over a period of 4 weeks (German Clinical Trials Register No. DRKS00017528). Primary outcome was the difference in motor symptom control as assessed by a motor diary. Secondary outcomes included energy consumption measures, non-motor effects, side-effects, and quality of life.

RESULTS

Due to a high dropout rate, the calculated sample size of 27 patients was not met and 24 patients with Parkinson's disease and STN-DBS were included in the final analysis. However, there were no differences in any investigated outcome parameter between the two treatment conditions.

CONCLUSION

This study demonstrates that short pulse width settings (30 μs) provide non-inferior motor symptom control as conventional (60 μs) stimulation without significant differences in energy consumption. Future studies are warranted to evaluate a potential benefit of short pulse width settings in patients with pronounced dyskinesia.

A Randomized, Double-Blinded Crossover Trial of Short Versus Conventional Pulse Width Subthalamic Deep Brain Stimulation in Parkinson's Disease

BACKGROUND

Subthalamic nucleus deep brain stimulation (STN-DBS) is a well-established treatment for patients with Parkinson's disease. Previous acute challenge studies suggested that short pulse widths might increase the therapeutic window while maintaining motor symptom control with a decrease in energy consumption. However, only little is known about the effect of short pulse width stimulation beyond the setting of an acute challenge.

OBJECTIVE

To compare 4 weeks of STN-DBS with conventional pulse width stimulation (60 μs) to 4 weeks of STN-DBS with short pulse width stimulation (30 μs) regarding motor symptom control.

METHODS

This study was a monocentric, double-blinded, randomized crossover non-inferiority trial investigating whether short pulse width stimulation with 30 μs maintains equal motor control as conventional 60 μs stimulation over a period of 4 weeks (German Clinical Trials Register No. DRKS00017528). Primary outcome was the difference in motor symptom control as assessed by a motor diary. Secondary outcomes included energy consumption measures, non-motor effects, side-effects, and quality of life.

RESULTS

Due to a high dropout rate, the calculated sample size of 27 patients was not met and 24 patients with Parkinson's disease and STN-DBS were included in the final analysis. However, there were no differences in any investigated outcome parameter between the two treatment conditions.

CONCLUSION

This study demonstrates that short pulse width settings (30 μs) provide non-inferior motor symptom control as conventional (60 μs) stimulation without significant differences in energy consumption. Future studies are warranted to evaluate a potential benefit of short pulse width settings in patients with pronounced dyskinesia.

Comparative Analysis of Acute Levodopa Challenge Test and the Outcomes of Deep Brain Stimulation in Parkinson's Disease

BACKGROUND

 We study the correlation between the preoperative levodopa challenge test and the efficacy of deep brain stimulation (DBS) surgery in Parkinson's disease (PD).

METHODS

 Fifty patients with PD who underwent DBS treatment in our hospital from October 2016 to October 2017 were enrolled in this study. Using the Unified Parkinson Disease Rating Scale-III (UPDRS-III) as an indicator, we analyzed the improvement in motor symptoms on the levodopa challenge test and by DBS surgery. We also discussed the correlation between the effects of the levodopa challenge test and DBS surgery.

RESULTS

 There was no correlation between the results of the levodopa challenge test and DBS surgery. There was a linear correlation between muscle rigidity and bradykinesia, whereas the linear correlation between other symptoms was weak.

CONCLUSION

 The levodopa challenge test can be used as a screening tool for patients undergoing DBS surgery, and can predict the degree of improvement in muscle rigidity and bradykinesia surgery. However, the prediction of the degree of improvement of total motor symptoms is poor.

Can Levodopa Challenge Testing Predict the Effect of Deep Brain Stimulation? One-Year Outcomes in a Chinese Cohort

Objective: Our study examined whether levodopa challenge test (LCT) results could predict quality of life (QoL) outcomes after surgery to implant subthalamic nucleus deep brain stimulation (STN-DBS) electrodes to treat advanced Parkinson’s disease (PD).

Methods: Forty patients with STN-DBS underwent a follow-up 1 year after implantation surgery to analyze the correlation between preoperative levodopa impact test results and postoperative Unified Parkinson’s Disease Rating Scale (UPDRS) III motor score, postoperative PD Questionnaire-39 (PDQ-39) score, and PDQ-39 improvement.

Results: Improvements in QoL were associated with several preoperative characteristics including preoperative UPDRS-III tremor, UPDRS-III tremor (off-60) (p = 0.049), UPDRS-III tremor (off-120) (p = 0.012), Mini-Mental State Examination (p = 0.012), and PDQ-39 (p = 0.012) before surgery. Multiple linear regression model using preoperative MMSE [odds ratio (OR) = 0.342, 95% confidence interval (CI) = 0.051–2.297], preoperative UPDRS-III tremor (OR = 2.099, 95% CI = 0.585–7.535), UPDRS-III tremor (off-60) [OR = 1.316, 95% CI = 0.804–2.154, UPDRS-III tremor (off-120) OR = 0.913, 95% CI = 0.691–1.207], correctly classified 88.5% of patients.

Conclusion: Levodopa challenge test results cannot predict the effect of DBS. However, the test can be incorporated into a regression prediction model to the quality of life of PD patients after DBS with other preoperative factors.

Correlation of active contact location with weight gain after subthalamic nucleus deep brain stimulation: a case series

Background

Weight gain (WG) is a frequently reported side effect of subthalamic deep brain stimulation; however, the underlying mechanisms remain unclear. The active contact locations influence the clinical outcomes of subthalamic deep brain stimulation, but it is unclear whether WG is directly associated with the active contact locations. We aimed to determine whether WG is associated with the subthalamic deep brain stimulation active contact locations.

Methods

We enrolled 14 patients with Parkinson’s disease who underwent bilateral subthalamic deep brain stimulation between 2013 and 2019. Bodyweight and body mass index were measured before and one year following the surgery. The Lead-DBS Matlab toolbox was used to determine the active contact locations based on magnetic resonance imaging and computed tomography. We also created sweet spot maps for WG using voxel-wise statistics, based on volume of tissue activation and the WG of each patient. Fluorodeoxyglucose-positron emission tomography data were also acquired before and one year following surgery, and statistical parametric mapping was used to evaluate changes in brain metabolism. We examined which brain regions’ metabolism fluctuation significantly correlated with increased body mass index scores and positron emission tomography data.

Results

One year after surgery, the body mass index increase was 2.03 kg/m². The sweet spots for WG were bilateral, mainly located dorsally outside of the subthalamic nucleus (STN). Furthermore, WG was correlated with increased metabolism in the left limbic and associative regions, including the middle temporal gyrus, inferior frontal gyrus, and orbital gyrus.

Conclusions

Although the mechanisms underlying WG following subthalamic deep brain stimulation are possibly multifactorial, our findings suggest that dorsal stimulation outside of STN may lead to WG. The metabolic changes in limbic and associative cortical regions after STN-DBS may also be one of the mechanisms underlying WG. Further studies are warranted to confirm whether dorsal stimulation outside of STN changes the activities of these cortical regions.

Preexisting Bipolar Disorder Influences the Subsequent Phenotype of Parkinson's Disease

Background

Patients with bipolar spectrum disorders (BSDs) exhibit an increased risk of Parkinson's disease (PD).

Objective

The aim is to investigate whether a previous diagnosis of BSDs influences the phenotype of PD.

Methods

Of 2660 PD patients followed for at least 6 years (6–27), 250 (BSD‐PD) had BSDs, 6–20 years before PD diagnosis; 48%–43% had a PD or BSD family history, and 34 carried glucocerebrosidase (GBA) and Parkin (PRKN) mutations. The cohort was split into a subset of 213 BSD‐PD patients, compared with 426 matched PD patients without BSDs, and a subset of 34 BSD‐PD and 79 PD patients carrying GBA or PRKN mutations. Carriers of mutations absent in BSD‐PD patients and of synuclein triplication were excluded. Structured clinical interviews and mood disorder questionnaires assessed BSDs. Linear mixed models evaluated the assessment scales over time. Thirteen BSD‐PD patients underwent subthalamic nucleus deep brain stimulation (STN‐DBS) and were compared with 27 matched STN‐DBS‐treated PD patients.

Results

Compared to PD patients, BSD‐PD showed (1) higher frequency of family history of PD (odds ratio [OR] 3.31; 2.32–4.71) and BSDs (OR 6.20; 4.11–9.35) 5); (2) higher incidence of impulse control disorders (hazard ratio [HR] 5.95, 3.89–9.09); (3) higher frequency of functional disorders occurring before PD therapy (HR, 5.67, 3.95–8.15); (4) earlier occurrence of delusions or mild dementia (HR, 7.70, 5.55–10.69; HR, 1.43, 1.16–1.75); and (5) earlier mortality (1.48; 1.11–1.97). Genetic BSD‐PD subjects exhibited clinical features indistinguishable from nongenetic BSD‐PD subjects. STN‐DBS‐treated BSD‐PD patients showed no improvements in quality of life compared to the control group.

Conclusions

BSDs as a prodrome to PD unfavorably shape their course and are associated with detrimental neuropsychiatric features and treatment outcomes. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society

Personalised Advanced Therapies in Parkinson's Disease: The Role of Non-Motor Symptoms Profile

Device-aided therapies, including levodopa-carbidopa intestinal gel infusion, apomorphine subcutaneous infusion, and deep brain stimulation, are available in many countries for the management of the advanced stage of Parkinson’s disease (PD). Currently, selection of device-aided therapies is mainly focused on patients’ motor profile while non-motor symptoms play a role limited to being regarded as possible exclusion criteria in the decision-making process for the delivery and sustenance of a successful treatment. Differential beneficial effects on specific non-motor symptoms of the currently available device-aided therapies for PD are emerging and these could hold relevant clinical implications. In this viewpoint, we suggest that specific non-motor symptoms could be used as an additional anchor to motor symptoms and not merely as exclusion criteria to deliver bespoke and patient-specific personalised therapy for advanced PD.

Assessment of Affective-Behavioral States in Parkinson's Disease Patients: Towards a New Screening Tool

BACKGROUND

Assessment of affective-behavioral states in patients with Parkinson's disease (PD) undergoing deep brain stimulation (DBS) is essential.

OBJECTIVE

To analyze well-established questionnaires as a pilot-study with the long term aim to develop a screening tool evaluating affective-behavioral dysfunction, including depression, anxiety, apathy, mania, and impulse control disorders, in PD patients screened for DBS.

METHODS

Two hundred ninety-seven inpatients with PD underwent standardized neuropsychiatric testing including German versions of Beck Depression Inventory-II, Hospital Anxiety and Depression Scale, Apathy Evaluation Scale, Self-Report Manic Inventory, and Questionnaire for Impulsive-Compulsive Disorders in PD-Rating Scale, to assess appropriateness for DBS. Statistical item reduction was based on exploratory factor analysis, Cronbach's alpha, item-total correlations, item difficulty, and inter-item correlations. Confirmatory factor analysis was conducted to assess factorial validity. An expert rating was performed to identify clinically relevant items in the context of PD and DBS, to maintain content validity. We compared the shortened subscales with the original questionnaires using correlations. To determine cutoff points, receiver operating characteristics analysis was performed.

RESULTS

The items of the initial questionnaires were reduced from 129 to 38 items. Results of confirmatory factor analyses supported the validity of the shortened pool. It demonstrated high internal consistency (Cronbach's alpha = 0.72-0.83 across subscales), and the individual subscales were correlated with the corresponding original scales (rs = 0.84-0.95). Sensitivities and specificities exceeded 0.7.

CONCLUSION

The shortened item pool, including 38 items, provides a good basis for the development of a screening tool, capturing affective-behavioral symptoms in PD patients before DBS implantation. Confirmation of the validity of such a screening tool in an independent sample of PD patients is warranted.

Locus Coeruleus Degeneration Correlated with Levodopa Resistance in Parkinson's Disease: A Retrospective Analysis

Background:

The widely divergent responsiveness of Parkinson’s disease (PD) patients to levodopa is an important clinical issue because of its relationship with quality of life and disease prognosis. Preliminary animal experiments have suggested that degeneration of the locus coeruleus (LC) attenuates the efficacy of levodopa treatment.

Objective:

To explore the relationship between LC degeneration and levodopa responsiveness in PD patients in vivo.

Methods:

Neuromelanin-sensitive magnetic resonance imaging (NM-MRI), a good indicator of LC and substantia nigra (SN) degeneration, and levodopa challenge tests were conducted in 57 PD patients. Responsiveness to levodopa was evaluated by the rates of change of the Unified Parkinson’s Disease Rating Scale Part III score and somatomotor network synchronization calculated from resting-state functional MRI before and after levodopa administration. Next, we assessed the relationship between the contrast-to-noise ratio of LC (CNR_LC) and levodopa responsiveness. Multiple linear regression analysis was conducted to rule out the potential influence of SN degeneration on levodopa responsiveness.

Results:

A significant positive correlation was found between CNR_LC and the motor improvement after levodopa administration (R = 0.421, p = 0.004). CNR_LC also correlated with improvement in somatomotor network synchronization (R = –0.323, p = 0.029). Furthermore, the relationship between CNR_LC and levodopa responsiveness was independent of SN degeneration.

Conclusion:

LC degeneration might be an essential factor for levodopa resistance. LC evaluation using NM-MRI might be an alternative tool for predicting levodopa responsiveness and for helping to stratify patients into clinical trials aimed at improving the efficacy of levodopa.

PassFlow: a multimodal workflow for predicting deep brain stimulation outcomes

PURPOSE

Deep Brain Stimulation (DBS) is a proven therapy for Parkinson's Disease (PD), frequently resulting in an enhancement of motor function. Nonetheless, several undesirable side effects can occur after DBS, which can worsen the quality of life of the patient. Thus, the clinical team has to carefully select patients on whom to perform DBS. Over the past decade, there have been some attempts to relate pre-operative data and DBS clinical outcomes, with most focused on the motor symptomatology. In this paper, we propose a machine learning-based method able to predict a large number of DBS clinical outcomes for PD.

METHODS

We propose a multimodal pipeline, referred to as PassFlow, which predicts 84 clinical post-operative clinical scores. PassFlow is composed of an artificial neural network to compress clinical information, an image processing method from the state-of-the-art to extract morphological biomarkers our of T1 imaging, and an SVM to perform the regressions. We validated PassFlow on 196 PD patients who undergone a DBS.

RESULTS

PassFlow showed correlation coefficients as high as 0.71 and were able to significantly predict 63 out of the 84 scores, outperforming a comparative linear method. The number of metrics that are predicted with this pre-operative information was also found to be correlated with the number of patients with this information available, indicating that the PassFlow method is still actively learning.

CONCLUSION

We presented a novel, machine learning-based pipeline to predict a variety of post-operative clinical outcomes of DBS for PD patients. PassFlow took into account various bio-markers, arising from different data modalities, showing high correlation coefficients for some scores from pre-operative data only. It indicates that many clinical outcomes of DBS can be predicted agnostic to the specific simulation parameters, as PassFlow has been validated without such stimulation-related information.

Non-motor predictors of 36-month quality of life after subthalamic stimulation in Parkinson disease

To identify predictors of 36-month follow-up quality of life (QoL) outcome after bilateral subthalamic nucleus deep brain stimulation (STN-DBS) in Parkinson’s disease (PD). In this ongoing, prospective, multicenter international study (Cologne, Manchester, London) including 73 patients undergoing STN-DBS, we assessed the following scales preoperatively and at 6-month and 36-month follow-up: PD Questionnaire-8 (PDQ-8), NMSScale (NMSS), Scales for Outcomes in PD (SCOPA)-motor examination, -activities of daily living, and -complications, and levodopa equivalent daily dose (LEDD). We analyzed factors associated with QoL improvement at 36-month follow-up based on (1) correlations between baseline test scores and QoL improvement, (2) step-wise linear regressions with baseline test scores as independent and QoL improvement as dependent variables, (3) logistic regressions and receiver operating characteristic curves using a dichotomized variable “QoL responders”/“non-responders”. At both follow-ups, NMSS total score, SCOPA-motor examination, and -complications improved and LEDD was reduced significantly. PDQ-8 improved at 6-month follow-up with subsequent decrements in gains at 36-month follow-up when 61.6% of patients were categorized as “QoL non-responders”. Correlations, linear, and logistic regression analyses found greater PDQ-8 improvements in patients with younger age, worse PDQ-8, and worse specific NMS at baseline, such as ‘difficulties experiencing pleasure’ and ‘problems sustaining concentration’. Baseline SCOPA scores were not associated with PDQ-8 changes. Our results provide evidence that 36-month QoL changes depend on baseline neuropsychological and neuropsychiatric non-motor symptoms burden. These findings highlight the need for an assessment of a wide range of non-motor and motor symptoms when advising and selecting individuals for DBS therapy.

Correlates of deep brain stimulation consensus conference decision to treat primary dystonia

BACKGROUND

Deep brain stimulation (DBS) is an effective treatment for motor disturbance in people with primary dystonia (PWD). Numerous factors are considered by an interdisciplinary consensus conference before deciding candidacy for DBS surgery (e.g., demographic, medical, cognitive, and behavioral factors). However, little is known about which of these factors are associated with PWD DBS surgery consensus conference decisions.

OBJECTIVE

Our goal was to examine whether pre-operative demographic, medical, and cognitive/behavioral variables are associated DBS consensus conference decisions in patients with dystonia.

METHODS

Thirty-two PWD completed comprehensive presurgery workup included neurological and neuropsychological exams, and neuroimaging in consideration for DBS surgery. An interdisciplinary conference committee either recommended or did not recommend DBS surgery based upon these data. Demographic and medical data (e.g., dystonia disease characteristics, medical comorbidities, medications) were also collected. We also examined impact from cardiovascular disease factors, using a Revised Cardiac Risk Index. PWD were grouped based on DBS conference decision (eligible: n = 21, ineligible: n = 11) and compared across demographic, medical, and cognitive/behavioral variables.

RESULTS

Across clinical variables, PWD who were deemed ineligible for DBS surgery had a higher Revised Cardiac Risk Index. PWD who were classified as ineligible displayed lower global cognitive functioning, working memory, phonemic fluency, memory retrieval, and cognitive flexibility.

CONCLUSIONS

Consensus decision making regarding DBS surgery eligibility involves a multifactorial process. We found that deficits in executive functioning were associated with the DBS consensus committee decision. We also observed elevated cardiac risk among these individuals, likely reflecting the relation between vascular health and cognition. Implications, and clinical and scientific applications of these findings are discussed.

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

Surgical Management of Parkinson's Disease in the Elderly

Background

Deep Brain Stimulation (DBS) is an increasingly popular therapy for Parkinson's Disease (PD). Despite the experience gained over time with DBS of either the subthalamus or the globus pallidus pars interna, there is still no consensus regarding the age limit for DBS indication.

Objectives

This narrative review of the literature discusses the issues of age and DBS, emphasizing the critical need for good quality evidence to support the surgical management of elderly patients with PD.

Methods

We searched PubMed using the terms Parkinson's Disease; Parkinson's Disease therapy; deep brain stimulation; antiparkinsonian agents therapeutic use; age factors; aged; aged, 80 and over; middle aged; treatment outcome; and risk assessments.

Results

We identified several limitations of the available evidence, such as under-representation of older patients in DBS studies, small sample sizes in studies with older participants, heterogeneity of outcomes, and conflicting results.

Conclusions

Despite preliminary suggestions that age might affect the outcomes of DBS, the evidence to support the hypothesis of age as an independent predictor of DBS outcomes is limited and results are controversial. Ultimately, finding an age-independent biomarker predicting DBS outcome is the final goal to expand this powerful treatment to all patients age in an effective and safe manner.

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

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

[Guidelines for the Neuropsychological Assessment of Patients with Parkinson's Disease]

BACKGROUND

Presence of mild cognitive impairment is currently the best predictor for the development of Parkinson's disease dementia. Diagnostic criteria for both Parkinson's with mild cognitive impairment and Parkinson's disease dementia have been suggested by the Movement Disorder Society. However, not all cognitive tests recommended are available in the German language with proper standard values.

OBJECTIVES

To define evidence-based guidelines for neuropsychological assessment of patients with Parkinson's disease in German.

METHODS

Two systematic literature searches were conducted. First, articles that presented international guidelines (consensus papers or reviews) for the application of standardized neuropsychological assessments for the diagnosis of cognitive impairment in Parkinson's disease were selected. Of those, only neuropsychological assessments in German language with normative values referring either to a German, Austrian, or Swiss population were considered. Second, articles comparing test performances of healthy controls vs. Parkinson's disease and/or different cognitive Parkinson's disease subtypes (e.g. no cognitive impairment, Parkinson's with mild cognitive impairment, Parkinson's disease dementia) were selected. Effect sizes for group differentiation were calculated.

RESULTS

Out of 127 full-text articles reviewed, 48 tests were identified during the first literature search. In the second search, 1716 articles were reviewed and 23 papers selected. The strongest effect sizes for group discrimination were revealed for tests assessing executive function, attention, and visuo-cognitive abilities. Based on the results of the two literature searches, consensus guidelines were defined by the authors, allowing for Level-II diagnosis for Parkinson's with mild cognitive impairment and Parkinson's disease dementia.

CONCLUSIONS

The presented guidelines may have the potential to standardize and improve the neuropsychological assessment of Parkinson's disease patients in German speaking countries.

Long term mortality of patients with Parkinson's disease treated with deep brain stimulation in a reference center

INTRODUCTION

Parkinson's disease (PD) is a common neurodegenerative disorder, with a higher risk of death than general population. Deep Brain Stimulation (DBS) has been used to treat PD for more than 2 decades, but few studies exist concerning mortality in this subset of patients. Our goal is to analyse mortality in PD patients treated with DBS in our centre.

METHODS

retrospective evaluation of clinical files of patients with PD who underwent DBS surgery consecutively between October 2002 and May 2019.

RESULTS

346 patients were included in the analysis, 60 % male, with a mean age at disease onset of 48± 8 years (18-64), mean age at surgery of 60 ± 7 years (33-75), and mean disease duration until surgery of 14 ± 6 years (3-52). Mean follow-up after surgery was 7 ± 4 years (range 1-17). Overall mortality rate was 17.9 % and mean age at time of death was 71 ± 6 years. The main causes of death were pneumonia, dementia and acute myocardial infarction. In our series, male gender and disease duration until surgery were the only predictors of mortality in multivariate analysis.

CONCLUSION

Our study showed a long-term survival higher than previously described, and suggests that the treatment of patients with shorter disease evolution might have a survival benefit. The leading causes of death in PD patients treated with DBS seems unrelated to surgery, as the main causes of death are comparable to non-DBS patients.

Improved depiction of subthalamic nucleus and globus pallidus internus with optimized high-resolution quantitative susceptibility mapping at 7 T

The subthalamic nucleus (STN) and globus pallidus internus (GPi) are commonly used targets in deep-brain stimulation (DBS) surgery for the treatment of movement disorders. The success of DBS critically depends on the spatial precision of stimulation. By taking advantage of good contrast between iron-rich deep-brain nuclei and surrounding tissues, quantitative susceptibility mapping (QSM) has shown promise in differentiating the STN and GPi from the adjacent substantia nigra and globus pallidus externus, respectively. Nonlinear morphology-enabled dipole inversion (NMEDI) is a widely used QSM algorithm, but the image quality of reconstructed susceptibility maps relies on the regularization parameter selection. To date, few studies have systematically optimized the regularization parameter at the ultra-high field of 7 T. In this study, we optimized the regularization parameter in NMEDI to improve the depiction of STN and GPi at different spatial resolutions at both 3 T and 7 T. The optimized QSM images were further compared with other susceptibility-based images, including T2*-weighted (T2*w), R2*, susceptibility-weighted, and phase images. QSM showed better depiction of deep-brain nuclei with clearer boundaries compared with the other methods, and 7 T QSM at 0.35 × 0.35 × 1.0 mm³ demonstrated superior performance to the others. Our findings suggest that optimized high-resolution QSM at 7 T allows for improved delineation of deep-brain nuclei with clear and sharp borders between nuclei, which may become a promising tool for DBS nucleus preoperative localization.

Levodopa Changes Functional Connectivity Patterns in Subregions of the Primary Motor Cortex in Patients With Parkinson's Disease

Background

The primary motor cortex (M1) is a critical node in Parkinson’s disease (PD)-related motor circuitry; however, the functional roles of its subregions are poorly understood. In this study, we investigated changes in the functional connectivity patterns of M1 subregions and their relationships to improved clinical symptoms following levodopa administration.

Methods

Thirty-six PD patients and 37 healthy controls (HCs) were enrolled. A formal levodopa challenge test was conducted in the PD group, and the Unified Parkinson’s Disease Rating Scale motor section (UPDRS-III) was assessed before (off state) and 1 h after administration of levodopa (on state). The PD group underwent resting-state functional magnetic resonance imaging in both off and on states, whereas the HC group was scanned once. We used the Human Brainnetome Atlas template to subdivide M1 into twelve regions of interest (ROIs). Functional connectivity (FC) was compared between PD on and off states [paired t-test, voxel-level p < 0.001, cluster-level p < 0.05, Gaussian random field (GRF) correction] and between patients and HC (two-sample t-test voxel-level p < 0.001, cluster-level p < 0.05). Correlations between ΔFC (differences in FC between PD off and on states) and clinical symptom improvements were examined.

Results

There was decreased FC between the right caudal dorsolateral area 6 and the anterior cingulate gyrus (ACC), the right upper limb region and the left medial dorsal thalamus (mdTHA), as well as increased FC between the left tongue and larynx region and the left medial frontal gyrus. ΔFC between the right caudal dorsolateral area 6 and ACC was positively correlated with improvements in UPDRS-III total scores as well as the rigidity (item 22) and bradykinesia (items 23–26 and 31) subscores. ΔFC between the right upper limb region and left thalamus was positively correlated with improvements in the left upper limb tremor (items 20c and 21b) and postural tremor (item 21b) subscores.

Conclusions

Our results reveal novel information regarding the underlying mechanisms in the motor circuits in the M1 and a promising way to explore the internal function of the M1 in PD patients. Notably, M1 is a potential therapeutic target in PD, and the exploration of its subregions provides a basis and a source of new insights for clinical intervention and precise drug treatment.

Subcortical Atrophy and Motor Outcomes in Pallidal Deep Brain Stimulation for Parkinson Disease

BACKGROUND

Appropriate patient selection is critical for successful deep brain stimulation (DBS) for Parkinson disease (PD). Subcortical atrophy is a possible determinant of postoperative DBS outcomes in patients with idiopathic PD, but it has not been well evaluated for DBS of the globus pallidus interna (GPi). We investigated perioperative subcortical atrophy measures in patients with PD and their relationship to postoperative motor response in bilateral GPi-targeted DBS.

METHODS

A retrospective cohort study examined correlations among indices of subcortical volumetry, disease duration, and age with postoperative outcomes at 6 months (Unified Parkinson's Disease Rating Scale Part III motor score quotient, levodopa equivalent daily dosing, and 39-item Parkinson's Disease Questionnaire mobility subscore). Subcortical volumetry was assessed by bicaudate ratio, Evans index, and third ventricular width on perioperative imaging. Linear regression models established correlations between preoperative variables and postoperative outcomes.

RESULTS

Data from 34 patients with PD who were treated with GPi-targeted DBS were evaluated. Age was found to exhibit statistically significant positive correlations with all 3 measures of subcortical atrophy (P ≤ 0.002). None of the measures correlated with disease duration. Only Evans index and third ventricular width correlated with preoperative medication response (P < 0.05). Age and all 3 measures of atrophy exhibited statistically significant correlations with Unified Parkinson's Disease Rating Scale Part III motor score quotient (P ≤ 0.01), but not with levodopa equivalent daily dosing or 39-item Parkinson's Disease Questionnaire motor subscores (P > 0.05).

CONCLUSIONS

Perioperative age and subcortical atrophy as measured in this study correlated with motor responsiveness at 6 months postoperatively among patients receiving bilateral GPi-targeted DBS stimulation for PD.

Non-motor outcomes depend on location of neurostimulation in Parkinson's disease

Deep brain stimulation of the subthalamic nucleus is an effective and established therapy for patients with advanced Parkinson's disease improving quality of life, motor symptoms and non-motor symptoms. However, there is a considerable degree of interindividual variability for these outcomes, likely due to variability in electrode placement and stimulation settings. Here, we present probabilistic mapping data from a prospective, open-label, multicentre, international study to investigate the influence of the location of subthalamic nucleus deep brain stimulation on non-motor symptoms in patients with Parkinson's disease. A total of 91 Parkinson's disease patients undergoing bilateral deep brain stimulation of the subthalamic nucleus were included, and we investigated NMSScale, NMSQuestionnaire, Scales for Outcomes in Parkinson's disease-motor examination, -activities of daily living, and -motor complications, and Parkinson's disease Questionnaire-8 preoperatively and at 6-month follow-up after surgery. Leads were localized in standard space using the Lead-DBS toolbox and individual volumes of tissue activated were calculated based on clinical stimulation settings. Probabilistic stimulation maps and non-parametric permutation statistics were applied to identify voxels with significant above or below average improvement for each scale and analysed using the DISTAL atlas. All outcomes improved significantly at follow-up. Significant spatial distribution patterns of neurostimulation were observed for NMSScale total score and its mood/apathy and attention/memory domains. For both domains, voxels associated with below average improvement were mainly located dorsal to the subthalamic nucleus. In contrast, above average improvement for mood/apathy was observed in the ventral border region of the subthalamic nucleus and in its sensorimotor subregion and for attention/memory in the associative subregion. A trend was observed for NMSScale sleep domain showing voxels with above average improvement located ventral to the subthalamic nucleus. Our study provides evidence that the interindividual variability of mood/apathy, attention/memory, and sleep outcomes after subthalamic nucleus deep brain stimulation depends on the location of neurostimulation. This study highlights the importance of holistic assessments of motor and non-motor aspects of Parkinson's disease to tailor surgical targeting and stimulation parameter settings to patients' personal profiles.

Should We Consider Deep Brain Stimulation Discontinuation in Late-Stage Parkinson's Disease?

BACKGROUND

Subthalamic deep brain stimulation (STN-DBS) effects may decrease with Parkinson's disease (PD) progression. There is no indication if, when, and how to consider the interruption of DBS treatment in late-stage PD. The objective of the current study was to investigate the percentage of "poor stimulation responders" among late-stage PD patients for elaborating an algorithm to decide whether and when DBS discontinuation may be considered.

METHODS

Late-stage PD patients (Hoehn Yahr stage ≥4 and Schwab and England Scale <50 in medication on/stimulation on condition) treated with STN-DBS for at least 5 years underwent a crossover, double-blind, randomized evaluation of acute effects of stimulation. Physicians, caregivers, and patients were blinded to stimulation conditions. Poor stimulation responders (MDS-UPDRS part III change <10% between stimulation on/medication off and stimulation off/medication off) maintained the stimulation off/medication on condition for 1 month for open-label assessment.

RESULTS

Thirty-six patients were included. The acute effect of stimulation was significant (17% MDS-UPDRS part III), with 80% of patients classified as "good responders." Seven patients were classified as "poor stimulation responders," and the stimulation was switched off, but in 4 cases the stimulation was switched back "on" because of worsening of parkinsonism and dysphagia with a variable time delay (up to 10 days). No serious adverse effects occurred.

CONCLUSIONS

The vast majority of late-stage PD patients (92%) show a meaningful response to STN-DBS. Effects of stimulation may take days to disappear after its discontinuation. We present a safe and effective decisional algorithm that could guide physicians and caregivers in making challenging therapeutic decisions in late-stage PD. © 2020 International Parkinson and Movement Disorder Society.

Surgical Treatment of Parkinson Disease

Surgery in Parkinson disease is effective for a select group of patients when optimal medical management is not sufficient. Functional neurosurgery can be used as either a salvage therapy in patients with disabling symptoms or to maintain quality of life and independence before progression to severe disability in high-functioning patients. With recent technological advancements in imaging and targeting as well as novel neuromodulation paradigms, there are numerous options for targeted brain lesions and deep brain stimulation. Surgical decision making and postoperative management in Parkinson disease therefore often requires a multidisciplinary team effort with neurology, neurosurgery, neuropsychology, and psychiatry.