Electrical stimulation of the subthalamic nucleus in advanced Parkinson's disease

Suicide and suicide attempts after subthalamic nucleus stimulation in Parkinson disease

OBJECTIVE

To determine the postoperative attempted and completed suicide rates after subthalamic nucleus deep brain stimulation (STN-DBS) in a single-center cohort and to determine factors associated with attempted and completed suicide.

METHODS

We retrospectively included all patients with Parkinson disease (PD) who underwent bilateral STN-DBS surgery at the Grenoble University Hospital between 1993 and 2016. For each patient who committed or attempted suicide, 2 patients with PD with STN-DBS without any suicidal behaviors were matched for age (±1 year), sex, and year of surgery (±2 years). Clinical data were collected from medical records. Detailed preoperative and postoperative neuropsychological evaluations, including frontal and Beck Depression Inventory (BDI) scores, were gathered.

RESULTS

A total of 534 patients with PD were included. Completed and attempted suicide percentages were 0.75% (4 of 534) and 4.11% (22 of 534), respectively. The observed suicide rate in the first postoperative year (187.20 of 100,000 per year, 1 of 534) was higher than the expected National Observatory on Suicide Risks rate adjusted for age and sex (standardized mortality ratio 8.1). This rate remained similar over the second and third postoperative years. In a comparison of the 26 patients completing/attempting suicide and the 52 controls, the first group showed more frequent history of suicidal ideation/suicide attempts and psychotic symptoms, higher percentage of family psychiatric history, higher psychiatric medication use, and higher preoperative frontal and BDI scores on neuropsychological evaluations.

CONCLUSIONS

Suicide behaviors can occur after STN-DBS, especially during the first 3 years. A careful multidisciplinary assessment and long-term follow-up are recommended to recognize and treat this potentially preventable risk for mortality.

Does Bilateral Deep Brain Stimulation of the Subthalamic Nucleus Modify Ano-Rectal Motility in Parkinson's Disease? Results of a Randomized Cross-Over Study

BACKGROUND

Ano-rectal motility impairment is often observed during Parkinson's disease (PD), generating symptoms as constipation and/or incontinence with impaired quality of life. Subthalamic nuclei (STN) deep brain stimulation (DBS) improves motor symptoms of PD, but its effects on anorectal motility are unknown. This study aimed to assess the effects of STN-DBS on the anorectal motility in PD patients, in a randomized cross-over study.

METHODS

Sixteen PD patients with bilateral STN-DBS for at least 6 months were included. The anal resting pressure, duration and maximal amplitude of squeeze effort, recto-anal inhibitory reflex, maximal tolerable rectal volume, and anal pressure during defecation effort were measured and compared after STN-DBS was switched OFF and then ON for 2 hours, or vice-versa, in a randomized order.

KEY RESULTS

STN-DBS increased maximal amplitude of anal squeezing pressure (OFF: 85.7 ± 14.5 vs ON: 108.4 ± 21.0 cmH₂ O; P = 0.02), with no significant difference in the duration (P = 0.10). No other significant difference was found between stimulation conditions (OFF vs ON) for anal resting pressure (OFF: 72.5 ± 8.6 cmH₂ O vs ON: 71.7 ± 9.0 cmH₂ O; P = 0.24), recto-anal inhibitory reflex, maximal tolerable rectal volume (OFF: 231 ± 24 mL vs ON: 241 ± 26 mL; P = 0.68), or anal pressure during defecation effort with a similar rate of ano-rectal dyssynergia (7/16 and 8/16 with and without STN-DBS, respectively). No order effect (ON-OFF vs OFF-ON) was observed.

CONCLUSION AND INFERENCES

STN-DBS increased anal squeezing pressure, but did not modify anorectal dyssynergia in PD patients, This study demonstrated the involvement of STN in the voluntary control of anorectal motility in PD patients.

A human prefrontal-subthalamic circuit for cognitive control

The subthalamic nucleus is a key site controlling motor function in humans. Deep brain stimulation of the subthalamic nucleus can improve movements in patients with Parkinson's disease; however, for unclear reasons, it can also have cognitive effects. Here, we show that the human subthalamic nucleus is monosynaptically connected with cognitive brain areas such as the prefrontal cortex. Single neurons and field potentials in the subthalamic nucleus are modulated during cognitive processing and are coherent with 4-Hz oscillations in medial prefrontal cortex. These data predict that low-frequency deep brain stimulation may alleviate cognitive deficits in Parkinson's disease patients. In line with this idea, we found that novel 4-Hz deep brain stimulation of the subthalamic nucleus improved cognitive performance. These data support a role for the human hyperdirect pathway in cognitive control, which could have relevance for brain-stimulation therapies aimed at cognitive symptoms of human brain disease.awx300media15660002226001.

Electrode Location in a Microelectrode Recording-Based Model of the Subthalamic Nucleus Can Predict Motor Improvement After Deep Brain Stimulation for Parkinson's Disease

Motor improvement after deep brain stimulation (DBS) in the subthalamic nucleus (STN) may vary substantially between Parkinson’s disease (PD) patients. Research into the relation between improvement and active contact location requires a correction for anatomical variation. We studied the relation between active contact location relative to the neurophysiological STN, estimated by the intraoperative microelectrode recordings (MER-based STN), and contralateral motor improvement after one year. A generic STN shape was transformed to fit onto the stereotactically defined MER sites. The location of 43 electrodes (26 patients), derived from MRI-fused CT images, was expressed relative to this patient-specific MER-based STN. Using regression analyses, the relation between contact location and motor improvement was studied. The regression model that predicts motor improvement based on levodopa effect alone was significantly improved by adding the one-year active contact coordinates (R² change = 0.176, p = 0.014). In the combined prediction model (adjusted R² = 0.389, p < 0.001), the largest contribution was made by the mediolateral location of the active contact (standardized beta = 0.490, p = 0.002). With the MER-based STN as a reference, we were able to find a significant relation between active contact location and motor improvement. MER-based STN modeling can be used to complement imaging-based STN models in the application of DBS.

Quality of life predicts outcome of deep brain stimulation in early Parkinson disease

Objective

To investigate predictors for improvement of disease-specific quality of life (QOL) after deep brain stimulation (DBS) of the subthalamic nucleus (STN) for Parkinson disease (PD) with early motor complications.

Methods

We performed a secondary analysis of data from the previously published EARLYSTIM study, a prospective randomized trial comparing STN-DBS (n = 124) to best medical treatment (n = 127) after 2 years follow-up with disease-specific QOL (39-item Parkinson's Disease Questionnaire summary index [PDQ-39-SI]) as the primary endpoint. Linear regression analyses of the baseline characteristics age, disease duration, duration of motor complications, and disease severity measured at baseline with the Unified Parkinson’s Disease Rating Scale (UPDRS) (UPDRS-III “off” and “on” medications, UPDRS-IV) were conducted to determine predictors of change in PDQ-39-SI.

Results

PDQ-39-SI at baseline was correlated to the change in PDQ-39-SI after 24 months in both treatment groups (p < 0.05). The higher the baseline score (worse QOL) the larger the improvement in QOL after 24 months. No correlation was found for any of the other baseline characteristics analyzed in either treatment group.

Conclusion

Impaired QOL as subjectively evaluated by the patient is the most important predictor of benefit in patients with PD and early motor complications, fulfilling objective gold standard inclusion criteria for STN-DBS. Our results prompt systematically including evaluation of disease-specific QOL when selecting patients with PD for STN-DBS.

Clinicaltrials.gov identifier

NCT00354133.

The Lived Experiences of Deep Brain Stimulation in Parkinson's Disease: An Interpretative Phenomenological Analysis

Deep brain stimulation of the subthalamic nucleus (STN-DBS) is an effective treatment for Parkinson's disease (PD). In this study, we used an interpretative phenomenological analysis to explore how 10 male people with PD experienced life after STN-DBS surgery. Two themes emerged. The first, "Healed and relieved: all that glitters is not gold," highlights the benefits and the personal "costs" of surgery. The second, "The change within: new interpretations of the present and future unfold," explores how patients reinterpreted their lives as individuals and members of society in the present and as they face their future. Relief, gratitude, disappointment, and the need for social support are expressed as well as a new appraisal of values and the future. STN-DBS alters the life course of people with PD, and this study provides new insight into psychological and social issues that surgery raises for the patient and their family system. These psychosocial issues should be taken into account when preparing the patient and their family for surgery or supporting them postoperatively.

Automatic localization of the subthalamic nucleus on patient-specific clinical MRI by incorporating 7 T MRI and machine learning: Application in deep brain stimulation

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has shown clinical potential for relieving the motor symptoms of advanced Parkinson's disease. While accurate localization of the STN is critical for consistent across-patients effective DBS, clear visualization of the STN under standard clinical MR protocols is still challenging. Therefore, intraoperative microelectrode recordings (MER) are incorporated to accurately localize the STN. However, MER require significant neurosurgical expertise and lengthen the surgery time. Recent advances in 7 T MR technology facilitate the ability to clearly visualize the STN. The vast majority of centers, however, still do not have 7 T MRI systems, and fewer have the ability to collect and analyze the data. This work introduces an automatic STN localization framework based on standard clinical MRIs without additional cost in the current DBS planning protocol. Our approach benefits from a large database of 7 T MRI and its clinical MRI pairs. We first model in the 7 T database, using efficient machine learning algorithms, the spatial and geometric dependency between the STN and its adjacent structures (predictors). Given a standard clinical MRI, our method automatically computes the predictors and uses the learned information to predict the patient-specific STN. We validate our proposed method on clinical T2 W MRI of 80 subjects, comparing with experts-segmented STNs from the corresponding 7 T MRI pairs. The experimental results show that our framework provides more accurate and robust patient-specific STN localization than using state-of-the-art atlases. We also demonstrate the clinical feasibility of the proposed technique assessing the post-operative electrode active contact locations.

Clinical and anatomical predictors for freezing of gait and falls after subthalamic deep brain stimulation in Parkinson's disease patients

INTRODUCTION

Freezing of gait (FOG) and falls are the most disabling motor symptoms in Parkinson's disease (PD) patients. The effects of subthalamic deep-brain-stimulation (STN-DBS) on FOG and falls are still a matter of controversy, and factors contributing to their outcome have yet to be defined.

METHODS

We examined the relationship between FOG and falls after STN-DBS and preoperative clinical features, MRI voxel-based-morphometry (VBM) analysis and statistical mapping of electrode locations.

RESULTS

331 patients (age at surgery = 57.7 ± 8.4 years; disease duration = 12.5 ± 5 years) were included in the final analysis, with VBM analysis in 151 patients. After surgery, FOG was aggravated in 93 patients and falls in 75 patients. After surgery, FOG severity was related to its level before surgery without dopaminergic treatment, the dopaminergic treatment dosage and severity of motor fluctuations after surgery; and falls severity to lower postoperative cognitive performance. VBM analyses revealed that, relative to other patient groups, patients with FOG worsening had putamen grey matter density decrease, and fallers patients a left postcentral gyrus atrophy. The best effects of STN-DBS on FOG and falls were associated with the location of contacts within the STN, but no specific location related to aggravation.

CONCLUSIONS

FOG and falls are reduced after STN-DBS in about 1/3 of patients, with the best effects obtained for electrodes located within the STN. Clinicians should be aware that, after STN-DBS, FOG severity is related to preoperative FOG severity whatever its dopa-sensitivity; and falls to lower postoperative cognitive performance; and atrophy of cortico-subcortical brain areas.

Admixing MPTP-resistant and MPTP-vulnerable mice enhances striatal field potentials and calbindin-D28K expression to avert motor behaviour deficits

Asian-Indians are less vulnerable to Parkinson's disease (PD) than the Caucasians. Their admixed populace has even lesser risk. Studying this phenomenon using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-susceptible C57BL/6J, MPTP-resistant CD-1 and their resistant crossbred mice revealed differences in the nigrostriatal cyto-molecular features. Here, we investigated the electrophysiological and behavioural correlates for differential MPTP-susceptibility and their outcome upon admixing. We recorded local field potentials (LFPs) from dorsal striatum and assessed motor co-ordination using rotarod and grip strength measures. Nigral calbindin-D28K expression, a regulator of striatal activity through nigrostriatal projections was evaluated using immunohistochemistry. The crossbreds had significantly higher baseline striatal LFPs. MPTP significantly increased the neuronal activity in delta (0.5-4 Hz) and low beta (12-16 Hz) ranges in C57BL/6J; significant increase across frequency bands till high beta (0.5-30 Hz) in CD-1, and caused no alterations in crossbreds. MPTP further depleted the already low nigral calbindin-D28K expression in C57BL/6J. While in crossbreds, it was further up-regulated. MPTP affected the rotarod and grip strength performance of the C57BL/6J, while the injected CD-1 and crossbreds performed well. The increased striatal β-oscillations are comparable to that in PD patients. Higher power in CD-1 may be compensatory in nature, which were also reported in pre-symptomatic monkeys. Concurrent up-regulation of nigral calbindin-D28K may assist maintenance of striatal activity by buffering calcium overload in nigra. Thus, preserved motor behaviour in PD reminiscent conditions in CD-1 and crossbreds complement compensated/unaffected striatal LFPs. Similar electrophysiological correlates and cytomorphological features are envisaged in human phenomenon of differential PD prevalence, which are modulated upon admixing.

Experimental factors effecting stability of Electrochemical Impedance Spectroscopy Measurements

Impedance measurement using Electrochemical Impedance Spectroscopy is a widely utilized technique in neural electrodes. Research and clinical devices that incorporate stimulating and recording microelectrodes routinely characterize the material's integrity and its functionality through impedance measurement. Nominal impedance values ensure a stable neural electrode-tissue contact capable of passing through power efficient electric signals with desired signal-tonoise ratio or effective volume coverage. However, the complexity of the in vivo environment limits the usage of the three-electrode setup, which has been accepted as the ideal method in providing a stable impedance measurement. Impedance data measured from microelectrodes in threeelectrode and two-electrode setups show that the two setups have similar outcomes in terms of the impedance modulus over a 0.5 Hz-100 kHz frequency range. Usage of a platinum counter electrode lowered the overall variance in impedance readings compared to the stainless steel counter electrode. However, correlation coefficient values $(>0.97)$ between three-electrode and two-electrode setups show that impedance values seldom deviate due to changes in electrode setup. Based on the results of this study, the usage of the two-electrode setup in vivo allowed acceptable electrochemical impedance spectroscopy accuracy, and the utilization of a platinum counter electrode is recommended to reduce measurement variance.

Different effects of levodopa and subthalamic stimulation on emotional conflict in Parkinson's disease

Parkinson's disease impairs the decoding of emotional stimuli reflecting alterations of the limbic cortico-subcortical network. The objective of this study was to assess and compare the behavioral and electrophysiological effects of both levodopa and subthalamic stimulation on emotional processing in Parkinson's disease. Operated patients (n =16) and matched healthy subjects performed an emotional Stroop task, in which the emotion expressed by a face must be recognized while ignoring an emotional distractive word and that includes a neutral control sub-task. Patients were tested in the four possible treatment conditions (off stim/off med; on stim/off med; off stim/on med; and on stim/on med). High-resolution electroencephalography was recorded while performing the task. Patients made significantly more mistakes in facial emotion recognition than healthy subjects (p < .005). Untreated patients performed worse in the emotional trials than in the control sub-task (p < .05). Fearful faces induced significantly slower reaction times than happy faces in patients (p = .0002), but not in the healthy subjects. The emotional Stroop effect with levodopa was significantly higher than with subthalamic stimulation when fearful faces were assessed (p = .0243). Conversely, treatments did not modulate the Stroop effect of the control sub-task. EEG demonstrated that, compared with the untreated state, levodopa but not subthalamic stimulation significantly increases the amplitude of the event-related potential N170 (p = .002 vs. p = .1, respectively), an electrophysiological biomarker of early aspects of facial processing. The activity of the N170 cortical sources within the right fusiform gyrus was increased by levodopa (p < .05) but not by stimulation. While levodopa normalizes the recognition of emotional facial expression and early EEG markers of emotional processing, subthalamic stimulation does not. Thus, operated patients require dopaminergic medication in addition to stimulation to treat emotional symptoms of Parkinson's disease.

Revealing a novel nociceptive network that links the subthalamic nucleus to pain processing

Pain is a prevalent symptom of Parkinson's disease, and is effectively treated by deep brain stimulation of the subthalamic nucleus (STN). However, the link between pain and the STN remains unclear. In the present work, using in vivo electrophysiology in rats, we report that STN neurons exhibit complex tonic and phasic responses to noxious stimuli. We also show that nociception is altered following lesions of the STN, and characterize the role of the superior colliculus and the parabrachial nucleus in the transmission of nociceptive information to the STN, physiologically from both structures and anatomically in the case of the parabrachial nucleus. We show that STN nociceptive responses are abnormal in a rat model of PD, suggesting their dependence on the integrity of the nigrostriatal dopaminergic system. The STN-linked nociceptive network that we reveal is likely to be of considerable clinical importance in neurological diseases involving a dysfunction of the basal ganglia.

Longer β oscillatory episodes reliably identify pathological subthalamic activity in Parkinsonism

BACKGROUND

The efficacy of deep brain stimulation (DBS) - primarily of the subthalamic nucleus (STN) - for advanced Parkinson's disease (PD) is commonly attributed to the suppression of pathological synchronous β oscillations along the cortico-thalamo-basal ganglia network. Conventional continuous high-frequency DBS indiscriminately influences pathological and normal neural activity. The DBS protocol would therefore be more effective if stimulation was only applied when necessary (closed-loop adaptive DBS).

OBJECTIVES AND METHODS

Our study aimed to identify a reliable biomarker of the pathological neuronal activity in parkinsonism that could be used as a trigger for adaptive DBS. To this end, we examined the oscillatory features of paired spiking activities recorded in three distinct nodes of the basal ganglia network of 2 African green monkeys before and after induction of parkinsonism (by MPTP intoxication).

RESULTS

Parkinsonism-related basal ganglia β oscillations consisted of synchronized time-limited episodes, rather than a continuous stretch, of β oscillatory activity. Episodic basal ganglia β oscillatory activity, although prolonged in parkinsonism, was not necessarily pathological given that short β episodes could also be detected in the healthy state. Importantly, prolongation of the basal ganglia β episodes was more pronounced than their intensification in the parkinsonian state-especially in the STN. Hence, deletion of longer β episodes was more effective than deletion of stronger β episodes in reducing parkinsonian STN synchronized oscillatory activity.

CONCLUSIONS

Prolonged STN β episodes are pathological in parkinsonism and can be used as optimal trigger for future adaptive DBS applications. © 2018 International Parkinson and Movement Disorder Society.

Development, Modeling, Fabrication, and Characterization of a Magnetic, Micro-Spring-Suspended System for the Safe Electrical Interconnection of Neural Implants

The development of innovative tools for neuroscientific research is based on in vivo tests typically applied to small animals. Most often, the interfacing of neural probes relies on commercially available connector systems which are difficult to handle during connection, particularly when freely behaving animals are involved. Furthermore, the connectors often exert high mechanical forces during plugging and unplugging, potentially damaging the fragile bone structure. In order to facilitate connector usage and increase the safety of laboratory animals, we developed a new magnetic connector system circumventing the drawbacks of existing tools. The connector system uses multiple magnet pairs and spring-suspended electrical contact pads realized using micro-electromechanical systems (MEMS) technologies. While the contact pad suspension increases the system tolerance in view of geometrical variations, we achieved a reliable self-alignment of the connector parts at ±50 µm provided by the specifically oriented magnet pairs and without the need of alignment pins. While connection forces are negligible, we can adjust the forces during connector release by modifying the magnet distance. With the connector test structures developed here, we achieved an electrical connection yield of 100%. Based on these findings, we expect that in vivo experiments with freely behaving animals will be facilitated with improved animal safety.

Ceftriaxone Treatment for Neuronal Deficits: A Histological and MEMRI Study in a Rat Model of Dementia with Lewy Bodies

Dementia with Lewy bodies (DLB) is characterized by neuronal deficits and α-synuclein inclusions in the brain. Ceftriaxone (CEF), a β-lactam antibiotic, has been suggested as a therapeutic agent in several neurodegenerative disorders for its abilities to counteract glutamate-mediated toxicity and to block α-synuclein polymerization. By using manganese-enhanced magnetic resonance imaging (MEMRI) and immunohistochemistry, we measured the effects of CEF on neuronal activity and α-synuclein accumulation in the brain in a DLB rat model. The data showed that CEF corrected neuronal density and activity in the hippocampal CA1 area, suppressed hyperactivity in the subthalamic nucleus, and reduced α-synuclein accumulation, indicating that CEF is a potential agent in the treatment of DLB.

Substituting the Target After Unsatisfactory Outcome of Deep Brain Stimulation in Advanced Parkinson's Disease: Cases From the NSTAPS Trial and Systematic Review of the Literature

BACKGROUND

Deep brain stimulation (DBS) of the globus pallidus pars interna (GPi) and the subthalamic nucleus (STN) are established treatment option in Parkinson's disease (PD). If DBS does not provide the desired effect, re-operation to the alternative target is a treatment option, but data on the effect of re-operation are scarce.

OBJECTIVES

The objective of this study is to evaluate the clinical effect of re-operation the alternative target after failure of initial STN or GPi DBS for Parkinson's disease.

MATERIALS AND METHODS

We descriptively analyzed the baseline characteristics, the effect of initial surgery and re-operation of eight NSTAPS (Netherlands SubThalamic and Pallidal Stimulation) patients and six previously published cases that underwent re-operation to a different target.

RESULTS

In the NSTAPS cohort, two of the eight patients showed more than 30% improvement of off-drug motor symptoms after re-operation. The initial DBS leads of these patients were off target. In the cases from the literature, 30% off-drug motor improvement was seen in all three patients re-operated from GPi to STN and none of the three patients re-operated from STN to GPi. Only one of the three cases from the literature where any improvement was seen with the operation had a confirmed on target lead location after the first surgery, while the other two patients did not undergo post-operative imaging after the first surgery.

CONCLUSIONS

Re-operation to a different target due to lack of effect appears to have a limited chance of leading to objective improvement if the leads were correctly placed during initial surgery.

Subthalamic stimulation and neuropsychiatric symptoms in Parkinson's disease: results from a long-term follow-up cohort study

BACKGROUND

Reports on behavioural outcomes after subthalamic nucleus deep brain stimulation in Parkinson's disease are controversial and limited to short-term data. Long-term observation in a large cohort allows a better counselling and management.

METHODS

To determine whether a long-term treatment with subthalamic stimulation induces or reduces impulse control behaviours, neuropsychiatric fluctuations and apathy, 69 patients treated with subthalamic stimulation are prospectively and retrospectively assessed using Ardouin Scale of Behavior in Parkinson's Disease before and after 3-10 years of stimulation.

RESULTS

At a mean follow-up of 6 years, all impulse control disorders and dopaminergic addiction were significantly decreased, apart from eating behaviour and hypersexuality. Neuropsychiatric fluctuations also significantly improved (ON euphoria: 38% of the patients before surgery and 1% after surgery, P<0.01; OFF dysphoria: 39% of the patients before surgery and 10% after surgery, P<0.01). However, apathy increased (25% of the patients after surgery and 3% before, P<0.01). With the retrospective analysis, several transient episodes of depression, apathy, anxiety and impulse control disorders occurred.

CONCLUSIONS

Bilateral subthalamic nucleus stimulation was overall very effective in improving impulse control disorders and neuropsychiatric fluctuations in parkinsonian patients in the long term despite a counteracting frequent apathy. Transient episodes of impulse control disorders still occurred within the follow-up. These findings recommend a close follow-up in parkinsonian patients presenting with neuropsychiatric symptoms before deep brain stimulation surgery.

CLINICAL TRIAL REGISTRATION

NCT01705418;Post-results.

Deep Brain Stimulation in Moroccan Patients With Parkinson's Disease: The Experience of Neurology Department of Rabat

Introduction: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is known as a therapy of choice of advanced Parkinson's disease. The present study aimed to assess the beneficial and side effects of STN DBS in Moroccan Parkinsonian patients. Material and Methods: Thirty five patients underwent bilateral STN DBS from 2008 to 2016 in the Rabat University Hospital. Patients were assessed preoperatively and followed up for 6 to 12 months using the Unified Parkinson's Disease Rating Scale in four conditions (stimulation OFF and ON and medication OFF and ON), the levodopa-equivalent daily dose (LEDD), dyskinesia and fluctuation scores and PDQ39 scale for quality of life (QOL). Postoperative side effects were also recorded. Results: The mean age at disease onset was 42.31 ± 7.29 years [28-58] and the mean age at surgery was 54.66 ± 8.51 years [34-70]. The median disease duration was 11.95 ± 4.28 years [5-22]. Sixty-three percentage of patients were male. 11.4% of patients were tremor dominant while 45.71 showed akinetic-rigid form and 42.90 were classified as mixed phenotype. The LEDD before surgery was 1200 mg/day [800-1500]. All patients had motor fluctuations whereas non-motor fluctuations were present in 61.80% of cases. STN DBS decreased the LEDD by 51.72%, as the mean LEDD post-surgery was 450 [188-800]. The UPDRS-III was improved by 52.27%, dyskinesia score by 66.70% and motor fluctuations by 50%, whereas QOL improved by 27.12%. Post-operative side effects were hypophonia (2 cases), infection (3 cases), and pneumocephalus (2 cases). Conclusion: Our results showed that STN DBS is an effective treatment in Moroccan Parkinsonian patients leading to a major improvement of the most disabling symptoms (dyskinesia, motor fluctuation) and a better QOL.

Functional Connectivity-Based Modelling Simulates Subject-Specific Network Spreading Effects of Focal Brain Stimulation

Neurostimulation remarkably alleviates the symptoms in a variety of brain disorders by modulating the brain-wide network. However, how brain-wide effects on the direct and indirect pathways evoked by focal neurostimulation elicit therapeutic effects in an individual patient is unknown. Understanding this remains crucial for advancing neural circuit-based guidance to optimize candidate patient screening, pre-surgical target selection, and post-surgical parameter tuning. To address this issue, we propose a functional brain connectome-based modeling approach that simulates the spreading effects of stimulating different brain regions and quantifies the rectification of abnormal network topology in silico. We validated these analyses by pinpointing nuclei in the basal ganglia circuits as top-ranked targets for 43 local patients with Parkinson’s disease and 90 patients from a public database. Individual connectome-based analysis demonstrated that the globus pallidus was the best choice for 21.1% and the subthalamic nucleus for 19.5% of patients. Down-regulation of functional connectivity (up to 12%) at these prioritized targets optimally maximized the therapeutic effects. Notably, the priority rank of the subthalamic nucleus significantly correlated with motor symptom severity (Unified Parkinson’s Disease Rating Scale III) in the local cohort. These findings underscore the potential of neural network modeling for advancing personalized brain stimulation therapy, and warrant future experimental investigation to validate its clinical utility.

Awake versus asleep deep brain stimulation for Parkinson's disease: a critical comparison and meta-analysis

OBJECTIVE

No definitive comparative studies of the efficacy of 'awake' deep brain stimulation (DBS) for Parkinson's disease (PD) under local or general anaesthesia exist, and there remains significant debate within the field regarding differences in outcomes between these two techniques.

METHODS

We conducted a literature review and meta-analysis of all published DBS for PD studies (n=2563) on PubMed from January 2004 to November 2015. Inclusion criteria included patient number >15, report of precision and/or clinical outcomes data, and at least 6 months of follow-up. There were 145 studies, 16 of which were under general anaesthesia. Data were pooled using an inverse-variance weighted, random effects meta-analytic model for observational data.

RESULTS

There was no significant difference in mean target error between local and general anaesthesia, but there was a significantly less mean number of DBS lead passes with general anaesthesia (p=0.006). There were also significant decreases in DBS complications, with fewer intracerebral haemorrhages and infections with general anaesthesia (p<0.001). There were no significant differences in Unified Parkinson's Disease Rating Scale (UPDRS) Section II scores off medication, UPDRS III scores off and on medication or levodopa equivalent doses between the two techniques. Awake DBS cohorts had a significantly greater decrease in treatment-related side effects as measured by the UPDRS IV off medication score (78.4% awake vs 59.7% asleep, p=0.022).

CONCLUSIONS

Our meta-analysis demonstrates that while DBS under general anaesthesia may lead to lower complication rates overall, awake DBS may lead to less treatment-induced side effects. Nevertheless, there were no significant differences in clinical motor outcomes between the two techniques. Thus, DBS under general anaesthesia can be considered at experienced centres in patients who are not candidates for traditional awake DBS or prefer the asleep alternative.

Subthalamic deep brain stimulation influences complex emotional musical experience in Parkinson's disease

Subthalamic deep brain stimulation (STN DBS) is an effective treatment for reducing the motor symptoms of patients with Parkinson's disease (PD), but several side effects have been reported, concerning the processing of emotions. Music has been shown to evoke powerful emotional experiences - not only basic emotions, but also complex, so-called aesthetic experiences. The goal of the present study was therefore to investigate how STN DBS influences the experience of both basic and more complex musical emotions in patients with PD. In a three-group between-participants design, we compared healthy controls (HC), patients receiving STN DBS (PD-DBS), and patients who were candidates for STN DBS and receiving medication only (PD-MO) on their assessments of subjectively experienced musical emotions. Results showed that in general, the experience of musical emotions differed only marginally between the PD-MO, PD-DBS, and HC groups. Nonetheless, we were able to discern subtle but distinct effects of PD and STN DBS in the emotional responses. Happy music, for instance, seemed to induce a heightened experience of negative emotions (tension) in PD-MO patients. STN DBS appeared to normalize this particular effect, but increased nostalgic feelings - a rather complex affective experience - in response to the same emotional stimuli. This should not be taken as indicating a bias for nostalgia in the PD-DBS subgroup, as these patients found music inducing melancholy to be less nostalgic and more joyful than HC did. In conclusion, our study showed that music elicits slightly altered emotional experiences in patients with and without STN DBS. In particular, STN DBS seems to induce less distinct emotional responses, blurring the boundaries between complex musical emotions.

Semi-automated application for estimating subthalamic nucleus boundaries and optimal target selection for deep brain stimulation implantation surgery

OBJECTIVEDeep brain stimulation (DBS) of the subthalamic nucleus (STN) has become standard care for the surgical treatment of Parkinson's disease (PD). Reliable interpretation of microelectrode recording (MER) data, used to guide DBS implantation surgery, requires expert electrophysiological evaluation. Recent efforts have endeavored to use electrophysiological signals for automatic detection of relevant brain structures and optimal implant target location.The authors conducted an observational case-control study to evaluate a software package implemented on an electrophysiological recording system to provide online objective estimates for entry into and exit from the STN. In addition, they evaluated the accuracy of the software in selecting electrode track and depth for DBS implantation into STN, which relied on detecting changes in spectrum activity.METHODSData were retrospectively collected from 105 MER-guided STN-DBS surgeries (4 experienced neurosurgeons; 3 sites), in which estimates for entry into and exit from the STN, DBS track selection, and implant depth were compared post hoc between those determined by the software and those determined by the implanting neurosurgeon/neurophysiologist during surgery.RESULTSThis multicenter study revealed submillimetric agreement between surgeon/neurophysiologist and software for entry into and exit out of the STN as well as optimal DBS implant depth.CONCLUSIONSThe results of this study demonstrate that the software can reliably and accurately estimate entry into and exit from the STN and select the track corresponding to ultimate DBS implantation.

Unilateral deep brain stimulation suppresses alpha and beta oscillations in sensorimotor cortices

Deep brain stimulation (DBS) is an established therapy to treat motor symptoms in movement disorders such as Parkinson's disease (PD). The mechanisms leading to the high therapeutic effectiveness of DBS are poorly understood so far, but modulation of oscillatory activity is likely to play an important role. Thus, investigating the effect of DBS on cortical oscillatory activity can help clarifying the neurophysiological mechanisms of DBS. Here, we aimed at scrutinizing changes of cortical oscillatory activity by DBS at different frequencies using magnetoencephalography (MEG). MEG data from 17 PD patients were acquired during DBS of the subthalamic nucleus (STN) the day after electrode implantation and before implanting the pulse generator. We stimulated the STN unilaterally at two different stimulation frequencies, 130 Hz and 340 Hz using an external stimulator. Data from six patients had to be discarded due to strong artefacts and two other datasets were excluded since these patients were not able to finalize the paradigm. After DBS artefact removal, power spectral density (PSD) values of MEG were calculated for each individual patient and averaged over the group. DBS at both 130 Hz and 340 Hz led to a widespread suppression of cortical alpha/beta band activity (8-22 Hz) specifically over bilateral sensorimotor cortices. No significant differences were observed between the two stimulation frequencies. Our finding of a widespread suppression of cortical alpha/beta band activity is particularly interesting as PD is associated with pathologically increased levels of beta band activity in the basal ganglia-thalamo-cortical circuit. Therefore, suppression of such oscillatory activity might be an essential effect of DBS for relieving motor symptoms in PD and can be achieved at different stimulation frequencies above 100 Hz.

Deep Brain Stimulation of the Subthalamic Nucleus Parameter Optimization for Vowel Acoustics and Speech Intelligibility in Parkinson's Disease

PURPOSE

The settings of 3 electrical stimulation parameters were adjusted in 12 speakers with Parkinson's disease (PD) with deep brain stimulation of the subthalamic nucleus (STN-DBS) to examine their effects on vowel acoustics and speech intelligibility.

METHOD

Participants were tested under permutations of low, mid, and high STN-DBS frequency, voltage, and pulse width settings. At each session, participants recited a sentence. Acoustic characteristics of vowel production were extracted, and naive listeners provided estimates of speech intelligibility.

RESULTS

Overall, lower-frequency STN-DBS stimulation (60 Hz) was found to lead to improvements in intelligibility and acoustic vowel expansion. An interaction between speaker sex and STN-DBS stimulation was found for vowel measures. The combination of low frequency, mid to high voltage, and low to mid pulse width led to optimal speech outcomes; however, these settings did not demonstrate significant speech outcome differences compared with the standard clinical STN-DBS settings, likely due to substantial individual variability.

CONCLUSIONS

Although lower-frequency STN-DBS stimulation was found to yield consistent improvements in speech outcomes, it was not found to necessarily lead to the best speech outcomes for all participants. Nevertheless, frequency may serve as a starting point to explore settings that will optimize an individual's speech outcomes following STN-DBS surgery.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.5899228.

Electroacupuncture Alleviates Motor Symptoms and Up-Regulates Vesicular Glutamatergic Transporter 1 Expression in the Subthalamic Nucleus in a Unilateral 6-Hydroxydopamine-Lesioned Hemi-Parkinsonian Rat Model

Previous studies have shown that electroacupuncture (EA) promotes recovery of motor function in Parkinson's disease (PD). However the mechanisms are not completely understood. Clinically, the subthalamic nucleus (STN) is a critical target for deep brain stimulation treatment of PD, and vesicular glutamate transporter 1 (VGluT1) plays an important role in the modulation of glutamate in the STN derived from the cortex. In this study, a 6-hydroxydopamine (6-OHDA)-lesioned rat model of PD was treated with 100 Hz EA for 4 weeks. Immunohistochemical analysis of tyrosine hydroxylase (TH) showed that EA treatment had no effect on TH expression in the ipsilateral striatum or substantia nigra pars compacta, though it alleviated several of the parkinsonian motor symptoms. Compared with the hemi-parkinsonian rats without EA treatment, the 100 Hz EA treatment significantly decreased apomorphine-induced rotation and increased the latency in the Rotarod test. Notably, the EA treatment reversed the 6-OHDA-induced down-regulation of VGluT1 in the STN. The results demonstrated that EA alleviated motor symptoms and up-regulated VGluT1 in the ipsilateral STN of hemi-parkinsonian rats, suggesting that up-regulation of VGluT1 in the STN may be related to the effects of EA on parkinsonian motor symptoms via restoration of function in the cortico-STN pathway.

Neuropsychological performance changes following subthalamic versus pallidal deep brain stimulation in Parkinson's disease: a systematic review and metaanalysis

BACKGROUND

Studies comparing subthalamus (STN) and globus pallidus internus (GPi) deep brain stimulation (DBS) for the management of Parkinson's disease in terms of neuropsychological performance are scarce and heterogeneous. Therefore, we performed a systematic review and metaanalysis to compare neuropsychological outcomes following STN DBS versus GPi DBS.

METHODS

A computer literature search of PubMed, the Web of Science, and Cochrane Central was conducted. Records were screened for eligible studies, and data were extracted and synthesized using Review Manager (v. 5.3 for Windows).

RESULTS

Seven studies were included in the qualitative synthesis. Of them, four randomized controlled trials (n=345 patients) were pooled in the metaanalysis models. The standardized mean difference (SMD) of change in the Stroop color-naming test favored the GPi DBS group (SMD=-0.31, p=0.009). However, other neuropsychological outcomes did not favor either of the two groups (Stroop word-reading: SMD=-0.21, p=0.08; the Wechsler Adult Intelligence Scale (WAIS) digits forward: SMD=0.08, p=0.47; Trail Making Test Part A: SMD=-0.05, p=0.65; WAIS-R digit symbol: SMD=-0.16, p=0.29; Trail Making Test Part B: SMD=-0.14, p=0.23; Stroop color-word interference: SMD=-0.16, p=0.18; phonemic verbal fluency: bilateral DBS SMD=-0.04, p=0.73, and unilateral DBS SMD=-0.05, p=0.83; semantic verbal fluency: bilateral DBS SMD=-0.09, p=0.37, and unilateral DBS SMD=-0.29, p=0.22; Boston Naming Test: SMD=-0.11, p=0.33; Beck Depression Inventory: bilateral DBS SMD=0.15, p=0.31, and unilateral DBS SMD=0.36, p=0.11).

CONCLUSIONS

There was no statistically significant difference in most of the neuropsychological outcomes. The present evidence does not favor any of the targets in terms of neuropsychological performance.

Subthalamic Nucleus Deep Brain Stimulation in Parkinson's Disease: The Effect of Varying Stimulation Parameters

Subthalamic Nucleus Deep Brain Stimulation (STN DBS) is a well-established and effective treatment modality for selected patients with Parkinson's disease (PD). Since its advent, systematic exploration of the effect of stimulation parameters including the stimulation intensity, frequency, and pulse width have been carried out to establish optimal therapeutic ranges. This review examines published data on these stimulation parameters in terms of efficacy of treatment and adverse effects. Altering stimulation intensity is the mainstay of titration in DBS programming via alterations in voltage or current settings, and is characterised by a lower efficacy threshold and a higher side effect threshold which define the therapeutic window. In addition, much work has been done in exploring the effects of frequency modulation, which may help patients with gait freezing and other axial symptoms. However, there is a paucity of data on the use of ultra-short pulse width settings which are now possible with technological advances. We also discuss current evidence for the use of novel programming techniques including directional and adaptive stimulation, and highlight areas for future research.

Electrical Neural Stimulation and Simultaneous in Vivo Monitoring with Transparent Graphene Electrode Arrays Implanted in GCaMP6f Mice

Electrical stimulation using implantable electrodes is widely used to treat various neuronal disorders such as Parkinson's disease and epilepsy and is a widely used research tool in neuroscience studies. However, to date, devices that help better understand the mechanisms of electrical stimulation in neural tissues have been limited to opaque neural electrodes. Imaging spatiotemporal neural responses to electrical stimulation with minimal artifact could allow for various studies that are impossible with existing opaque electrodes. Here, we demonstrate electrical brain stimulation and simultaneous optical monitoring of the underlying neural tissues using carbon-based, fully transparent graphene electrodes implanted in GCaMP6f mice. Fluorescence imaging of neural activity for varying electrical stimulation parameters was conducted with minimal image artifact through transparent graphene electrodes. In addition, full-field imaging of electrical stimulation verified more efficient neural activation with cathode leading stimulation compared to anode leading stimulation. We have characterized the charge density limitation of capacitive four-layer graphene electrodes as 116.07-174.10 μC/cm² based on electrochemical impedance spectroscopy, cyclic voltammetry, failure bench testing, and in vivo testing. This study demonstrates the transparent ability of graphene neural electrodes and provides a method to further increase understanding and potentially improve therapeutic electrical stimulation in the central and peripheral nervous systems.

Stopping and slowing manual and spoken responses: Similar oscillatory signatures recorded from the subthalamic nucleus

Response control in the forms of stopping and slowing responses is thought to be implemented by a frontal-subcortical network, which includes the subthalamic nucleus (STN). For manual control, stopping is linked to STN beta (13-30 Hz) and slowing responses are linked to lower frequencies (<12 Hz). Whether similar STN oscillatory activities are associated with the control of spoken responses is not clear. We studied 16 patients with STN LFP recordings during manual and vocal stop signal tasks in two experiments. We found increased beta activities for stopping spoken responses, similar to manual stopping. However, unlike manual stopping, stopping spoken responses elicited a right-lateralized beta power increase, which may be related to previously reported hyperactivity of right-sided motor control regions in stuttering. We additionally studied STN power changes associated with slowing responses in the same stop-signal tasks by comparing slower vs. faster go trials. Now, rather than beta, there was an alpha power increase after Go cues, which remained elevated only in slower Go trials in both the vocal and manual tasks. These data show that different types of response control are generalizable across effectors and relate to different frequencies recorded from the STN.

Parkinson disease

Parkinson disease (PD) is a complex, multisystem disorder with both neurologic and systemic nonmotor manifestations. It is neurodegenerative in nature in which disordered balance, gait, and falls are universal problems that can be present at initial diagnosis, and which progress over time. Freezing of gait is a particularly debilitating feature of PD that becomes more prevalent over time with disease progression, being present in approximately 7% after 2 years of disease and 28% after 5 years. Approximately 60% of people with PD fall each year, with around 70% of fallers falling recurrently, and some recurrent fallers falling multiple times per week. Many risk factors for falls in people with PD have been identified; these include a history of falls, freezing of gait, and abnormalities in measures of balance, leg muscle strength, mobility, cognition, and fear of falling. Therapies for improving physical function and mobility include levodopa, cholinesterase inhibitors, methylphenidate, deep-brain stimulation, cuing for freezing of gait, and exercise. This chapter reviews the clinical, pathologic, and physiologic correlates of gait disturbance and falls in PD, as well as the evidence for medical and nonmedical interventions.

Dopamine dysregulation syndrome in Parkinson's disease: a systematic review of published cases

OBJECTIVES

Dopamine dysregulation syndrome (DDS) is an uncommon complication of the treatment of Parkinson's disease, characterised by addictive behaviour and excessive use of dopaminergic medication. DDS may frequently go unrecognised or misdiagnosed. We aimed to clarify current understanding of presentation, risk factors, comorbidities and management of DDS.

METHODS

Case reports were identified through a systematic search of databases (PubMed, Embase) with the following terms: dopaminergic dysregulation syndrome, hedonistic homeostatic dysregulation, dopamine/levodopa addiction.

RESULTS

We reviewed 390 articles, identifying 98 cases of DDS. Early-onset Parkinson's disease (67%) and male gender (83%) were common. DDS presented with significant physical and social impairment, actions to enable or prevent detection of overuse, as well as mood, anxiety and motor fluctuations. All DDS cases met DSM-V (Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition) substance use disorder criteria. Past substance and psychiatric history was present in 15.3% and 10.2% of cases. Comorbid impulse control disorders (61%), psychosis (32%) and panic attacks (14%) were common. A large variety of management strategies were used; only 56% of cases resolving. Sodium valproate was successful in 5/5 cases. The response to deep brain stimulation varied.

CONCLUSIONS

Given the functional impairment, medical and psychiatric consequences and the difficulties of treatment, early identification of DDS should be a priority.

Cognitive Impact of Deep Brain Stimulation on Parkinson's Disease Patients

Subthalamic nucleus (STN) or globus pallidus interna (GPi) deep brain stimulation (DBS) is considered a robust therapeutic tool in the treatment of Parkinson's disease (PD) patients, although it has been reported to potentially cause cognitive decline in some cases. We here provide an in-depth and critical review of the current literature regarding cognition after DBS in PD, summarizing the available data on the impact of STN and GPi DBS as monotherapies and also comparative data across these two therapies on 7 cognitive domains. We provide evidence that, in appropriately screened PD patients, worsening of one or more cognitive functions is rare and subtle after DBS, without negative impact on quality of life, and that there is very little data supporting that STN DBS has a worse cognitive outcome than GPi DBS.

Electrical Properties Tomography Based on $B_{{1}}$ Maps in MRI: Principles, Applications, and Challenges

OBJECTIVE

The purpose is to provide a comprehensive review of the electrical properties tomography (EPT) technique, which was introduced to image the electrical properties (EPs) of tissue noninvasively by exploiting the measured field data of MRI.

METHODS

We reviewed the principle of EPT, reconstruction methods, biomedical applications such as tumor imaging, and existing challenges. As a key application of EPT, the estimation of specific absorption rate (SAR) due to MRI was discussed in the background of elevated risk of tissue heating at high field.

RESULTS AND CONCLUSION

Since the originally proposed local, homogeneous Helmholtz equation-based reconstruction algorithm, advanced EPT algorithms have emerged to address the challenges of EPT, including reconstruction error near tissue boundaries, noise sensitivity, inaccurate phase estimation, and elimination of the unmeasurable component, along with demonstrations of in vivo experiments. EPT techniques have been applied to investigate EPs of both healthy and pathological tissues in vivo and factors contributing to various EP value, including sodium, water content, etc. More studies are anticipated to consolidate the current findings. EPT-based subject-specific SAR estimation has led to in vivo demonstration of its feasibility and prediction of temperature increase of phantom during MRI scans merely using measured data.

SIGNIFICANCE

EPT has the advantage of high resolution and practical feasibility in a clinical setup for imaging the biomedically interesting EPs of tissue in the radiofrequency range. EPT-based SAR estimation is another promising topic for predicting tissue heating of individual subjects during a specific MRI scan.

The Relationship of Electrophysiologic Subthalamic Nucleus Length as a Predictor of Outcomes in Deep Brain Stimulation for Parkinson Disease

BACKGROUND

Intraoperative measurement of subthalamic nucleus (STN) width through microelectrode recording (MER) is a common proxy for optimal electrode location during deep brain stimulation (DBS) surgery for Parkinson disease. We assessed whether the MER-determined STN width is a predictor of postoperative Unified Parkinson Disease Rating Scale (UPDRS) improvement.

METHODS

Records were reviewed for patients who underwent single-sided STN DBS placement for Parkinson disease between 2005 and 2010 at the UAB Medical Center. Reviews of preoperative and 3-month postoperative UPDRS part III, intraoperative MER records, and postoperative MRI scans were conducted.

RESULTS

The final cohort consisted of 73 patients (mean age 59 ± 9.7 years, length of disease 13 ± 9.7 years). STN widths were defined as depths associated with increased background activity and motor-driven, spiking action potentials on MER. The mean contralateral UPDRS improvement was 58% (± 24). The mean STN width was 5.1 mm (± 1.6, min = 0.0, max = 8.7). No significant relationship between STN width and UPDRS improvement was found, with and without AC-PC normalization (R2 < 0.05).

CONCLUSION

This analysis raises questions about seeking the maximal electrophysiological width of STN as a proxy for optimal outcome in DBS for PD. We suggest this strategy for DBS placement in Parkinson disease be subject to more robust prospective investigation.

Comparison of General and Local Anesthesia for Deep Brain Stimulator Insertion: A Systematic Review

BACKGROUND

Subthalamic nucleus deep brain stimulation (STN-DBS) has become a standard treatment for many patients with Parkinson's disease (PD). The reported clinical outcome measures for procedures done under general anesthesia (GA) compared to traditional local anesthetic (LA) technique are quite heterogeneous and difficult to compare. The aim of this systematic review and metaanalysis was to determine whether the clinical outcome after STN-DBS insertion under GA is comparable to that under LA in patients with Parkinson's disease.

METHODS

The databases of Medline Embase, Cochrane library and Pubmed were searched for eligible studies (human trials, English language, published between 1946 and January of 2016). The primary outcome of this study was to assess the postoperative improvement in the symptoms, evaluated using either Unified Parkinson's Disease Rating Scale (UPDRS) scores or levodopa equivalent dosage (LEDD) requirement.

RESULTS

The literature searches yielded 395 citations and six retrospective cohort studies with a sample size of 455 (194 in GA and 261 in LA) were included in the analysis. Regarding the clinical outcomes, there were no significant differences in the postoperative Unified Parkinson's disease rating scale and levodopa equivalent drug dosage between the GA and the LA groups. Similarly, the adverse events and target accuracy were also comparable between the groups.

CONCLUSIONS

This systematic review and meta-analysis shows that currently there is no good quality data to suggest equivalence of GA to LA during STN-DBS insertion in patients with PD, with some factors trending towards LA. There is a need for a prospective randomized control trial to validate our results.

Pathological crying induced by deep brain stimulation of the subthalamic nucleus in Parkinson's disease

We report on a patient with deep brain stimulation (DBS) of the subthalamic nucleus (STN) for Parkinson's disease (PD) who developed pathologic crying (PC) immediately postoperatively. A spread of DBS current to adjacent cortico-ponto-cerebellar pathways might be responsible. In contrast to the few cases published previously, there was no pre-existing additional lesion that would have favoured occurrence of PC. Treating physicians should be aware of DBS-induced PC.