Long term effects of bilateral subthalamic nucleus stimulation on cognitive function, mood, and behaviour in Parkinson's disease

Pavlovian bias in Parkinson's disease: an objective marker of impulsivity that modulates with deep brain stimulation

Impulsivity is a common symptom in Parkinson's disease (PD). Adaptive behavior is influenced by prepotent action-reward and inaction-avoid loss Pavlovian biases. We aimed to assess the hypothesis that impulsivity in PD is associated with Pavlovian bias, and to assess whether dopaminergic medications and deep brain stimulation (DBS) influence Pavlovian bias. A PD DBS cohort (N = 37) completed a reward-based Go/No-Go task and bias measures were calculated. This DBS cohort completed the task under three conditions: on-med/pre-DBS, off-med/off-DBS, and on-med/on-DBS. Participants also completed self-reported measures of impulsivity. Dopaminergic medication was associated with lower action-reward bias while DBS was associated with higher action-reward bias. Impulsivity was associated with higher action-reward bias but not inaction-avoid loss bias. We furthermore replicated this association in an independent, non-DBS PD cohort (N = 88). Overall we establish an objective behavioral marker of impulsivity and show that DBS affects impulsivity by amplifying automated responding. Our results point to the importance of reward rather than punishment avoidance in driving impulsive behaviors. This work provides insight into the pathophysiological underpinnings of impulsivity and especially medication and DBS-associated impulsivity in PD.

Suicide and suicide attempts after subthalamic nucleus stimulation in Parkinson's disease: a systematic review and meta-analysis

BACKGROUND

Deep-brain stimulation is a well-established, effective treatment for patients with advanced Parkinson's disease. Recent studies examining rates of suicide attempts and suicides after deep-brain stimulation in the bilateral subthalamic nucleus have reported varying results. Using this systematic review and meta-analysis, we aim to obtain a comprehensive understanding of suicidality in Parkinson's patients after subthalamic nucleus deep brain stimulation.

METHODS

We systematically examined Medline, PubMed, Web of Science, and Embase databases to identify studies published before November 2019 that measured rates of suicidality in Parkinson's patients who underwent subthalamic nucleus stimulation. A meta-analysis of the data from the included studies was conducted using Stata 12.0.

RESULTS

A total of 18 studies met the eligibility criteria of this study. We found that the pooled rate of suicidal ideation was 4% (95% CI 0.00-7.2%, range 2-17%). The pooled rate of suicide attempts was 1% (95% CI 1.0-2.0%), while the pooled rate of suicide was 1% (95% CI 0.0-1.0%).

CONCLUSIONS

Our findings indicate a relatively high rate of suicidality among Parkinson's patients after subthalamic nucleus deep-brain stimulation. It is important for clinicians to carefully monitor psychiatric disorders, especially suicidal ideation and suicide attempts, in Parkinson's patients before and after subthalamic nucleus deep-brain stimulation.

Executive Functions in Parkinson's disease with and without Deep Brain Stimulation (DBS): A systematic review

Given the aging of the world population, it is essential to investigate which methods are most effective for treating the diseases that manifest with age. This study addresses Parkinson’s disease (PD), for which Deep Brain Stimulation (DBS) has been increasingly used to treat the disease.

A prospective, controlled study of non-motor effects of subthalamic stimulation in Parkinson's disease: results at the 36-month follow-up

OBJECTIVE

To examine 36-month effects of bilateral subthalamic nucleus deep brain stimulation (STN-DBS) on non-motor symptoms (NMS) compared with standard-of-care medical treatment (MED) in Parkinson's disease (PD).

METHODS

Here we report the 36-month follow-up of a prospective, observational, controlled, international multicentre study of the NILS cohort. Assessments included NMSScale (NMSS), PDQuestionnaire-8 (PDQ-8), Scales for Outcomes in PD (SCOPA)-motor examination, -activities of daily living, and -complications, and levodopa equivalent daily dose (LEDD). Propensity score matching resulted in a pseudo-randomised sub-cohort balancing baseline demographic and clinical characteristics between the STN-DBS and MED groups. Within-group longitudinal outcome changes were analysed using Wilcoxon signed-rank and between-group differences of change scores with Mann-Whitney U test. Strength of clinical responses was quantified with Cohen's effect size. In addition, bivariate correlations of change scores were explored.

RESULTS

Propensity score matching applied on the cohort of 151 patients (STN-DBS n=67, MED n=84) resulted in a well-balanced sub-cohort including 38 patients per group. After 36 months, STN-DBS significantly improved NMSS, PDQ-8, SCOPA-motor examination and -complications and reduced LEDD. Significant between-group differences, all favouring STN-DBS, were found for NMSS, SCOPA-motor complications, LEDD (large effects), motor examination and PDQ-8 (moderate effects). Furthermore, significant differences were found for the sleep/fatigue, urinary (large effects) and miscellaneous NMSS domains (moderate effects). NMSS total and PDQ-8 change scores correlated significantly.

CONCLUSIONS

This study provides Class IIb evidence for beneficial effects of STN-DBS on NMS at 36-month follow-up which also correlated with quality of life improvements. This highlights the importance of NMS for DBS outcomes assessments.

Lewy Body Degenerations as Neuropsychiatric Disorders

Parkinson disease has historically been conceptualized as a movement disorder. In recent decades, nonmotor and neuropsychiatric symptoms have become increasingly recognized as being of paramount importance for patients with Parkinson disease. Neuropsychiatric phenomena dominate the course of the other major Lewy body disease, dementia with Lewy bodies. In this review, we survey the clinical relevance of nonmotor and neuropsychiatric symptoms to the heterogeneous presentations of Lewy body disease and their significance to ongoing research in this area. We consider how the nature of Lewy body neuropathology may help explicate the basis of nonmotor and neuropsychiatric symptoms in these two disorders.

Parkinsonism and subthalamic deep brain stimulation dysregulate behavioral motivation in a rodent model

BACKGROUND

Apathy and impulsivity constitute opposite poles of a behavioral motivation spectrum often disrupted by both the symptoms and therapies for Parkinson's Disease (PD). Upwards of 70% of PD patients experience symptoms of apathy, frequently unresolved or worsened by deep brain stimulation (DBS) of the subthalamic nucleus (STN). Worse, more than half of patients receiving DBS for PD experience new-onset impulse control disorders of varying severity following therapy initiation. While these symptoms and side-effects have been widely reported in clinical studies, they are largely unexplored in animal models.

METHODS

We applied high-frequency DBS in a 6-OHDA hemiparkinsonian rat model. We trained rats on a series of go/stop and go/no-go behavioral paradigms and examined how parkinsonism and DBS modulated task responses.

RESULTS

STN DBS in healthy rodents drove impulsive behavior in the form of stop and no-go task failure, impulsive reward seeking, and noninstructed task attempts. While trained rats without DBS only tended to fail stop and no-go cues very shortly after the cue, DBS led to failures at significantly later time points. Hemiparkinsonism slowed response times and reduced response rates, not alleviated by effective DBS.

INTERPRETATIONS

PD interrupts neural signaling responsible for healthy action selection, not restored by DBS. PD may be associated with a dearth of action commands, manifesting as apathy. Conversely, effective DBS may bias the system toward the impulsive end of the behavioral motivation spectrum without restoring behaviorally reasonable actions, mis-weighting reward-based action selection and manifesting as impulsivity, aided by DBS interfering with stop signaling.

Vascularization of the Subthalamic Nucleus: Highlighting the Significance of the Premamillary Artery

BACKGROUND

The need for a better understanding of the subthalamic nucleus (STN)'s vascular anatomy is still evident because revealing its vascular supply may increase insight in the pathogenesis of related disorders, such as STN ischemia. The mechanisms under motor, behavioral, and cognitive changes following deep brain stimulation treatment may also be explained by its pattern of vascularization. The primary goal of this study was to delineate the vascularization of the STN and highlight the predominant perforating arteries supplying its territory.

METHODS

Fiber dissections were performed with the modified Klingler technique under 6-40× magnification by preserving all vascular structures.

RESULTS

The thalamic and subthalamic regions were dissected from medial to lateral in silicone-injected cadavers. The STN was revealed as a biconvex-shaped structure surrounded by dense inferolateral bundles of myelinated fibers, the zona incerta, bordering the superolateral portion of the red nucleus. The ventral limit of the STN was the substantia nigra, and the internal capsule traversed from its inferior to anterolateral side. The premamillary artery, a large perforator arising from the posterior communicating artery, constantly supplied the STN and was followed proximally along the anterior third ventricular floor toward its origin. The premamillary artery was found to be one of the posterior perforators of the posterior communicating artery in all hemispheres.

CONCLUSIONS

The 3-dimensional microsurgical anatomy of the deep-seated STN region is complex, and the additional knowledge on its vascularization should improve our understanding of its surgical anatomy.

Transcranial Ultrasound Stimulation Directly Influences the Cortical Excitability of the Motor Cortex in Parkinsonian Mice

BACKGROUND

Low-intensity transcranial ultrasound stimulation is a new noninvasive brain modulation method with high spatial resolution and high penetration depth. However, until now, it was unclear whether transcranial ultrasound stimulation has a significant effect on PD.

OBJECTIVES

In order to evaluate the effect of transcranial ultrasound stimulation on PD.

METHODS

We used transcranial ultrasound stimulation to modulate parkinsonian-related activity in mice administered MPTP and recorded local field potentials in the motor cortex before and after ultrasound stimulation. We analyzed neuronal oscillatory activity known to be relevant to the pathophysiology of PD.

RESULTS

After ultrasound stimulation, mean power intensity in the beta band (13-30 Hz) significantly decreased, and the phase-amplitude coupling strength between the beta and high gamma (55-100 Hz) bands and between the beta and ripple (100-200 Hz) bands also became significantly weaker.

CONCLUSIONS

This study demonstrates that ultrasonic neuromodulation can significantly decrease parkinsonian-related activity in mice administered MPTP. © 2019 International Parkinson and Movement Disorder Society.

Drug Choices and Advancements for Managing Depression in Parkinson's Disease

Depression is a frequent non-motor symptom of Parkinson’s disease (PD), and may even precede the onset of motor symptoms of parkinsonism. Beyond its negative influence on mood, depression in PD is frequently associated with other neuropsychiatric symptoms and with late-stage complications such as dementia. Despite its profound impact on the quality of life and cognitive functioning in PD, depression in PD is often under-recognized and poorly treated.

Pathophysiological studies demonstrated that depression in PD is associated with global dysfunction of interactions between discrete brain areas rather than focal structural or functional abnormalities, and that it is sustained by pathological changes of several neurotransmitter/receptor complexes.

In general, all traditional antidepressants and some dopamine agonists have been found to be safe and well-tolerated to treat depressive symptoms in PD, despite initial warning on worsening of parkinsonism. Available data suggest that the time-course of response differs among antidepressants. Efficacy results from clinical trials with antidepressant in PD are, however, rather uncertain, although pooled analysis suggests a moderate benefit. Several issues may critically impact the results of clinical trials with antidepressants in PD, including the correct psychiatric diagnosis, the overlap of symptoms between depression and PD, and the selection of appropriate end-points and rating scales.

Suicide in Parkinson's disease

Persons with Parkinson's disease (PwP) have many known risk factors for suicide and suicidal ideation (SI). Despite this, there is limited understanding of suicidality in this population. We conducted a systematic review to synthesise the available literature on suicidality in PwP and highlight areas for potential intervention and further research. We identified 116 articles discussing SI, suicidal behaviours, suicide attempts and/or fatal suicide in PwP. These articles describe prevalence, suicide methods, risk factors for suicide and SI and treatment of suicidality. In this review, we summarise the current literature and provide suggestions for how clinicians can identify and treat PwP who are at risk for suicide, for example, through aggressive treatment of depression and improved screening for access to lethal means.

Deep Brain Stimulation and Drug-Resistant Epilepsy: A Review of the Literature

Introduction: Deep brain stimulation is a safe and effective neurointerventional technique for the treatment of movement disorders. Electrical stimulation of subcortical structures may exert a control on seizure generators initiating epileptic activities. The aim of this review is to present the targets of the deep brain stimulation for the treatment of drug-resistant epilepsy. Methods: We performed a structured review of the literature from 1980 to 2018 using Medline and PubMed. Articles assessing the impact of deep brain stimulation on seizure frequency in patients with DRE were selected. Meta-analyses, randomized controlled trials, and observational studies were included. Results: To date, deep brain stimulation of various neural targets has been investigated in animal experiments and humans. This article presents the use of stimulation of the anterior and centromedian nucleus of the thalamus, hippocampus, basal ganglia, cerebellum and hypothalamus. Anterior thalamic stimulation has demonstrated efficacy and there is evidence to recommend it as the target of choice. Conclusion: Deep brain stimulation for seizures may be an option in patients with drug-resistant epilepsy. Anterior thalamic nucleus stimulation could be recommended over other targets.

Deep Brain Stimulation Programming for Movement Disorders: Current Concepts and Evidence-Based Strategies

Deep brain stimulation (DBS) has become the treatment of choice for advanced stages of Parkinson's disease, medically intractable essential tremor, and complicated segmental and generalized dystonia. In addition to accurate electrode placement in the target area, effective programming of DBS devices is considered the most important factor for the individual outcome after DBS. Programming of the implanted pulse generator (IPG) is the only modifiable factor once DBS leads have been implanted and it becomes even more relevant in cases in which the electrodes are located at the border of the intended target structure and when side effects become challenging. At present, adjusting stimulation parameters depends to a large extent on personal experience. Based on a comprehensive literature search, we here summarize previous studies that examined the significance of distinct stimulation strategies for ameliorating disease signs and symptoms. We assess the effect of adjusting the stimulus amplitude (A), frequency (f), and pulse width (pw) on clinical symptoms and examine more recent techniques for modulating neuronal elements by electrical stimulation, such as interleaving (Medtronic®) or directional current steering (Boston Scientific®, Abbott®). We thus provide an evidence-based strategy for achieving the best clinical effect with different disorders and avoiding adverse effects in DBS of the subthalamic nucleus (STN), the ventro-intermedius nucleus (VIM), and the globus pallidus internus (GPi).

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.

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

Introduction: Although the benefit in motor symptoms for well-selected patients with deep brain stimulation (DBS) has been established, cognitive declines associated with DBS can produce suboptimal clinical responses. Small decrements in cognition can lead to profound effects on quality of life. The growth of indications, the expansion of surgical targets, the increasing complexity of devices, and recent changes in stimulation paradigms have all collectively drawn attention to the need for re-evaluation of DBS related cognitive outcomes.

Methods: To address the impact of cognitive changes following DBS, we performed a literature review using PubMed. We searched for articles focused on DBS and cognition. We extracted information about the disease, target, number of patients, assessment of time points, cognitive battery, and clinical outcomes. Diseases included were dystonia, Tourette syndrome (TS), essential tremor (ET), and Parkinson's disease (PD).

Results: DBS was associated with mild cognitive issues even when rigorous patient selection was employed. Dystonia studies reported stable or improved cognitive scores, however one study using reliable change indices indicated decrements in sustained attention. Additionally, DBS outcomes were convoluted with changes in medication dose, alleviation of motor symptoms, and learning effects. In the largest, prospective TS study, an improvement in attentional skills was noted, whereas smaller studies reported variable declines across several cognitive domains. Although, most studies reported stable cognitive outcomes. ET studies largely demonstrated deficits in verbal fluency, which had variable responses depending on stimulation setting. Recently, studies have focused beyond the ventral intermediate nucleus, including the post-subthalamic area and zona incerta. For PD, the cognitive results were heterogeneous, although deficits in verbal fluency were consistent and related to the micro-lesion effect.

Conclusion: Post-DBS cognitive issues can impact both motor and quality of life outcomes. The underlying pathophysiology of cognitive changes post-DBS and the identification of pathways underpinning declines will require further investigation. Future studies should employ careful methodological designs. Patient specific analyses will be helpful to differentiate the effects of medications, DBS and the underlying disease state, including disease progression. Disease progression is often an underappreciated factor that is important to post-DBS cognitive issues.

Deep brain stimulation in the obsessive-compulsive syndrome

Introduction The authors present an overview of current views on the treatment of obsessive-compulsive disorder refractory to pharmacological and psychological treatment.

Aim: To review the mechanisms of stimulation of deep brain structures and to evaluate the effectiveness of therapy in obsessive-compulsive disorder.

Method: Review and analysis of the Polish and foreign scientific articles from the years 1999-2016.

Conclusions: According to the literature considered, in half of the examined patients there was an improvement of over 35% on the Y-BOCS scale, in some patients even a reduction of symptoms reaching 81-83% was described. Previous studies have been carried out on small groups of patients. Since 2009, the method of invasive treatment with deep brain stimulation of the obsessive-compulsive syndrome is registered in the EU. In spite of the above, additional studies are necessary on a larger group of patients in order to precisely estimate the effectiveness of the procedure and elaborate the criteria for qualifying patients for inclusion in the procedure.

Neuropsychological predictors of patient-reported cognitive decline after deep brain stimulation in Parkinson's disease

BACKGROUND

Deep brain stimulation (DBS) is effective for treatment of motor complications of dopaminergic therapy in Parkinson's disease (PD) but occasionally has been associated with multidomain cognitive decline. Patient- and caregiver-reported cognitive decline are clinically meaningful and increasingly recognized as important to consider when evaluating therapeutic interventions for PD.

OBJECTIVE

The objective was to assess presurgical neuropsychological and clinical factors associated with PD patient- and caregiver-reported cognitive decline in two or more domains after DBS.

METHOD

A single telephone survey was used to assess patient- and caregiver-reported cognitive decline in five domains at both one and four months after DBS surgery. Decline in two or more domains was considered multidomain cognitive decline (MDCD). Baseline demographic, clinical, and neuropsychological factors were compared in those with or without MDCD. Preoperative neuropsychological measures were evaluated as risk factors and regressed on the presence of MDCD, with demographic covariates, using multiple logistic regression.

RESULTS

Preoperative performance in verbal recognition memory, language knowledge, and verbal processing decline were associated with postoperative, patient-reported MDCD in the first four weeks. MDCD at four months after DBS was associated with worse preoperative verbal reasoning, verbal recall, and semantic verbal fluency. Caregiver-reported MDCD one month after DBS was associated with poorer baseline verbal memory recognition accuracy/discriminability, visuospatial problem solving, and constructional praxis.

CONCLUSION

Poor presurgical performance in verbal memory recognition, language processing, and visuospatial performance is associated with patient- or caregiver-reported decline following DBS surgery. Posterior cortical dysfunction seems to portend significant self-reported cognitive decline following deep brain stimulation.

Predictors to quality of life improvements after subthalamic stimulation in Parkinson's disease

INTRODUCTION

Subthalamic deep brain stimulation (STN DBS) has been reported to improve the quality of life (QoL) related to Parkinson's disease (PD). However, not all subjects are satisfied with the postsurgical QoL outcome. We aimed to detect the related factors and possible predictors to QoL improvement for those PD patients one year after STN DBS.

MATERIALS AND METHODS

A total of 45 PD patients with bilateral STN DBS surgery were included and followed up for 1 year. The Reliable Change Index (RCI) was adapted to determine the individual postsurgical QoL outcome. The changes of QoL were correlated with baseline parameters and the changes of progression parameters using Pearson's correlation. The exploratory stepwise regressions were adopted to detect the extents of baseline variables and progression parameters. The predictors to QoL outcome were detected using the logistic regression analysis.

RESULTS

A total of 51.1% of the patients reported a better QoL, 40.0% of patients reported an unchanged QoL, while 8.9% of patients reported a worsening of QoL. The subdomains of mobility, activity of daily living, cognition, and bodily discomfort improved significantly after the surgery. The presurgical factors including QoL, dopaminergic medication burden, disease stages, depression scores, and postsurgical reductions in depression and nonmotor scores were found to correlate with QoL changes. Furthermore, the greater presurgical QoL burden, lesser dopaminergic medication exposure, and earlier disease stages were predictors to QoL improvements.

CONCLUSION

The clinicians should carefully evaluate the nonmotor symptoms and life quality in those patients at relatively earlier stages and with lower medicine dosage to get more successful DBS outcomes.

Revisiting eligibility for deep brain stimulation: Do preoperative mood symptoms predict outcomes in Parkinson's disease patients?

INTRODUCTION

Anxiety and depression are common in PD, occurring in an estimated 30%-40% of PD patients. However, the extent to which these emotional symptoms interfere with Deep Brain Stimulation (DBS) outcomes is not well established. This study examined the association between pre-operative emotional well-being and postsurgical cognitive, emotional, and motor performance in PD.

METHODS

Forty-nine PD patients underwent neurological, neuropsychological (global cognition, processing speed, language, visuospatial, memory), and emotional assessments pre- and post-DBS. Fifteen patients were administered the UPDRS. Patients were divided into Anxious (Anx; n = 21), Comorbid Anxious and Depressed (Anx + Dep; n = 15), and Emotionally Asymptomatic (EA; n = 13) based on BAI and BDI-II cutoffs, and compared on pre-post changes in neurocognitive, mood, and motor scores using analyses of covariance (ANCOVA), controlling for education, ethnicity, and disease duration.

RESULTS

Pre-DBS, there were no significant differences between the three groups on any neuropsychological measure. Overall change from pre-to post-DBS revealed declines on multiple cognitive measures and lower symptom endorsement on the BAI among all participants. No group differences were observed on neurocognitive measures, mood, or UPDRS.

CONCLUSIONS

PD patients with mild-moderate anxiety or comorbid anxiety/depression pre-DBS do not show greater cognitive, emotional, and motor changes post-DBS compared to emotionally asymptomatic patients. These data emphasize the importance of discussing potential DBS outcomes, while keeping in mind that psychiatric comorbidity should not necessarily exclude patients from DBS. The notion that premorbid mood symptoms could disqualify a candidate for surgery would be a disservice, as this group performs comparably to asymptomatic peers.

Medications, Deep Brain Stimulation, and Other Factors Influencing Impulse Control Disorders in Parkinson's Disease

Impulse control disorders (ICDs) in Parkinson's disease (PD) have a high cumulative incidence and negatively impact quality of life. ICDs are influenced by a complex interaction of multiple factors. Although it is now well-recognized that dopaminergic treatments and especially dopamine agonists underpin many ICDs, medications alone are not the sole cause. Susceptibility to ICD is increased in the setting of PD. While causality can be challenging to ascertain, a wide range of modifiable and non-modifiable risk factors have been linked to ICDs. Common characteristics of PD patients with ICDs have been consistently identified across many studies; for example, males with an early age of PD onset and dopamine agonist use have a higher risk of ICD. However, not all cases of ICDs in PD can be directly attributable to dopamine, and studies have concluded that additional factors such as genetics, smoking, and/or depression may be more predictive. Beyond dopamine, other ICD associations have been described but remain difficult to explain, including deep brain stimulation surgery, especially in the setting of a reduction in dopaminergic medication use. In this review, we will summarize the demographic, genetic, behavioral, and clinical contributions potentially influencing ICD onset in PD. These associations may inspire future preventative or therapeutic strategies.

Affective modulation of the associative-limbic subthalamic nucleus: deep brain stimulation in obsessive-compulsive disorder

Affective states underlie daily decision-making and pathological behaviours relevant to obsessive-compulsive disorders (OCD), mood disorders and addictions. Deep brain stimulation targeting the motor and associative-limbic subthalamic nucleus (STN) has been shown to be effective for Parkinson's disease (PD) and OCD, respectively. Cognitive and electrophysiological studies in PD showed responses of the motor STN to emotional stimuli, impairments in recognition of negative affective states and modulation of the intensity of subjective emotion. Here we studied whether the stimulation of the associative-limbic STN in OCD influences the subjective emotion to low-intensity positive and negative images and how this relates to clinical symptoms. We assessed 10 OCD patients with on and off STN DBS in a double-blind randomized manner by recording ratings of valence and arousal to low- and high-intensity positive and negative emotional images. STN stimulation increased positive ratings and decreased negative ratings to low-intensity positive and negative stimuli, respectively, relative to off stimulation. We also show that the change in severity of obsessive-compulsive symptoms pre- versus post-operatively interacts with both DBS and valence ratings. We show that stimulation of the associative-limbic STN might influence the negative cognitive bias in OCD and decreasing the negative appraisal of emotional stimuli with a possible relationship with clinical outcomes. That the effect is specific to low intensity might suggest a role of uncertainty or conflict related to competing interpretations of image intensity. These findings may have implications for the therapeutic efficacy of DBS.

Enhanced Motivational Modulation of Motor Behaviour with Subthalamic Nucleus Deep Brain Stimulation in Parkinson's Disease

Background

Motivational improvement of movement speed in Parkinson's disease (PD) is observed in life-threatening situations and has been empirically demonstrated in experimental studies using reaction time paradigms.

Objectives

To address two clinically relevant questions: first, if in PD, motivational modulation through provision of monetary incentive on a sorting task that approximates performance on everyday life tasks affects movement speed. Second, how this effect is compared between PD patients treated with medication or subthalamic deep brain stimulation.

Methods

We used the Card Arranging Reward Responsivity Objective Test that shares component processes with everyday life tasks to compare reward responsivity of movement speed in 10 PD patients with STN-DBS, 10 nonoperated medicated PD patients, both OFF and ON their usual medications/stimulation, and 11 age-matched healthy controls.

Results

Despite longer disease duration and more severe motor symptoms, STN-DBS PD patients with the stimulator turned ON showed greater improvement of movement speed with the prospect of monetary incentive compared to both medicated PD patients and healthy participants.

Discussion

The effect of monetary incentive on movement speed in PD patients is more pronounced with STN-DBS than dopaminergic medications, suggesting that motivational modulation of movement speed may be enhanced as a direct consequence of STN stimulation.

Beneficial effects of bilateral subthalamic stimulation on alexithymia in Parkinson's disease

BACKGROUND AND PURPOSE

Subthalamic nucleus (STN) deep brain stimulation (DBS) improves quality of life (QoL) and motor and non-motor symptoms in advanced Parkinson's disease (PD). However, its effect on alexithymia and its relationship to other neuropsychiatric symptoms and QoL in PD is unclear.

METHODS

In this prospective, observational study of 39 patients with PD undergoing STN-DBS, we examined the Parkinson's Disease Questionnaire-8 (PDQ-8), 20-item Toronto Alexithymia Scale (TAS-20), Hospital Anxiety and Depression Scale (HADS), Self-Report Manic Inventory (SRMI), Apathy Evaluation Scale (AES), Unified Parkinson's Disease Rating Scale (UPDRS) activities of daily living, UPDRS motor examination and UPDRS complications (UPDRS-II/-III/-IV) and levodopa-equivalent daily dose (LEDD) pre-operatively and at 5-month follow-up. Outcome changes were tested with Wilcoxon signed-rank or paired t-test when parametric tests were applicable and corrected for multiple comparisons. The relationship between outcome changes was explored with bivariate correlations. Additionally, partial correlations between PDQ-8 and TAS-20 were computed controlling for HADS, SRMI and AES change scores. Predictor analyses for PDQ-8 improvement were calculated for all baseline parameters.

RESULTS

The baseline prevalence of alexithymia was 17.9%. We observed significant beneficial effects of STN-DBS on PDQ-8, TAS-20, HADS, UPDRS-II, -III and -IV scores and significant LEDD reduction. The correlation between TAS-20 and PDQ-8 improvements remained significant after controlling for all other aforementioned outcomes. Predictor analyses for PDQ-8 improvement were significant for PDQ-8 and TAS-20.

CONCLUSIONS

This is the first report of beneficial effects of STN-DBS on alexithymia. Alexithymia was significantly associated with QoL outcome independent of anxiety, depression, mania and apathy. Our study highlights the importance of alexithymia for holistic assessments of DBS outcomes.

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.

Psychometric properties of apathy scales in Parkinson's disease: a systematic review

Apathy is among the most prevalent neuropsychiatric symptom experienced in Parkinson's disease (PD) and can be assessed with a variety of scales. To identify which scale is most suitable for apathy assessment in PD, the psychometric properties of each scale and its sensitivity to change were analyzed. The methodological quality of the studies ranged from adequate to excellent. The Lille Apathy Rating Scale demonstrated consistently favorable psychometric properties and was used in two of four clinical trials found. The Starkstein Apathy Scale was the only other scale used in clinical trials. Further work is necessary to develop a gold standard for assessing apathy in PD.

Some Clinically Useful Information that Neuropsychology Provides Patients, Carepartners, Neurologists, and Neurosurgeons About Deep Brain Stimulation for Parkinson's Disease

Deep brain stimulation (DBS) is an effective (but non-curative) treatment for some of the motor symptoms and treatment complications associated with dopaminergic agents in Parkinson's disease (PD). DBS can be done relatively safely and is associated with quality of life gains. In most DBS centers, neuropsychological evaluations are performed routinely before surgery, and sometimes after surgery. The purpose of such evaluation is not to decide solely on its results whether or not to offer DBS to a given candidate, but to provide the patient and treatment team with the best available information to make reasonable risk-benefit assessments. This review provides information relevant to the questions often asked by patients and their carepartners, neurologists, and neurosurgeons about neuropsychological outcomes of DBS, including neuropsychological adverse event rates, magnitude of cognitive changes, outcomes after unilateral versus bilateral surgery directed at various targets, impact of mild cognitive impairment (MCI) on outcome, factors implicated in neurobehavioral outcomes, and safety of newer interventions or techniques such as asleep surgery and current steering.

Standardised Neuropsychological Assessment for the Selection of Patients Undergoing DBS for Parkinson's Disease

DBS is an increasingly offered advanced treatment for Parkinson's disease (PD). Neuropsychological assessment is considered to be an important part of the screening for selection of candidates for this treatment. However, no standardised screening procedure currently exists. In this study, we examined the use of our standardised neuropsychological assessment for the evaluation of surgical candidates and to identify risk factors for subsequent decline in cognition and mood. A total of 40 patients were assessed before and after DBS. Evaluation of mood and case notes review was also undertaken. Before DBS, patients with PD demonstrated frequent impairments in intellectual functioning, memory, attention, and executive function, as well as high rates of mood disorder. Post-DBS, there was a general decline in verbal fluency only, and in one patient, we documented an immediate and irreversible global cognitive decline, which was associated with older age and more encompassing cognitive deficits at baseline. Case note review revealed that a high proportion of patients developed mood disorder, which was associated with higher levels of depression at baseline and greater reduction in levodopa medication. We conclude that our neuropsychological assessment is suitable for the screening of candidates and can identify baseline risk factors, which requires careful consideration before and after surgery.

Anatomical predictors of cognitive decline after subthalamic stimulation in Parkinson's disease

We investigated whether pre-operative MRI measures of focal brain atrophy could predict cognitive decline occurring after deep brain stimulation (DBS) of the subthalamic nucleus (STN) in patients with Parkinson's disease (PD). For that purpose, we prospectively collected data of 42 consecutive patients with PD who underwent bilateral STN-DBS. Normalized brain structure volumes and cortical thicknesses were measured on pre-operative T1-weighted MRI. Patients were tested for their cognitive performances before surgery and 1 year after. After controlling for age, gender, pre-operative disease severity, change in dopaminomimetic dose after surgery and contact location, we found correlations: (1) between the variation of the total Mattis dementia rating scale (MDRS) score and left lateral ventricle volume (p = 0.032), (2) between the variation of the initiation/perseveration subscore of the MDRS and the left nucleus accumbens volume (p = 0.042) and the left lateral ventricle volume (p = 0.017) and (3) between the variation of the backward digit-span task and the right and left superior frontal gyrus thickness (p = 0.004 and p = 0.007, respectively). Left nucleus accumbens atrophy was associated with decline in the initiation/perseveration subscore with the largest effect size (d = - 1.64). Pre-operative left nucleus accumbens volume strongly predicted postoperative decline in the initiation/attention subscore (AUC = 0.92, p < 0.001, 96.3% sensitivity, 80.0% specificity, 92.9% PPV and 92.9% NPV). We conclude that the morphometric measures of brain atrophy usually associated with cognitive impairment in PD can also explain or predict a part of cognitive decline after bilateral STN-DBS. In particular, the left accumbens nucleus volume could be considered as a promising marker for guiding surgical decisions.

Deep brain stimulation for treatment-resistant depression: an integrative review of preclinical and clinical findings and translational implications

Although deep brain stimulation (DBS) is an established treatment choice for Parkinson's disease (PD), essential tremor and movement disorders, its effectiveness for the management of treatment-resistant depression (TRD) remains unclear. Herein, we conducted an integrative review on major neuroanatomical targets of DBS pursued for the treatment of intractable TRD. The aim of this review article is to provide a critical discussion of possible underlying mechanisms for DBS-generated antidepressant effects identified in preclinical studies and clinical trials, and to determine which brain target(s) elicited the most promising outcomes considering acute and maintenance treatment of TRD. Major electronic databases were searched to identify preclinical and clinical studies that have investigated the effects of DBS on depression-related outcomes. Overall, 92 references met inclusion criteria, and have evaluated six unique DBS targets namely the subcallosal cingulate gyrus (SCG), nucleus accumbens (NAc), ventral capsule/ventral striatum or anterior limb of internal capsule (ALIC), medial forebrain bundle (MFB), lateral habenula (LHb) and inferior thalamic peduncle for the treatment of unrelenting TRD. Electrical stimulation of these pertinent brain regions displayed differential effects on mood transition in patients with TRD. In addition, 47 unique references provided preclinical evidence for putative neurobiological mechanisms underlying antidepressant effects of DBS applied to the ventromedial prefrontal cortex, NAc, MFB, LHb and subthalamic nucleus. Preclinical studies suggest that stimulation parameters and neuroanatomical locations could influence DBS-related antidepressant effects, and also pointed that modulatory effects on monoamine neurotransmitters in target regions or interconnected brain networks following DBS could have a role in the antidepressant effects of DBS. Among several neuromodulatory targets that have been investigated, DBS in the neuroanatomical framework of the SCG, ALIC and MFB yielded more consistent antidepressant response rates in samples with TRD. Nevertheless, more well-designed randomized double-blind, controlled trials are warranted to further assess the efficacy, safety and tolerability of these more promising DBS targets for the management of TRD as therapeutic effects have been inconsistent across some controlled studies.

Challenges in PD Patient Management After DBS: A Pragmatic Review

BACKGROUND

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) or internal globus pallidus (GPi) represents an effective and universally applied therapy for Parkinson's disease (PD) motor complications. However, certain procedure-related problems and unrealistic patient expectations may detract specialists from indicating DBS more widely despite significant clinical effects.

METHODS

This review provides a pragmatic educational summary of the most conflicting postoperative management issues in patients undergoing DBS for PD.

RESULTS

DBS in PD has been associated with certain complications and post-procedural management issues, which can complicate surgical outcome interpretation. Many PD patients consider DBS outcomes negative due to unfulfilled expectations, even when significant motor symptom improvement is achieved. Speech, gait, postural stability, and cognition may worsen after DBS and body weight may increase. Although DBS may induce impulse control disorders in some cases, in others, it may actually improve them when dopamine agonist dosage is reduced after surgery. However, apathy may also arise, especially when dopaminergic medication tapering is rapid. Gradual loss of response with time suggests disease progression, rather than the wearing off of DBS effects. Furthermore, implantable pulse generator expiration is considered a movement disorder emergency, as it may worsen parkinsonian symptoms or cause life-threatening akinetic crises due to malignant DBS withdrawal syndrome.

CONCLUSION

Major unsolved issues occurring after DBS therapy preclude complete patient satisfaction. Multidisciplinary management at experienced centers, as well as careful and comprehensive delivery of information to patients, should contribute to make DBS outcome expectations more realistic and allow post procedural complications to be better accepted.

The pathophysiological mechanisms of motivational deficits in Parkinson's disease

Parkinson's disease (PD) is a progressive degenerative disorder that leads to disabling motor symptoms and a wide variety of neuropsychiatric symptoms. Apathy is the most common psychiatric disorder in the early stages of untreated PD and can be defined as a hypodopaminergic syndrome, which also includes anxiety and depression. Apathy is also considered the core feature of the parkinsonian triad (apathy, anxiety and depression) of behavioural non-motor signs, including a motivational deficit. Moreover, apathy is recognised as a distinct chronic neuropsychiatric behavioural disorder based on specific diagnostic criteria. Given the prevalence of apathy in approximately 40% of the general Parkinson's disease population, this appears to be a contributing factor to dementia in PD; also, apathy symptoms are factors that potentially contribute to morbidity, leading to a major impairment of health-related quality of life, thus stressing the importance of understanding the pathophysiology of this disease. Several studies have clearly established a prominent role for DA-mediated signals in PD apathy. However, synergistic interaction between dopaminergic impairment resulting from the neurodegenerative process and deep brain stimulation of the subthalamic nucleus may cause or exacerbate apathy. Furthermore, serotoninergic mechanism signalling is also likely to be of importance in this pathophysiology.

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.

7T MRI subthalamic nucleus atlas for use with 3T MRI

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) reduces motor symptoms in most patients with Parkinson disease (PD), yet may produce untoward effects. Investigation of DBS effects requires accurate localization of the STN, which can be difficult to identify on magnetic resonance images collected with clinically available 3T scanners. The goal of this study is to develop a high-quality STN atlas that can be applied to standard 3T images. We created a high-definition STN atlas derived from seven older participants imaged at 7T. This atlas was nonlinearly registered to a standard template representing 56 patients with PD imaged at 3T. This process required development of methodology for nonlinear multimodal image registration. We demonstrate mm-scale STN localization accuracy by comparison of our 3T atlas with a publicly available 7T atlas. We also demonstrate less agreement with an earlier histological atlas. STN localization error in the 56 patients imaged at 3T was less than 1 mm on average. Our methodology enables accurate STN localization in individuals imaged at 3T. The STN atlas and underlying 3T average template in MNI space are freely available to the research community. The image registration methodology developed in the course of this work may be generally applicable to other datasets.

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.

Cognitive, Emotional, and Auto-Activation Dimensions of Apathy in Parkinson's Disease

Apathy is one of the most frequent non-motor manifestations in Parkinson's disease (PD) that can lead to a whole range of deleterious outcomes. In 2006, Levy and Dubois proposed a model that distinguishes three different apathy aetiologies in PD divided into three subtypes of disrupted processing: “emotional-affective,” “cognitive,” and “auto-activation.” These three dimensions associated with dopamine depletion present in the pathology would lead to the emergence of apathy in PD. The aim of this mini-review was to describe and discuss studies that have explore links between apathy and the three subtypes of disrupted processing proposed by Levy and Dubois (2006) and as well as the links between these dimensions and dopamine depletion in Parkinson's disease. The lack of consensus regarding the emotional-affective correlates of apathy and the lack of evidence supporting the hypothesis of the auto-activation deficit, do not clearly confirm the validity of Levy and Dubois's model. Furthermore, the suggested association between dopaminergic depletion and apathy must also be clarified.

l-Dopa/carbidopa intestinal gel and subthalamic nucleus stimulation: Effects on cognition and behavior

OBJECTIVE

In Parkinson's disease (PD), effects on behavior and cognition of levodopa/carbidopa intestinal gel (LCIG) and subthalamic stimulation (STN-DBS) and their practical consequences remain controversial. This study was designed to analyze the possible effects of these therapies on cognition and behavior after 1 year follow-up.

METHODS

This was an open-label, nonrandomized prospective study for pre- and postintervention analyses. Twenty-four patients were considered eligible to be candidates for complex therapies such as STN-DBS or LCIG; 23 patients treated with standard medication were included as controls. Several cognitive, behavioral, and motor scales were administered before and at 6 and 12 months after the intervention.

RESULTS

Patients treated with LCIG experienced significant improvement in specific neuropsychological functions when compared with patients receiving STN-DBS and conventional medical treatment after 1 year from the onset of the intervention. In this study, no significant cognitive or behavioral changes occurred in patients treated with subthalamic stimulation when compared to patients receiving conventional medical treatment at 1 year follow-up.

CONCLUSIONS

Patients treated with LCIG may significantly improve some specific neuropsychological functions when compared with patients receiving STN-DBS and with patients receiving conventional medical treatment after 1 year from the intervention; there are not significant cognitive or behavioral changes in patients treated with STN-DBS when compared to PD patients receiving conventional medical treatment after 1 year from the intervention. The outcomes showed in the study can help to the selection of the appropriate candidates for STN-DBS and LCIG.

Clinical Ethics in the Context of Deep Brain Stimulation for Movement Disorders

OBJECTIVE

Discuss common clinical ethical challenges encountered in working with patients who are candidates for deep brain stimulation (DBS) for the treatment of motor symptoms of Parkinson's disease (PD).

METHOD

The relevant literature is reviewed and supplemented by descriptive, ethically challenging cases stemming from decades of combined experience working on DBS teams. We outline ethical arguments and provide pragmatic recommendations to assist neuropsychologists working in movement disorder teams.

RESULTS

The goals of the pre-operative neuropsychological DBS assessment include: (1) identification of potential cognitive risk factors; (2) identification of relevant neuropsychiatric or neurobehavioral factors; (3) assessment of level of family support; and (4) systematic assessment of patient's and family member's goals or expectations for DBS. The information gleaned from the pre-operative neuropsychological assessment is highly relevant to the most commonly studied clinical ethics challenges encountered in DBS: (1) assessment of risk/benefit; (2) determinations regarding inclusion/exclusion; (3) autonomy; and (4) patient's perception of benefit and quality of life.

CONCLUSIONS

Neuropsychologists are particularly well poised to provide unique and important insights to assist with developing the most ethically sound practices that take into account patient's values as well as fiduciary responsibilities to the patient, the team, the profession, and the broader community.

Programming for Stimulation-Induced Transient Nonmotor Psychiatric Symptoms after Bilateral Subthalamic Nucleus Deep Brain Stimulation for Parkinson's Disease

Background

Stimulation-induced transient nonmotor psychiatric symptoms (STPSs) are side effects following bilateral subthalamic nucleus deep brain stimulation (STN-DBS) in Parkinson's disease (PD) patients. We designed algorithms which (1) determine the electrode contacts that induce STPSs and (2) provide a programming protocol to eliminate STPS and maintain the optimal motor functions. Our objective is to test the effectiveness of these algorithms.

Materials and Methods

454 PD patients who underwent programming sessions after STN-DBS implantations were retrospectively analyzed. Only STPS patients were enrolled. In these patients, the contacts inducing STPS were found and the programming protocol algorithms used.

Results

Eleven patients were diagnosed with STPS. Of these patients, two had four episodes of crying, and two had four episodes of mirthful laughter. In one patient, two episodes of abnormal sense of spatial orientation were observed. Hallucination episodes were observed twice in one patient, while five patients recorded eight episodes of hypomania. There were no statistical differences between the UPDRS-III under the final stimulation parameter (without STPS) and previous optimum UPDRS-III under the STPSs (p = 1.000).

Conclusion

The flow diagram used for determining electrode contacts that induce STPS and the programming protocol employed in the treatment of these symptoms are effective.

Psychiatric and Cognitive Effects of Deep Brain Stimulation for Parkinson's Disease

Deep brain stimulation (DBS) is effective for Parkinson's disease (PD), dystonia, and essential tremor (ET). While motor benefits are well documented, cognitive and psychiatric side effects from the subthalamic nucleus (STN) and globus pallidus interna (GPi) DBS for PD are increasingly recognized. Underlying disease, medications, microlesions, and post-surgical stimulation likely all contribute to non-motor symptoms (NMS).

Adverse events in deep brain stimulation: A retrospective long-term analysis of neurological, psychiatric and other occurrences

Background and objective

The extent to which deep brain stimulation (DBS) can improve quality of life may be perceived as a permanent trade-off between neurological improvements and complications of therapy, comorbidities, and disease progression.

Patients and methods

We retrospectively investigated 123 consecutive and non-preselected patients. Indications for DBS surgery were Parkinson's disease (82), dystonia (18), tremor of different etiology (21), Huntington's disease (1) and Gilles de la Tourette syndrome (1). AEs were defined as any untoward clinical occurrence, sign or patient complaint or unintended disease if related or unrelated to the surgical procedures, implanted devices or ongoing DBS therapy.

Results

Over a mean/median follow-up period of 4.7 years (578 patient-years) 433 AEs were recorded in 106 of 123 patients (86.2%). There was no mortality or persistent morbidity from the surgical procedure. All serious adverse events (SAEs) that occurred within 4 weeks of surgery were reversible. Neurological AEs (193 in 85 patients) and psychiatric AEs (78 in 48 patients) were documented most frequently. AEs in 4 patients (suicide under GPI stimulation, weight gain >20 kg, impairment of gait and speech, cognitive decline >2 years following surgery) were severe or worse, at least possibly related to DBS and non reversible. In PD 23.1% of the STN-stimulated patients experienced non-reversible (or unknown reversibility) AEs that were at least possibly related to DBS in the form of impaired speech or gait, depression, weight gain, cognitive disturbances or urinary incontinence (severity was mild or moderate in 15 of 18 patients). Age and Hoehn&Yahr stage of STN-simulated PD patients, but not preoperative motor impairment or response to levodopa, showed a weak correlation (r = 0.24 and 0.22, respectively) with the number of AEs.

Conclusions

DBS-related AEs that were severe or worse and non-reversible were only observed in PD (4 of 82 patients; 4.9%), but not in other diseases. PD patients exhibited a significant risk for non-severe AEs most of which also represented preexisting and progressive axial and non-motor symptoms of PD. Mild gait and/or speech disturbances were rather frequent complaints under VIM stimulation. GPI stimulation for dystonia could be applied with negligible DBS-related side effects.