Does subthalamic nucleus stimulation induce apathy in Parkinson's disease?

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

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

A multicenter double-blind randomized crossover study comparing the impact of dorsal subthalamic nucleus deep brain stimulation versus standard care on apathy in Parkinson's disease: a study protocol

BACKGROUND

Neuroimaging studies suggest an association between apathy after deep brain stimulation (DBS) and stimulation of the ventral part of the subthalamic nucleus (STN) due to the associative fibers connected to the non-motor limbic circuits that are involved in emotion regulation and motivation. We have previously described three patients with severe apathy that could be fully treated after switching stimulation from a ventral electrode contact point to a more dorsal contact point.

OBJECTIVES

To determine whether more dorsal stimulation of the STN decreases apathy compared to standard care in a multicenter randomized controlled trial with a crossover design.

METHODS

We will include 26 patients with a Starkstein Apathy Scale (SAS) score of 14 or more after subthalamic nucleus (STN) deep brain stimulation (DBS) for refractory Parkinson's disease. This is a multicenter trial conducted in two teaching hospitals and one university medical center in the Netherlands after at least 3 months of STN DBS. Our intervention will consist of 1 month of unilateral dorsal STN stimulation compared to treatment as usual. The primary outcome is a change in SAS score following 1 month of DBS on the original contact compared to the SAS score following 1 month of DBS on the more dorsal contact. Secondary outcomes are symptom changes on the Movement Disorders Society-Unified Parkinson's Disease Rating Scale motor part III, Montgomery-Åsberg Depression Rating Scale, 39-item Parkinson's disease questionnaire, Parkinson's disease impulsive-compulsive disorders questionnaire, changes in levodopa-equivalent daily dosage, apathy rated by the caregiver, and burden and quality of life of the caregiver.

TRIAL REGISTRATION

ClinicalTrials.gov NL8279. Registered on January 10, 2020.

Motivational and cognitive predictors of apathy after subthalamic nucleus stimulation in Parkinson's disease

Postoperative apathy is a frequent symptom in Parkinson's disease patients who have undergone bilateral deep brain stimulation of the subthalamic nucleus. Two main hypotheses for postoperative apathy have been suggested: (i) dopaminergic withdrawal syndrome relative to postoperative dopaminergic drug tapering; and (ii) direct effect of chronic stimulation of the subthalamic nucleus. The primary objective of our study was to describe preoperative and 1-year postoperative apathy in Parkinson's disease patients who underwent chronic bilateral deep brain stimulation of the subthalamic nucleus. We also aimed to identify factors associated with 1-year postoperative apathy considering: (i) preoperative clinical phenotype; (ii) dopaminergic drug management; and (iii) volume of tissue activated within the subthalamic nucleus and the surrounding structures. We investigated a prospective clinical cohort of 367 patients before and 1 year after chronic bilateral deep brain stimulation of the subthalamic nucleus. We assessed apathy using the Lille Apathy Rating Scale and carried out a systematic evaluation of motor, cognitive and behavioural signs. We modelled the volume of tissue activated in 161 patients using the Lead-DBS toolbox and analysed overlaps within motor, cognitive and limbic parts of the subthalamic nucleus. Of the 367 patients, 94 (25.6%) exhibited 1-year postoperative apathy: 67 (18.2%) with 'de novo apathy' and 27 (7.4%) with 'sustained apathy'. We observed disappearance of preoperative apathy in 22 (6.0%) patients, who were classified as having 'reversed apathy'. Lastly, 251 (68.4%) patients had neither preoperative nor postoperative apathy and were classified as having 'no apathy'. We identified preoperative apathy score [odds ratio (OR) 1.16; 95% confidence interval (CI) 1.10, 1.22; P < 0.001], preoperative episodic memory free recall score (OR 0.93; 95% CI 0.88, 0.97; P = 0.003) and 1-year postoperative motor responsiveness (OR 0.98; 95% CI 0.96, 0.99; P = 0.009) as the main factors associated with postoperative apathy. We showed that neither dopaminergic dose reduction nor subthalamic stimulation were associated with postoperative apathy. Patients with 'sustained apathy' had poorer preoperative fronto-striatal cognitive status and a higher preoperative action initiation apathy subscore. In these patients, apathy score and cognitive status worsened postoperatively despite significantly lower reduction in dopamine agonists (P = 0.023), suggesting cognitive dopa-resistant apathy. Patients with 'reversed apathy' benefited from the psychostimulant effect of chronic stimulation of the limbic part of the left subthalamic nucleus (P = 0.043), suggesting motivational apathy. Our results highlight the need for careful preoperative assessment of motivational and cognitive components of apathy as well as executive functions in order to better prevent or manage postoperative apathy.

Apathy in Parkinson's Disease: Clinical Patterns and Neurobiological Basis

Apathy is commonly defined as a loss of motivation leading to a reduction in goal-directed behaviors. This multidimensional syndrome, which includes cognitive, emotional and behavioral components, is one of the most prevalent neuropsychiatric features of Parkinson's disease (PD). It has been established that the prevalence of apathy increases as PD progresses. However, the pathophysiology and anatomic substrate of this syndrome remain unclear. Apathy seems to be underpinned by impaired anatomical structures that link the prefrontal cortex with the limbic system. It can be encountered in the prodromal stage of the disease and in fluctuating PD patients receiving bilateral chronic subthalamic nucleus stimulation. In these stages, apathy may be considered as a disorder of motivation that embodies amotivational behavioral syndrome, is underpinned by combined dopaminergic and serotonergic denervation and is dopa-responsive. In contrast, in advanced PD patients, apathy may be considered as cognitive apathy that announces cognitive decline and PD dementia, is underpinned by diffuse neurotransmitter system dysfunction and Lewy pathology spreading and is no longer dopa-responsive. In this review, we discuss the clinical patterns of apathy and their treatment, the neurobiological basis of apathy, the potential role of the anatomical structures involved and the pathways in motivational and cognitive apathy.

Psychiatric Symptoms in Parkinson's Disease Patients before and One Year after Subthalamic Nucleus Deep Brain Stimulation Therapy: Role of Lead Positioning and Not of Total Electrical Energy Delivered

Parkinson’s disease (PD) patients may experience neuropsychiatric symptoms, including depression, anxiety, sleep disturbances, psychosis, as well as behavioral and cognitive symptoms during all the different stages of the illness. Deep Brain Stimulation (DBS) therapy has proven to be successful in controlling the motor symptoms of PD and its possible correlation with the occurrence or worsening of neuropsychiatric symptoms has been reported. We aimed to assess the neuropsychiatric symptoms of 14 PD patients before and after one year of Subthalamic Nucleus (STN)-DBS and to correlate the possible changes to the lead placement and to the total electrical energy delivered. We assessed PD motor symptoms, depression, anxiety, apathy, impulsivity, and suicidality using clinician- and/or self-administered rating scales and correlated the results to the lead position using the Medtronic SuretuneTM software and to the total electrical energy delivered (TEED). At the 12-month follow-up, the patients showed a significant improvement in PD symptoms on the UPDRS (Unified Parkinson’s disease Rating Scale) (−38.5%; p < 0.001) and in anxiety on the Hamilton Anxiety Rating Scale (HAM-A) (−29%; p = 0.041), with the most significant reduction in the physiological anxiety subscore (−36.26%; p < 0.001). A mild worsening of impulsivity was detected on the Barratt Impulsiveness Scale (BIS-11) (+9%; p = 0.048), with the greatest increase in the attentional impulsiveness subscore (+13.60%; p = 0.050). No statistically significant differences were found for the other scales. No correlation was found between TEED and scales’ scores, while the positioning of the stimulating electrodes in the different portions of the STN was shown to considerably influence the outcome, with more anterior and/or medial lead position negatively influencing psychiatric symptoms.

Apathy following Bilateral Deep Brain Stimulation of Subthalamic Nucleus and Globus Pallidus Internus in Parkinson's Disease: A Meta-Analysis

Parkinson's disease (PD) is a progressive neurodegenerative disorder typically manifested by its motor symptoms. In addition, PD patients also suffer from many nonmotor symptoms (NMSs), such as apathy. Bilateral deep brain stimulation (DBS) of the subthalamic nucleus (STN) and the globus pallidus internus (GPi) are recommended as therapeutic interventions for PD, given their pronounced benefit in reducing troublesome dyskinesia. Apathy, a mood disorder recognized as a NMS of PD, has a negative impact on the prognosis of PD patients. However, the effect of STN-DBS and GPi-DBS on apathy is controversial. In the current meta-analysis, we analyzed apathy following bilateral STN-DBS and GPi-DBS in PD patients. Relevant literature was retrieved from public databases, including PubMed, Cochrane Library, and Embase. Studies were included in our analysis based on the following criterion: such studies should report apathy scores presurgery and postsurgery determined by using the Starkstein Apathy Scale or Apathy Evaluation Scale in patients receiving STN or GPi-DBS with at least three months of follow-up. Upon applying this strict criterion, a total of 13 out of 302 studies were included in our study. A mean difference (MD) and 95% confidence interval (CI) were calculated to show the change in apathy scores. We found a statistically significant difference between the presurgery and postsurgery scores in patients receiving STN-DBS (MD = 2.59, 95% CI = 2.23-2.96, P < 0.00001), but not in patients receiving GPi-DBS (MD = 0.32, 95% CI = -2.78-3.41, P=0.84). STN-DBS may worsen the condition of apathy, which may result from the reduction of dopaminergic medication. In conclusion, STN-DBS seems to relatively worsen the condition of apathy compared to GPi-DBS. Further studies should focus on the mechanisms of postoperatively apathy and the degree of apathy in STN-DBS versus GPi-DBS.

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

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

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Dopamine D3 Receptors: A Potential Target to Treat Motivational Deficits in Parkinson's Disease

Parkinson's disease (PD), which is traditionally viewed as a motor disorder involving the degeneration of dopaminergic (DA) neurons, has recently been identified as a quintessential neuropsychiatric condition. Indeed, a plethora of non-motor symptoms may occur in PD, including apathy. Apathy can be defined as a lack of motivation or a deficit of goal-directed behaviors and results in a pathological decrease of self-initiated voluntary behavior. Apathy in PD appears to fluctuate with the DA state of the patients, suggesting a critical role of DA neurotransmission in the pathophysiology of this neuropsychiatric syndrome. Using a lesion-based approach, we developed a rodent model which exhibits specific alteration in the preparatory component of motivational processes, reminiscent to apathy in PD. We found a selective decrease of DA D₃ receptors (D₃R) expression in the dorsal striatum of lesioned rats. Next, we showed that inhibition of D₃R neurotransmission in non-lesioned animals was sufficient to reproduce the motivational deficit observed in our model. Interestingly, we also found that pharmacologically targeting D₃R efficiently reversed the motivational deficit induced by the lesion. Our findings, among other recent data, suggest a critical role of D₃R in parkinsonian apathy and highlight this receptor as a promising target for treating motivational deficits.

Preoperative REM Sleep Behavior Disorder and Subthalamic Nucleus Deep Brain Stimulation Outcome in Parkinson Disease 1 Year After Surgery

BACKGROUND AND OBJECTIVES

To determine whether patients with Parkinson disease (PD) eligible for subthalamic nucleus deep brain stimulation (STN-DBS) with probable REM sleep behavior disorder (RBD) preoperatively could be more at risk of poorer motor, nonmotor, and quality of life outcomes 12 months after surgery compared to those without RBD.

METHODS

We analyzed the preoperative clinical profile of 448 patients with PD from a French multicentric prospective study (PREDISTIM) according to the presence or absence of probable RBD based on the RBD Single Question and RBD Screening Questionnaire. Among the 215 patients with PD with 12 months of follow-up after STN-DBS, we compared motor, cognitive, psycho-behavioral profile, and quality of life outcomes in patients with (pre-opRBD+) or without (pre-opRBD-) probable RBD preoperatively.

RESULTS

At preoperative evaluation, pre-opRBD+ patients were older (61 ± 7.2 vs 59.5 ± 7.7 years; p = 0.02), had less motor impairment (Movement Disorder Society-sponsored version of the Unified Parkinson's Disease Rating Scale [MDS-UPDRS] III "off": 38.7 ± 16.2 vs 43.4 ± 7.1; p = 0.03) but more nonmotor symptoms on daily living activities (MDS-UPDRS I: 12.6 ± 5.5 vs 10.7 ± 5.3; p < 0.001), had more psychobehavioral manifestations (Ardouin Scale of Behavior in Parkinson's Disease total: 7.7 ± 5.1 vs 5.1 ± 0.4; p = 0.003), and had worse quality of life (Parkinson's Disease Questionnaire-39: 33 ± 12 vs 29 ± 12; p = 0.03), as compared to pre-opRBD- patients. Both pre-opRBD+ and pre-opRBD- patients had significant MDS-UPDRS IV score decrease (-37% and -33%, respectively), MDS-UPDRS III "med 'off'/stim 'on'" score decrease (-52% and -54%), and dopaminergic treatment decrease (-52% and -49%) after surgery, with no between-group difference. There was no between-group difference for cognitive and global quality of life outcomes.

CONCLUSIONS

In patients with PD eligible for STN-DBS, the presence of probable RBD preoperatively is not associated with a different clinical outcome 1 year after neurosurgery.

TRIAL REGISTRATION INFORMATION

NCT02360683.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that in patients with PD eligible for STN-DBS, the presence of probable RBD preoperatively is not associated with poorer outcomes 1 year post surgery.

Toward living neuroprosthetics: developing a biological brain pacemaker as a living neuromodulatory implant for improving parkinsonian symptoms

Objective.Therapeutic intervention for Parkinson's disease (PD) via deep brain stimulation (DBS) represents the current paradigm for managing the advanced stages of the disease in patients when treatment with pharmaceuticals becomes inadequate. Although DBS is the prevailing therapy in these cases, the overall effectiveness and reliability of DBS can be diminished over time due to hardware complications and biocompatibility issues with the electronic implants. To achieve a lifetime solution, we envision that the next generation of neural implants will be entirely 'biological' and 'autologous', both physically and functionally. Thus, in this study, we set forth toward developing a biological brain pacemaker for treating PD. Our focus is to investigate engineering strategies for creating a multicellular biological circuit that integrates innate biological design and function while incorporating principles of neuromodulation to create a biological mechanism for delivering high-frequency stimulation with cellular specificity.Approach.We engineer a 3D multicellular circuit design built entirely from biological and biocompatible components using established tissue engineering protocols to demonstrate the feasibility of creating a living neural implant. Furthermore, using 2D co-culture systems, we investigate the physiologically relevant parameters that would be necessary to further develop a therapeutic benefit of high-frequency stimulation with cellular specificity within our construct design.Main results.Our results demonstrate the feasibility of fabricating a 3D multicellular circuit device in an implantable form. Furthermore, we show we can organize cellular materials to create potential functional connections in normal physiological conditions, thus laying down the foundation of designing a high-frequency pacing system for selective and controlled therapeutic neurostimulation.Significance.The findings from this study may lead to the future development of autologous living neural implants that both circumvent the issues inherent in electronic neural implants and form more biocompatible devices with lifelong robustness to repair and restore motor functions, with the ultimate benefit for patients with PD.

Deep Brain Stimulation of the Subthalamic Nucleus in Parkinson's Disease: A Meta-Analysis of Mood Effects

This meta-analysis examines mood changes after bilateral subthalamic deep brain stimulation (STN-DBS) in patients with Parkinson's disease (PD). Deep brain stimulation improves motor outcomes in Parkinson's disease but there appears to be conflicting reports as to subsequent mood outcomes. Pubmed, PsychINFO and SCOPUS were searched for studies assessing mood outcomes in PD patients who had undergone STN-DBS published between January 2003 and the end of January 2019. Random effects meta-analyses were conducted for all outcome groups with at least two studies homogenous in design and measure. Forty-eight studies, providing data on negative moods (such as depression, anxiety, apathy, and anger) and positive moods (pleasure and euphoria) were assessed. Results of the meta-analysis suggest that post-DBS, depression and anxiety symptoms improve and there is a reduction in negative affect, an increase in apathy, and in energy level. Although there have been reported cases of mania post-DBS surgery, the meta-analysis suggested no significant changes in symptoms of mania in the broader DBS population. Considerable heterogeneity was found and partially addressed through meta-regression and qualitative assessment of the included STN-DBS controlled studies. The major strengths of this meta-analysis, include attention to outcome validity, heterogeneity, independence of samples, and clinical utility, with the potential to improve post-operative safety through comprehensive consideration of mood and psychological adjustment. It appears that STN-DBS is a relatively safe and, in the case of mood symptomatology, an advantageous treatment of Parkinson's disease.

Apathy Induced by Subthalamic Nucleus Deep Brain Stimulation in Parkinson's Disease: A Meta-Analysis

Apathy, the loss of motivation, is a common problem in Parkinson's disease (PD) and often observed following deep brain stimulation (DBS) of the subthalamic nucleus (STN). The aim of this meta-analysis was to determine the occurrence of apathy following STN DBS in literature. Relevant articles were searched in PubMed/Medline, SCOPUS, EMBASE, and Web of Sciences electronic databases. Studies were included if they reported apathy scores pre- and post-DBS or the cross-sectional difference between PD patients receiving STN DBS and patients receiving medication only. Thirty-three articles were included in the meta-analyses from 6,658 screened articles by two authors independently. A total of 1,286 patients were included with a mean age (±standard deviation [SD]) of 58.4 ± 8.5 years and a disease duration of 11.0 ± 5.8 years. The apathy score measured by means of the Apathy Evaluation Scale (AES), Starkstein Apathy Scale (SAS), and the Lille Apathy Rating Scale (LARS) was significantly higher after DBS than pre-operatively (g = 0.34, 95% confidence interval [CI] = 0.19-0.48, P < 0.001). An equal, significant difference in severity of apathy was found between STN DBS and medication only (g = 0.36, 95% CI = 0.03-0.65; P = 0.004). Statistical heterogeneity was moderately high, but the effects stood strong after multiple analyses and were independent of tapering off dopaminergic medication. The findings of this meta-analysis indicate that apathy is increased after STN DBS compared to the pre-operative state and to medication only (systematic review registration number: PROSPERO CRD42019133932). © 2020 Universiteit van Amsterdam. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Deep Brain Stimulation of the Subthalamic Nucleus Modulates Reward-Related Behavior: A Systematic Review

Deep brain stimulation of the subthalamic nucleus (STN-DBS) is an effective treatment for the motor symptoms of movement disorders including Parkinson's Disease (PD). Despite its therapeutic benefits, STN-DBS has been associated with adverse effects on mood and cognition. Specifically, apathy, which is defined as a loss of motivation, has been reported to emerge or to worsen following STN-DBS. However, it is often challenging to disentangle the effects of STN-DBS per se from concurrent reduction of dopamine replacement therapy, from underlying PD pathology or from disease progression. To this end, pre-clinical models allow for the dissociation of each of these factors, and to establish neural substrates underlying the emergence of motivational symptoms following STN-DBS. Here, we performed a systematic analysis of rodent studies assessing the effects of STN-DBS on reward seeking, reward motivation and reward consumption across a variety of behavioral paradigms. We find that STN-DBS decreases reward seeking in the majority of experiments, and we outline how design of the behavioral task and DBS parameters can influence experimental outcomes. While an early hypothesis posited that DBS acts as a "functional lesion," an analysis of lesions and inhibition of the STN revealed no consistent pattern on reward-related behavior. Thus, we discuss alternative mechanisms that could contribute to the amotivational effects of STN-DBS. We also argue that optogenetic-assisted circuit dissection could yield important insight into the effects of the STN on motivated behavior in health and disease. Understanding the mechanisms underlying the effects of STN-DBS on motivated behavior-will be critical for optimizing the clinical application of STN-DBS.

Deep brain stimulation of the internal globus pallidus does not affect the limbic circuit in patients with Parkinson's disease: a PET study

INTRODUCTION

Internal globus pallidus (GPi) deep brain stimulation (DBS) is a safe and effective alternative treatment in Parkinson's disease (PD) for patients with cognitive impairment. However, no study has yet investigated metabolic changes within a large series of patients undergoing GPi stimulation.

OBJECTIVE

We assessed motor, cognitive and psychiatric changes, as well as modifications in brain glucose metabolism measured with FDG-PET, before and after bilateral GPi-DBS.

METHODS

In the same week, 32 patients with PD underwent a motor, cognitive and psychiatric assessment and a resting-state FDG-PET scan, 4 months before and 4 months after GPi-DBS surgery. For the voxelwise metabolic change assessment, the p value was controlled for multiple comparisons using the family wise error rate.

RESULTS

After GPi-DBS surgery, patients showed a significant overall improvement in motor status. No cognitive or psychiatric changes were observed after surgery. Nor were any clusters with significantly relative metabolic changes found in the limbic circuit after surgery. Clusters with significantly relative metabolic changes were observed in the left and right Brodmann area (BA) 6, the right BA 9, the right and left BA 39 and the left BA 17.

CONCLUSION

The present study confirmed that GPi-DBS is an effective treatment in patients with advanced PD, owing to metabolic changes in the areas involved in motor execution. The absence of relative metabolic decrease in the limbic circuit and the few changes affecting the associative circuit could explain why GPi-DBS is cognitively safe.

Subthalamic Nucleus Stimulation Does Not Have Any Acute Effects on Verbal Fluency or on Speed of Word Generation in Parkinson's Disease

BACKGROUND

Deep brain stimulation of the subthalamic nucleus (STN-DBS) has been shown to be generally safe from a cognitive perspective, with consistent evidence that the major impact of STN-DBS in Parkinson's disease (PD) is on verbal fluency.

OBJECTIVE

The aim of this study was first to identify the influence of acute manipulation of STN-DBS in PD on the number and time pattern of word generation on different verbal fluency (VF) tasks, phonemic, switching, and cued switching, and second to determine whether cueing improved VF and if cueing effects interacted with STN-DBS effects.

METHODS

Parallel versions of these three verbal fluency tasks were completed by 31 patients with Parkinson's disease who had had bilateral DBS of the STN, twice, with DBS On and Off, with the order counterbalanced across patients.

RESULTS

There was no effect of acute STN-DBS on the total number of words generated during verbal fluency. As expected, the number of words generated significantly declined over the six 10-second intervals of the verbal fluency tasks, but this time pattern of word generation was not altered by STN-DBS. External cueing significantly increased the number of words generated relative to an uncued switching verbal fluency task, but the cueing effect on VF was not altered by STN-DBS.

CONCLUSION

In conclusion, (i) acute STN-DBS manipulation did not alter either verbal fluency performance or the time pattern of word generation and (ii) external cueing significantly improved verbal fluency performance both with STN-DBS On and Off.

Clinimetric approach to rating scales for the assessment of apathy in Parkinson's disease: A systematic review

A number of rating scales for the assessment of apathy in Parkinson's disease (PD) were developed. Unfortunately, previous studies focused mainly on psychometric criteria rather than on clinimetric principles to develop these assessment instruments. In the clinimetric approach, the clinical validity of a rating scale, rather than its statistical significance, has the priority. The aim of the present systematic review was to capture the clinimetric properties of these rating scales and to identify the measures, which display clinical validity for the assessment of apathy in PD. The systematic search was conducted on Scopus, PsycINFO, PubMed, Web of Science, ScienceDirect, and Medline following the PRISMA guidelines. A total of 44 studies were included and analyzed in this systematic review. The apathy rating scales, which were found to be psychometrically robust and reliable, were actually clinically questionable. The apathy measures, which displayed clinimetric properties, were the Starkstein Apathy Scale (SAS), the 5-item version of the World Health Organization Well-Being Index (WHO-5), the Neurasthenia Scale and the Lille Apathy Rating Scale (LARS). The SAS was found to be clinically valid at a macro-analytic level, particularly when used either to exclude the presence of symptoms of apathy or to evaluate the side effects of medications. The WHO-5 and the Neurasthenia Scale were found to be clinically valid only at a micro-analytic level and can be used as screening measures for the assessment of the severity of symptoms of apathy. The LARS was a clinically valid instrument to be used for the diagnosis of apathy.

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.

Apathy Associated With Impaired Recognition of Happy Facial Expressions in Huntington's Disease

OBJECTIVES

Previous research has demonstrated an association between emotion recognition and apathy in several neurological conditions involving fronto-striatal pathology, including Parkinson's disease and brain injury. In line with these findings, we aimed to determine whether apathetic participants with early Huntington's disease (HD) were more impaired on an emotion recognition task compared to non-apathetic participants and healthy controls.

METHODS

We included 43 participants from the TRACK-HD study who reported apathy on the Problem Behaviours Assessment - short version (PBA-S), 67 participants who reported no apathy, and 107 controls matched for age, sex, and level of education. During their baseline TRACK-HD visit, participants completed a battery of cognitive and psychological tests including an emotion recognition task, the Hospital Depression and Anxiety Scale (HADS) and were assessed on the PBA-S.

RESULTS

Compared to the non-apathetic group and the control group, the apathetic group were impaired on the recognition of happy facial expressions, after controlling for depression symptomology on the HADS and general disease progression (Unified Huntington's Disease Rating Scale total motor score). This was despite no difference between the apathetic and non-apathetic group on overall cognitive functioning assessed by a cognitive composite score.

CONCLUSIONS

Impairment of the recognition of happy expressions may be part of the clinical picture of apathy in HD. While shared reliance on frontostriatal pathways may broadly explain associations between emotion recognition and apathy found across several patient groups, further work is needed to determine what relationships exist between recognition of specific emotions, distinct subtypes of apathy and underlying neuropathology. (JINS, 2019, 25, 453-461).

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.

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.

Intermittent subthalamic nucleus deep brain stimulation induces risk-aversive behavior in human subjects

The subthalamic nucleus (STN) is a small almond-shaped subcortical structure classically known for its role in motor inhibition through the indirect pathway within the basal ganglia. Little is known about the role of the STN in mediating cognitive functions in humans. Here, we explore the role of the STN in human subjects making decisions under conditions of uncertainty using single-neuron recordings and intermittent deep brain stimulation (DBS) during a financial decision-making task. Intraoperative single-neuronal data from the STN reveals that on high-uncertainty trials, spiking activity encodes the upcoming decision within a brief (500 ms) temporal window during the choice period, prior to the manifestation of the choice. Application of intermittent DBS selectively prior to the choice period alters decisions and biases subject behavior towards conservative wagers.

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.

Apathy following Bilateral Deep Brain Stimulation of Subthalamic Nucleus in Parkinson's Disease: A Meta-Analysis

Bilateral deep brain stimulation of subthalamic nucleus (STN-DBS) has proven effective in improving motor symptoms in Parkinson's disease (PD) patients. However, psychiatric changes after surgery are controversial. In this study, we specifically analyzed apathy following bilateral STN-DBS in PD patients using a meta-analysis. Relevant articles utilized for this study were obtained through literature search on PubMed, ScienceDirect, and Embase databases. The articles included were those contained both pre- and postsurgery apathy data acquired using the Starkstein Apathy Scale or Apathy Evaluation Scale with patient follow-up of at least three months. A total of 9 out of 86 articles were included in our study through this strict screening process. Standardized mean difference (SMD), that is, Cohen's d, with a 95% confidence interval (CI) was calculated to show the change. We found a significant difference between the presurgery stage and the postsurgery stage scores (SMD = 0.35, 95% CI: 0.17∼0.52, P < 0.001). STN-DBS seems to relatively worsen the condition of apathy, which may result from both the surgery target (subthalamic nucleus) and the reduction of dopaminergic medication. Further studies should focus on the exact mechanisms of possible postoperative apathy in the future.

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.

Apathy following traumatic brain injury: A review

Apathy is a common problem after traumatic brain injury (TBI) and can have a major impact on cognitive function, psychosocial outcome and engagement in rehabilitation. For scientists and clinicians it remains one of the least understood aspects of brain-behaviour relationships encompassing disturbances of cognition, motivation, emotion and action, and is variously an indication of organic brain disease or psychiatric disorder. Apathy can be both sign and symptom and has been proposed as a diagnosis in its own right as well as a secondary feature of other conditions. This review considers previous approaches to apathy in terms of relevant psychological constructs and those neural counterparts most likely to be implicated after TBI. Neurobehavioural disorders of apathy are characterised chiefly by dysfunction of executive control of goal-oriented behaviour or the neural substrates of reward-based and emotional learning. We argue that it is possible to distinguish a primary disorder of apathy as an organic neurobehavioural state from secondary presentations due to an impoverished environment or psychological disturbance which has implications for treatment.

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.

Sleep-wake functions and quality of life in patients with subthalamic deep brain stimulation for Parkinson's disease

OBJECTIVES

Sleep-wake disturbances (SWD) are frequent in Parkinson's disease (PD). The effect of deep brain stimulation (DBS) on SWD is poorly known. In this study we examined the subjective and objective sleep-wake profile and the quality of life (QoL) of PD patients in the context of subthalamic DBS.

PATIENTS AND METHODS

We retrospectively analyzed data from PD patients and candidates for DBS in the nucleus suthalamicus (STN). Pre-DBS, sleep-wake assessments included subjective and objective (polysomnography, vigilance tests and actigraphy) measures. Post-DBS, subjective measures were collected. QoL was assessed using the Parkinson's Disease Questionnaire (PDQ-39) and the RAND SF-36-item Health Survey (RAND SF-36).

RESULTS

Data from 74 PD patients (62% male, mean age 62.2 years, SD = 8.9) with a mean UPDRS-III (OFF) of 34.2 (SD = 14.8) and 11.8 (SD = 4.5) years under PD treatment were analyzed. Pre-DBS, daytime sleepiness, apathy, fatigue and depressive symptoms were present in 49%, 34%, 38% and 25% of patients respectively but not always as co-occurring symptoms. Sleep-wake disturbances were significantly correlated with QoL scores. One year after STN DBS, motor signs, QoL and sleepiness improved but apathy worsened. Changes in QoL were associated with changes in sleepiness and apathy but baseline sleep-wake functions were not predictive of STN DBS outcome.

CONCLUSION

In PD patients presenting for STN DBS, subjective and objective sleep-wake disturbances are common and have a negative impact on QoL before and after neurosurgery. Given the current preliminary evidence, prospective observational studies assessing subjective and objective sleep-wake variables prior to and after DBS are needed.

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).

Deep Brain Stimulation Emergencies: How the New Technologies Could Modify the Current Scenario

After 25 years of deep brain stimulation (DBS) for the treatment of Parkinson's disease, it has become increasingly recognized that a range of postoperative urgent situations and emergencies may occur. In this review we describe the possible scenarios of DBS-related emergencies: perioperative (intraoperative and early postoperative) and postoperative settings and issues from suboptimal control of motor and nonmotor symptoms in the early programming phase and during long-term follow-up. We also outline potential advantages in the management of these emergencies offered by the newest devices, emerging technologies, and new possibilities in programming.

Comprehensive Psychopathological Assessment Based on the Association for Methodology and Documentation in Psychiatry (AMDP) System: Development, Methodological Foundation, Application in Clinical Routine, and Research

The documentation of psychopathology is core to the clinical practice of the psychiatrist and clinical psychologist. However, both in initial as well as further training and specialization in their fields, this particular aspect of their work receives scanty attention only. Yet, for the past 50 years, the Association for Methodology and Documentation in Psychiatry (AMDP) System has been in existence and available as a tool to serve precisely the purpose of offering a systematic introduction to the terminology and documentation of psychopathology. The motivation for its development was based on the need for an assessment procedure for the reliable documentation of the effectiveness of newly developed psychopharmacological substances. Subsequently, the AMDP-System began to be applied in the context of investigations into a number of methodological issues in psychiatry (e.g., the frequency and specificity of particular symptoms, the comparison of rating scales). The System then became increasingly important also in clinical practice and, today, represents the most used instrument for the documentation of psychopathology in the German-speaking countries of Europe. This paper intends to offer an overview of the AMDP-System, its origins, design, and functionality. After an initial account of the history and development of the AMDP-System, the discussion will in turn focus on the System's underlying methodological principles, the transfer of clinical skills and competencies in its practical application, and its use in research and clinical practice. Finally, potential future areas of development in relation to the AMDP-System are explored.

Apathy and Reduced Speed of Processing Underlie Decline in Verbal Fluency following DBS

Objective. Reduced verbal fluency is a strikingly uniform finding following deep brain stimulation (DBS) for Parkinson's disease (PD). The precise cognitive mechanism underlying this reduction remains unclear, but theories have suggested reduced motivation, linguistic skill, and/or executive function. It is of note, however, that previous reports have failed to consider the potential role of any changes in speed of processing. Thus, the aim of this study was to examine verbal fluency changes with a particular focus on the role of cognitive speed. Method. In this study, 28 patients with PD completed measures of verbal fluency, motivation, language, executive functioning, and speed of processing, before and after DBS. Results. As expected, there was a marked decline in verbal fluency but also in a timed test of executive functions and two measures of speed of processing. Verbal fluency decline was associated with markers of linguistic and executive functioning, but not after speed of processing was statistically controlled for. In contrast, greater decline in verbal fluency was associated with higher levels of apathy at baseline, which was not associated with changes in cognitive speed. Discussion. Reduced generativity and processing speed may account for the marked reduction in verbal fluency commonly observed following DBS.

Impact of STN-DBS on mood, drive, anhedonia and risk of psychiatric side-effects in the population of PD patients

BACKGROUND

DBS is a surgical method of choice for various movement disorders, especially for Parkinson's disease (PD). Many publications showing improvement in motor symptoms and quality of life have been presented while there is little comprehensive research evaluation of the impact of DBS on mental state and psychiatric side-effects.

OBJECT

The purpose of this study was to assess the impact of DBS on mood, drive, anhedonia and psychotic symptoms in the group of PD patients.

METHODS

60 patients with PD were treated with STN-DBS. Mental state and psychiatric side effects were assessed with the use of MADRS, HADRS, BDI, BPRS, YMS, SHAPS, CGI and PGI rating scales. Evaluation was performed five times in the period from the day before surgery to six months after implantation of the DBS.

RESULTS

This study showed an improvement of mood, which has followed within a month after the start of stimulation and manifested in MADRS, HADRS, BDI scores reduction. The trend towards improvement was maintained over the following 6months. No manic episodes appeared, 2 cases of mild hypomania were observed. Psychotic symptoms occurred in 1 patient. Anhedonia reduction observed during the first 30days after initiating the stimulation persisted in the assessment six months after implantation of the DBS.

CONCLUSIONS

The survey results confirm the effect of stimulation on mood, drive, ability to feel pleasure. Psychiatric side effects such as phase change were rare and mild, while psychotic symptoms that occurred in one patient ware manageable through medication. Further intensive research in this topic are required.

Subthalamic nucleus deep brain stimulation on motor-symptoms of Parkinson's disease: Focus on neurochemistry

Deep brain stimulation (DBS) has become a standard therapy for Parkinson's disease (PD) and it is also currently under investigation for other neurological and psychiatric disorders. Although many scientific, clinical and ethical issues are still unresolved, DBS delivered into the subthalamic nucleus (STN) has improved the quality of life of several thousands of patients. The mechanisms underlying STN-DBS have been debated extensively in several reviews; less investigated are the biochemical consequences, which are still under scrutiny. Crucial and only partially understood, for instance, are the complex interplays occurring between STN-DBS and levodopa (LD)-centred therapy in the post-surgery follow-up. The main goal of this review is to address the question of whether an improved motor control, based on STN-DBS therapy, is also achieved through the additional modulation of other neurotransmitters, such as noradrenaline (NA) and serotonin (5-HT). A critical issue is to understand not only acute DBS-mediated effects, but also chronic changes, such as those involving cyclic nucleotides, capable of modulating circuit plasticity. The present article will discuss the neurochemical changes promoted by STN-DBS and will document the main results obtained in microdialysis studies. Furthermore, we will also examine the preliminary achievements of voltammetry applied to humans, and discuss new hypothetical investigational routes, taking into account novel players such as glia, or subcortical regions such as the pedunculopontine (PPN) area. Our further understanding of specific changes in brain chemistry promoted by STN-DBS would further disseminate its utilisation, at any stage of disease, avoiding an irreversible lesioning approach.

Reward sensitivity deficits modulated by dopamine are associated with apathy in Parkinson's disease

Apathy is a debilitating and under-recognized condition that has a significant impact in many neurodegenerative disorders. In Parkinson's disease, it is now known to contribute to worse outcomes and a reduced quality of life for patients and carers, adding to health costs and extending disease burden. However, despite its clinical importance, there remains limited understanding of mechanisms underlying apathy. Here we investigated if insensitivity to reward might be a contributory factor and examined how this relates to severity of clinical symptoms. To do this we created novel ocular measures that indexed motivation level using pupillary and saccadic response to monetary incentives, allowing reward sensitivity to be evaluated objectively. This approach was tested in 40 patients with Parkinson's disease, 31 elderly age-matched control participants and 20 young healthy volunteers. Thirty patients were examined ON and OFF their dopaminergic medication in two counterbalanced sessions, so that the effect of dopamine on reward sensitivity could be assessed. Pupillary dilation to increasing levels of monetary reward on offer provided quantifiable metrics of motivation in healthy subjects as well as patients. Moreover, pupillary reward sensitivity declined with age. In Parkinson's disease, reduced pupillary modulation by incentives was predictive of apathy severity, and independent of motor impairment and autonomic dysfunction as assessed using overnight heart rate variability measures. Reward sensitivity was further modulated by dopaminergic state, with blunted sensitivity when patients were OFF dopaminergic drugs, both in pupillary response and saccadic peak velocity response to reward. These findings suggest that reward insensitivity may be a contributory mechanism to apathy and provide potential new clinical measures for improved diagnosis and monitoring of apathy.media-1vid110.1093/brain/aww188_video_abstractaww188_video_abstract.

The hidden sister of motor fluctuations in Parkinson's disease: A review on nonmotor fluctuations

Only a few years after the introduction of levodopa, the first descriptions of motor fluctuations and dyskinesia related to dopaminergic therapy appeared. In PD, attention turned to their management, that had dampened the euphoria of the "levodopa miracle." It soon became clear that neuropsychiatric, autonomic, and sensory features also tend to develop fluctuations after chronic exposure to l-dopa. The diversity of fluctuating nonmotor symptoms, their largely subjective nature, coupled with a frequent lack of insight led to difficulties in identification and quantification. This may explain why, despite the high impact of nonmotor symptoms on patient autonomy and quality of life, evaluation of nonmotor fluctuations is not part of clinical routine. In view of the lack of specific validated assessment tools, detailed anamnesis should ideally be coupled with an evaluation in both ON and OFF drug conditions. The mechanisms of nonmotor fluctuations are not well understood. It is thought that they share dopaminergic presynaptic pharmacokinetic and postsynaptic pharmacodynamic mechanisms with the classical motor complications, but involve different neural pathways. Although symptoms fluctuate with dopaminergic treatment, serotonine and norepinephrine denervation, as well as interactions between neurotransmitter systems, probably contribute to their diversity. The lack of validated tools for assessment of these phenomena explains the almost complete absence of treatment studies. Management, largely resulting from expert opinion, includes psychiatric follow-up, nondopaminergic drugs, and advanced dopaminergic treatment, including drug delivery pumps and DBS. This review aims to provide a starting point for the understanding, diagnosis, and management of nonmotor fluctuations. © 2016 International Parkinson and Movement Disorder Society.

Apathy in patients with Parkinson's disease following deep brain stimulation of the subthalamic nucleus

OBJECTIVE

Apathy has been reported as a possible adverse effect of deep brain stimulation of the subthalamic nucleus (STN-DBS). We investigated the prevalence and severity of apathy in 22 patients with Parkinson's disease (PD) who underwent STN-DBS, as well as the effects of apathy on quality of life (QOL).

METHODS

All patients were assessed with the Lille Apathy Rating Scale (LARS), the Apathy Scale (AS), and the Parkinson's Disease Questionnaire and were compared to a control group of 38 patients on pharmacotherapy alone.

RESULTS

There were no significant differences in the prevalence or severity of apathy between patients who had undergone STN-DBS and those on pharmacotherapy alone. Significant correlations were observed between poorer QOL and degree of apathy, as measured by the LARS (p<0.001) and the AS (p=0.021). PD-related disability also correlated with both apathy ratings (p<0.001 and p=0.017, respectively).

CONCLUSION

Our findings suggest that STN-DBS is not necessarily associated with apathy in the PD population; however, more severe apathy appears to be associated with a higher level of disability due to PD and worse QOL, but no other clinico-demographic characteristics.