Manic behaviour induced by deep-brain stimulation in Parkinson's disease: evidence of substantia nigra implication?

Elevated Mood Induced by Subthalamic Nucleus Deep Brain Stimulation: A Video-Recorded Case Report

Background

Deep brain stimulation (DBS) can be an effective therapy to control motor signs in patients with Parkinson's disease (PD). However, subthalamic nucleus (STN) DBS can induce undesirable psychiatric adverse effects, including elevated mood.

Case report

We reported a video case of a 73-year-old male implanted with bilateral STN DBS who experienced stimulation-induced elevated mood. A correlation between mood changes and enhanced activation of the ventromedial region in the left STN was observed.

Discussion

This video case report illustrates STN DBS-induced elevated mood and enhances early symptom recognition for patients and diagnostic awareness for professionals.

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.

Electrophysiologic Evidence That Directional Deep Brain Stimulation Activates Distinct Neural Circuits in Patients With Parkinson Disease

OBJECTIVES

Deep brain stimulation (DBS) delivered via multicontact leads implanted in the basal ganglia is an established therapy to treat Parkinson disease (PD). However, the different neural circuits that can be modulated through stimulation on different DBS contacts are poorly understood. Evidence shows that electrically stimulating the subthalamic nucleus (STN) causes a therapeutic effect through antidromic activation of the hyperdirect pathway-a monosynaptic connection from the cortex to the STN. Recent studies suggest that stimulating the substantia nigra pars reticulata (SNr) may improve gait. The advent of directional DBS leads now provides a spatially precise means to probe these neural circuits and better understand how DBS affects distinct neural networks.

MATERIALS AND METHODS

We measured cortical evoked potentials (EPs) using electroencephalography (EEG) in response to low-frequency DBS using the different directional DBS contacts in eight patients with PD.

RESULTS

A short-latency EP at 3 milliseconds originating from the primary motor cortex appeared largest in amplitude when stimulating DBS contacts closest to the dorsolateral STN (p < 0.001). A long-latency EP at 10 milliseconds originating from the premotor cortex appeared strongest for DBS contacts closest to the SNr (p < 0.0001).

CONCLUSIONS

Our results show that at the individual patient level, electrical stimulation of different nuclei produces distinct EP signatures. Our approach could be used to identify the functional location of each DBS contact and thus help patient-specific DBS programming.

CLINICAL TRIAL REGISTRATION

The ClinicalTrials.gov registration number for the study is NCT04658641.

Limbic stimulation drives mania in STN-DBS in Parkinson disease: a prospective study

In this one-year prospective study, Parkinson's disease (PD) patients with or without mania following STN-DBS were compared to investigate risk and etiological factors, clinical management and consequences. Eighteen (16.2%) out of 111 consecutive PD patients developed mania, of whom 17 were males. No preoperative risk factor was identified. Postoperative mania was related to ventral limbic subthalamic stimulation in 15 (83%) patients, and resolved as stimulation was relocated to the sensorimotor STN, besides discontinuation or reduction of dopamine agonists and use of low-dose clozapine in 12 patients, while motor and nonmotor outcomes were similar. These findings underpin the prominent role of limbic subthalamic stimulation in postoperative mania. This article is protected by copyright. All rights reserved.

Bipolar Spectrum disorders in Parkinson's disease: a systematic evaluation

OBJECTIVE

Psychiatric disorders are very common in patients affected by Parkinson's disease (PD). However, comorbidity with Bipolar Spectrum disorders is understudied. The aim of this study is to explore the clinical correlates of PD associated with Bipolar Spectrum disorders.

METHODS

One hundred PD patients were screened for psychiatric comorbidities, cognitive profile, motor, and non-motor symptoms. The sample was divided into three groups: PD-patients with Bipolar Spectrum disorders (bipolar disorder type I, type II, and spontaneous or induced hypomania; N = 32), PD-patients with others psychiatric comorbidities (N = 39), PD-patients without psychiatric comorbidities (N = 29). Clinical features were compared among the groups using analysis of variance and chi-square test. A logistic regression was performed to evaluate the association between Bipolar Spectrum disorders and early onset of PD (≤50 years) controlling for lifetime antipsychotic use.

RESULTS

In comparison with PD patients with and without other psychiatric comorbidity, subjects affected by Bipolar Spectrum disorders were younger, showed more frequently an early onset PD, reported more involuntary movements and a higher rate of impulse control disorders and compulsive behaviors. No differences were observed in indexes of exposure to dopamine agonist treatments. The early onset of PD was predicted by Bipolar Spectrum comorbidity, independently from lifetime antipsychotic use.

CONCLUSION

Bipolar Spectrum disorders are common in early onset PD. The presence of bipolar comorbidity could identify a particular subtype of PD, showing higher rates of neurological and psychiatric complications and deserving further investigation.

Target selection for deep brain stimulation in treatment resistant schizophrenia

The use of deep brain stimulation (DBS) in treatment resistant patients with schizophrenia is of considerable current interest, but where to site the electrodes is challenging. This article reviews rationales for electrode placement in schizophrenia based on evidence for localized brain abnormality in the disorder and the targets that have been proposed and employed to date. The nucleus accumbens and the subgenual anterior cingulate cortex are of interest on the grounds that they are sites of potential pathologically increased brain activity in schizophrenia and so susceptible to the local inhibitory effects of DBS; both sites have been employed in trials of DBS in schizophrenia. Based on other lines of reasoning, the ventral tegmental area, the substantia nigra pars reticulata and the habenula have also been proposed and in some cases employed. The dorsolateral prefrontal cortex has not been suggested, probably reflecting evidence that it is underactive rather than overactive in schizophrenia. The hippocampus is also of theoretical interest but there is no clear functional imaging evidence that it shows overactivity in schizophrenia. On current evidence, the nucleus accumbens may represent the strongest candidate for DBS electrode placement in schizophrenia, with the substantia nigra pars reticulata also showing promise in a single case report; the ventral tegmental area is also of potential interest, though it remains untried.

Elevated Mood States in Patients With Parkinson's Disease Treated With Deep Brain Stimulation: Diagnosis and Management Strategies

OBJECTIVE

Deep brain stimulation (DBS) is an effective surgical treatment for patients with Parkinson's disease (PD). DBS therapy, particularly with the subthalamic nucleus (STN) target, has been linked to rare psychiatric complications, including depression, impulsivity, irritability, and suicidality. Stimulation-induced elevated mood states can also occur. These episodes rarely meet DSM-5 criteria for mania or hypomania.

METHODS

The investigators conducted a chart review of 82 patients with PD treated with DBS.

RESULTS

Nine (11%) patients developed stimulation-induced elevated mood. Five illustrative cases are described (all males with STN DBS; mean age=62.2 years [SD=10.5], mean PD duration=8.6 years [SD=1.6]). Elevated mood states occurred during or shortly after programming changes, when more ventral contacts were used (typically in monopolar mode) and lasted minutes to months. Four patients experienced elevated mood at low amplitudes (1.0 V/1.0 mA); all had psychiatric risk factors (history of impulse-control disorder, dopamine dysregulation syndrome, substance use disorder, and/or bipolar diathesis) that likely contributed to mood destabilization.

CONCLUSIONS

Preoperative DBS evaluations should include a thorough assessment of psychiatric risk factors. The term "stimulation-induced elevated mood states" is proposed to describe episodes of elevated, expansive, or irritable mood and psychomotor agitation that occur during or shortly after DBS programming changes and may be associated with increased goal-directed activity, impulsivity, grandiosity, pressured speech, flight of ideas, or decreased need for sleep and may persist beyond stimulation adjustments. This clinical phenomenon should be considered for inclusion in the bipolar disorder category in future DSM revisions, allowing for increased recognition and appropriate management.

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.

Clinical research in psychopharmacology, the current situation and its perspectives. A conversation with Pierre-Michel Llorca

For this issue, Luc Zimmer, professor of pharmacology and chair of the Neuropsychopharmacology Committee of the French Society of Pharmacology and Therapeutics (SFPT), talked with Michel Llorca, professor of psychiatry at the Université d'Auvergne and head of a department of psychiatry at the University Hospital of Clermond-Ferrand. They discuss together the positioning of psychiatry in the neurosciences and the need to build bridges with other medical disciplines. Through examples and professional experiences, they also talk about the difficulties of developing clinical biomarkers for psychiatry and ultimately for psychopharmacology. Finally, they discuss the current difficulties facing research of drugs for psychiatry, pointing out some success stories.

Mapping mania symptoms based on focal brain damage

BACKGROUNDAlthough mania is characteristic of bipolar disorder, it can also occur following focal brain damage. Such cases may provide unique insight into brain regions responsible for mania symptoms and identify therapeutic targets.METHODSLesion locations associated with mania were identified using a systematic literature search (n = 41) and mapped onto a common brain atlas. The network of brain regions functionally connected to each lesion location was computed using normative human connectome data (resting-state functional MRI, n = 1000) and contrasted with those obtained from lesion locations not associated with mania (n = 79). Reproducibility was assessed using independent cohorts of mania lesions derived from clinical chart review (n = 15) and of control lesions (n = 490). Results were compared with brain stimulation sites previously reported to induce or relieve mania symptoms.RESULTSLesion locations associated with mania were heterogeneous and no single brain region was lesioned in all, or even most, cases. However, these lesion locations showed a unique pattern of functional connectivity to the right orbitofrontal cortex, right inferior temporal gyrus, and right frontal pole. This connectivity profile was reproducible across independent lesion cohorts and aligned with the effects of therapeutic brain stimulation on mania symptoms.CONCLUSIONBrain lesions associated with mania are characterized by a specific pattern of brain connectivity that lends insight into localization of mania symptoms and potential therapeutic targets.FUNDINGFundação para a Ciência e Tecnologia (FCT), Harvard Medical School DuPont-Warren Fellowship, Portuguese national funds from FCT and Fundo Europeu de Desenvolvimento Regional, Child Neurology Foundation Shields Research, Sidney R. Baer, Jr. Foundation, Nancy Lurie Marks Foundation, Mather's Foundation, and the NIH.

Transcending the brain: is there a cost to hacking the nervous system?

Great advancements have recently been made to understand the brain and the potential that we can extract out of it. Much of this has been centred on modifying electrical activity of the nervous system for improved physical and cognitive performance in those with clinical impairment. However, there is a risk of going beyond purely physiological performance improvements and striving for human enhancement beyond traditional human limits. Simple ethical guidelines and legal doctrine must be examined to keep ahead of technological advancement in light of the impending mergence between biology and machine. By understanding the role of modern ethics, this review aims to appreciate the fine boundary between what is considered ethically justified for current neurotechnology.

MRI Atlas of the Human Deep Brain

Mastering detailed anatomy of the human deep brain in clinical neurosciences is challenging. Although numerous pioneering works have gathered a large dataset of structural and topographic information, it is still difficult to transfer this knowledge into practice, even with advanced magnetic resonance imaging techniques. Thus, classical histological atlases continue to be used to identify structures for stereotactic targeting in functional neurosurgery. Physicians mainly use these atlases as a template co-registered with the patient's brain. However, it is possible to directly identify stereotactic targets on MRI scans, enabling personalized targeting. In order to help clinicians directly identify deep brain structures relevant to present and future medical applications, we built a volumetric MRI atlas of the deep brain (MDBA) on a large scale (infra millimetric). Twelve hypothalamic, 39 subthalamic, 36 telencephalic, and 32 thalamic structures were identified, contoured, and labeled. Nineteen coronal, 18 axial, and 15 sagittal MRI plates were created. Although primarily designed for direct labeling, the anatomic space was also subdivided in twelfths of AC-PC distance, leading to proportional scaling in the coronal, axial, and sagittal planes. This extensive work is now available to clinicians and neuroscientists, offering another representation of the human deep brain ([https://hal.archives-ouvertes.fr/] [hal-02116633]). The atlas may also be used by computer scientists who are interested in deciphering the topography of this complex region.

Treatment of psychiatric disturbances in hypokinetic movement disorders

Introduction: We reviewed studies that assessed the treatment of psychiatric disturbances in Parkinson's disease and atypical parkinsonisms. Neuropsychiatric disturbances in these conditions are frequent and have a profound impact on quality of life of patients and of their caregivers. It is therefore important to be familiar with the appropriate pharmacological and non-pharmacological interventions for treating these disorders. Areas covered: The authors searched for papers in English in Pubmed using the following keywords: Parkinson's disease, multiple system atrophy, progressive supranuclear palsy, corticobasal degeneration, Lewy body dementia, depression, apathy, anxiety, fatigue, sleep disorders, obsessive compulsive disorders, psychosis, hallucinations, delusions, impulse control disorders. Expert opinion: In Parkinson's disease, depression may benefit from the optimization of dopaminergic therapy, from the use of antidepressants acting on both the serotoninergic and noradrenergic pathways and from cognitive behavioral therapy. Psychosis in Parkinson's disease may improve with the use of clozapine; the serotonin inverse agonist pimavanserin has been shown to be effective. Treatment of impulse control disorders is primarily based on the removal of dopamine agonists. No controlled studies have investigated the treatment of neuropsychiatric disorders in multiple system atrophy, progressive supranuclear palsy or corticobasal degeneration. Acethylcholinesterase inhibitors may be used to treat hallucinations in Lewy body dementia.

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).

Transcriptome Changes in Relation to Manic Episode

Bipolar disorder (BD) is highly heritable and well known for its recurrent manic and depressive episodes. The present study focused on manic episode in BD patients and aimed to investigate state-specific transcriptome alterations between acute episode and remission, including messenger RNAs (mRNAs), long noncoding RNAs (lncRNAs), and micro-RNAs (miRNAs), using microarray and RNA sequencing (RNA-Seq) platforms. BD patients were enrolled with clinical information, and peripheral blood samples collected at both acute and remission status spanning for at least 2 months were confirmed by follow-ups. Symptom severity was assessed by Young Mania Rating Scale. We enrolled six BD patients as the discovery samples and used the Affymetrix Human Transcriptome Array 2.0 to capture transcriptome data at the two time points. For replication, expression data from Gene Expression Omnibus that consisted of 11 BD patients were downloaded, and we performed a mega-analysis for microarray data of 17 patients. Moreover, we conducted RNA sequencing (RNA-Seq) in additional samples of 7 BD patients. To identify intraindividual differentially expressed genes (DEGs), we analyzed data using a linear model controlling for symptom severity. We found that noncoding genes were of majority among the top DEGs in microarray data. The expression fold change of coding genes among DEGs showed moderate to high correlations (∼0.5) across platforms. A number of lncRNAs and two miRNAs (MIR181B1 and MIR103A1) exhibited high levels of gene expression in the manic state. For coding genes, we reported that the taste function-related genes, including TAS2R5 and TAS2R3, may be mania state-specific markers. Additionally, four genes showed a nominal p-value of less than 0.05 in all our microarray data, mega-analysis, and RNA-Seq analysis. They were upregulated in the manic state and consisted of MS4A14, PYHIN1, UTRN, and DMXL2, and their gene expression patterns were further validated by quantitative real-time polymerase chain reaction (PCR) (qRT-PCR). We also performed weight gene coexpression network analysis to identify gene modules for manic episode. Genes in the mania-related modules were different from the susceptible loci of BD obtained from genome-wide association studies, and biological pathways in relation to these modules were mainly related to immune function, especially cytokine-cytokine receptor interaction. Results of the present study elucidated potential molecular targets and genomic networks that are involved in manic episode. Future studies are needed to further validate these biomarkers for their roles in the etiology of bipolar illness.

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.

Anatomical Correlates of Uncontrollable Laughter With Unilateral Subthalamic Deep Brain Stimulation in Parkinson's Disease

Introduction

Subthalamic nucleus deep brain stimulation (STN-DBS) is a well-established treatment for the management of motor complications in Parkinson’s disease. Uncontrollable laughter has been reported as a rare side effect of STN stimulation. The precise mechanism responsible for this unique phenomenon remains unclear. We examined in detail the DBS electrode position and stimulation parameters in two patients with uncontrollable laughter during programming after STN-DBS surgery and illustrated the anatomical correlates of the acute mood changes with STN stimulation.

Case report

Unilateral STN-DBS induced uncontrollable laughter with activation of the most ventral contacts in both patients. However, the location of the electrodes responsible for this adverse effect differed between the patients. In the first patient, the DBS lead was placed more inferiorly and medially within the STN. In the second patient, the DBS lead was implanted more anteriorly and inferiorly than initially planned at the level of the substantia nigra reticulata (SNr).

Conclusion

Unilateral STN-DBS can induce acute uncontrollable laughter with activation of electrodes located more anterior, medial, and inferior in relationship with the standard stereotactic STN target. We suggest that simulation of ventral and medial STN, surrounding limbic structures or the SNr, is the most plausible anatomical substrate responsible for this acute mood and behavioral change. Our findings provide insight into the complex functional neuroanatomical relationship of the STN and adjacent structures important for mood and behavior. DBS programming with more dorsal and lateral contacts within the STN should be entertained to minimize the emotional side effects.

Deep Brain Stimulation in Parkinson's Disease: New and Emerging Targets for Refractory Motor and Nonmotor Symptoms

Parkinson's disease (PD) is a progressive neurodegenerative condition characterized by bradykinesia, tremor, rigidity, and postural instability (PI), in addition to numerous nonmotor manifestations. Many pharmacological therapies now exist to successfully treat PD motor symptoms; however, as the disease progresses, it often becomes challenging to treat with medications alone. Deep brain stimulation (DBS) has become a crucial player in PD treatment, particularly for patients who have disabling motor complications from medical treatment. Well-established DBS targets include the subthalamic nucleus (STN), the globus pallidus pars interna (GPi), and to a lesser degree the ventral intermediate nucleus (VIM) of the thalamus. Studies of alternative DBS targets for PD are ongoing, the majority of which have shown some clinical benefit; however, more carefully designed and controlled studies are needed. In the present review, we discuss the role of these new and emerging DBS targets in treating refractory axial motor symptoms and other motor and nonmotor symptoms (NMS).

Impact of Combined Subthalamic Nucleus and Substantia Nigra Stimulation on Neuropsychiatric Symptoms in Parkinson's Disease Patients

The goal of the study was to compare the tolerability and the effects of conventional subthalamic nucleus (STN) and combined subthalamic nucleus and substantia nigra (STN+SNr) high-frequency stimulation in regard to neuropsychiatric symptoms in Parkinson's disease patients. In this single center, randomized, double-blind, cross-over clinical trial, twelve patients with advanced Parkinson's disease (1 female; age: 61.3 ± 7.3 years; disease duration: 12.3 ± 5.4 years; Hoehn and Yahr stage: 2.2 ± 0.39) were included. Apathy, fatigue, depression, and impulse control disorder were assessed using a comprehensive set of standardized rating scales and questionnaires such as the Lille Apathy Rating Scale (LARS), Modified Fatigue Impact Scale (MFIS), Becks Depression Inventory (BDI-I), Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease Rating Scale (QUIP-RS), and Parkinson's Disease Questionnaire (PDQ-39). Three patients that were initially assigned to the STN+SNr stimulation mode withdrew from the study within the first week due to discomfort. Statistical comparison of data retrieved from patients who completed the study revealed no significant differences between both stimulation conditions in terms of mean scores of scales measuring apathy, fatigue, depression, impulse control disorder, and quality of life. Individual cases showed an improvement of apathy under combined STN+SNr stimulation. In general, combined STN+SNr stimulation seems to be safe in terms of neuropsychiatric side effects, although careful patient selection and monitoring in the short-term period after changing stimulation settings are recommended.

Stop! border ahead: Automatic detection of subthalamic exit during deep brain stimulation surgery

BACKGROUND

Microelectrode recordings along preplanned trajectories are often used for accurate definition of the subthalamic nucleus (STN) borders during deep brain stimulation (DBS) surgery for Parkinson's disease. Usually, the demarcation of the STN borders is performed manually by a neurophysiologist. The exact detection of the borders is difficult, especially detecting the transition between the STN and the substantia nigra pars reticulata. Consequently, demarcation may be inaccurate, leading to suboptimal location of the DBS lead and inadequate clinical outcomes.

METHODS

We present machine-learning classification procedures that use microelectrode recording power spectra and allow for real-time, high-accuracy discrimination between the STN and substantia nigra pars reticulata.

RESULTS

A support vector machine procedure was tested on microelectrode recordings from 58 trajectories that included both STN and substantia nigra pars reticulata that achieved a 97.6% consistency with human expert classification (evaluated by 10-fold cross-validation). We used the same data set as a training set to find the optimal parameters for a hidden Markov model using both microelectrode recording features and trajectory history to enable real-time classification of the ventral STN border (STN exit). Seventy-three additional trajectories were used to test the reliability of the learned statistical model in identifying the exit from the STN. The hidden Markov model procedure identified the STN exit with an error of 0.04 ± 0.18 mm and detection reliability (error < 1 mm) of 94%.

CONCLUSIONS

The results indicate that robust, accurate, and automatic real-time electrophysiological detection of the ventral STN border is feasible. © 2016 International Parkinson and Movement Disorder Society.

Post-operative imaging in deep brain stimulation: A controversial issue

In deep brain stimulation (DBS), post-operative imaging has been used on the one hand to assess complications, such as haemorrhage; and on the other hand, to detect misplaced contacts. The post-operative determination of the accurate location of the final electrode plays a critical role in evaluating the precise area of effective stimulation and for predicting the potential clinical outcome; however, safety remains a priority in postoperative DBS imaging. A plethora of diverse post-operative imaging methods have been applied at different centres. There is neither a consensus on the most efficient post-operative imaging methodology, nor is there any standardisation for the automatic or manual analysis of the images within the different imaging modalities. In this article, we give an overview of currently applied post-operative imaging modalities and discuss the current challenges in post-operative imaging in DBS.

Psychiatric Conditions in Parkinson Disease: A Comparison With Classical Psychiatric Disorders

Psychiatric conditions often complicate the outcome of patients affected by Parkinson disease (PD), but they differ from classical psychiatric disorders in terms of underlying biological mechanisms, clinical presentation, and treatment response. The purpose of the present review is to illustrate the biological and clinical aspects of psychiatric conditions associated with PD, with particular reference to the differences with respect to classical psychiatric disorders. A careful search of articles on main databases was performed in order to obtain a comprehensive review about the main psychiatric conditions associated with PD. A manual selection of the articles was then performed in order to consider only those articles that concerned with the topic of the review. Psychiatric conditions in patients with PD present substantial differences with respect to classical psychiatric disorders. Their clinical presentation does not align with the symptom profiles represented by Diagnostic and Statistical Manual for Mental Disorders and International Classification of Diseases. Furthermore, psychiatry treatment guidelines are of poor help in managing psychiatric symptoms of patients with PD. Specific diagnostic tools and treatment guidelines are needed to allow early diagnosis and adequate treatment of psychiatric conditions in comorbidity with PD.

The Quantitative Measurement of Reversible Acute Depression after Subthalamic Deep Brain Stimulation in a Patient with Parkinson Disease

Background. Depression is the most commonly reported mood symptom affecting 2–8% of patients after deep brain stimulation (DBS). Usually, symptoms develop gradually; however there have been cases of reproducible events that the mood symptoms were elicited within seconds to minutes after stimulation and were immediately reversible upon cessation of the stimulus. In the current study, we applied a self-reported questionnaire to assess the patient's mood state. Objective. To objectively measure the reversible acute depression induced by DBS in a patient with Parkinson disease (PD). Methods. A statistically validated Spanish version of the Beck Depression Inventory Short Form (BDI-SF) was used. The questionnaire was administered three times. Results. The patient became acutely depressed within ninety seconds of monopolar stimulation on the right side. His symptoms resolved immediately after changing the setting to bipolar stimulation. The BDI-SF scores during stimulation off, on, and off again were 15, 19, and 6, respectively. Conclusions. The BDI-SF scores increased during stimulation and decreased after cessation. This is consistent with a reversible depressive state. The poststimulation BDI-SF score decreased to less than half of the baseline score. This may suggest that the depression was more severe than the patient was able to express during the stimulation.

Acute and Chronic Mood and Apathy Outcomes from a randomized study of unilateral STN and GPi DBS

Objective

To study mood and behavioral effects of unilateral and staged bilateral subthalamic nucleus (STN) and globus pallidus internus (GPi) deep brain stimulation (DBS) for Parkinson's disease (PD).

Background

There are numerous reports of mood changes following DBS, however, most have focused on bilateral simultaneous STN implants with rapid and aggressive post-operative medication reduction.

Methods

A standardized evaluation was applied to a subset of patients undergoing STN and GPi DBS and who were also enrolled in the NIH COMPARE study. The Unified Parkinson Disease Rating Scale (UPDRS III), the Hamilton depression (HAM-D) and anxiety rating scales (HAM-A), the Yale-Brown obsessive-compulsive rating scale (YBOCS), the Apathy Scale (AS), and the Young mania rating scale (YMRS) were used. The scales were repeated at acute and chronic intervals. A post-operative strategy of non-aggressive medication reduction was employed.

Results

Thirty patients were randomized and underwent unilateral DBS (16 STN, 14 GPi). There were no baseline differences. The GPi group had a higher mean dopaminergic dosage at 1-year, however the between group difference in changes from baseline to 1-year was not significant. There were no differences between groups in mood and motor outcomes. When combining STN and GPi groups, the HAM-A scores worsened at 2-months, 4-months, 6-months and 1-year when compared with baseline; the HAM-D and YMRS scores worsened at 4-months, 6-months and 1-year; and the UPDRS Motor scores improved at 4-months and 1-year. Psychiatric diagnoses (DSM-IV) did not change. No between group differences were observed in the cohort of bilateral cases.

Conclusions

There were few changes in mood and behavior with STN or GPi DBS. The approach of staging STN or GPi DBS without aggressive medication reduction could be a viable option for managing PD surgical candidates. A study of bilateral DBS and of medication reduction will be required to better understand risks and benefits of a bilateral approach.

Mood and behavioural effects of subthalamic stimulation in Parkinson's disease

Deep-brain stimulation (DBS) of the subthalamic nucleus (STN) is an established treatment for motor complications in Parkinson's disease. 20 years of experience with this procedure have contributed to improved understanding of the role of the STN in motor, cognitive, and emotional control. In Parkinson's disease, the pathological STN neuronal activity leads to motor, cognitive, and emotional inhibition. Deafferentation of the STN by DBS can reverse such behavioural inhibition. The release of this brake allows both motor and non-motor improvement, but can also be associated with excessive motor, cognitive, and emotional behavioural disinhibition. Conversely, the notable reduction in anti-parkinsonian drug dose allowed by motor improvement can unveil mesolimbic hypodopaminergic behaviours such as apathy, anxiety, or depression. Fine-tuning of stimulation parameters with dopaminergic drugs is necessary to prevent or improve pathological behaviours.

Transient Manic-like Episode Following Bilateral Deep Brain Stimulation of the Nucleus Accumbens and the Internal Capsule in a Patient With Tourette Syndrome

Objective.  Deep brain stimulation (DBS) increasingly attracts attention as a potential treatment of mental disorders. Beside depression and obsessive-compulsive disorders, DBS has already been shown to be beneficial for Tourette syndrome (TS). Clinical Presentation/Method.  The authors report on the outcome of a patient with treatment-resistant TS who underwent bilateral DBS of the nucleus accumbens and the internal capsule. Results.  Within the 10-month follow-up, a substantial reduction of tics has been observed. Yet, as a side-effect of DBS, the patient developed a transient manic-like episode when primarily stimulated by the most proximally contact in the internal capsule. Conclusions.  This case supports the hypothesis that DBS of the nucleus accumbens and the internal capsule represents an effective therapeutic alternative for otherwise treatment-resistant TS. Yet, future controlled studies are needed to determine optimal stimulation parameters and to reduce negative side-effects such as transient hypomanic episodes.

Psychosis from subthalamic nucleus deep brain stimulator lesion effect

Background:

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) in particular is highly effective in relieving symptoms of Parkinson's disease (PD). However, it can also have marked psychiatric side effects, including delirium, mania, and psychosis. The etiologies of those effects are not well-understood, and both surgeons and consulting psychiatrists are in need of treatment strategies.

Case Description:

Two patients with young onset of PD and without significant prior psychiatric problems presented for bilateral STN DBS when medications became ineffective. Both had uneventful operative courses but developed florid psychosis 1-2 weeks later, before stimulator activation. Neither showed signs of delirium, but both required hospitalization, and one required treatment with a first-generation antipsychotic drug. Use of that drug did not worsen PD symptoms, contrary to usual expectations.

Conclusion:

These cases describe a previously unreported post-DBS syndrome in which local tissue reaction to lead implantation produces psychosis even without electrical stimulation of subcortical circuits. The lesion effect also appears to have anti-Parkinsonian effects that may allow the safe use of otherwise contraindicated medications. These cases have implications for management of PD DBS patients postoperatively, and may also be relevant as DBS is further used in other brain regions to treat behavioral disorders.

Postoperative management of deep brain stimulation in Parkinson's disease

Deep brain stimulation has become an established treatment for advanced Parkinson's disease. Its postoperative management is a delicate phase, dedicated to finding the optimal balance between stimulation and dopaminergic treatment. Postoperative management can be divided into an acute phase, aimed at the selection of the best stimulation contact, and a stabilization phase, aimed at the progressive adjustment of stimulation parameters and medications. A good knowledge of the electrophysiological anatomy of the target and surrounding structures, of the potential consequences of dopaminergic treatment modifications, and of the time course and interactions between stimulation and medication effects is mandatory for optimal outcome. This chapter focuses on the main strategies for the acute and chronic management of stimulation parameters and medication in the three main nuclei targeted in Parkinson's disease, namely the subthalamic nucleus, the ventral intermediate thalamic nucleus, and the internal part of the globus pallidus.

[Imaging non motor signs in Parkinson's disease]

Parkinson's disease is mainly considered as a motor disorder defined by a motor triad. However, various non-motor manifestations may be encountered in Parkinson's disease, including hyposmia, pain, fatigue, sleep disorders, cognitive and behavioral disorders. The pathophysiology of these signs is complex, not univocal and remains poorly understood. Functional imaging techniques either by positron emission tomography, single photon emission tomography or functional magnetic resonance imaging provide an invaluable opportunity to better understand the pathophysiology of these signs. In this paper, we present a review of the recent advances provided by functional imaging in this area.

The combined effect of subthalamic nuclei deep brain stimulation and L-dopa increases emotion recognition in Parkinson's disease

Deep brain stimulation of the subthalamic nucleus (DBS) is a widely used surgical technique to suppress motor symptoms in Parkinson's disease (PD), and as such improves patients' quality of life. However, DBS may produce emotional disorders such as a reduced ability to recognize emotional facial expressions (EFE). Previous studies have not considered the fact that DBS and l-dopa medication can have differential, common, or complementary consequences on EFE processing. A thorough way of investigating the effect of DBS and l-dopa medication in greater detail is to compare patients' performances after surgery, with the two therapies either being administered ('on') or not administered ('off'). We therefore used a four-condition (l-dopa 'on'/DBS 'on', l-dopa 'on'/DBS 'off', l-dopa 'off'/DBS 'on', and l-dopa 'off'/DBS 'off') EFE recognition paradigm and compared implanted PD patients to healthy controls. The results confirmed those of previous studies, yielding a significant impairment in the detection of some facial expressions relative to controls. Disgust recognition was impaired when patients were 'off' l-dopa and 'on' DBS, and fear recognition impaired when 'off' of both therapies. More interestingly, the combined effect of both DBS and l-dopa administration seems much more beneficial for EFE recognition than the separate administration of each individual therapy. We discuss the implications of these findings in the light of the inverted U curve function that describes the differential effects of dopamine level on the right orbitofrontal cortex (OFC). We propose that, while l-dopa could "overdose" in dopamine the ventral stream of the OFC, DBS would compensate for this over-activation by decreasing OFC activity, thereby restoring the necessary OFC-amygdala interaction. Another finding is that, when collapsing over all treatment conditions, PD patients recognized more neutral faces than the matched controls, a result that concurs with embodiment theories.

Deep brain stimulation induces BOLD activation in motor and non-motor networks: an fMRI comparison study of STN and EN/GPi DBS in large animals

The combination of deep brain stimulation (DBS) and functional MRI (fMRI) is a powerful means of tracing brain circuitry and testing the modulatory effects of electrical stimulation on a neuronal network in vivo. The goal of this study was to trace DBS-induced global neuronal network activation in a large animal model by monitoring the blood oxygenation level-dependent (BOLD) response on fMRI. We conducted DBS in normal anesthetized pigs, targeting the subthalamic nucleus (STN) (n=7) and the entopeduncular nucleus (EN), the non-primate analog of the primate globus pallidus interna (n=4). Using a normalized functional activation map for group analysis and the application of general linear modeling across subjects, we found that both STN and EN/GPi DBS significantly increased BOLD activation in the ipsilateral sensorimotor network (FDR<0.001). In addition, we found differential, target-specific, non-motor network effects. In each group the activated brain areas showed a distinctive correlation pattern forming a group of network connections. Results suggest that the scope of DBS extends beyond an ablation-like effect and that it may have modulatory effects not only on circuits that facilitate motor function but also on those involved in higher cognitive and emotional processing. Taken together, our results show that the swine model for DBS fMRI, which conforms to human implanted DBS electrode configurations and human neuroanatomy, may be a useful platform for translational studies investigating the global neuromodulatory effects of DBS.

Hypomania induced by subthalamic nucleus stimulation in a Parkinson's disease patient: does it suggest a dysfunction of the limbic circuit?

The aim of this report was to describe a case of hypomania after deep brain stimulation of the subthalamic nucleus (STN DBS) in a Parkinson’s disease (PD) patient. 59-year-old man with a 15-year history of PD underwent bilateral implantation of electrodes to the STN. Immediately after surgery, his motor function was markedly improved and his mood was elevated to hypomania. Fusion images of the preoperative MRI and postoperative CT scan showed that the electrodes were located in the medial portion of the STN. In this case, behavioral mood change was related to the deep brain stimulation. Moreover, the anatomical location and the functional alteration of the STN after the DBS surgery might be related to the regulatory system of the associative and limbic cortico-subcortical circuits.

Evidence of a non-motor microlesion effect following deep brain surgery: a case report

We report the case of a patient who developed acute transient psychosis after implantation, but not activation of pallidal deep brain electrodes for generalised dystonia. Psychotic symptoms coincided temporally with postoperative motor improvement induced by the microlesion effect after electode implantation. This finding suggests that the microlesion effect may not be confined to motor improvement, but also comprises non-motor symptoms. In our case, affection of adjacent dopaminergic fibres of passages has to be assumed.

Pharmacological treatment of deep brain stimulation-induced hypomania leads to clinical remission while preserving motor benefits

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an effective treatment for Parkinson's disease, but can lead to adverse effects including psychiatric disturbance. Little is known about the risk factors and treatment options for such effects. Here, we describe a patient who reproducibly developed stimulation-induced hypomania when using ventrally located electrodes and responded well to pharmacological intervention while leaving the stimulation parameters unchanged to preserve motor benefits. In spite of clinical remission, [¹⁵O]-positron-emission-tomography (PET) demonstrated activation patterns similar to those reported during mania. This case, therefore, highlights an important treatment option of adverse effects of DBS, but also points toward the need for investigations of its risk factors and their underlying neurobiological mechanisms.

Long-term time course of affective lability after subthalamic deep brain stimulation electrode implantation

The mechanism and time course of emotional side effects of subthalamic deep brain stimulation in Parkinson's disease are a matter for discussion. We report a 53-month follow-up of a patient with affective lability. Postoperative lesion plus bilateral stimulation strongly influenced mood in the first week in terms of laughing behavior, while voltage changes had only minor long-term impact up to 37 months on negative emotion, possibly caused by the right electrode stimulating the subthalamic nucleus and adjacent fiber tracts involving the internal capsule. Thus we conclude that affective lability can occur with different temporal dynamics of microlesion, and early and chronic stimulation.

Bipolar affective disorder and Parkinson's disease

Little is known about comorbidities of bipolar disorder such as Parkinson's disease. A case history and a literature survey indicate that bipolar disorder is linked with or influences Parkinson's disease and vice versa. Underlying mechanisms are poorly understood, and, more importantly, no treatment options are established in such double diagnoses. The few data in comorbid Parkinson cases seem to point to a rapid cycling pattern of bipolar symptoms. With regard to therapeutic intervention, the literature supports pramipexole for treatment of both Parkinson and depressive symptoms in bipolar depression. Lithium, the mood stabilizer of choice for treating manic states, is problematical for use in Parkinson patients because of its side effects. Valproate might be an alternative, especially for treatment of rapid cycling.

Embodying Emotional Disorders: New Hypotheses about Possible Emotional Consequences of Motor Disorders in Parkinson's Disease and Tourette's Syndrome

Parkinson's disease (PD) and Tourette's syndrome (TS) lead to important motor disorders among patients such as possible facial amimia in PD and tics in Tourette's syndrome. Under the grounded cognition framework that shows the importance of motor embodiment in emotional feeling (Niedenthal, 2007), both types of pathology with motor symptoms should be sufficient to induce potential impairments for these patients when recognizing emotional facial expressions (EFE). In this opinion paper, we describe a theoretical framework that assumes potential emotional disorders in Parkinson's disease and Tourette's syndrome based on motor disorders characterizing these two pathologies. We also review different methodological barriers in previous experimental designs that could enable the identification of emotional facial expressions despite emotional disorders in PD and TS.

Functional imaging of subthalamic nucleus deep brain stimulation in Parkinson's disease

Deep brain stimulation of the subthalamic nucleus is an accepted treatment for the motor complications of Parkinson's disease. The therapeutic mechanism of action remains incompletely understood. Although the results of deep brain stimulation are similar to the results that can be obtained by lesional surgery, accumulating evidence from functional imaging and clinical neurophysiology suggests that the effects of subthalamic nucleus-deep brain stimulation are not simply the result of inhibition of subthalamic nucleus activity. Positron emission tomography/single-photon emission computed tomography has consistently demonstrated changes in cortical activation in response to subthalamic nucleus-deep brain stimulation. However, the technique has limited spatial and temporal resolution, and therefore the changes in activity of subcortical projection sites of the subthalamic nucleus (such as the globus pallidus, substantia nigra, and thalamus) are not as clear. Clarifying whether clinically relevant effects from subthalamic nucleus-deep brain stimulation in humans are mediated through inhibition or excitation of orthodromic or antidromic pathways (or both) would contribute to our understanding of the precise mechanism of action of deep brain stimulation and may allow improvements in safety and efficacy of the technique. In this review we discuss the published evidence from functional imaging studies of patients with subthalamic nucleus-deep brain stimulation to date, together with how these data inform the mechanism of action of deep brain stimulation.

Deep brain stimulation: from neurology to psychiatry?

Functional stereotaxy was introduced in the late 1940s to reduce the morbidity of lobotomy in psychiatric disease by using more focal lesions. The advent of neuroleptics led to a drastic decline in psychosurgery for several decades. Functional stereotactic neurosurgery has recently been revitalized, starting with treatment of Parkinson's disease, in which deep brain stimulation (DBS) facilitates reversible focal neuromodulation of altered basal ganglia circuits. DBS is now being extended to treatment of neuropsychiatric conditions such as Gilles de la Tourette syndrome, obsessive-compulsive disorder, depression and addiction. In this review, we discuss the concept that dysfunction of motor, limbic and associative cortico-basal ganglia-thalamocortical loops underlies these various disorders, which might now be amenable to DBS treatment.

Non-motor dopamine withdrawal syndrome after surgery for Parkinson's disease: predictors and underlying mesolimbic denervation

Apathy has been reported to occur after subthalamic nucleus stimulation, a treatment of motor complications in advanced Parkinson's disease. We carried out a prospective study of the occurrence of apathy and associated symptoms, predictors and mechanisms in the year following subthalamic stimulation. Dopamine agonist drugs were discontinued immediately after surgery and levodopa was markedly reduced within 2 weeks. Apathy and depression were assessed monthly, using the Starkstein apathy scale and the Beck Depression Inventory. Dopamine agonists were re-introduced if patients developed apathy or depression. Preoperative non-motor fluctuations were evaluated using the Ardouin Scale. Depression, apathy and anxiety were evaluated both on and off levodopa. Analysis of predictors of apathy was performed using a Cox proportional hazard model. Twelve patients who developed apathy and a control group of 13 patients who did not underwent [11C]-raclopride positron emission tomography scanning before and after oral intake of methylphenidate. In 63 patients with Parkinson's disease treated with subthalamic stimulation, dopaminergic treatment was decreased by 82% after surgery. Apathy occurred after a mean of 4.7 (3.3-8.2) months in 34 patients and was reversible in half of these by the 12-month follow-up. Seventeen patients developed transient depression after 5.7 (4.7-9.3) months and these fell into the apathy group with one single exception. At baseline, fluctuations in depression, apathy and anxiety scores were greater in the group with apathy. Fluctuations in apathy, depression and anxiety ratings during a baseline levodopa challenge were also significant predictors of postoperative apathy in univariate analysis, but not motor and cognitive states or the level of reduction of dopaminergic medication. The multivariate model identified non-motor fluctuations in everyday life and anxiety score during the baseline levodopa challenge as two independent significant predictors of postoperative apathy. Without methylphenidate, [11C]-raclopride binding potential values were greater in apathetic patients bilaterally in the orbitofrontal, dorsolateral prefrontal, posterior cingulate and temporal cortices, left striatum and right amygdala, reflecting greater dopamine D2/D3 receptor density and/or reduced synaptic dopamine level in these areas. The variations of [11C]-raclopride binding potential values induced by methylphenidate were greater in non-apathetic patients in the left orbitofrontal cortex, dorsolateral prefrontal cortex, thalamus and internal globus pallidus and bilaterally in the anterior and posterior cingulate cortices, consistent with a more important capacity to release dopamine. Non-motor fluctuations are related to mesolimbic dopaminergic denervation. Apathy, depression and anxiety can occur after surgery as a delayed dopamine withdrawal syndrome. A varying extent of mesolimbic dopaminergic denervation and differences in dopaminergic treatment largely determine mood, anxiety and motivation in patients with Parkinson's disease, contributing to different non-motor phenotypes.

PET functional imaging of deep brain stimulation in movement disorders and psychiatry

Deep brain stimulation (DBS) represents a major advance in the treatment of various severe movement disorders or neuropsychiatric diseases. Our understanding of the mechanism of action of this surgical treatment has greatly benefited from functional imaging studies. Most of these studies have been conducted in patients with Parkinson's disease (PD) treated by bilateral subthalamic nucleus (STN) stimulation. These studies have notably underlined the fact that STN stimulation influences motor, limbic, or associative cortical-subcortical loops in various (sometimes contradictory) ways. We present an up-to-date review of the information provided by functional imaging studies in surgery for PD, dystonia, tremor, as well as in psychiatric disorders such as depression or obsessive-compulsive disorder. On the basis of this information, proposed mechanisms of action of DBS are discussed, as well as the need for additional approaches such as improved anatomical localization of the contact used for stimulation or a better understanding of the electrical distribution around the electrode.