Deep brain stimulation: neuropsychological and neuropsychiatric issues

Unilateral Magnetic Resonance-Guided Focused Ultrasound Lesion of the Subthalamic Nucleus in Parkinson's Disease: A Prospective Study

BACKGROUND

Unilateral subthalamic nucleus (STN) ablation using magnetic resonance-guided focused ultrasound (MRgFUS) is being explored as a new treatment for asymmetric Parkinson's disease (PD).

OBJECTIVES

The aims were to study the efficacy and safety of this treatment in asymmetric PD patients and to characterize the lesions.

METHODS

This prospective, single-center, open-label study evaluated asymmetric PD patients at 6 (n = 20) and 12 months (n = 12) after MRgFUS lesion of the STN. The primary outcome was the change in the Movement Disorders Society-Unified Parkinson's Disease Rating Scale, Part III (MDS-UPDRS III), score in off medication on the treated side and the adverse events (AEs) at 6-month follow-up. We also evaluated cognitive-neuropsychological changes, self-assessment of clinical improvement, and the correlation of the lesion volume with the motor outcomes.

RESULTS

On the treated side, the MDS-UPDRS III score (mean difference = 13.8) and the scores in rigidity, bradykinesia, and tremor improved (P < 0.001) throughout the follow-up compared to baseline (at 6 months: rigidity mean difference = 2.8, improvement: 83.5%; bradykinesia mean difference = 6.0, improvement: 69.4%; tremor mean difference = 4.7, improvement: 91.5%). One patient had severe weakness in the treated hemibody, 1 had moderate dyskinesia, and 1 was in moderate confusional state that became mild (weakness) or completely resolved (dyskinesia and confusional state) at 6 months. The rest of the AEs were mild. We observed no clinically relevant changes in cognitive-neuropsychological tests. The percentage of ablation of the STN correlated with the improvement in the total MDS-UPDRS III and contralateral tremor scores (P < 0.05).

CONCLUSION

Unilateral MRgFUS lesion of the STN resulted in a significant motor improvement. We observed no persistent severe AEs, although mild, mostly transient AEs were frequent. © 2024 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

A Patient-Centered Perspective on Changes in Personal Characteristics After Deep Brain Stimulation

Importance

Deep brain stimulation (DBS) results in improvements in motor function and quality of life in patients with Parkinson disease (PD), which might impact a patient's perception of valued personal characteristics. Prior studies investigating whether DBS causes unwanted changes to oneself or one's personality have methodological limitations that should be addressed.

Objective

To determine whether DBS is associated with changes in characteristics that patients with PD identify as personally meaningful.

Design, Setting, and Participants

This cohort study assessed changes in visual analog scale (VAS) ratings reflecting the extent to which patients with PD manifested individually identified personal characteristics before and 6 and 12 months after DBS at a large academic medical center from February 21, 2018, to December 9, 2021. The VAS findings were tailored to reflect the top 3 individually identified personal characteristics the patient most feared losing. The VASs were scored from 0 to 10, with 0 representing the least and 10 the most extreme manifestation of the trait. Change scores were examined at the individual level. Content analysis was used to code the qualitative data. Qualitative and quantitative analyses were performed from January 12, 2019 (initial qualitative coding), to December 15, 2023.

Exposure

Deep brain stimulation.

Main Outcomes and Measures

The primary outcome variable was the mean VAS score for the top 3 personal characteristics. The secondary outcome was the incidence of meaningful changes on the patients' top 3 characteristics at the individual level.

Results

Fifty-two of 54 dyads of patients with PD and their care partners (96.3%) were recruited from a consecutive series approved for DBS (36 patients [69.2%] were male and 45 care partners [86.5%] were female; mean [SD] age of patients, 61.98 [8.55] years). Two patients and 1 care partner were lost to follow-up. Increases in the mean VAS score (indicative of greater manifestation of [ie, positive changes in] specific characteristics) were apparent following DBS for ratings of both the patients (Wald χ2 = 16.104; P < .001) and care partners (Wald χ2 = 6.746; P < .001) over time. The slopes of the changes for both the patient and care partners were correlated, indicating agreement in observed changes over time. The individual level analyses indicated that scores for most patients and care partners remained the same or increased.

Conclusions and Relevance

In this cohort study, participants reported greater (more positive) manifestations of individually identified, valued characteristics after DBS. These findings may be relevant to informing decision-making for patients with advanced PD who are considering DBS.

Anterior capsulotomy combined with subthalamic nucleus deep brain stimulation for tardive dystonia

BACKGROUND

Deep brain stimulation (DBS) has been reported as a therapy option for the motor dysfunction of severe tardive dystonia (TD). The major psychiatric diseases, however, are contraindications to DBS treatment in TD patients.

METHODS

Six severe, medically refractory TD patients undergoing bilateral anterior capsulotomy combined with bilateral subthalamic nucleus (STN)-DBS treatment were studied retrospectively at two time points: pre-operation, and 1-3 years post-operation. Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) was used to assess the dystonia and disability. Depressive, anxiety, psychiatric symptoms, and Quality of Life (QoL) were evaluated using the 17-item Hamilton Depression Scale (HAMD-17), the 14-item Hamilton Anxiety Scale (HAMA-14), the Positive and Negative Syndrome Scale (PANSS), and 36-item Short-Form Health Survey (SF-36), respectively.

RESULTS

After receiving the combination treatment for 25 ± 11.6 months (range, 12-41 months), significant clinical symptom improvements were reported in TD patients. BFMDRS motor and disability scores were ameliorated by 78.5 ± 32.0% (p = 0.031) and 76.5 ± 38.6% (p = 0.031), respectively. The HAMD-17 and HAMA-14 scores were reduced by 60.3 ± 27.9% (p = 0.007) and 60.0 ± 24.6% (p = 0.009), respectively. Furthermore, the PANSS scores of the comorbidity schizophrenia TD patients decreased by 58.1 ± 6.0% (p = 0.022), and the QoL improved by 59.7 ± 14.1% (SF-36, p = 0.0001). During the research, there were no notable adverse effects or problems.

CONCLUSION

Bilateral anterior capsulotomy combined with bilateral STN-DBS may be an effective and relatively safe treatment option for severe TD comorbid with major psychiatric disorders.

Double dissociation of dopamine and subthalamic nucleus stimulation on effortful cost/benefit decision making

Deep brain stimulation (DBS) and dopaminergic therapy (DA) are common interventions for Parkinson's disease (PD). Both treatments typically improve patient outcomes, and both can have adverse side effects on decision making (e.g., impulsivity).1,2 Nevertheless, they are thought to act via different mechanisms within basal ganglia circuits.3 Here, we developed and formally evaluated their dissociable predictions within a single cost/benefit effort-based decision-making task. In the same patients, we manipulated DA medication status and subthalamic nucleus (STN) DBS status within and across sessions. Using a series of descriptive and computational modeling analyses of participant choices and their dynamics, we confirm a double dissociation: DA medication asymmetrically altered participants' sensitivities to benefits vs. effort costs of alternative choices (boosting the sensitivity to benefits while simultaneously lowering sensitivity to costs); whereas STN DBS lowered the decision threshold of such choices. To our knowledge, this is the first study to show, using a common modeling framework, a dissociation of DA and DBS within the same participants. As such, this work offers a comprehensive account for how different mechanisms impact decision making, and how impulsive behavior (present in DA-treated patients with PD and DBS patients) may emerge from separate physiological mechanisms.

A role for the subthalamic nucleus in aversive learning

The subthalamic nucleus (STN) is critical for behavioral control; its dysregulation consequently correlated with neurological and neuropsychiatric disorders, including Parkinson's disease. Deep brain stimulation (DBS) targeting the STN successfully alleviates parkinsonian motor symptoms. However, low mood and depression are affective side effects. STN is adjoined with para-STN, associated with appetitive and aversive behavior. DBS aimed at STN might unintentionally modulate para-STN, causing aversion. Alternatively, the STN mediates aversion. To investigate causality between STN and aversion, affective behavior is addressed using optogenetics in mice. Selective promoters allow dissociation of STN (e.g., Pitx2) vs. para-STN (Tac1). Acute photostimulation results in aversion via both STN and para-STN. However, only STN stimulation-paired cues cause conditioned avoidance and only STN stimulation interrupts on-going sugar self-administration. Electrophysiological recordings identify post-synaptic responses in pallidal neurons, and selective photostimulation of STN terminals in the ventral pallidum replicates STN-induced aversion. Identifying STN as a source of aversive learning contributes neurobiological underpinnings to emotional affect.

Deep Brain Stimulation for the Management of Refractory Neurological Disorders: A Comprehensive Review

In recent decades, deep brain stimulation (DBS) has been extensively studied due to its reversibility and significantly fewer side effects. DBS is mainly a symptomatic therapy, but the stimulation of subcortical areas by DBS is believed to affect the cytoarchitecture of the brain, leading to adaptability and neurogenesis. The neurological disorders most commonly studied with DBS were Parkinson's disease, essential tremor, obsessive-compulsive disorder, and major depressive disorder. The most precise approach to evaluating the location of the leads still relies on the stimulus-induced side effects reported by the patients. Moreover, the adequate voltage and DBS current field could correlate with the patient's symptoms. Implantable pulse generators are the main parts of the DBS, and their main characteristics, such as rechargeable capability, magnetic resonance imaging (MRI) safety, and device size, should always be discussed with patients. The safety of MRI will depend on several parameters: the part of the body where the device is implanted, the part of the body scanned, and the MRI-tesla magnetic field. It is worth mentioning that drug-resistant individuals may have different pathophysiological explanations for their resistance to medications, which could affect the efficacy of DBS therapy. Therefore, this could explain the significant difference in the outcomes of studies with DBS in individuals with drug-resistant neurological conditions.

Neural dynamics underlying self-control in the primate subthalamic nucleus

The subthalamic nucleus (STN) is hypothesized to play a central role in neural processes that regulate self-control. Still uncertain, however, is how that brain structure participates in the dynamically evolving estimation of value that underlies the ability to delay gratification and wait patiently for a gain. To address that gap in knowledge, we studied the spiking activity of neurons in the STN of monkeys during a task in which animals were required to remain motionless for varying periods of time in order to obtain food reward. At the single-neuron and population levels, we found a cost-benefit integration between the desirability of the expected reward and the imposed delay to reward delivery, with STN signals that dynamically combined both attributes of the reward to form a single integrated estimate of value. This neural encoding of subjective value evolved dynamically across the waiting period that intervened after instruction cue. Moreover, this encoding was distributed inhomogeneously along the antero-posterior axis of the STN such that the most dorso-posterior-placed neurons represented the temporal discounted value most strongly. These findings highlight the selective involvement of the dorso-posterior STN in the representation of temporally discounted rewards. The combination of rewards and time delays into an integrated representation is essential for self-control, the promotion of goal pursuit, and the willingness to bear the costs of time delays.

How I became myself after merging with a computer: Does human-machine symbiosis raise human rights issues?

Novel usages of brain stimulation combined with artificially intelligent (AI) systems promise to address a large range of diseases. These new conjoined technologies, such as brain-computer interfaces (BCI), are increasingly used in experimental and clinical settings to predict and alleviate symptoms of various neurological and psychiatric disorders. Due to their reliance on AI algorithms for feature extraction and classification, these BCI systems enable a novel, unprecedented, and direct connection between human cognition and artificial information processing. In this paper, we present the results of a study that investigates the phenomenology of human-machine symbiosis during a first-in-human experimental BCI trial designed to predict epileptic seizures. We employed qualitative semi-structured interviews to collect user experience data from a participant over a six-years period. We report on a clinical case where a specific embodied phenomenology emerged: namely, after BCI implantation, the patient reported experiences of increased agential capacity and continuity; and after device explantation, the patient reported persistent traumatic harms linked to agential discontinuity. To our knowledge, this is the first reported clinical case of a patient experiencing persistent agential discontinuity due to BCI explantation and potential evidence of an infringement on patient right, where the implanted person was robbed of her de novo agential capacities when the device was removed.

Wireless stimulation of the subthalamic nucleus with nanoparticles modulates key monoaminergic systems similar to contemporary deep brain stimulation

BACKGROUND

Deep brain stimulation (DBS) is commonly used to alleviate motor symptoms in several movement disorders. However, the procedure is invasive, and the technology has remained largely stagnant since its inception decades ago. Recently, we have shown that wireless nanoelectrodes may offer an alternative approach to conventional DBS. However, this method is still in its infancy, and more research is required to characterize its potential before it can be considered as an alternative to conventional DBS.

OBJECTIVES

Herein, we aimed to investigate the effect of stimulation via magnetoelectric nanoelectrodes on primary neurotransmitter systems that have implications for DBS in movement disorders.

METHODS

Mice were injected with either magnetoelectric nanoparticles (MENPs) or magnetostrictive nanoparticles (MSNPs, as a control) in the subthalamic nucleus (STN). Mice then underwent magnetic stimulation, and their motor behavior was assessed in the open field test. In addition, magnetic stimulation was applied before sacrifice and post-mortem brains were processed for immunohistochemistry (IHC) to assess the co-expression of c-Fos with either tyrosine hydroxylase (TH), tryptophan hydroxylase-2 (TPH2) or choline acetyltransferase (ChAT).

RESULTS

Stimulated animals covered longer distances in the open field test when compared to controls. Moreover, we found a significant increase in c-Fos expression in the motor cortex (MC) and paraventricular region of the thalamus (PV-thalamus) after magnetoelectric stimulation. Stimulated animals showed fewer TPH2/c-Fos double-labeled cells in the dorsal raphe nucleus (DRN), as well as TH/c-Fos double-labeled cells in the ventral tegmental area (VTA), but not in the substantia nigra pars compacta (SNc). There was no significant difference in the number of ChAT/ c-Fos double-labeled cells in the pedunculopontine nucleus (PPN).

CONCLUSIONS

Magnetoelectric DBS in mice enables selective modulation of deep brain areas and animal behavior. The measured behavioral responses are associated with changes in relevant neurotransmitter systems. These changes are somewhat similar to those observed in conventional DBS, suggesting that magnetoelectric DBS might be a suitable alternative.

Energy Delivered by Subthalamic Deep Brain Stimulation for Parkinson Disease Correlates With Depressive Personality Trait Shift

OBJECTIVES

Despite the large amount of literature examining the potential influence of subthalamic nucleus deep brain stimulation (STN-DBS) on psychiatric symptoms and cognitive disorders, only a few studies have focused on its effect on personality. We investigated the correlation between total electrical energy delivered (TEED) and the occurrence of depressive traits in patients with Parkinson disease (PD) after one year of DBS.

MATERIALS AND METHODS

Our study involved 20 patients with PD (12 women, mean [±SD] age 57.60 ± 7.63 years) who underwent bilateral STN-DBS, whose personality characteristics were assessed using the Minnesota Multiphasic Personality Inventory-2 (MMPI-2), according to the core assessment program for surgical interventional therapies in Parkinson's disease (CAPSIT-PD) procedure.

RESULTS

We found that despite a marked improvement in motor functions and quality of life after 12 months, patients showed a significant increase in MMPI-2 subscales for depression (D scale and Depression scale) and in other content component scales (low self-esteem, work interference, and negative treatment indicators). Interestingly, only the TEED on the right side was inversely correlated with the changes in scale D (r_s = -0.681, p = 0.007), whereas depressive traits did not correlate with disease duration, levodopa equivalent daily dose (LEDD) reduction, patient's age, or severity of motor symptoms.

CONCLUSIONS

Our preliminary observations indicate that despite the excellent motor outcome and general improvement in quality of life, DBS treatment can result in patients poorly adjusting to their personal, familiar, and socio-professional life. Different influences and multiple factors (such as TEED, intra/postsurgical procedure, coping mechanisms, and outcome expectations) may affect depressive traits. Further advances are expected to improve stimulation methods.

Formal Neuropsychological Testing: Test Batteries, Interpretation, and Added Value in Practice

Neuropsychologists evaluate patients for cognitive decline and dementia, using validated psychometric tests, along with behavioral observation, record review, clinical interview, and information about psychological functioning, to evaluate brain-behavior relationships and aid in differential diagnosis and treatment planning. Also considered are premorbid functioning, education, sex, socioeconomic status, primary language, culture, and race-related health disparities when selecting tests, interpreting performance, and providing a diagnostic impression. Neuropsychologists provide diagnostic clarity, explain symptoms and likely disease course to patients and family members, and assist the family with future planning, behavioral management strategies, and ways to mitigate caregiver burden.

The zona incerta in control of novelty seeking and investigation across species

Many organisms rely on a capacity to rapidly replicate, disperse, and evolve when faced with uncertainty and novelty. But mammals do not evolve and replicate quickly. They rely on a sophisticated nervous system to generate predictions and select responses when confronted with these challenges. An important component of their behavioral repertoire is the adaptive context-dependent seeking or avoiding of perceptually novel objects, even when their values have not yet been learned. Here, we outline recent cross-species breakthroughs that shed light on how the zona incerta (ZI), a relatively evolutionarily conserved brain area, supports novelty-seeking and novelty-related investigations. We then conjecture how the architecture of the ZI's anatomical connectivity - the wide-ranging top-down cortical inputs to the ZI, and its specifically strong outputs to both the brainstem action controllers and to brain areas involved in action value learning - place the ZI in a unique role at the intersection of cognitive control and learning.

High-frequency stimulation of the subthalamic nucleus induces a sustained inhibition of serotonergic system via loss of cell phenotype

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has become a standard treatment for Parkinson's disease (PD). However, in a considerable number of patients debilitating psychiatric side-effects occur. Recent research has revealed that external stimuli can alter the neurotransmitters' homeostasis in neurons, which is known as "neurotransmitter respecification". Herein, we addressed if neurotransmitter respecification could be a mechanism by which DBS suppresses the serotonergic function in the dorsal raphe nucleus (DRN) leading to mood changes. We infused transgenic 5-HT-Cre (ePET-Cre) mice with AAV viruses to achieve targeted expression of eYFP and the genetically encoded calcium indicator GCaMP6s in the DRN prior to methyl-4phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment. Mice received bilateral DBS electrodes in the STN and an optic fiber in the DRN for calcium photometry. MPTP-treated mice demonstrated behavioral and histological PD phenotype, whereas all STN-DBS animals exhibited an increased immobility time in the forced swim test, reduced calcium activity, and loss of tryptophan hydroxylase-2 expression in the DRN. Given the prominent role of calcium transients in mediating neurotransmitter respecification, these results suggest a loss of serotonergic phenotype in the DRN following STN-DBS. These findings indicate that loss of serotonergic cell phenotype may underlie the unwanted depressive symptoms following STN-DBS.

Effects of Bilateral Subthalamic Nucleus Stimulation on Depressive Symptoms and Cerebral Glucose Metabolism in Parkinson's Disease: A 18F-Fluorodeoxyglucose Positron Emission Tomography/Computerized Tomography Study

Subthalamic nucleus (STN) deep brain stimulation (DBS) can improve motor symptoms in Parkinson's disease (PD), as well as potentially improving otherwise intractable comorbid depressive symptoms. To address the latter issue, we evaluated the severity of depressive symptoms along with the severity of motor symptoms in 18 PD patients (mean age, 58.4 ± 5.4 years; 9 males, 9 females; mean PD duration, 9.4 ± 4.4 years) with treatment-resistant depression (TRD) before and after approximately 1 year of STN-DBS treatment. Moreover, to gain more insight into the brain mechanism mediating the therapeutic action of STN-DBS, we utilized ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) to assess cerebral regional glucose metabolism in the patients at baseline and 1-year follow-up. Additionally, the baseline PET data from patients were compared with PET data from an age- and sex-matched control group of 16 healthy volunteers. Among them, 12 PD patients underwent post-operative follow-up PET scans. Results showed that the severity of both motor and depressive symptoms in patients with PD-TRD was reduced significantly at 1-year follow-up. Also, patients used significantly less antiparkinsonian medications and antidepressants at 1-year follow-up, as well as experiencing improved daily functioning and a better quality of life. Moreover, relative to the PET data from healthy controls, PD-TRD patients displayed widespread abnormalities in cerebral regional glucose metabolism before STN-DBS treatment, which were partially recovered at 1-year follow-up. Additionally, significant correlations were observed between the patients' improvements in depressive symptoms following STN-DBS and post-operative changes in glucose metabolism in brain regions implicated in emotion regulation. These results support the view that STN-DBS provides a promising treatment option for managing both motor and depressive symptoms in patients who suffer from PD with TRD. However, the results should be interpreted with caution due to the observational nature of the study, small sample size, and relatively short follow-up.

Hot and Cold Cognitive Disturbances in Parkinson Patients Treated with DBS-STN: A Combined PET and Neuropsychological Study

Patients with Parkinson’s disease (PD) often suffer from non-motor symptoms, which may be caused by serotonergic dysfunction. Deep Brain Stimulation (DBS) in the subthalamic nucleus (STN) may also influence non-motor symptoms. The aim of this study is to investigate how the cerebral 5-HT system associates to disturbances in cognition and mood in PD patients with DBS-STN turned on and off. We used psychological tests and questionnaires to evaluate cognitive function and the effects on mood from turning DBS-STN off. We applied a novel PET neuroimaging methodology to evaluate the integrity of the cerebral serotonin system. We measured 5-HT1BR binding in 13 DBS-STN-treated PD patients, at baseline and after turning DBS off. Thirteen age-matched volunteers served as controls. The measures for cognition and mood were correlated to the 5-HT1BR availability in temporal limbic cortex. 5-HT1BR binding was proportional to working memory performance and inverse proportional to affective bias for face recognition. When DBS is turned off, patients feel less vigorous; the higher the limbic and temporal 5-HT1BR binding, the more they are affected by DBS being turned off. Our study suggests that cerebral 5-HTR binding is associated with non-motor symptoms, and that preservation of serotonergic functions may be predictive of DBS-STN effects.

Functional connectivity maps of theta/alpha and beta coherence within the subthalamic nucleus region

The subthalamic nucleus (STN) is a primary target for deep brain stimulation in Parkinson's disease (PD). Although small in size, the STN is commonly partitioned into sensorimotor, cognitive/associative, and limbic subregions based on its structural connectivity profile to cortical areas. We investigated whether such a regional specialization is also supported by functional connectivity between local field potential recordings and simultaneous magnetoencephalography. Using a novel data set of 21 PD patients, we replicated previously reported cortico-STN coherence networks in the theta/alpha and beta frequency ranges, and looked for the spatial distribution of these networks within the STN region. Although theta/alpha and beta coherence peaks were both observed in on-medication recordings from electrode contacts at several locations within and around the STN, sites with theta/alpha coherence peaks were situated at significantly more inferior MNI coordinates than beta coherence peaks. Sites with only theta/alpha coherence peaks, i.e. without distinct beta coherence, were mostly located near the border of sensorimotor and cognitive/associative subregions as defined by a tractography-based atlas of the STN. Peak coherence values were largely unaltered by the medication state of the subject, however, theta/alpha peaks were more often identified in recordings obtained after administration of dopaminergic medication. Our findings suggest the existence of a frequency-specific topography of cortico-STN coherence within the STN, albeit with considerable spatial overlap between functional networks. Consequently, optimization of deep brain stimulation targeting might remain a trade-off between alleviating motor symptoms and avoiding adverse neuropsychiatric side effects.

Modulation of sensory cortical activity by deep brain stimulation in advanced Parkinson's Disease

Despite optimal oral drug treatment, about 90% of patients with Parkinson's disease develop motor fluctuation and dyskinesia within 5-10 years from the diagnosis. Moreover, the patients show non-motor symptoms in different sensory domains. Bilateral deep brain stimulation applied to the subthalamic nucleus is considered the most effective treatment in advanced Parkinson's disease and it has been suggested to affect sensorimotor modulation and relate to motor improvement in patients. However, observations on the relationship between sensorimotor activity and clinical improvement have remained sparse. Here we studied the somatosensory evoked magnetic fields in thirteen right-handed patients with advanced Parkinson's disease before and 7 months after stimulator implantation. Somatosensory processing was addressed with magnetoencephalography during alternated median nerve stimulation at both wrists. The strengths and the latencies of the ~60-ms responses at the contralateral primary somatosensory cortices were highly variable but detectable and reliably localized in all patients. The response strengths did not differ between preoperative and postoperative DBS_ON measurements. The change in the response strength between pre- and postoperative condition in the dominant left hemisphere of our right-handed patients correlated with the alleviation of their motor symptoms (p = 0.04). However, the result did not survive correction for multiple comparisons. Magnetoencephalography appears an effective tool to explore non-motor effects in patients with Parkinson's disease, and it may help in understanding the neurophysiological basis of deep brain stimulation. However, the high interindividual variability in the somatosensory responses and poor tolerability of DBS_OFF condition warrants larger patient groups and measurements also in non-medicated patients.

Non-motor effects of subthalamic nucleus stimulation in Parkinson patients

The current white matter connectivity analyses of the subthalamic region have focused on the motor effects of deep brain stimulation. We investigate white matter connectivity associated with the stimulation-induced non-motor acute clinical effects in three domains: mood changes, dizziness, and sweating. We performed whole-brain probabilistic tractography seeded from the domain-specific stimulation volumes. The resultant connectivity maps were statistically compared across patients. The cortical voxels associated with each non-motor domain were compared with stimulation-induced motor improvements in a multivariate model. The resulting voxel maps were thresholded for false discovery (FDR q < 0.05) and clustered using a multimodal atlas. We also performed a group-level parcellation of stimulation volumes to identify the local pathways associated with each non-motor domain. The non-motor effects were rarely observed during stimulation titration: from 1100 acute clinical effects, mood change was observed in 14, dizziness in 23, and sweating in 20. Distinct cortical clusters were associated with each domain; notably, mood change was associated with voxels in the salience network and dizziness with voxels in the visual association cortex. The subthalamic parcellation yielded a mediolateral gradient, with the motor parcel being lateral and the non-motor parcels medial. We also observed an anteroposterior organization in the medial non-motor clusters with mood changes being anterior, followed posteriorly by dizziness, and sweating. We interpret these findings based on the literature and foresee these to be useful in guiding DBS programming.

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.

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.

A Pilot Trial of Cognitive Behavioral Therapy for Caregivers After Deep Brain Stimulation for Parkinson's Disease

Subthalamic deep brain stimulation for Parkinson's disease may not ameliorate burden among caregivers. An 8-session, manualized program of cognitive-behavioral therapy (CBT) was delivered to a pilot sample of 10 caregivers (6 females, mean age: 60, age range: 34-79). Primary outcome measures were caregiver burden (Zarit Burden Interview) and caregiver quality of life (Parkinson's Disease Questionnaire-Carer). Secondary outcome measures comprised ratings of depression and anxiety in the caregiver, in addition to relationship quality. Caregiver burden (t = 2.91 P = .017) and caregiver anxiety (t = 2.82 P = .020) symptoms were significantly reduced at completion of the program, and these benefits were maintained 3 months later. Caregiver quality of life had significantly improved by the end of the intervention (t = 3.02 P = .015), but this effect was not sustained after 3 months. The longitudinal influence of participation in the program on caregiver burden was confirmed in a linear, mixed-effects model, χ² (3) = 15.1, P = .0017). The intervention was well received by participants, and qualitative feedback was obtained. These results indicate that caregiver burden is modifiable in this cohort with a short course of CBT, that benefits are maintained after termination of the program, and that psychological treatment is acceptable to participants. Larger, controlled trials are justified.

Parkinson patients have a presynaptic serotonergic deficit: A dynamic deep brain stimulation PET study

Patients with Parkinson's disease (PD) often suffer from non-motor symptoms, which may be caused by serotonergic dysfunction. Apart from alleviating the motor symptoms, Deep Brain Stimulation (DBS) in the subthalamic nucleus (STN) may also influence non-motor symptoms. The aim of this study is to investigate how turning DBS off affects the serotonergic system. We here exploit a novel functional PET neuroimaging methodology to evaluate the preservation of serotonergic neurons and capacity to release serotonin. We measured cerebral 5-HT_1BR binding in 13 DBS-STN treated PD patients, at baseline and after turning DBS off. Ten age-matched volunteers served as controls. Clinical measures of motor symptoms were assessed under the two conditions and correlated to the PET measures of the static and dynamic integrity of the serotonergic system. PD patients exhibited a significant loss of frontal and parietal 5-HT_1BR, and the loss was significantly correlated to motor symptom severity. We saw a corresponding release of serotonin, but only in brain regions with preserved 5-HT_1BR, suggesting the presence of a presynaptic serotonergic deficit. Our study demonstrates that DBS-STN dynamically regulates the serotonin system in PD, and that preservation of serotonergic functions may be predictive of DBS-STN effects.

Does Personality Change Follow Deep Brain Stimulation in Parkinson's Disease Patients?

Deep Brain Stimulation (DBS) has emerged as a safe, effective, and appealing treatment for Parkinson's Disease (PD), particularly for improving motor symptoms (e. g., tremor, bradykinesia, and rigidity). However, concerns have been raised about whether DBS causes psychological changes, including changes to personality: characteristic and relatively stable patterns of affect, behavior, cognition, and desire. In this article, after first presenting some background information about PD and DBS, we examined evidence obtained from various empirical research methods (quantitative, qualitative, and mixed methods for evaluating patient valued characteristics) pertaining to whether DBS causes personality change. General limitations across research methods include a lack of randomized clinical trials and small sample sizes. We organized our review of findings according to different layers of personality variables: dispositional traits (including personality pathology), characteristic adaptations, and narrative identity. Though most work has been done on dispositional traits, there is not much evidence that dispositional traits change following DBS. Little work has been done on characteristic adaptations, but there is somewhat consistent evidence for positive perceived progress toward goals across a number of domains: routine activities, work, social/relational, and leisure. Nascent work on narrative identity holds promise for revealing issues around self-image that may be common following DBS. We listed a number of strategies for advancing research, highlighting opportunities related to personality conceptualization, personality assessment, and interdisciplinary scholarship. Finally, we offer practical applications of our findings for the informed consent process and for ongoing treatment.

The Effect of Deep Brain Stimulation of the Subthalamic Nucleus on Language Function in Parkinson's Disease: A Systematic Review

Purpose This systematic review focuses on the effect of bilateral deep brain stimulation (DBS) of the subthalamic nucleus (STN) on language function in Parkinson's disease (PD). It fills an important gap in recent reviews by considering other language tasks in addition to verbal fluency. Method We critically and systematically reviewed the literature on studies that investigated the effect of bilateral STN-DBS on language function in PD. All studies included a matched PD control group who were on best medical treatment, with language testing at similar baseline and follow-up intervals as the DBS PD group. Results Thirteen identified studies included a form of a verbal fluency task, seven studies included picture naming, and only two studies included more language-oriented tasks. We found that verbal fluency was negatively affected after DBS, whereas picture naming was unaffected. Studies investigating individual change patterns using reliable change indices showed that individual variability is larger for picture naming than for verbal fluency. Conclusions Verbal fluency is the most frequently investigated aspect of language function. Our analysis showed a pattern of decline in verbal fluency across multiple studies after STN-DBS, whereas picture naming was unaffected. Data on more language-oriented tests in a large DBS sample and best medical treatment control group are sparse. The investigation of language function in PD after DBS requires sensitive language tests (with and without time pressure) and experimental designs as used in the studies reviewed here. Reliable change index statistics are a promising tool for investigating individual differences in performance after DBS. Supplemental Material https://doi.org/10.23641/asha.14794458.

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.

Does the Personality of Patients with Parkinson's Disease Affect the Decision to Perform Deep Brain Stimulation Surgery? A Cross-Sectional Study in a Chinese Cohort

We investigated whether the personality of patients with Parkinson's disease (PD) before subthalamic brain stimulation differed from patients receiving drug treatments and whether the personality of patients affected surgical decisions. We recruited 38 patients with advanced PD scheduled for deep brain stimulation (DBS), 40 patients with PD receiving the very best medical treatment, and 51 healthy control subjects. All participants were evaluated by the Minnesota multiphasic personality inventory-1 (MMPI-1). PD patients who were candidates for DBS did not exhibit any significant differences in personality when compared with PD patients who were treated with drugs. Compared with healthy controls, patients with PD had remarkably higher MMPI-1 scores for spiritual quality, neuroticism, and introversion, but significantly lower scores for socialization. In addition, patients with PD were more submissive, more dependent on others, and less active in social activities. Our data indicated that the main deciding factor relating to whether to undergo DBS was the disease itself and not the pathological personality. However, neurotic and psychotic symptoms accompanying PD may influence the effect of DBS. We found that greater benefit is obtained by surgical or medical interventions if abnormal neurotic characteristics are considered early in the course of PD.

Serotonergic control of the glutamatergic neurons of the subthalamic nucleus

The subthalamic nucleus (STN) houses a dense cluster of glutamatergic neurons that play a central role in the functional dynamics of the basal ganglia, a group of subcortical structures involved in the control of motor behaviors. Numerous anatomical, electrophysiological, neurochemical and behavioral studies have reported that serotonergic neurons from the midbrain raphe nuclei modulate the activity of STN neurons. Here, we describe this serotonergic innervation and the nature of the regulation exerted by serotonin (5-hydroxytryptamine, 5-HT) on STN neuron activity. This regulation can occur either directly within the STN or at distal sites, including other structures of the basal ganglia or cortex. The effect of 5-HT on STN neuronal activity involves several 5-HT receptor subtypes, including 5-HT_1A, 5-HT_1B, 5-HT_2C and 5-HT₄ receptors, which have garnered the highest attention on this topic. The multiple regulatory effects exerted by 5-HT are thought to be modified under pathological conditions, altering the activity of the STN, or due to the benefits and side effects of treatments used for Parkinson's disease, notably the dopamine precursor l-DOPA and high-frequency STN stimulation. Originally understood as a motor center, the STN is also associated with decision making and participates in mood regulation and cognitive performance, two domains of personality that are also regulated by 5-HT. The literature concerning the link between 5-HT and STN is already important, and the functional overlap is evident, but this link is still not entirely understood. The understanding of this link between 5-HT and STN should be increased due to the possible importance of this regulation in the control of fronto-STN loops and inherent motor and non-motor behaviors.

The structural connectivity of subthalamic deep brain stimulation correlates with impulsivity in Parkinson's disease

Subthalamic deep brain stimulation (STN-DBS) for Parkinson's disease treats motor symptoms and improves quality of life, but can be complicated by adverse neuropsychiatric side-effects, including impulsivity. Several clinically important questions remain unclear: can 'at-risk' patients be identified prior to DBS; do neuropsychiatric symptoms relate to the distribution of the stimulation field; and which brain networks are responsible for the evolution of these symptoms? Using a comprehensive neuropsychiatric battery and a virtual casino to assess impulsive behaviour in a naturalistic fashion, 55 patients with Parkinson's disease (19 females, mean age 62, mean Hoehn and Yahr stage 2.6) were assessed prior to STN-DBS and 3 months postoperatively. Reward evaluation and response inhibition networks were reconstructed with probabilistic tractography using the participant-specific subthalamic volume of activated tissue as a seed. We found that greater connectivity of the stimulation site with these frontostriatal networks was related to greater postoperative impulsiveness and disinhibition as assessed by the neuropsychiatric instruments. Larger bet sizes in the virtual casino postoperatively were associated with greater connectivity of the stimulation site with right and left orbitofrontal cortex, right ventromedial prefrontal cortex and left ventral striatum. For all assessments, the baseline connectivity of reward evaluation and response inhibition networks prior to STN-DBS was not associated with postoperative impulsivity; rather, these relationships were only observed when the stimulation field was incorporated. This suggests that the site and distribution of stimulation is a more important determinant of postoperative neuropsychiatric outcomes than preoperative brain structure and that stimulation acts to mediate impulsivity through differential recruitment of frontostriatal networks. Notably, a distinction could be made amongst participants with clinically-significant, harmful changes in mood and behaviour attributable to DBS, based upon an analysis of connectivity and its relationship with gambling behaviour. Additional analyses suggested that this distinction may be mediated by the differential involvement of fibres connecting ventromedial subthalamic nucleus and orbitofrontal cortex. These findings identify a mechanistic substrate of neuropsychiatric impairment after STN-DBS and suggest that tractography could be used to predict the incidence of adverse neuropsychiatric effects. Clinically, these results highlight the importance of accurate electrode placement and careful stimulation titration in the prevention of neuropsychiatric side-effects after STN-DBS.

Management of psychiatric disorders in Parkinson's disease : Neurotherapeutics - Movement Disorders Therapeutics

Affective disorders (depression and anxiety), psychosis, impulse control disorders, and apathy are common and sometimes disabling psychiatric conditions in Parkinson disease (PD). Psychiatric aspects of PD are associated with numerous adverse outcomes, yet in spite of this and their high frequency, there remains incomplete understanding of epidemiology, presentation, risk factors, neural substrate, and management strategies. Psychiatric features are typically co- or multimorbid, and there is great intra- and interindividual variability in presentation [1]. The neuropathophysiological changes that occur in PD, as well as the association between PD treatment and particular psychiatric disorders, suggest a neurobiological contribution to many psychiatric symptoms. There is evidence that psychiatric disorders in PD are still under-recognized and undertreated, and although psychotropic medication use is common, randomized controlled trials demonstrating efficacy and tolerability are largely lacking. Future research on neuropsychiatric complications in PD should be oriented toward determining modifiable correlates or risk factors, and most importantly, establishing efficacious and well-tolerated treatment strategies.

Functional segregation and integration within the human subthalamic nucleus from a micro- and meso-level perspective

The subthalamic nucleus (STN) is a core basal ganglia structure involved in the control of motor, cognitive, motivational and affective functions. The (challenged) tripartite subdivision hypothesis places these functions into distinct sensorimotor, cognitive/associative, and limbic subregions based on the topography of cortical projections. To a large extent, this hypothesis is used to motivate the choice of target coordinates for implantation of deep brain stimulation electrodes for treatment of neurological and psychiatric disorders. Yet, the parallel organization of basal ganglia circuits has been known to allow considerable cross-talk, which might contribute to the occurrence of neuropsychiatric side effects when stimulating the dorsolateral, putative sensorimotor, part of the STN for treatment of Parkinson's disease. Any functional segregation within the STN is expected to be reflected both at micro-level microscopy and meso-level neural population activity. As such, we review the current empirical evidence from anterograde tracing and immunocytochemistry studies and from local field potential recordings for delineating the STN into distinct subregions. The spatial distribution of immunoreactivity presents as a combination of gradients, and although neural activity in distinct frequency bands appears spatially clustered, there is substantial overlap in peak locations. We argue that regional specialization without sharply defined borders is likely most representative of the STN's functional organization.

Effects of Subthalamic Nucleus Deep Brain Stimulation on Facial Emotion Recognition in Parkinson's Disease: A Critical Literature Review

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an effective therapy for Parkinson's disease (PD). Nevertheless, DBS has been associated with certain nonmotor, neuropsychiatric effects such as worsening of emotion recognition from facial expressions. In order to investigate facial emotion recognition (FER) after STN DBS, we conducted a literature search of the electronic databases MEDLINE and Web of science. In this review, we analyze studies assessing FER after STN DBS in PD patients and summarize the current knowledge of the effects of STN DBS on FER. The majority of studies, which had clinical and methodological heterogeneity, showed that FER is worsening after STN DBS in PD patients, particularly for negative emotions (sadness, fear, anger, and tendency for disgust). FER worsening after STN DBS can be attributed to the functional role of the STN in limbic circuits and the interference of STN stimulation with neural networks involved in FER, including the connections of the STN with the limbic part of the basal ganglia and pre- and frontal areas. These outcomes improve our understanding of the role of the STN in the integration of motor, cognitive, and emotional aspects of behaviour in the growing field of affective neuroscience. Further studies using standardized neuropsychological measures of FER assessment and including larger cohorts are needed, in order to draw definite conclusions about the effect of STN DBS on emotional recognition and its impact on patients' quality of life.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Clarifying the Normative Significance of 'Personality Changes' Following Deep Brain Stimulation

There is evidence to suggest that some patients who undergo Deep Brain Stimulation can experience changes to dispositional, emotional and behavioural states that play a central role in conceptions of personality, identity, autonomy, authenticity, agency and/or self (PIAAAS). For example, some patients undergoing DBS for Parkinson's Disease have developed hypersexuality, and some have reported increased apathy. Moreover, experimental psychiatric applications of DBS may intentionally seek to elicit changes to the patient's dispositional, emotional and behavioural states, in so far as dysfunctions in these states may undergird the targeted disorder. Such changes following DBS have been of considerable interest to ethicists, but there is a considerable degree of conflict amongst different parties to this debate about whether DBS really does change PIAAAS, and whether this matters. This paper explores these conflicting views and suggests that we may be able to mediate this conflict by attending more closely to what parties to the debate mean when they invoke the concepts lumped together under the acronym PIAAAS. Drawing on empirical work on patient attitudes, this paper outlines how these different understandings of the concepts incorporated into PIAAAS have been understood in this debate, and how they may relate to other fundamental concepts in medical ethics such as well-being and autonomy. The paper clarifies some key areas of disagreement in this context, and develops proposals for how ethicists might fruitfully contribute to future empirical assessments of apparent changes to PIAAAS following DBS treatment.

Motor Function Improvement After Electroconvulsive Therapy in a Parkinson's Disease Patient With Deep Brain Stimulator

In patients with a deep brain stimulator (DBS), electroconvulsive therapy (ECT) has proven to be a safe and effective treatment option after several medication failures in major depression, especially in the presence of psychotic symptoms. Electroconvulsive therapy has also proven to be effective in the treatment of Parkinson's disease (PD). To date, there have been no reports on the effect of ECT on motor function in PD patients with a functioning DBS. We present the case of a woman with DBS as a treatment for PD, safely treated with ECT for a psychotic depression. Depression severity and motor changes were evaluated on a weekly basis using the Montgomery-Åsberg Depression Rating Scale and the Unified Parkinson's Disease Rating Scale. During the course of ECT, the Montgomery-Åsberg Depression Rating Scale score declined from 34 to 13, and the Unified Parkinson's Disease Rating Scale motor score from 44 to 12 with positive impact on rigidity. Considering the positive impact of ECT on the motor function in our patient, new research should look into ECT as an augmentation strategy in motor dysfunction in patients treated with DBS for PD.

Building Intricate Partnerships with Neurotechnology: Deep Brain Stimulation and Relational Agency

Deep Brain Stimulation (DBS) is an FDA-approved treatment for symptoms of motor disorders—with experimental use for psychiatric disorders. DBS, however, causes a variety of side effects. Moral philosophers question DBS’s influence on users’ experiences of authenticity, identity, and/or autonomy. These characterizations of DBS, however, may not make sense of how DBS complicates, rather than simply impedes or bolsters, users’ abilities to exercise agency. Empirical work exploring DBS users’ lived-experiences and feminist accounts of relational autonomy demonstrate that the issues users face are better characterized in terms of the user’s relationship to their stimulator, that is, in terms of “relational agency.”

Deep brain stimulation in treatment resistant schizophrenia: A pilot randomized cross-over clinical trial

Background

Up to 30% of patients with schizophrenia are resistant to antipsychotic drug treatment, with 60% of such cases also failing to respond to clozapine. Deep brain stimulation (DBS) has been used in treatment resistant patients with other psychiatric disorders, but there is a lack of trials in schizophrenia, partly due to uncertainties over where to site the electrodes. This trial aimed to examine the effectiveness of nucleus accumbens (NAcc) and subgenual anterior cingulate cortex (subgenual ACC) targeted DBS; the primary outcome measure was PANSS total score, as assessed fortnightly.

Methods

Eight patients with schizophrenia, who met criteria for treatment resistance and were also resistant to/intolerant of clozapine, were randomly assigned using central allocation to receive DBS in the NAcc or subgenual ACC. An open stabilization phase lasting at least six months was followed by a randomized double-blind crossover phase lasting 24 weeks in those who met symptomatic improvement criteria. The primary end-point was a 25% improvement in PANSS total score. (ClinicalTrials.gov Identifier: NCT02377505; trial completed).

Findings

One implanted patient did not receive DBS due to complications of surgery. Of the remaining 7 patients, 2/3 with NAcc and 2/4 with subgenual ACC electrode placements met the symptomatic improvement criteria (58% and 86%, and 37% and 68% improvement in PANSS total score, respectively). Three of these patients entered the crossover phase and all showed worsening when the stimulation was discontinued. The fourth patient worsened after the current was switched off accidentally without her or the investigators’ knowledge. Physical adverse events were uncommon, but two patients developed persistent psychiatric adverse effects (negative symptoms/apathy and mood instability, respectively).

Interpretation

These preliminary findings point to the possibility of DBS having therapeutic effects in patients with schizophrenia who do not respond to any other treatment. Larger trials with careful attention to blinding will be necessary to establish the extent of the benefits and whether these can be achieved without psychiatric side-effects.

Subjective estimates of uncertainty during gambling and impulsivity after subthalamic deep brain stimulation for Parkinson's disease

Subthalamic deep brain stimulation (DBS) for Parkinson’s disease (PD) may modulate chronometric and instrumental aspects of choice behaviour, including motor inhibition, decisional slowing, and value sensitivity. However, it is not well known whether subthalamic DBS affects more complex aspects of decision-making, such as the influence of subjective estimates of uncertainty on choices. In this study, 38 participants with PD played a virtual casino prior to subthalamic DBS (whilst ‘on’ medication) and again, 3-months postoperatively (whilst ‘on’ stimulation). At the group level, there was a small but statistically significant decrease in impulsivity postoperatively, as quantified by the Barratt Impulsiveness Scale (BIS). The gambling behaviour of participants (bet increases, slot machine switches and double or nothing gambles) was associated with this self-reported measure of impulsivity. However, there was a large variance in outcome amongst participants, and we were interested in whether individual differences in subjective estimates of uncertainty (specifically, volatility) were related to differences in pre- and postoperative impulsivity. To examine these individual differences, we fit a computational model (the Hierarchical Gaussian Filter, HGF), to choices made during slot machine game play as well as a simpler reinforcement learning model based on the Rescorla-Wagner formalism. The HGF was superior in accounting for the behaviour of our participants, suggesting that participants incorporated beliefs about environmental uncertainty when updating their beliefs about gambling outcome and translating these beliefs into action. A specific aspect of subjective uncertainty, the participant’s estimate of the tendency of the slot machine’s winning probability to change (volatility), increased subsequent to DBS. Additionally, the decision temperature of the response model decreased post-operatively, implying greater stochasticity in the belief-to-choice mapping of participants. Model parameter estimates were significantly associated with impulsivity; specifically, increased uncertainty was related to increased postoperative impulsivity. Moreover, changes in these parameter estimates were significantly associated with the maximum post-operative change in impulsivity over a six month follow up period. Our findings suggest that impulsivity in PD patients may be influenced by subjective estimates of uncertainty (environmental volatility) and implicate a role for the subthalamic nucleus in the modulation of outcome certainty. Furthermore, our work outlines a possible approach to characterising those persons who become more impulsive after subthalamic DBS, an intervention in which non-motor outcomes can be highly variable.

Contact Location and Neuropsychological Outcomes in Subthalamic Deep Brain Stimulation

BACKGROUND

A host of influences contribute to cognitive and behavioral changes following deep brain stimulation. The location of the active cathode is likely an important variable but it has received little attention.

OBJECTIVE

To determine whether active contact location relative to the subthalamic nucleus and other neighboring structures is related to nonmotor outcomes.

METHODS

We identified a retrospective, cross-sectional sample of 46 patients who underwent subthalamic nucleus deep brain stimulation for treatment of idiopathic Parkinson's disease. T-tests or nonparametric equivalents were used to detect baseline differences between unilateral left, unilateral right, and bilateral surgical groups. Correlation and partial correlational analyses identified relationships between contact location variables and alterations in cognitive, mood, quality of life, motor, and disease variables.

RESULTS

Medial contact locations within the left subthalamic nucleus were correlated with improvements in self-reported mood (r12 = -0.78, P = .001; 95% confidence interval [CI] = -0.43 to -0.93) but worsening semantic fluency (r26 = -0.38, P = .048; 95% CI = -0.01 to -0.66). Phonemic fluency worsened with more posterior left placement (r34 = 0.35, P = .036; 95% CI = 0.03 to 0.61). Memory outcome was related to right hemisphere stimulation voltage (r29 = -0.40, P = .022; 95% CI = -0.05 to -0.66), which is likely a proxy for variable electrode location.

CONCLUSION

Location of the active contact is related to nonmotor outcomes, even in electrodes that are adequately placed. This is relevant to clinical care as there appears to be a trade-off between mood and fluency abilities that should be considered during surgical planning according to preoperative patient characteristics.

The Neuropsychiatry of Parkinson Disease: A Perfect Storm

Affective disorders, cognitive decline, and psychosis have long been recognized as common in Parkinson disease (PD), and other psychiatric disorders include impulse control disorders, anxiety symptoms, disorders of sleep and wakefulness, and apathy. Psychiatric aspects of PD are associated with numerous adverse outcomes, yet in spite of this and their frequent occurrence, there is incomplete understanding of epidemiology, presentation, risk factors, neural substrate, and management strategies. Psychiatric features are typically multimorbid, and there is great intra- and interindividual variability in presentation. The hallmark neuropathophysiological changes that occur in PD, plus the association between exposure to dopaminergic medications and certain psychiatric disorders, suggest a neurobiological basis for many psychiatric symptoms, although psychological factors are involved as well. There is evidence that psychiatric disorders in PD are still under-recognized and undertreated and although psychotropic medication use is common, controlled studies demonstrating efficacy and tolerability are largely lacking. Future research on neuropsychiatric complications in PD should be oriented toward determining modifiable correlates or risk factors and establishing efficacious and well-tolerated treatment strategies.

Mood Effects After Deep Brain Stimulation for Parkinson's Disease: An Update

Depression in Parkinson's Disease (PD) is a prevalent and invalidating symptom. Deep brain stimulation (DBS) allows for an improvement of PD motor features, but its effects on mood are difficult to predict. Here, we review the evidence regarding mood effects after DBS of either subthalamic nucleus (STN) or globus pallidus pars interna (GPi). Different influences of multiple factors contribute to impact the neuropsychiatric outcome after surgery. Psychosocial presurgical situation, postsurgical coping mechanisms, dopaminergic treatment modifications, and direct effects of the stimulation of either target are all playing a distinct role on the psychological well-being of patients undergoing DBS. No clear advantage of either target (STN vs. GPi) has been consistently found, both being effective and with a favorable profile on depression symptoms. However, specific patients' characteristics or anatomical considerations can guide the neurosurgeon in the target choice. Further research together with technological advances are expected to confine the stimulation area within dysfunctional circuits causing motor symptoms of PD.

Suicide and suicide attempts after subthalamic nucleus stimulation in Parkinson disease

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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