Criteria for deep-brain stimulation in Parkinson’s disease: review and analysis

Is PDQ-39 a reliable measure of quality of life of patients at advanced stages of Parkinson's disease considered for Deep Brain Stimulation

Purpose

Parkinson's disease (PD) significantly impedes, especially at its advanced stages, the health-related quality of life (QoL) of patients. The Parkinson's disease questionnaire (PDQ-39) is a widely-used measure assessing the impact of the disease on the patients' QoL. To date, the reliability of PDQ-39 has not been selectively evaluated for patients at a particular delineated stage of the PD progression. Against this backdrop, the study aimed firstly to evaluate comprehensively the internal consistency reliability of PDQ-39 and the constituent scales specifically for patients at the advanced stages of PD who were candidates for Deep Brain Stimulation (DBS) surgery, and secondly, to compare the Cronbach's alpha coefficients with those reported in other studies conducted with patients across all stages of the PD progression.

Methods

The sample included 36 Bulgarian patients (29 men and 7 women) at advanced stages of PD (Hoehn and Yahr stage 4), PD duration, M = 11.06, SD = 3.50). The internal consistency reliability of the questionnaire and the constituent scales was assessed using three criteria: Cronbach's alpha coefficients, inter-item and item-total correlations.

Results

The internal consistency reliability indicators were satisfactory for the entire instrument and for most of the scales and similar to those reported in previous studies. None of the scales had low internal consistency reliability results across the three criteria. Except for the Communication scale, seven of the eight scales had Cronbach's alpha values that were satisfactory or marginally below the cut off score. All scales had acceptable inter-item correlations. Three of the scales (Emotional Well-Being, Cognition and Communication) contained more than one item with non-satisfactory item-total correlations. With minor exceptions, the removal of the items with low item-total correlations either did not improve or improved marginally or even decreased the Cronbach's alpha coefficients of the respective scale. The Communication scale was the only scale with a Cronbach's alpha coefficient that was both low and comparatively different to other studies and had as well low item-total correlations for all constituent items, thus showing non-satisfactory results on two of the three internal consistency reliability estimates. In contrast, the Mobility scale met all three internal consistency reliability criteria.

Conclusion

PDQ-39 is a reliable tool for assessing the QoL of patients at advanced stages of PD across multiple health-related domains. The questionnaire can be recommended for inclusion in the best practice guidelines for evaluating DBS candidacy and the efficacy of DBS treatment for patients' QoL.

Fundamentals of deep brain stimulation for Parkinson's disease in clinical practice: part 1

Deep brain stimulation (DBS) is recognized as an established therapy for Parkinson's disease (PD) and other movement disorders in the light of the developments seen over the past three decades. Long-term efficacy is established for PD with documented improvement in the cardinal motor symptoms of PD and levodopa-induced complications, such as motor fluctuations and dyskinesias. Timing of patient selection is crucial to obtain optimal benefits from DBS therapy, before PD complications become irreversible. The objective of this first part review is to examine the fundamental concepts of DBS for PD in clinical practice, discussing the historical aspects, patient selection, potential effects of DBS on motor and non-motor symptoms, and the practical management of patients after surgery.

Predicting Motor Outcome and Quality of Life After Subthalamic Deep Brain Stimulation for Parkinson's Disease: The Role of Standard Screening Measures and Wearable-Data

BACKGROUND

Standardized screening for subthalamic deep brain stimulation (STN DBS) in Parkinson's disease (PD) patients is crucial to determine eligibility, but its utility to predict postoperative outcomes in eligible patients is inconclusive. It is unknown whether wearable data can contribute to this aim.

OBJECTIVE

To evaluate the utility of universal components incorporated in the DBS screening, complemented by a wearable sensor, to predict motor outcomes and Quality of life (QoL) one year after STN DBS surgery.

METHODS

Consecutive patients were included in the OPTIMIST cohort study from two DBS centers. Standardized assessments included a preoperative Levodopa Challenge Test (LCT), and questionnaires on QoL and non-motor symptoms including cognition, psychiatric symptoms, impulsiveness, autonomic symptoms, and sleeping problems. Moreover, an ambulatory wearable sensor (Parkinson Kinetigraph (PKG)) was used. Postoperative assessments were similar and also included a Stimulation Challenge Test to determine DBS effects on motor function.

RESULTS

Eighty-three patients were included (median (interquartile range) age 63 (56-68) years, 36% female). Med-OFF (Stim-OFF) motor severity deteriorated indicating disease progression, but patients significantly improved in terms of Med-ON (Stim-ON) motor function, motor fluctuations, QoL, and most non-motor domains. Motor outcomes were not predicted by preoperative tests, including covariates of either LCT or PKG. Postoperative QoL was predicted by better preoperative QoL, lower age, and more preoperative impulsiveness scores in multivariate models.

CONCLUSION

Data from the DBS screening including wearable data do not predict postoperative motor outcome at one year. Post-DBS QoL appears primarily driven by non-motor symptoms, rather than by motor improvement.

Non-motor effects of deep brain stimulation in Parkinson's disease motor subtypes

INTRODUCTION

Deep brain stimulation (DBS) is a well-established treatment for patients with Parkinson's disease (PD) improving quality of life, motor, and non-motor symptoms. However, non-motor effects in PD subtypes are understudied. We hypothesized that patients with 'postural instability and gait difficulty' (PIGD) experience more beneficial non-motor effects than 'tremor-dominant' patients undergoing DBS for PD.

METHODS

In this prospective, observational, international multicentre study with a 6-month follow-up, we assessed the Non-Motor Symptom Scale (NMSS) as primary and the following secondary outcomes: Unified PD Rating Scale-motor examination (UPDRS-III), Scales for Outcomes in PD (SCOPA)-activities of daily living (ADL) and -motor complications, PDQuestionnaire-8 (PDQ-8), and levodopa-equivalent daily dose (LEDD). We analysed within-group longitudinal changes with Wilcoxon signed-rank test and Benjamini-Hochberg correction for multiple comparisons. Additionally, we explored outcome between-group differences of motor subtypes with Mann-Whitney U-tests.

RESULTS

In 82 PIGD and 33 tremor-dominant patients included in this study, baseline NMSS total scores were worse in PIGD patients, both groups experienced postoperative improvements of the NMSS sleep/fatigue domain, and between-group differences in postoperative outcomes were favourable in the PIGD group for the NMSS total and miscellaneous domain scores.

CONCLUSIONS

This study provides evidence of a favourable outcome of total non-motor burden in PIGD compared to tremor-dominant patients undergoing DBS for PD. These differences of clinical efficacy on non-motor aspects should be considered when advising and monitoring patients with PD undergoing DBS.

Developments in the mechanistic understanding and clinical application of deep brain stimulation for Parkinson's disease

INTRODUCTION. Deep brain stimulation (DBS) is a life-changing treatment for patients with Parkinson's disease (PD) and gives the unique opportunity to directly explore how basal ganglia work. Despite the rapid technological innovation of the last years, the untapped potential of DBS is still high.

AREAS COVERED. This review summarizes the developments in the mechanistic understanding of DBS and the potential clinical applications of cutting-edge technological advances. Rather than a univocal local mechanism, DBS exerts its therapeutic effects through several multimodal mechanisms and involving both local and network-wide structures, although crucial questions remain unexplained. Nonetheless, new insights in mechanistic understanding of DBS in PD have provided solid bases for advances in preoperative selection phase, prediction of motor and non-motor outcomes, leads placement and postoperative stimulation programming.

EXPERT OPINION. DBS has not only strong evidence of clinical effectiveness in PD treatment, but technological advancements are revamping its role of neuromodulation of brain circuits and key to better understanding PD pathophysiology. In the next few years, the worldwide use of new technologies in clinical practice will provide large data to elucidate their role and to expand their applications for PD patients, providing useful insights to personalize DBS treatment and follow-up.

VGLUT3 neurons in median raphe control the efficacy of spatial memory retrieval via ETV4 regulation of VGLUT3 transcription

The raphe nucleus is critical for feeding, rewarding and memory. However, how the heterogenous raphe neurons are molecularly and structurally organized to engage their divergent functions remains unknown. Here, we genetically target a subset of neurons expressing VGLUT3. VGLUT3 neurons control the efficacy of spatial memory retrieval by synapsing directly with parvalbumin-expressing GABA interneurons (PGIs) in the dentate gyrus. In a mouse model of Alzheimer's disease (AD mice), VGLUT3→PGIs synaptic transmission is impaired by ETV4 inhibition of VGLUT3 transcription. ETV4 binds to a promoter region of VGLUT3 and activates VGLUT3 transcription in VGLUT3 neurons. Strengthening VGLUT3→PGIs synaptic transmission by ETV4 activation of VGLUT3 transcription upscales the efficacy of spatial memory retrieval in AD mice. This study reports a novel circuit and molecular mechanism underlying the efficacy of spatial memory retrieval via ETV4 inhibition of VGLUT3 transcription and hence provides a promising target for therapeutic intervention of the disease progression.

The Role of Genetic Data in Selecting Device-Aided Therapies in Patients With Advanced Parkinson's Disease: A Mini-Review

Parkinson’s disease (PD) is a common neurodegenerative disease. At present, 5–10% of PD patients are found to have monogenic form of the disease. Each genetic mutation has its own unique clinical features and disease trajectory. It is unclear if the genetic background can affect the outcome of device-aided therapies in these patients. In general, monogenic PD patients have satisfactory motor outcome after receiving invasive therapies. However, their long-term outcome can vary with their genetic mutations. It appears that patients with leucine-rich repeat kinase-2 (LRRK2) and PRKN mutations tended to have good outcome following deep brain stimulation (DBS) surgery. However, those with Glucocerebrosidase (GBA) mutation were found to have poorer cognitive performance, especially after undergoing subthalamic nucleus DBS surgery. In this review, we will provide an overview of the outcomes of device-aided therapies in PD patients with different genetic mutations.

The Instrumental Activities of Daily Living in Parkinson’s Disease Patients Treated by Subthalamic Deep Brain Stimulation

Background

Everyday functioning and instrumental activities of daily living (IADL) play a vital role in preserving the quality of life in patients with Parkinson’s disease (PD) after deep brain stimulation of the subthalamic nucleus (STN-DBS).

Objective

The main goal of the current study was to examine IADL change in pre-and post-surgery of the STN-DBS. We also analyzed the influence of the levodopa equivalent daily dose (LEDD) and global cognitive performance (Dementia Rating Scale; DRS-2) as covariates in relation to IADL.

Methods

Thirty-two non-demented PD patients were administered before and after STN-DBS neurosurgery the Penn Parkinson’s Daily Activities Questionnaire (PDAQ; self-report), the DRS-2 and Beck Depression Inventory (BDI-II) to assess IADL change, global cognition, and depression.

Results

We found a positive effect of STN-DBS on IADL in the post-surgery phase. Moreover, lower global cognition and lower LEDD are predictive of lower IADL in both pre-surgery and post-surgery examinations.

Summary/Conclusion

STN-DBS in PD is a safe method for improvement of everyday functioning and IADL. In the post-surgery phase, we show a relation of IADL to the severity of cognitive impairment in PD and to LEDD.

Patient-Related Factors Influencing Caregiver Burden in Parkinson’s Disease Patients: Comparison of Effects Before and After Deep Brain Stimulation

Background:

Caregivers of Parkinson’s disease (PD) patients provide important support during the pre- and postoperative phase of deep brain stimulation (DBS). High levels of caregiver burden have been reported after DBS. However, a comparison between preoperative and postoperative burden and associated factors has been insufficiently studied.

Objective:

To investigate the influence of DBS on caregiver burden, and to identify the differential impact of patient-related factors on caregiver burden before and after DBS.

Methods:

Consecutive patients referred for DBS eligibility screening or during one-year follow-up assessments were included. Caregiver burden was measured with the short Zarit Burden Interview (ZBI-12). Inverse Probability Weighting (IPW) was used to compare caregiver burden between preoperative and postoperative assessments.

Results:

We included 47 patients (24 screening, 23 follow-up) (median age 65 years, 29.4% female sex). DBS did not impact caregiver burden (screening: median ZBI-12 9.5 (IQR 3.25, 16.75); follow-up median ZBI-12 6 (IQR 4, 14); IPW-coefficient 0.57 (95% CI –2.75, 3.89)). Worse caregiver burden during DBS screening was associated with worse patient-related scores on depressive symptoms, anxiety, QoL, and impulsiveness. Worse scores on depressive symptoms, anxiety, apathy, postural-instability-gait-disorder, and QoL were associated with worse caregiver burden at one-year follow-up.

Conclusion:

DBS appears not associated with changes in caregiver burden. Various symptoms are valued differently between screening and follow-up assessments in terms of caregiver burden. Early recognition of caregivers “at risk” may improve guidance of patient-caregiver dyads throughout the DBS process.

Controlling Alzheimer's Disease Through the Deep Brain Stimulation to Thalamic Relay Cells

Experimental and clinical studies have shown that the technique of deep brain stimulation (DBS) plays a potential role in the regulation of Alzheimer’s disease (AD), yet it still desires for ongoing studies including clinical trials, theoretical approach and action mechanism. In this work, we develop a modified thalamo-cortico-thalamic (TCT) model associated with AD to explore the therapeutic effects of DBS on AD from the perspective of neurocomputation. First, the neuropathological state of AD resulting from synapse loss is mimicked by decreasing the synaptic connectivity strength from the Inter-Neurons (IN) neuron population to the Thalamic Relay Cells (TRC) neuron population. Under such AD condition, a specific deep brain stimulation voltage is then implanted into the neural nucleus of TRC in this TCT model. The symptom of AD is found significantly relieved by means of power spectrum analysis and nonlinear dynamical analysis. Furthermore, the therapeutic effects of DBS on AD are systematically examined in different parameter space of DBS. The results demonstrate that the controlling effect of DBS on AD can be efficient by appropriately tuning the key parameters of DBS including amplitude A, period P and duration D. This work highlights the critical role of thalamus stimulation for brain disease, and provides a theoretical basis for future experimental and clinical studies in treating AD.

Adaptive, personalized closed-loop therapy for Parkinson's disease: biochemical, neurophysiological, and wearable sensing systems

INTRODUCTION

Motor complication management is one of the main unmet needs in Parkinson's disease patients.

AREAS COVERED

Among the most promising emerging approaches for handling motor complications in Parkinson's disease, adaptive deep brain stimulation strategies operating in closed-loop have emerged as pivotal to deliver sustained, near-to-physiological inputs to dysfunctional basal ganglia-cortical circuits over time. Existing sensing systems that can provide feedback signals to close the loop include biochemical-, neurophysiological- or wearable-sensors. Biochemical sensing allows to directly monitor the pharmacokinetic and pharmacodynamic of antiparkinsonian drugs and metabolites. Neurophysiological sensing relies on neurotechnologies to sense cortical or subcortical brain activity and extract real-time correlates of symptom intensity or symptom control during DBS. A more direct representation of the symptom state, particularly the phenomenological differentiation and quantification of motor symptoms, can be realized via wearable sensor technology.

EXPERT OPINION

Biochemical, neurophysiologic, and wearable-based biomarkers are promising technological tools that either individually or in combination could guide adaptive therapy for Parkinson's disease motor symptoms in the future.

Long-term Outcomes (15 Years) After Subthalamic Nucleus Deep Brain Stimulation in Patients With Parkinson Disease

OBJECTIVE

To evaluate the effects of deep brain stimulation of the subthalamic nucleus (STN-DBS) on motor complications in patients with Parkinson disease (PD) beyond 15 years after surgery.

METHODS

Data on motor complications, quality of life (QoL), activities of daily living, Unified Parkinson's Disease Rating Scale motor scores, dopaminergic treatment, stimulation measures, and side effects of STN-DBS were retrospectively retrieved and compared before surgery, at 1 year, and beyond 15 years after bilateral STN-DBS.

RESULTS

Fifty-one patients with 17.06 ± 2.18 years STN-DBS follow-up were recruited. Compared to baseline, the time spent with dyskinesia and the time spent in the "off" state were reduced by 75% (p < 0.001) and by 58.7% (p < 0.001), respectively. Moreover, dopaminergic drugs were reduced by 50.6% (p < 0.001). Parkinson's Disease Quality of Life Questionnaire total score and the emotional function and social function domains improved 13.8% (p = 0.005), 13.6% (p = 0.01), and 29.9% (p < 0.001), respectively. Few and mostly manageable device-related adverse events were observed during the follow-up.

CONCLUSIONS

STN-DBS is effective beyond 15 years from the intervention, notably with significant improvement in motor complications and stable reduction of dopaminergic drugs. Furthermore, despite the natural continuous progression of PD with worsening of levodopa-resistant motor and nonmotor symptoms over the years, patients undergoing STN-DBS could maintain an improvement in QoL.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence that, for patients with PD, STN-DBS remains effective at treating motor complications 15 years after surgery.

Predictors of Long-Term Outcome of Subthalamic Stimulation in Parkinson Disease

OBJECTIVE

This study was undertaken to identify preoperative predictive factors of long-term motor outcome in a large cohort of consecutive Parkinson disease (PD) patients with bilateral subthalamic nucleus deep brain stimulation (STN-DBS).

METHODS

All consecutive PD patients who underwent bilateral STN-DBS at the Grenoble University Hospital (France) from 1993 to 2015 were evaluated before surgery, at 1 year (short-term), and in the long term after surgery. All available demographic variables, neuroimaging data, and clinical characteristics were collected. Preoperative predictors of long-term motor outcome were investigated by performing survival and univariate/multivariate Cox regression analyses. Loss of motor benefit from stimulation in the long term was defined as a reduction of less than 25% in the Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS) part III scores compared to the baseline off-medication scores. As a secondary objective, potential predictors of short-term motor outcome after STN-DBS were assessed by performing univariate and multivariate linear regression analyses.

RESULTS

In the long-term analyses (mean follow-up = 8.4 ± 6.26 years, median = 10 years, range = 1-17 years), 138 patients were included. Preoperative higher frontal score and off-medication MDS-UPDRS part III scores predicted a better long-term motor response to stimulation, whereas the presence of vascular changes on neuroimaging predicted a worse motor outcome. In 357 patients with available 1-year follow-up, preoperative levodopa response, tremor dominant phenotype, baseline frontal score, and off-medication MDS-UPDRS part III scores predicted the short-term motor outcome.

INTERPRETATION

Frontal lobe dysfunction, disease severity in the off-medication condition, and the presence of vascular changes on neuroimaging represent the main preoperative clinical predictors of long-term motor STN-DBS effects. ANN NEUROL 2021;89:587-597.

Differential effects of deep brain stimulation and levodopa on brain activity in Parkinson's disease

Levodopa is the first-line treatment for Parkinson’s disease, although the precise mechanisms mediating its efficacy remain elusive. We aimed to elucidate treatment effects of levodopa on brain activity during the execution of fine movements and to compare them with deep brain stimulation of the subthalamic nuclei. We studied 32 patients with Parkinson’s disease using functional MRI during the execution of finger-tapping task, alternating epochs of movement and rest. The task was performed after withdrawal and administration of a single levodopa dose. A subgroup of patients (n = 18) repeated the experiment after electrode implantation with stimulator on and off. Investigating levodopa treatment, we found a significant interaction between both factors of treatment state (off, on) and experimental task (finger tapping, rest) in bilateral putamen, but not in other motor regions. Specifically, during the off state of levodopa medication, activity in the putamen at rest was higher than during tapping. This represents an aberrant activity pattern probably indicating the derangement of basal ganglia network activity due to the lack of dopaminergic input. Levodopa medication reverted this pattern, so that putaminal activity during finger tapping was higher than during rest, as previously described in healthy controls. Within-group comparison with deep brain stimulation underlines the specificity of our findings with levodopa treatment. Indeed, a significant interaction was observed between treatment approach (levodopa, deep brain stimulation) and treatment state (off, on) in bilateral putamen. Our functional MRI study compared for the first time the differential effects of levodopa treatment and deep brain stimulation on brain motor activity. We showed modulatory effects of levodopa on brain activity of the putamen during finger movement execution, which were not observed with deep brain stimulation.

Medical management after subthalamic stimulation in Parkinson's disease: a phenotype perspective

Subthalamic nucleus deep brain stimulation (STN DBS) is an established treatment that improves motor fluctuations, dyskinesia, and tremor in Parkinson's disease (PD). After the surgery, a careful electrode programming strategy and medical management are crucial, because an imbalance between them can compromise the quality of life over time. Clinical management is not straightforward and depends on several perioperative motor and non-motor symptoms. In this study, we review the literature data on acute medical management after STN DBS in PD and propose a clinical algorithm on medical management focused on the patient's phenotypic profile at the perioperative period. Overall, across the trials, the levodopa equivalent daily dose is reduced by 30 to 50% one year after surgery. In patients taking high doses of dopaminergic drugs or with high risk of impulse control disorders, an initial reduction in dopamine agonists after STN DBS is recommended to avoid the hyperdopaminergic syndrome, particularly hypomania. On the other hand, a rapid reduction of dopaminergic agonists of more than 70% during the first months can lead to dopaminergic agonist withdrawal syndrome, characterized by apathy, pain, and autonomic features. In a subset of patients with severe dyskinesia before surgery, an initial reduction in levodopa seems to be a more reasonable approach. Finally, when the patient's phenotype before the surgery is the severe parkinsonism (wearing-off) with or without tremor, reduction of the medication after surgery can be more conservative. Individualized medical management following DBS contributes to the ultimate therapy success.

Dementia and subthalamic deep brain stimulation in Parkinson disease

Objectives

To assess the prevalence and the cumulative incidence of dementia at short-, medium- and long-term follow-up after deep brain stimulation (DBS) of the subthalamic nucleus (STN) (at 1, 5, and 10 years) and to evaluate potential risk factors for postoperative dementia.

Methods

The presence of dementia (according to the DSM-V) was retrospectively evaluated at each postoperative follow-up in patients with Parkinson disease (PD) who underwent bilateral STN-DBS. Preoperative and perioperative risk factors of developing postoperative dementia were also investigated. Demographic data, disease features, medications, comorbidities, nonmotor symptoms, PD motor scales, neuropsychological scales at baseline, and perioperative complications were collected for each patient.

Results

A total of 175 patients were included, and 104 were available at 10-year follow-up. Dementia prevalence was 2.3% at 1 year, 8.5% at 5 years, and 29.8% at 10 years. Dementia cumulative incidence at 1, 5, and 10 years was 2.3%, 10.9%, and 25.7%, respectively. The corresponding dementia incidence rate was 35.6 per 1,000 person-years. Male sex, higher age, hallucinations, lower frontal score at baseline, and perioperative cerebral hemorrhage were predictors of dementia.

Conclusions

In patients with PD with longstanding STN-DBS, dementia prevalence and incidence are not higher than those reported in the general PD population. Except for few patients with perioperative cerebral hemorrhage, STN-DBS is cognitively safe, and does not provide dementia risk factors in addition to those reported for PD itself. Identification of dementia predictors in this population may improve patient selection and information concerning the risk of poor cognitive outcome.

Parkinson's disease and changes in the appreciation of art: A comparison of aesthetic and formal evaluations of paintings between PD patients and healthy controls

Parkinson's disease (PD) is a progressing neurodegenerative disease predominantly involving the loss of dopamine producing neurons with hallmark symptoms of motor disorders and cognitive, motivational, emotional, and perceptual impairments. Intriguingly, PD can also be connected-often anecdotally-with a sudden burst of artistic creativity, motivation, or changed quality/style of produced art. This has led to growing empirical interest, promising a window into brain function and the unique neurological signature of artists. This topic also fits a growing interest from researchers in other areas, including Alzheimer's or other dementia, which have suggested that specific changes in art production/appraisal may provide a unique basis for therapy, diagnosis, or understanding of these diseases. However, whether PD also shows similar impacts on how we perceive and evaluate art has never been systematically addressed. We compared a cohort of PD patients against age-matched healthy controls, asking participants to rate paintings using scales of liking and beauty and terms pertaining to artworks' formal and conceptual qualities previously designed to provide a rubric for symptom identification. We found no evidence for PD-related differences in liking or beauty. However, PD patients showed higher ratings on assessed "emotionality," potentially relating to the tie between PD, dopamine pathways, and emotion/reward.

Oscillations in cortico-basal ganglia circuits: implications for Parkinson’s disease and other neurologic and psychiatric conditions

Cortico-basal ganglia circuits are thought to play a crucial role in the selection and control of motor behaviors and have also been implicated in the processing of motivational content and in higher cognitive functions. During the last two decades, electrophysiological recordings in basal ganglia circuits have shown that several disease conditions are associated with specific changes in the temporal patterns of neuronal activity. In particular, synchronized oscillations have been a frequent finding suggesting that excessive synchronization of neuronal activity may be a pathophysiological mechanism involved in a wide range of neurologic and psychiatric conditions. We here review the experimental support for this hypothesis primarily in relation to Parkinson’s disease but also in relation to dystonia, essential tremor, epilepsy, and psychosis/schizophrenia.

Current treatment of behavioral and cognitive symptoms of Parkinson's disease

Cognitive and behavioral symptoms are common in Parkinson's disease, may occur even in the prodromal stages of the disease, worsen with disease progression, and surpass motor symptoms as the major factors affecting patient quality of life and caregiver burden. The symptoms may be caused by the disease pathology or they may represent adverse effects of treatment, or both etiological factors may contribute. Although many of these symptoms are related to dopaminergic dysfunction or dopaminergic medication, other neurotransmitters are involved as well. Behavioral symptoms including impulse control disorders, apathy, psychosis, as well as mild cognitive impairment and dementia are reviewed with a special focus on current treatment approaches.

Why would Parkinson's disease lead to sudden changes in creativity, motivation, or style with visual art?: A review of case evidence and new neurobiological, contextual, and genetic hypotheses

Parkinson's disease (PD) is a devastating diagnosis with, however, potential for an extremely intriguing aesthetic component. Despite motor and cognitive deficits, an emerging collection of studies report a burst of visual artistic output and alterations in produced art in a subgroup of patients. This provides a unique window into the neurophysiological bases for why and how we might create and enjoy visual art, as well as into general brain function and the nature of PD or other neurodegenerative diseases. However, there has not been a comprehensive organization of literature on this topic. Nor has there been an attempt to connect case evidence and knowledge on PD with present understanding of visual art making in psychology and neuroaesthetics in order to propose hypotheses for documented artistic changes. Here, we collect the current research on this topic, tie this to PD symptoms and neurobiology, and provide new theories focusing on dopaminergic neuron damage, over-stimulation from dopamine agonist therapy, and context or genetic factors revealing the neurobiological basis of the visual artistic brain.

Liquid Metal Enabled Electrobiology: A New Frontier to Tackle Disease Challenges

In this article, a new conceptual biomedical engineering strategy to tackle modern disease challenges, called liquid metal (LM) enabled electrobiology, is proposed. This generalized and simple method is based on the physiological fact that specially administrated electricity induces a series of subsequent desired biological effects, either shortly, transitionally, or permanently. Due to high compliance within biological tissues, LM would help mold a pervasive method for treating physiological or psychological diseases. As highly conductive and non-toxic multifunctional flexible materials, such LMs can generate any requested electric treating fields (ETFields), which can adapt to various sites inside the human body. The basic mechanisms of electrobiology in delivering electricity to the target tissues and then inducing expected outputs for disease treatment are interpreted. The methods for realizing soft and conformable electronics based on LM are illustrated. Furthermore, a group of typical disease challenges are observed to illustrate the basic strategies for performing LM electrobiology therapy, which include but are not limited to: tissue electronics, brain disorder, immunotherapy, neural functional recovery, muscle stimulation, skin rejuvenation, cosmetology and dieting, artificial organs, cardiac pacing, cancer therapy, etc. Some practical issues regarding electrobiology for future disease therapy are discussed. Perspectives in this direction for incubating a simple biomedical tool for health care are pointed out.

A novel mechanism of memory loss in Alzheimer's disease mice via the degeneration of entorhinal-CA1 synapses

The entorhinal cortex (EC) is one of the most vulnerable brain regions that is attacked during the early stage of Alzheimer's disease (AD). Here, we report that the synaptic terminals of pyramidal neurons in the EC layer II (ECII_PN) directly innervate CA1 parvalbumin (PV) neurons (CA1_PV) and are selectively degenerated in AD mice, which exhibit amyloid-β plaques similar to those observed in AD patients. A loss of ECII_PN-CA1_PV synapses disables the excitatory and inhibitory balance in the CA1 circuit and impairs spatial learning and memory. Optogenetic activation of ECII_PN using a theta burst paradigm rescues ECII_PN-CA1_PV synaptic defects and intercepts the decline in spatial learning and memory. These data reveal a novel mechanism of memory loss in AD mice via the selective degeneration of the ECII_PN-CA1_PV pathway.

Assessing health-related quality of life with the SCOPA-PS in French individuals with Parkinson's disease having undergone DBS-STN: A validation study

INTRODUCTION

The aims of this study were to validate the French version of the SCales for Outcomes in Parkinson's Disease-PsychoSocial (SCOPA-PS) in individuals with Parkinson's disease (PD) who underwent deep brain stimulation of the subthalamic nucleus (DBS-STN), to confirm the unifactorial structure of this questionnaire, and to establish its psychometric properties.

METHODS

Routinely used psychological questionnaires (BDI-II, STAI-Y, PDQ-39, UPDRS III) and the SCOPA-PS were used for a cross-sectional observational study of 154 PD patients. SCOPA-PS acceptability, scaling assumption, reliability, ordinal confirmatory factor analysis and validity were assessed.

RESULTS

The ICC for two-week test-retest reliability was 0.88. SEM was 8.42. In confirmatory factor analysis, the one-factor model showed an acceptable fit to the data (Chi(2)/df=2.130; CFI=0.976; RMSEA=0.086). No floor or ceiling effects were observed. Skewness was 0.33. Item-total correlation coefficients ranged from 0.47 to 0.71. Cronbach's alpha was 0.86. SCOPA-PS SI correlated with PDQ-39 SI (rs=0.83) and with state-anxiety and depression (rs=0.56 and 0.69 respectively). The SCOPA-PS SI was higher in more depressed patients and in those with the most severe PD motor symptoms.

CONCLUSION AND DISCUSSION

SCOPA-PS French version is a one-factor scale with satisfactory psychometric properties consistent with other language versions. This short scale can be used to evaluate the psychosocial component of QoL in PD patients treated with DBS-STN.

An active method for tracking connectivity in temporally changing brain networks

The inference of connectivity in brain networks has typically been performed using passive measurements of ongoing activity across recording sites. Passive measures of connectivity are harder to interpret, however, in terms of causality - how evoked activity in one region might induce activity in another. To obviate this issue, recent work has proposed the use of active stimulation in conjunction with network estimation. By actively stimulating the network, more accurate information can be gleaned regarding evoked connectivity. The assumption in these previous works, however, was that the underlying networks were static and do not change in time. Such an assumption may be limiting in situations of clinical relevance, where the introduction of a drug or of brain pathology, might change the underlying networks structure. Here, an extension of the evoked connectivity paradigm is introduced that enables tracking networks that change in time.

Timing of deep brain stimulation in Parkinson disease: a need for reappraisal?

We review the current application of deep brain stimulation (DBS) in Parkinson disease (PD) and consider the evidence that earlier use of DBS confers long-term symptomatic benefit for patients compared to best medical therapy. Electronic searches were performed of PubMed, Web of Knowledge, Embase, Cochrane Database of Systematic Reviews, and Cochrane Central Register of Controlled Trials to identify all article types relating to the timing of DBS in PD. Current evidence suggests that DBS is typically performed in late stage PD, a mean of 14 to 15 years after diagnosis. Current guidelines recommend that PD patients who are resistant to medical therapies, have significant medication side effects and lengthening off periods, but are otherwise cognitively intact and medically fit for surgery be considered for DBS. If these criteria are rigidly interpreted, it may be that, by the time medical treatment options have been exhausted, the disease has progressed to the point that the patient may no longer be fit for neurosurgical intervention. From the evidence available, we conclude that surgical management of PD alone or in combination with medical therapy results in greater improvement of motor symptoms and quality of life than medical treatment alone. There is evidence to support the use of DBS in less advanced PD and that it may be appropriate for earlier stages of the disease than for which it is currently used. The improving short and long-term safety profile of DBS makes early application a realistic possibility.

Inferring evoked brain connectivity through adaptive perturbation

Inference of functional networks-representing the statistical associations between time series recorded from multiple sensors-has found important applications in neuroscience. However, networksexhibiting time-locked activity between physically independent elements can bias functional connectivity estimates employing passive measurements. Here, a perturbative and adaptive method of inferring network connectivity based on measurement and stimulation-so called "evoked network connectivity" is introduced. This procedure, employing a recursive Bayesian update scheme, allows principled network stimulation given a current network estimate inferred from all previous stimulations and recordings. The method decouples stimulus and detector design from network inference and can be suitably applied to a wide range of clinical and basic neuroscience related problems. The proposed method demonstrates improved accuracy compared to network inference based on passive observation of node dynamics and an increased rate of convergence relative to network estimation employing a naïve stimulation strategy.

Deep brain stimulation and cognitive decline in Parkinson's disease: a clinical review

Parkinson’s disease is a common and often debilitating disorder, with a growing prevalence accompanying global population aging. Current drug therapy is not satisfactory enough for many patients, especially after a few years of symptom progression. This is mainly due to the motor complications that frequently emerge as disease progresses. Deep brain stimulation (DBS) is a useful therapeutic option in carefully selected patients that significantly improves motor symptoms, functional status, and quality of life. However, cognitive impairment may limit patient selection for DBS, as patients need to have sufficient mental capabilities in order to understand the procedure, as well as its benefits and limitations, and cooperate with the medical team throughout the process of selection, surgery, and postsurgical follow-up. On the other hand it has been observed that certain aspects of cognitive performance may decline after DBS, namely when the therapeutic target is the widely used subthalamic nucleus. These are important pieces of information for patients, their families, and health care professionals. This manuscript reviews these aspects and their clinical implications.

Polycrystalline-Diamond MEMS Biosensors Including Neural Microelectrode-Arrays

Diamond is a material of interest due to its unique combination of properties, including its chemical inertness and biocompatibility. Polycrystalline diamond (poly-C) has been used in experimental biosensors that utilize electrochemical methods and antigen-antibody binding for the detection of biological molecules. Boron-doped poly-C electrodes have been found to be very advantageous for electrochemical applications due to their large potential window, low background current and noise, and low detection limits (as low as 500 fM). The biocompatibility of poly-C is found to be comparable, or superior to, other materials commonly used for implants, such as titanium and 316 stainless steel. We have developed a diamond-based, neural microelectrode-array (MEA), due to the desirability of poly-C as a biosensor. These diamond probes have been used for in vivo electrical recording and in vitro electrochemical detection. Poly-C electrodes have been used for electrical recording of neural activity. In vitro studies indicate that the diamond probe can detect norepinephrine at a 5 nM level. We propose a combination of diamond micro-machining and surface functionalization for manufacturing diamond pathogen-microsensors.

Dopaminergic neurotransmission in the human brain: new lessons from perturbation and imaging

Dopamine plays an important role in several brain functions and is involved in the pathogenesis of several psychiatric and neurological disorders. Neuroimaging techniques such as positron emission tomography allow us to quantify dopaminergic activity in the living human brain. Combining these with brain stimulation techniques offers us the unique opportunity to tackle questions regarding region-specific neurochemical activity. Such studies may aid clinicians and scientists to disentangle neural circuitries within the human brain and thereby help them to understand the underlying mechanisms of a given function in relation to brain diseases. Furthermore, it may also aid the development of alternative treatment approaches for various neurological and psychiatric conditions.

Characterizing Deep Brain Stimulation effects in computationally efficient neural network models

BACKGROUND

Recent studies on the medical treatment of Parkinson's disease (PD) led to the introduction of the so called Deep Brain Stimulation (DBS) technique. This particular therapy allows to contrast actively the pathological activity of various Deep Brain structures, responsible for the well known PD symptoms. This technique, frequently joined to dopaminergic drugs administration, replaces the surgical interventions implemented to contrast the activity of specific brain nuclei, called Basal Ganglia (BG). This clinical protocol gave the possibility to analyse and inspect signals measured from the electrodes implanted into the deep brain regions. The analysis of these signals led to the possibility to study the PD as a specific case of dynamical synchronization in biological neural networks, with the advantage to apply the theoretical analysis developed in such scientific field to find efficient treatments to face with this important disease. Experimental results in fact show that the PD neurological diseases are characterized by a pathological signal synchronization in BG. Parkinsonian tremor, for example, is ascribed to be caused by neuron populations of the Thalamic and Striatal structures that undergo an abnormal synchronization. On the contrary, in normal conditions, the activity of the same neuron populations do not appear to be correlated and synchronized.

RESULTS

To study in details the effect of the stimulation signal on a pathological neural medium, efficient models of these neural structures were built, which are able to show, without any external input, the intrinsic properties of a pathological neural tissue, mimicking the BG synchronized dynamics.We start considering a model already introduced in the literature to investigate the effects of electrical stimulation on pathologically synchronized clusters of neurons. This model used Morris Lecar type neurons. This neuron model, although having a high level of biological plausibility, requires a large computational effort to simulate large scale networks. For this reason we considered a reduced order model, the Izhikevich one, which is computationally much lighter. The comparison between neural lattices built using both neuron models provided comparable results, both without traditional stimulation and in presence of all the stimulation protocols. This was a first result toward the study and simulation of the large scale neural networks involved in pathological dynamics.Using the reduced order model an inspection on the activity of two neural lattices was also carried out at the aim to analyze how the stimulation in one area could affect the dynamics in another area, like the usual medical treatment protocols require.The study of population dynamics that was carried out allowed us to investigate, through simulations, the positive effects of the stimulation signals in terms of desynchronization of the neural dynamics.

CONCLUSIONS

The results obtained constitute a significant added value to the analysis of synchronization and desynchronization effects due to neural stimulation. This work gives the opportunity to more efficiently study the effect of stimulation in large scale yet computationally efficient neural networks. Results were compared both with the other mathematical models, using Morris Lecar and Izhikevich neurons, and with simulated Local Field Potentials (LFP).

Therapeutic armamentarium for treating depression

Depressive disorders are highly prevalent and are a leading cause of disability, morbidity, and mortality worldwide; however, they often remain undertreated or untreated. This article provides a broad overview of the many strategies for treating depression. More than 24 antidepressant medications and depression-focused psychotherapies are available as first-choice options for treating depression. When patients have not had a satisfactory treatment response, the 2 main strategies are switching to an alternative antidepressant therapy or adding a second antidepressant therapy. A large number of medication combinations have been reported in the literature, and some have been shown to be effective in controlled studies. Nonstandard alternatives to conventional antidepressant treatments include exercise, light therapy, sleep deprivation, and various complementary and alternative therapies. For more chronic and refractory forms of depression, various neuromodulation therapies are available or are being investigated. Because depressive disorders are common in primary care and other medical settings, medical practitioners should be aware of the therapeutic armamentarium available for treating depression.

Parkinson's disease and deep brain stimulator placement

Deep brain stimulation (DBS) has added to the comfort and quality of life for an increasing number of Parkinson's disease (PD) patients. The anesthesiologist needs to understand the pathophysiology of the disease, the surgical procedure, and its postoperative implications to most effectively manage these patients. This article examines the role of the anesthesiologist in the pre- and perioperative management of patients undergoing DBS procedures. In terms of the general anesthetic management of PD patients, it is clear that no simple anesthetic regimen exists. Anesthesiologists can provide the best care through preoperative assessment, maintenance of PD drug therapy, and avoidance of known precipitating agents.

Reoperation for suboptimal outcomes after deep brain stimulation surgery

OBJECTIVE

To examine a case series of reoperations for deep brain stimulation (DBS) leads in which clinical scenarios revealed suboptimal outcome from a previous operation. Suboptimally placed DBS leads are one potential reason for unsatisfactory results after surgery for Parkinson's disease (PD), essential tremor (ET), or dystonia. In a previous study of patients who experienced suboptimal results, 19 of 41 patients had misplaced leads. Similarly, another report commented that lead placement beyond a 2- to 3-mm window resulted in inadequate clinical benefit, and, in 1 patient, revision improved outcome. The goal of the current study was to perform an unblinded retrospective chart review of DBS patients with unsatisfactory outcomes who presented for reoperation.

METHODS

Patients who had DBS lead replacements after reoperation were assessed with the use of a retrospective review of an institutional review board-approved movement disorders database. Cases of reoperation for suboptimal clinical benefit were included, and cases of replacement of DBS leads caused by infection or hardware malfunction were excluded. Data points studied included age, disease duration, diagnosis, motor outcomes (the Unified Parkinson Disease Rating Scale III in PD, the Tremor Rating Scale in ET, and the Unified Dystonia Rating Scale in dystonia), quality of life (Parkinson's Disease Questionnaire-39 in PD), and the Clinician Global Impression scale. The data from before and after reoperation were examined to determine the estimated impact of repeat surgery.

RESULTS

There were 11 patients with PD, 7 with ET, and 4 with dystonia. The average age of the PD group was 52 years, the disease duration was 10 years, and the average vector distance of the location of the active DBS contact was adjusted 5.5 mm. Six patients (54%) with PD had preoperative off medication on DBS Unified Parkinson Disease Rating Scale scores that could be compared with postoperative off medication on DBS scores. The average improvement across this group of patients was 24.4%. The Parkinson's Disease Questionnaire-39 improved in the areas of mobility (28.18), activities of daily living (14.77), emotion (14.72), stigma (17.61), and discomfort (17.42). The average age of the ET group was 66 years, the disease duration was 29 years, and the average adjusted distance was 6.1 mm. Five ET patients (83.3%) in the cohort had a prereplacement on DBS Tremor Rating Scale and a postreplacement on DBS Tremor Rating Scale with the average improvement of 60.4%. The average age of the dystonia group was 39 years, the average disease duration was 7 years, and the average adjusted lead distance was 6.7 mm. Three patients (75%) with dystonia had prereplacement on DBS Unified Dystonia Rating Scale and postreplacement on DBS Unified Dystonia Rating Scale scores. Across these 3 dystonia patients, the improvement was 12.8%. Clinician Global Impression scale scores (1, very much improved; 2, much improved; 3, minimally improved; 4, no change; 5, minimally worse; 6, much worse; 7, very much worse) after replacement revealed the following results in patients with PD: 1, 7 patients; 2, 3 patients; 3, 1 patient); with ET (1, 4 patients; 2, 3 patients); and with dystonia (1, 1 patient; 2, 2 patients; 3, 1 patient). The latency from original lead placement to reoperation (repositioning/revision) overall was 28.9 months (range, 2-104 mo); however, in leads referred from outside institutions (n = 11 patients), this latency was 48 months (range, 12-104 mo) compared with leads implanted by surgeons from the University of Florida (n = 11 patients), which was 9.7 months (range, 2-19 mo). The most common clinical history was failure to achieve a perceived outcome; however, history of an asymmetric benefit was present in 4 (18.2%) of 22 patients, and lead migration was present in 3 (13.6%) of 22 patients.

CONCLUSION

There are many potential causes of suboptimal benefit after DBS. Timely identification of suboptimal lead placements followed by reoperation and repositioning/replacement in a subset of patients may improve outcomes.

A decision tool to support appropriate referral for deep brain stimulation in Parkinson's disease

BACKGROUND AND OBJECTIVE

Although Deep Brain Stimulation (DBS) has been proven to be an effective treatment for patients with advanced Parkinson's disease (PD), it may be difficult for general neurologists to identify appropriate candidates for this procedure. We developed an electronic decision tool that can assist neurologists in deciding which PD patients should be referred for DBS consideration.

METHODS

Using the RAND/UCLA Appropriateness Method, an international expert panel assessed the appropriateness of referral for 972 theoretical patient profiles. Panel results were embedded in an electronic decision support tool which displays the panel statement on referral (appropriate, inappropriate and uncertain) after completion of the patient profile.

RESULTS

Referral was considered appropriate for 33% of the theoretical profiles. Logistic regression showed excellent internal consistency of the ratings (predictive value 92%). Symptom severity (OFF-symptoms, dyskinesias, refractory tremor) and PD duration were positively associated with the panel judgment that referral is appropriate. Presence of levodopa-resistant axial symptoms, age >or= 70 years and presence of cognitive impairment showed the strongest negative impact.

CONCLUSIONS

The RAND/UCLA method proved to be useful in determining the appropriate criteria for DBS referral. Validity and applicability of the decision tool (accessible via http://test.stimulus-dbs.org) in clinical practice need to be further determined.

Technology insight: noninvasive brain stimulation in neurology-perspectives on the therapeutic potential of rTMS and tDCS

In neurology, as in all branches of medicine, symptoms of disease and the resulting burden of illness and disability are not simply the consequence of the injury, inflammation or dysfunction of a given organ; they also reflect the consequences of the nervous system's attempt to adapt to the insult. This plastic response includes compensatory changes that prove adaptive for the individual, as well as changes that contribute to functional disability and are, therefore, maladaptive. In this context, brain stimulation techniques tailored to modulate individual plastic changes associated with neurological diseases might enhance clinical benefits and minimize adverse effects. In this Review, we discuss the use of two noninvasive brain stimulation techniques--repetitive transcranial magnetic stimulation and transcranial direct current stimulation--to modulate activity in the targeted cortex or in a dysfunctional network, to restore an adaptive equilibrium in a disrupted network for best behavioral outcome, and to suppress plastic changes for functional advantage. We review randomized controlled studies, in focal epilepsy, Parkinson's disease, recovery from stroke, and chronic pain, to illustrate these principles, and we present evidence for the clinical effects of these two techniques.