Risk factors for executive dysfunction after subthalamic nucleus stimulation in Parkinson's disease

Developments in the prediction of cognitive changes following deep brain stimulation in persons with Parkinson's disease

INTRODUCTION

Deep brain stimulation (DBS) is an effective treatment for Parkinson's disease (PD) motor symptoms that improves function and quality of life in appropriately selected patients. Because mild to moderate cognitive declines can follow DBS and impact quality of life in a minority of patients, an important consideration involves the cognitive deficit and its prediction.

AREAS COVERED

The author briefly summarizes cognitive outcomes from DBS and reviews in more detail the risks/predictors of post-DBS cognitive dysfunction by mainly focusing on work published between 2018 and 2024 and using comprehensive neuropsychological (NP) evaluations. Most publications concern bilateral subthalamic nucleus (STN) DBS. Comment is offered on challenges and potential avenues forward.

EXPERT OPINION

STN DBS is relatively safe cognitively but declines occur especially in verbal fluency and executive function/working memory. Numerous predictors and risk factors for cognitive outcomes have been identified (age and pre-operative neuropsychological status appear the most robust) but precise risk estimates cannot yet be confidently offered. Future studies should employ study center consortia, follow uniform reporting criteria (to be developed), capitalize on advances in stimulation, biomarkers, and artificial intelligence, and address DBS in diverse groups. Advances offer an avenue to investigate the amelioration of cognitive deficits in PD using neuromodulation.

Long-term neuropsychological outcomes of deep brain stimulation in early-stage Parkinson's disease

INTRODUCTION

The pilot trial of deep brain stimulation (DBS) in early-stage Parkinson's disease (PD) randomized 30 patients (medication duration 0.5-4 years; without dyskinesia or motor fluctuations) to receive optimal drug therapy alone (early ODT) or subthalamic nucleus (STN) DBS plus ODT (early DBS + ODT). This study reports long-term neuropsychological outcomes from the early DBS pilot trial.

METHODS

This is an extension of an earlier study that examined two-year neuropsychological outcomes in the pilot trial. The primary analysis was conducted on the five-year cohort (n = 28), and a secondary analysis was conducted on the 11-year cohort (n = 12). Linear mixed effects models for each analysis compared overall trend in outcomes for randomization groups. All subjects who completed the 11-year assessment were also pooled to evaluate long-term change from baseline.

RESULTS

There were no significant differences between groups in either the five- or 11-year analyses. Across all PD patients who completed the 11-year visit, there was significant decline in Stroop Color and Color-Word and Purdue Pegboard from baseline to 11 years.

CONCLUSIONS

Previous significant differences between the groups in phonemic verbal fluency and cognitive processing speed showing more decline for early DBS + ODT subjects one year after baseline diminished as PD progressed. No cognitive domains were worse for early DBS + ODT subjects compared to standard of care subjects. There were shared declines across all subjects on cognitive processing speed and motor control, likely reflecting disease progression. More study is needed to understand the long-term neuropsychological outcomes associated with early DBS in PD.

Decline of verbal fluency with lateral superior frontal gyrus penetration in subthalamic nucleus deep brain stimulation for Parkinson disease

OBJECTIVE

Verbal fluency (VF) decline is a well-recognized adverse cognitive outcome following subthalamic nucleus deep brain stimulation (STN DBS) in patients with Parkinson disease (PD). The mechanisms underlying VF decline, whether from stimulation, lesioning, or both, remain unclear. This study aims to investigate the unique effects of DBS lead trajectory on VF beyond previously reported effects of active contact location.

METHODS

The study population included 56 patients with idiopathic PD who underwent bilateral STN DBS. Phonemic and semantic VF scores were compared pre- and postoperatively. Features of the electrode trajectory were measured on postoperative imaging, including distance from the falx cerebri, distance from the superior frontal sulcus, and caudate nucleus penetration. The authors used t-tests, Pearson's correlation, and multiple linear regression analyses to examine the relationship between VF change and demographic, disease, and electrode trajectory variables.

RESULTS

The laterality of entry within the left superior frontal gyrus (SFG) predicted greater phonemic VF decline (sr2 = 0.28, p < 0.001) after controlling for active contact location. VF change did not differ by the presence of caudate nucleus penetration in either hemisphere (p > 0.05).

CONCLUSIONS

Lateral penetration of the SFG in the left hemisphere is associated with worsening phonemic VF and has greater explanatory power than active contact location. This may be explained by lesioning of the lateral SFG-Broca area pathway, which is implicated in language function.

Cognitive Impact of Deep Brain Stimulation in Parkinson’s Disease Patients: A Systematic Review

Introduction

Parkinson’s disease (PD) patients have a significantly higher risk of developing dementia in later disease stages, leading to severe impairments in quality of life and self-functioning. Questions remain on how deep brain stimulation (DBS) affects cognition, and whether we can individualize therapy and reduce the risk for adverse cognitive effects. Our aim in this systematic review is to assess the current knowledge in the field and determine if the findings could influence clinical practice.

Methods

We have conducted a systematic review according to PRISMA guidelines through MEDLINE and Embase databases, with studies being selected for inclusion via a set inclusion and exclusion criteria.

Results

Sixty-seven studies were included in this systematic review according to the selected criteria. This includes 6 meta-analyses, 18 randomized controlled trials, 17 controlled clinical trials, and 26 observational studies with no control arms. The total number of PD patients encompassed in the studies cited in this review is 3677, not including the meta-analyses.

Conclusion

Cognitive function in PD patients can deteriorate, in most cases mildly, but still impactful to the quality of life. The strongest evidence is present for deterioration in verbal fluency, while inconclusive evidence is still present for executive function, memory, attention and processing speed. Global cognition does not appear to be significantly impacted by DBS, especially if cognitive screening is performed prior to the procedure, as lower baseline cognitive function is connected to poor outcomes. Further randomized controlled studies are required to increase the level of evidence, especially in the case of globus pallidus internus DBS, pedunculopontine nucleus DBS, and the ventral intermediate nucleus of thalamus DBS, and more long-term studies are required for all respective targets.

Comparison of Montreal cognitive assessment and Mattis dementia rating scale in the preoperative evaluation of subthalamic stimulation in Parkinson’s disease

Introduction

The preoperative evaluation of Parkinson’s Disease (PD) patients for subthalamic nucleus deep brain stimulation (STN-DBS) includes the assessment of the neuropsychological status of the patient. A widely used preoperative test is the Mattis Dementia rating scale (MDRS). However, the Montreal cognitive assessment (MoCA) has also been proven to be a sensitive, time-sparing tool with high diagnostic validity in PD. We evaluate the utility of the MoCA as a preoperative screening test for PD patients undergoing bilateral STN-DBS.

Methods

In this single-centre, retrospective study, we analysed pre- and postoperative assessments of MoCA, MDRS, Movement disorder society-Unified PD Rating Scale-motor examination, PD Questionnaire-39 and levodopa equivalent daily dose. Longitudinal outcome changes were analysed using paired t-test, Pearson’s correlation coefficient, linear regression and CHAID (chi-square automatic interaction detector) regression tree model.

Results

Clinical motor and cognitive scores of 59 patients (61.05±7.73 years, 24 females) were analysed. The MoCA, but not the MDRS, identified significant postoperative cognitive decline in PD patients undergoing STN-DBS. The preoperative MoCA score correlated with postoperative quality of life improvement, whereas the MDRS did not. PD patients with a MoCA score ≤ 23 points had a significant decline of quality of life after DBS surgery compared to patients > 23 points.

Conclusion

This study identifies the MoCA as an alternative test within the preoperative evaluation of PD patients for the detection of neuropsychological deficits and prediction of the postoperative improvement of quality of life.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Predictors of multi-domain cognitive decline following DBS for treatment of Parkinson's disease

BACKGROUND

Statistically and clinically significant cognitive declines are observed in a small subset of individuals with Parkinson's Disease (PD) following treatment with Deep Brain Stimulation (DBS).

OBJECTIVES

We examine the association between multi-domain cognitive decline (MCD) and demographic and baseline clinical variables and the incidence of serious adverse events (SAE) arising within a six-month interval following DBS for PD.

METHOD

Study participants with PD who displayed MCD at 6-month follow-up evaluation after DBS (n = 18) were contrasted with individuals with PD from the same study who did not show cognitive decline after DBS (n = 146). Logistic regression analyses were employed to assess relationship between predictors, including age (>70 years old), pre-DBS cognitive screening test performance, SAE, and MCD. MCD+ and MCD-groups were also compared on other baseline clinical and demographic variables.

RESULTS

MCD showed modest association with older age and lower baseline neurocognitive screening performance, whereas the groups did not differ on most other baseline clinical and demographic variables. SAEs during the study interval were the most robust predictor of MCD in the DBS group. A variety of SAEs were documented in study participants experiencing MCD after DBS surgery, including, but not limited to, infections and small intracranial hemorrhages.

CONCLUSIONS

Older age and lower baseline cognition measured prior to treatment are associated with MCD measured at six-months after DBS. SAE occurring following DBS surgery are also predictive of MCD. These predictors may reflect aspects of "frailty" in advanced PD. Risk factors for SAE warrant careful consideration in clinical trials.

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.

The clinical meaning of levodopa equivalent daily dose in Parkinson's disease

Levodopa (L-dopa) remains the basis of pharmacological treatment of Parkinson's disease (PD). However, L-dopa therapy is associated with the development of complications and presents major challenges in the long-term treatment. Thus, other medications may be suggested to delay and/or reduce the doses of L-dopa in order to prevent complications. The interpretation of treatment evolution reported in clinical trials on PD may be tricky, especially due to some variability in medications and dose regimens. Some authors have suggested a conversion factor to generate a total L-dopa equivalent daily dose (LEDD), calculated as a sum of each parkinsonian medication. Therefore, LEDD provides an artificial summary of the total daily medication a patient is receiving, and to date, there is no report focusing on the clinical interpretation of this parameter. Thus, based on a 3-year, multi-center retrospective study assessing the impact of second-line therapy initiation on LEDD in PD patients, the aim of our article was to discuss LEDD as a quantitative outcome to estimate the impact of second-line therapies on medication regimens; and in the second part of the discussion, to provide a narrative review of the clinical outcomes associated with LEDD in the literature.

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.

How is cognition in subthalamic nucleus deep brain stimulation Parkinson's disease patients?

The impairments in cognitive functions such as memory, executive function, visuospatial skills and language in Parkinson's disease (PD) are drawing increasing attention in the current literature. Studies dedicated to investigating the relationship between subthalamic nucleus deep brain stimulation (STN-DBS) and cognitive functioning are contradictory. This systematic review aims to analyze the impact on the cognitive functioning of patients with PD and STN-DBS. Articles published in the 2007-2017 period were retrieved from the Medline/Pubmed databases using PRISMA criteria. The analysis of 27 articles revealed many conflicting results, precluding a consensus on a cognitive functioning standard and hampering the establishment of a neuropsychological profile for PD patients who underwent STN-DBS surgery. Further studies investigating this relationship are needed.

Predictive Factors of Antiparkinsonian Drug Reduction after Subthalamic Stimulation for Parkinson's Disease

Subthalamic nucleus deep brain stimulation (STN-DBS) improves motor symptoms in individuals with advanced Parkinson’s disease (PD) and enables physicians to reduce doses of antiparkinsonian drugs. We investigated possible predictive factors for the successful reduction of antiparkinsonian drug dosage after STN-DBS. We evaluated 33 PD patients who underwent bilateral STN-DBS. We assessed rates of reduction of the levodopa-equivalent daily dose (LEDD) and levodopa daily dose (LDD) by comparing drug doses before vs. 6-months post-surgery. We used correlation coefficients to measure the strength of the relationships between LEDD and LDD reduction rates and preoperative factors including age, disease duration, preoperative LEDD and LDD, unified Parkinson’s Disease Rating Scale part-II and -III, levodopa response rate, Mini-Mental State Examination score, dyskinesia score, Hamilton Rating Scale for depression, and the number of non-motor symptoms. The average LEDD and LDD reduction rates were 61.0% and 70.4%, respectively. Of the variables assessed, only the number of psychiatric/cognitive symptoms was significantly correlated with the LEDD reduction rate. No other preoperative factors were correlated with the LEDD or LDD reduction rate. A wide range of preoperative psychiatric and cognitive symptoms may predict the successful reduction of antiparkinsonian drugs after STN-DBS.

Systematic review of neuropsychological instruments used in subthalamic nucleus deep brain stimulation in Parkinson´s disease patients

In addition to drug treatment, surgical intervention represents an alternative to PD patients with motor deficits. The most common intervention is subthalamic nucleus deep brain stimulation (STN-DBS). It is extremely important to perform a neuropsychological assessment in patients with STN-DBS, not only to identify losses related to the disease, but also to compare influence on cognition both pre and postoperatively.

OBJECTIVE

the objective of this systematic review was to investigate the instruments frequently used in studies related to STN-DBS in PD patients.

METHODS

articles were retrieved from Medline/Pubmed databases published in the 2007-2017 period using PRISMA criteria.

RESULTS

after analyzing 27 articles, the absence of a specific evaluation protocol for PD with STN-DBS was evident.

CONCLUSION

non-motor symptoms are not given due importance in neuropsychological assessments. It is crucial to acknowledge that these symptoms have a major impact on the quality of life of patients. Greater engagement in assessing these aspects is required, in order to bridge the gaps in research.

White matter tracts lesions and decline of verbal fluency after deep brain stimulation in Parkinson's disease

Decline of verbal fluency (VF) performance is one of the most systematically reported neuropsychological adverse effects after subthalamic nucleus deep brain stimulation (STN-DBS). It has been suggested that this worsening of VF may be related to a microlesion due to the electrode trajectories. We describe the disruption of surrounding white matter tracts following electrode implantation in Parkinson's disease (PD) patients with STN-DBS and assess whether damage of fiber pathways is associated with VF impairment after surgery. We retrospectively analyzed 48 PD patients undergoing bilateral STN DBS. The lesion mask along the electrode trajectory transformed into the MNI 152 coordinate system, was compared with white matter tract atlas in Tractotron software, which provides a probability and proportion of fibers disconnection. Combining tract- and atlas-based analysis reveals that the trajectory of the electrodes intersected successively with the frontal aslant tract, anterior segment of arcuate tract, the long segment of arcuate tract, the inferior longitudinal fasciculus, the superior longitudinal fasciculus, the anterior thalamic radiation, and the fronto striatal tract. We found no association between the proportion fiber disconnection and the severity of VF impairment 6 months after surgery. Our findings demonstrated that microstructural injury associated with electrode trajectories involved white matter bundles implicated in VF networks.

Quantitative EEG and Verbal Fluency in DBS Patients: Comparison of Stimulator-On and -Off Conditions

Introduction: Deep brain stimulation of the subthalamic nucleus (STN-DBS) ameliorates motor function in patients with Parkinson's disease and allows reducing dopaminergic therapy. Beside effects on motor function STN-DBS influences many non-motor symptoms, among which decline of verbal fluency test performance is most consistently reported. The surgical procedure itself is the likely cause of this decline, while the influence of the electrical stimulation is still controversial. STN-DBS also produces widespread changes of cortical activity as visualized by quantitative EEG. The present study aims to link an alteration in verbal fluency performance by electrical stimulation of the STN to alterations in quantitative EEG.

Methods: Sixteen patients with STN-DBS were included. All patients had a high density EEG recording (256 channels) while testing verbal fluency in the stimulator on/off situation. The phonemic, semantic, alternating phonemic and semantic fluency was tested (Regensburger Wortflüssigkeits-Test).

Results: On the group level, stimulation of STN did not alter verbal fluency performance. EEG frequency analysis showed an increase of relative alpha2 (10–13 Hz) and beta (13–30 Hz) power in the parieto-occipital region (p ≤ 0.01). On the individual level, changes of verbal fluency induced by stimulation of the STN were disparate and correlated inversely with delta power in the left temporal lobe (p < 0.05).

Conclusion: STN stimulation does not alter verbal fluency performance in a systematic way at group level. However, when in individual patients an alteration of verbal fluency performance is produced by electrical stimulation of the STN, it correlates inversely with left temporal delta power.

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

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

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

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

Neuropsychological performance changes following subthalamic versus pallidal deep brain stimulation in Parkinson's disease: a systematic review and metaanalysis

BACKGROUND

Studies comparing subthalamus (STN) and globus pallidus internus (GPi) deep brain stimulation (DBS) for the management of Parkinson's disease in terms of neuropsychological performance are scarce and heterogeneous. Therefore, we performed a systematic review and metaanalysis to compare neuropsychological outcomes following STN DBS versus GPi DBS.

METHODS

A computer literature search of PubMed, the Web of Science, and Cochrane Central was conducted. Records were screened for eligible studies, and data were extracted and synthesized using Review Manager (v. 5.3 for Windows).

RESULTS

Seven studies were included in the qualitative synthesis. Of them, four randomized controlled trials (n=345 patients) were pooled in the metaanalysis models. The standardized mean difference (SMD) of change in the Stroop color-naming test favored the GPi DBS group (SMD=-0.31, p=0.009). However, other neuropsychological outcomes did not favor either of the two groups (Stroop word-reading: SMD=-0.21, p=0.08; the Wechsler Adult Intelligence Scale (WAIS) digits forward: SMD=0.08, p=0.47; Trail Making Test Part A: SMD=-0.05, p=0.65; WAIS-R digit symbol: SMD=-0.16, p=0.29; Trail Making Test Part B: SMD=-0.14, p=0.23; Stroop color-word interference: SMD=-0.16, p=0.18; phonemic verbal fluency: bilateral DBS SMD=-0.04, p=0.73, and unilateral DBS SMD=-0.05, p=0.83; semantic verbal fluency: bilateral DBS SMD=-0.09, p=0.37, and unilateral DBS SMD=-0.29, p=0.22; Boston Naming Test: SMD=-0.11, p=0.33; Beck Depression Inventory: bilateral DBS SMD=0.15, p=0.31, and unilateral DBS SMD=0.36, p=0.11).

CONCLUSIONS

There was no statistically significant difference in most of the neuropsychological outcomes. The present evidence does not favor any of the targets in terms of neuropsychological performance.

The impact of white matter lesions on the cognitive outcome of subthalamic nucleus deep brain stimulation in Parkinson's disease

OBJECTIVES

White Matter lesions (WML) are a risk factor for cognitive impairment in Parkinson's disease. There is no clear evidence of reduced general cognitive function after DBS. However, a subgroup of patients develops dementia rapidly after DBS despite careful patient selection processes. The aim of this study was to evaluate the load of WML as a possible risk factor for cognitive decline following STN DBS.

PATIENTS AND METHODS

40 PD-patients receiving bilateral STN-DBS were followed at least three years after surgery to detect dementia. All patients underwent comprehensive neuropsychological assessment and MRI before surgery. The extent of WML was assessed using an automated approach. WML volume was correlated to the onset of dementia and the decline of a cognitive composite score retrospectively.

RESULTS

Patients with a rapid onset of dementia within one, respective three following DBS showed significant higher WML volumes compared to cognitive normal and MCI patients (55.8cm³±18.836 vs. 9.3cm³±12.2; p=0.002). The same significant association was found in a multivariable model, including the covariables age, gender and PD disease duration (p=0.01). WML volume was associated to the rate of decline in cognitive composite score within three years after DBS surgery (p=0.006; R²=0.40) after correction for age.

CONCLUSIONS

Damaged white matter may lead to a reduced compensation of disconnections in cognitive circuits caused by the implantation of the DBS electrodes or by chronic stimulation. The role of WML as a prognostic factor for the cognitive outcome after DBS may be underestimated. The WML burden should be taken seriously in preoperative risk stratification.

Effects of subthalamic nucleus deep brain stimulation on emotional working memory capacity and mood in patients with Parkinson's disease

BACKGROUND

In Parkinson's disease (PD), cognitive symptoms and mood changes may be even more distressing for the patient than motor symptoms.

OBJECTIVE

Our aim was to determine the effects of bilateral subthalamic nucleus deep brain stimulation (STN-DBS) on working memory (WM) and mood.

METHODS

Sixteen patients with PD were assessed with STN-DBS switched on (DBS-ON) and with dopaminergic treatment (Med-ON) compared to switched off (DBS-OFF) and without dopaminergic treatment (Med-OFF). The primary outcome measures were a Visual Analog Mood Scale (VAMS) and an emotional 2-back WM task at 12 months after DBS in the optimal DBS-ON/Med-ON setting compared to DBS-OFF/Med-OFF.

RESULTS

Comparison of DBS-OFF/Med-OFF to DBS-ON/Med-ON revealed a significant increase in alertness (mean_off/off =51.59±24.54; mean_on/on =72.75; P=0.016) and contentedness (mean_off/off =38.73±24.41; mean_on/on =79.01±17.66; P=0.001, n=16), and a trend for reduction in sedation (P=0.060), which was related to stimulation as shown in a subgroup of seven patients. The N-back task revealed a significant increase in accuracy with DBS-ON/Med-ON compared to DBS-OFF/Med-OFF (82.0% vs 76.0%, respectively) (P=0.044), regardless of stimulus valence.

CONCLUSION

In line with previous studies, we found that patients rated themselves subjectively as more alert, content, and less sedated during short-term DBS-ON. Accuracy in the WM task increased with the combination of DBS and medication, possibly related to higher alertness of the patients. Our results add to the currently mixed results described for DBS on WM and suggest that there are no deleterious DBS effects on this specific cognitive domain.

Parkinson's Disease and Cognitive Impairment

Parkinson's disease (PD) is a progressive neurodegenerative disease primarily characterized by the hallmarks of motor symptoms, such as tremor, bradykinesia, rigidity, and postural instability. However, through clinical investigations in patients and experimental findings in animal models of Parkinson's disease for years, it is now well recognized that Parkinson's disease is more than just a motor-deficit disorder. The majority of Parkinson's disease patients suffer from nonmotor disabilities, for instance, cognitive impairment, autonomic dysfunction, sensory dysfunction, and sleep disorder. So far, anti-PD prescriptions and surgical treatments have been mainly focusing on motor dysfunctions, leaving cognitive impairment a marginal clinical field. Within the nonmotor symptoms, cognitive impairment is one of the most common and significant aspects of Parkinson's disease, and cognitive deficits such as dysexecutive syndrome and visuospatial disturbances could seriously affect the quality of life, reduce life expectancy, prolong the duration of hospitalization, and therefore increase burdens of caregiver and medical costs. In this review, we have done a retrospective study of the recent related researches on epidemiology, clinical manifestation and diagnosis, genetics, and potential treatment of cognitive deficits in Parkinson's disease, aiming to provide a summary of cognitive impairment in Parkinson's disease and make it easy for clinicians to tackle this challenging issue in their future practice.

Worsening of Verbal Fluency After Deep Brain Stimulation in Parkinson's Disease: A Focused Review

Worsening of verbal fluency after treatment with deep brain stimulation in Parkinson's disease patients is one of the most often reported cognitive adverse effect. The underlying mechanisms of this decline are not well understood. The present focused review assesses the evidence for the reliability of the often-reported decline of verbal fluency, as well as the evidence for the suggested mechanisms including disease progression, reduced medication levels, electrode positions, and stimulation effect vs. surgical effects. Finally, we highlight the need for more systematic investigations of the large degree of heterogeneity in the prevalence of verbal fluency worsening after DBS, as well as provide suggestions for future research.

Neuropsychological outcomes from constant current deep brain stimulation for Parkinson's disease

Objective

The aim of this study was to evaluate the neurobehavioral safety of constant‐current subthalamic deep brain stimulation and to compare the neuropsychological effects of stimulation versus electrode placement alone.

Methods

A total of 136 patients with Parkinson's disease underwent bilateral subthalamic device implantation in this randomized trial. Patients received stimulation either immediately after device implantation (n = 101; active stimulation) or beginning 3 months after surgery (n = 35; delayed activation control). Patients were administered neuropsychological tests before, 3, and 12 months after device implantation.

Results

Neuropsychological change in stimulation and control groups were comparable. Within‐group analyses revealed declines in category and switching verbal fluency in both groups, but only the stimulation group had letter verbal fluency and Stroop task declines. Depression symptom improvements occurred in both groups, but more often in the stimulation group. Letter fluency declines were associated with worse Parkinson's Disease Questionnaire Communication subscale scores. Baseline and 12‐month comparisons (in the combined group) revealed gains in verbal and visual delayed recall scores and improvement in depression symptoms, but decrements in verbal fluency and Stroop scores.

Conclusions

Constant‐current bilateral subthalamic stimulation had a good cognitive safety profile except for decrements in verbal fluency and on the Stroop task. These abnormalities are related to device implantation, but stimulation likely had an additive effect. One year after surgery, the cognitive changes did not exert a detrimental effect on quality of life, although letter fluency declines were associated with communication dissatisfaction at 12 months. Improvement in depressive symptom severity appears dependent on stimulation and not placebo or lesion effects. © 2016 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

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

Background. Nowadays, it has been largely acknowledged that deep brain stimulation of subthalamic nucleus (STN DBS) can alleviate motor symptoms of Parkinson's disease, but its effects on cognitive function remain unclear, which are not given enough attention by many clinical doctors and researchers. To date, 3 existing meta-analyses focusing on this issue included self-control studies and have not drawn consistent conclusions. The present study is the first to compare effect sizes of primary studies that include control groups, hoping to reveal the net cognitive outcomes after STN DBS and the clinical significance. Methods. A structured literature search was conducted using strict criteria. Only studies with control group could be included. Data on age, duration of disease, levodopa equivalent dosage (LED), and multiple cognitive scales were collected and pooled. Results. Of 172 articles identified, 10 studies (including 3 randomized controlled trials and 7 nonrandomized controlled studies) were eligible for inclusion. The results suggest that STN DBS results in decreased global cognition, memory, verbal fluency, and executive function compared with control group. No significant difference is found in other cognitive domains. Conclusions. STN DBS seems relatively safe with respect to cognitive function, and further studies should focus on the exact mechanisms of possible verbal deterioration after surgery in the future.

Challenges in Recruitment for the Study of Noninvasive Brain Stimulation in Stroke: Lessons from Deep Brain Stimulation

OBJECTIVE

Noninvasive brain stimulation (NIBS) can augment functional recovery following stroke; however, the technique lacks regulatory approval. Low enrollment in NIBS clinical trials is a key roadblock. Here, we pursued evidence to support the prevailing opinion that enrollment in trials of NIBS is even lower than enrollment in trials of invasive, deep brain stimulation (DBS).

METHODS

We compared 2 clinical trials in stroke conducted within a single urban hospital system, one employing NIBS and the other using DBS, (1) to identify specific criteria that generate low enrollment rates for NIBS and (2) to devise strategies to increase recruitment with guidance from DBS.

RESULTS

Notably, we found that enrollment in the NIBS case study was 5 times lower (2.8%) than the DBS trial (14.5%) (χ(2) = 20.815, P < .0001). Although the number of candidates who met the inclusion criteria was not different (χ(2) = .04, P < .841), exclusion rates differed significantly between the 2 studies (χ(2) = 21.354, P < .0001). Beyond lack of interest, higher exclusion rates in the NIBS study were largely due to exclusion criteria that were not present in the DBS study, including restrictions for recurrent strokes, seizures, and medications.

CONCLUSIONS

Based on our findings, we conclude and suggest that by (1) establishing criteria specific to each NIBS modality, (2) adjusting exclusion criteria based on guidance from DBS, and (3) including patients with common contraindications based on a probability of risk, we may increase enrollment and hence significantly impact the feasibility and generalizability of NIBS paradigms, particularly in stroke.

The treatment of Parkinson's disease with deep brain stimulation: current issues

Deep brain stimulation has become a well-established symptomatic treatment for Parkinson's disease during the last 25 years. Besides improving motor symptoms and long-term motor complications, positive effects on patients' mobility, activities of daily living, emotional well-being and health-related quality of life have been recognized. Apart from that, numerous clinical trials analyzed effects on non-motor symptoms and side effects of deep brain stimulation. Several technical issues and stimulation paradigms have been and are still being developed to optimize the therapeutic effects, minimize the side effects and facilitate handling. This review summarizes current therapeutic issues, i.e., patient and target selection, surgical procedure and programming paradigms. In addition it focuses on neuropsychological effects and side effects of deep brain stimulation.

High-Frequency Stimulation of the Rat Entopeduncular Nucleus Does Not Provide Functional or Morphological Neuroprotection from 6-Hydroxydopamine

Deep brain stimulation (DBS) is the most common neurosurgical treatment for Parkinson’s disease (PD). Whereas the globus pallidus interna (GPi) has been less commonly targeted than the subthalamic nucleus (STN), a recent clinical trial suggests that GPi DBS may provide better outcomes for patients with psychiatric comorbidities. Several laboratories have demonstrated that DBS of the STN provides neuroprotection of substantia nigra pars compacta (SNpc) dopamine neurons in preclinical neurotoxin models of PD and increases brain-derived neurotrophic factor (BDNF). However, whether DBS of the entopeduncular nucleus (EP), the homologous structure to the GPi in the rat, has similar neuroprotective potential in preclinical models has not been investigated. We investigated the impact of EP DBS on forelimb use asymmetry and SNpc degeneration induced by 6-hydroxydopamine (6-OHDA) and on BDNF levels. EP DBS in male rats received unilateral, intrastriatal 6-OHDA and ACTIVE or INACTIVE stimulation continuously for two weeks. Outcome measures included quantification of contralateral forelimb use, stereological assessment of SNpc neurons and BDNF levels. EP DBS 1) did not ameliorate forelimb impairments induced by 6-OHDA, 2) did not provide neuroprotection for SNpc neurons and 3) did not significantly increase BDNF levels in any of the structures examined. These results are in sharp contrast to the functional improvement, neuroprotection and BDNF-enhancing effects of STN DBS under identical experimental parameters in the rat. The lack of functional response to EP DBS suggests that stimulation of the rat EP may not represent an accurate model of clinical GPi stimulation.

Cognitive impairment and dementia in Parkinson's disease: practical issues and management

Cognitive impairment and dementia pose particular challenges in the management of patients with Parkinson's disease (PD). Decision-making capacity can render patients vulnerable in a way that requires careful ethical considerations by clinicians with respect to medical decision making, research participation, and public safety. Clinicians should discuss how future decisions will be made as early in the disease course as possible. Because of cognitive, visual, and motor impairments, PD may be associated with unsafe driving, leading to early driving cessation in many. DBS of the STN and, to a lesser degree, globus pallidus interna (GPi) has consistently been associated with decreased verbal fluency, but significant global cognitive decline is usually not observed in patients who undergo rigorous selection. There are some observations suggesting lesser cognitive decline in GPi DBS than STN DBS, but further research is required. Management of PD dementia (PDD) patients involves both pharmacological and nonpharmacological measures. Patients with PDD should be offered treatment with a cholinesterase inhibitor taking into account expected benefits and potential risks. Treatment with neuroleptics may be necessary to treat psychosis; classical neuroleptics, as well as risperidone and olanzapine, should be avoided. Quetiapine might be considered first-line treatment because it does not need special monitoring, although the strongest evidence for efficacy exists for clozapine. Evidence from randomized, controlled studies in the PDD population is lacking; selective serotonin reuptake inhibitors or serotonin-norepinephrine reuptake inhibitors may be used to treat depressive features. Clonazepam or melatonin may be useful in the treatment of rapid eye movement behavior disorder.

Subthalamic nucleus high-frequency stimulation for advanced Parkinson's disease: motor and neuropsychological outcome after 10 years

BACKGROUND

Since the introduction of subthalamic nucleus deep brain stimulation (STN DBS), many clinical studies have shown that this therapy is safe and effective in the short and medium term. Only little is known about long-term results.

OBJECTIVES

To provide an analysis of motor and cognitive outcome 10 years after STN DBS.

METHODS

In this observational cohort study, we report on the motor and cognitive outcome in a cohort of 26 Parkinson's disease patients who were prospectively followed up for 10 years after STN DBS surgery.

RESULTS

In the early post-operative phase, improvement in the Unified Parkinson's Disease Rating Scale (UPDRS) III (10.6, p < 0.01) and IV (2.5, p < 0.01) was seen as well as a 32% reduction in levodopa equivalent dose (p < 0.01). After 5 years, a worsening of the motor performance was observed. The worsening of motor performance was mainly due to a deterioration in bradykinesia (12.4 ± 4.6, p < 0.05) and axial symptoms (6.9 ± 2.8, p < 0.01). Memory function seemed to improve in the short term, but there was a significant decline between 1 and 5 years after surgery (p < 0.01). Mood remained relatively stable during follow-up, and one third of the patients showed impulsive behaviour after surgery.

CONCLUSIONS

The motor performance of patients showed deterioration over time, due to an increase in bradykinesia and axial symptoms.

[Deep brain stimulation for Parkinson's disease: timing and patient selection]

Deep brain stimulation (DBS) is an effective and evidence-based treatment option for Parkinson's disease. Studies have shown that DBS has good and long-term effects on motor function and quality of life for patients in an advanced stage of the disease and that it is more effective than medical therapy alone. Moreover, a favorable effect of DBS could also be detected at an earlier stage of the disease. On the other hand, possible risks and side effects of the procedure need to be taken into consideration. These can manifest as procedure-related complications, such as bleeding and infections in addition to stimulation-associated phenomena, such as neuropsychiatric disorders and motor side effects. Despite the good effects of DBS important issues still need to be addressed which will be discussed in this article considering the results of several new randomized and controlled clinical studies. For patients with Parkinson's disease with early fluctuations and dyskinesia, DBS has been found to be superior to the best pharmaceutical treatment; therefore, DBS can be considered as a treatment option in the earlier course of the disease. The diagnostic evaluation and the exclusion of contraindications are crucial for patient selection. The choice of the target should be based on the individual symptoms in patients although the subthalamic nucleus (STN) can be considered the standard target. In every case an individual assessment of chances and risks must be conducted and realistic goals and reasonable expectations must be defined.

Impact of bilateral subthalamic stimulation on motor/cognitive functions in Parkinson's disease

It is still unclear whether deep brain stimulation targeted to the bilateral subthalamic nucleus (STN-DBS) affects cognitive function in Parkinson's disease (PD). This prospective study was aimed to systemically evaluate the impact of bilateral STN-DBS on motor and cognitive functions in patients with PD. This study included totally 11 Japanese patients with medically intolerant PD. Neurological and cognitive status was precisely evaluated before and 1 year after bilateral STN-DBS, using unified Parkinson's disease rating scale (UPDRS), levodopa equivalent doses, mini-mental state examination (MMSE), Japanese adult reading test (JART), repeatable battery for the assessment of neuropsychological status (RBANS), and Wechsler adult intelligence scale-revised (WAIS-R). Preoperative RBANS and WAIS-R identified cognitive dysfunction that could not be detected by MMSE and JART. Before surgery, PD patients had significantly impaired immediate memory and attention. Motor function significantly improved 1 year after bilateral STN-DBS. Bilateral STN-DBS did not affect any score on cognitive examinations. However, postoperative improvements of total score on RBANS and performance intelligence quotient (PIQ) scores on WAIS-R were closely related to those of UPDRS part III off (R² = 0.61, P < 0.01; R² = 0.39, P < 0.05, respectively). These findings strongly suggest that bilateral STN-DBS may significantly improve cognitive function in a certain subgroup of patients whose therapeutic effects on motor function are prominent.

Long-term cognitive outcome of bilateral subthalamic deep brain stimulation in Parkinson's disease

The effect of subthalamic deep brain stimulation (STN DBS) on cognition in Parkinson's disease (PD) remains controversial, and it is unclear which factors are related to cognitive decline and dementia after STN DBS, especially over the long term. To this end, we analyzed the cognitive outcome of 103 non-demented patients with PD who were followed-up for at least 12 months after bilateral STN DBS surgery. Preoperatively, the patients were evaluated with the Unified Parkinson's Disease Rating Scale and neuropsychological tests. The rate of global cognitive decline and the incidence of dementia during follow-up for up to 7 years (mean 42.4 ± 24.5 months) were calculated, and preoperative clinical and neuropsychological factors associated with postoperative global cognitive decline or dementia were analyzed. The prevalence of mild cognitive impairment (MCI) and its relation to later cognitive decline or dementia were also evaluated. The annual decline in the mini-mental state examination score was 0.4 ± 1.7 with impaired attention and executive function and a higher levodopa equivalent dose at baseline being the predictors of a faster global cognitive decline after STN DBS. Dementia developed in 13 patients with an incidence rate of 35.7 per 1,000 person-years. Impaired executive function at baseline predicted dementia. At baseline, 63.1 % of the patients had PD-MCI, and these patients were more likely to develop dementia than those without PD-MCI. This study showed that dysfunctions in the frontostriatal circuitry at baseline were associated with a risk of subsequent global cognitive decline and dementia in patients with PD who underwent STN DBS. In addition, preoperative PD-MCI was a risk factor for dementia after STN DBS.

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

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

Relation of lead trajectory and electrode position to neuropsychological outcomes of subthalamic neurostimulation in Parkinson's disease: results from a randomized trial

Deep brain stimulation of the subthalamic nucleus improves motor functions in patients suffering from advanced Parkinson's disease but in some patients, it is also associated with a mild decline in cognitive functioning about one standard deviation from the preoperative state. We assessed the impact of the cortical lead entry point, the subcortical electrode path and the position of the active electrode contacts on neuropsychological changes after subthalamic nucleus-deep brain stimulation compared to a control group of patients receiving best medical treatment. Sixty-eight patients with advanced Parkinson's disease were randomly assigned to have subthalamic nucleus-deep brain stimulation or best medical treatment for Parkinson's disease. All patients had a blinded standardized neuropsychological exam (Mattis Dementia Rating scale, backward digit span, verbal fluency and Stroop task performance) at baseline and after 6 months of treatment. Patients with subthalamic nucleus-deep brain stimulation were defined as impaired according to a mild decline of one or more standard deviations compared to patients in the best medical treatment group. The cortical entry point of the electrodes, the electrode trajectories and the position of the active electrode contact were transferred into a normalized brain volume by an automated, non-linear registration algorithm to allow accurate statistical group analysis using pre- and postoperative magnetic resonance imaging data. Data of 31 patients of the subthalamic nucleus-deep brain stimulation group and 31 patients of the best medical treatment group were analysed. The subthalamic nucleus-deep brain stimulation group showed impaired semantic fluency compared with the best medical treatment group 6 months after surgery (P = 0.02). Electrode trajectories intersecting with caudate nuclei increased the risk of a decline in global cognition and working memory performance. Statistically, for every 0.1 ml overlap with a caudate nucleus, the odds for a decline >1 standard deviation increased by a factor of 37.4 (odds ratio, confidence interval 2.1-371.8) for the Mattis Dementia Rating Scale and by a factor of 8.8 (odds ratio, confidence interval 1.0-70.9) for the backward digit span task. Patients with subthalamic nucleus-deep brain stimulation who declined in semantic verbal fluency, Stroop task and the backward digit span task performance showed a position of the active electrode outside the volume built by the active electrodes of stable performers. Passage of the chronic stimulation lead through the head of the caudate increases the risk of global cognitive decline and working memory performance after subthalamic nucleus-deep brain stimulation in Parkinson's disease. Therefore the electrode path should be planned outside the caudate nuclei, whenever possible. This study also stresses the importance of precise positioning of the active stimulating contact within the subthalamic volume to avoid adverse effects on semantic verbal fluency and response inhibition.

The serendipity case of the pedunculopontine nucleus low-frequency brain stimulation: chasing a gait response, finding sleep, and cognition improvement

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an efficacious therapy for Parkinson’s disease (PD) but its effects on non-motor facets may be detrimental. The low-frequency stimulation (LFS) of the pedunculopontine nucleus (PPN or the nucleus tegmenti pedunculopontini – PPTg-) opened new perspectives. In our hands, PPTg-LFS revealed a modest influence on gait but increased sleep quality and degree of attentiveness. At odds with potential adverse events following STN-DBS, executive functions, under PPTg-ON, ameliorated. A recent study comparing both targets found that only PPTg-LFS improved night-time sleep and daytime sleepiness. Chances are that different neurosurgical groups influence either the PPN sub-portion identified as pars dissipata (more interconnected with GPi/STN) or the caudal PPN region known as pars compacta, preferentially targeting intralaminar and associative nucleus of the thalamus. Yet, the wide electrical field delivered affects a plethora of en passant circuits, and a fine distinction on the specific pathways involved is elusive. This review explores our angle of vision, by which PPTg-LFS activates cholinergic and glutamatergic ascending fibers, influencing non-motor behaviors.

Initial cognitive dip after subthalamic deep brain stimulation in Parkinson disease

Although many studies have shown no significant change in global cognitive function after subthalamic brain stimulation (STN DBS) in patients with Parkinson disease (PD) and have concluded that STN DBS is generally safe from a cognitive standpoint, some studies have reported a decline in global cognitive function after STN DBS. Interestingly, in some studies, the decline in cognitive function appears to be greater during the initial short period after surgery (within 6 or 12 months after surgery) than the decline thereafter. To this end, we examined whether the rate of change in global cognitive function during the initial 6 months after STN DBS was different from the mean 6-month change that occurred between 6 and 36 months after surgery. Thirty-six PD patients who underwent bilateral STN DBS and were followed for more than 3 years were included. Change in Mini-Mental Status Examination (MMSE) score during the first 6 months after surgery was compared with the 6-month MMSE score change between 6 and 36 months after surgery. Mean MMSE change during the first 6 months after surgery was significantly greater than the mean 6-month MMSE change between 6 to 36 months after surgery. The levodopa equivalent daily dose at baseline and the score for Stroop Color-word test at baseline were significantly associated with the decline in MMSE score during the first 6 months after surgery. Our result showed that decline in global cognitive function was faster in the first 6 months after surgery, compared with that after 6 months.

Review: management of Parkinson's disease

Parkinson's disease (PD) is one of the most frequent neurological diseases. Despite the modern imaging and nuclear techniques which help to diagnose it in a very early stage and lead to a better discrimination of similar diseases, PD has remained a clinical diagnosis. The increasing number of available treatment options makes the disease management often complicated even when the presence of PD seems undoubted. In addition, nonmotor symptoms and side effects of some therapies constitute some pitfalls already in the preclinical state or at the beginnings of the disease, especially with the progressive effect on patients. Therefore, this review aimed to summarize study results and depict recommended medical treatments for the most common motor and nonmotor symptoms in PD. Additionally, emerging new therapeutic options such as continuous pump therapies, eg, with apomorphine or parenteral levodopa, or the implantation of electrodes for deep brain stimulation were also considered.

Psychiatric side-effects of bilateral deep brain stimulation for movement disorders

INTRODUCTION

The effects of deep brain stimulation (DBS) on cognitive functions, and its psychiatric side-effects, are still controversial. The present study investigated psychiatric comorbidity and postoperative effects of DBS of different targets on mood and psychological functions in 81 patients with a mean follow-up of 37 months.

METHODS

A total of 109 patients underwent implantation of DBS electrodes between 2001 and 2006; it was possible to evaluate 81 patients by a psychiatric test battery using the "Neuropsychiatric Inventory". To evaluate the possible influence of the target, we analyzed the data without 16 patients with DBS surgery for other diseases (e.g., epilepsia, cluster headache) or unilateral implantation only. The resulting population (n = 65, mean age 61 years, range 23-78 years, male:female 42:23) consisted of 43 Parkinson's disease patients stimulated in the subthalamic nucleus, ten dystonia patients stimulated in the globus pallidus internus, and 12 tremor patients in the ventral intermediate nucleus.

RESULTS

There was a high rate of preoperative psychiatric comorbidity, which is reflected by a high rate of patients with preoperative medication of neuroleptic drugs (18.4 %, especially clozapin 14.7 %) and antidepressive drugs (16.5 %). Depression was the most common psychiatric side-effect after DBS, occurring in 47.7 % of all patients (31/65 patients), without significant preference to a specific target (STN: 42 %, Gpi: 60 %, VIM: 58 %). Delusion (n = 5 out of 43 PD patients, 11.6 %), euphoria (n = 1, 2.3 %) and disinhibition (n = 3, 7.0 %) were seen in the PD patients only.

CONCLUSION

A wide range of behavioural changes may be seen following DBS. Depression was the most common side-effect after DBS, and occurred independently of the target. PD patients, in contrast to dystonia and tremor patients, developed complications in all tested subgroups, with varying frequencies. Preoperative evaluation for psychiatric and cognitive dysfunction is crucial to identify patients who are at specific risk for psychiatric complications.