Impact of mild cognitive impairment on outcome following deep brain stimulation surgery for 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.

Health-related quality of life in Parkinson's disease: systematic review and meta-analysis of EuroQol (EQ-5D) utility scores

INTRODUCTION

Evaluating the Health-related quality of life (HRQoL) of individuals with Parkinson's disease (PD) holds significant importance in clinical and research settings. The EQ-5D is a widely recognized tool for comprehensive measurement of HRQoL using utility values. This study aims to systematically review and synthesize EQ-5D utility values from existing literature on patients with PD and their caregivers.

METHODS

We conducted a systematic search for studies that provided EQ-5D utility scores for patients with PD, using PubMed-Medline, Scopus, and Embase and selected the studies. The selected studies underwent systematic review, including an assessment of their quality. We performed a meta-analysis using a random-effect model and conducted a meta-regression analysis to investigate sources of heterogeneity among the studies.

RESULTS

The search result of 13,417 articles that were reviewed, 130 studies with 33,914 participants were selected for systematic review, and 79 studies were included for meta-analysis. The pooled EQ-5D utility values and visual analog score (VAS) among PD were 62.72% (60.53-64.93, I2 = 99.56%) and 0.60 (0.55-0.65, I2 = 99.81%), respectively. The pooled scores for caregivers' EQ-VAS and EQ-5D utility were 70.10% (63.99-76.20, I2 = 98.25%) and 0.71 (0.61-0.81, I2 = 94.88%), respectively. Disease duration (P < 0.05) showed a negative correlation with EQ-5D utility values on meta-regression.

CONCLUSION

The pooled utility values of PD and their caregivers help to understand their HRQoL and aid in conducting health economics research. The negative association between disease duration and utility values highlights the evolving nature of HRQoL challenges, suggesting the need for appropriate long-term disease management.

Deep brain stimulation in PD: risk of complications, morbidity, and hospitalizations: a systematic review

Introduction

Parkinson's disease (PD) is a progressive and debilitating neurological disorder. While dopaminergic medication improves PD symptoms, continued management is complicated by continued symptom progression, increasing medication fluctuations, and medication-related dyskinesia. Deep brain stimulation (DBS) surgery is a well-accepted and widespread treatment often utilized to address these symptoms in advanced PD. However, DBS may also lead to complications requiring hospitalization. In addition, patients with PD and DBS may have specialized care needs during hospitalization.

Methods

This systematic review seeks to characterize the complications and risk of hospitalization following DBS surgery. Patient risk factors and modifications to DBS surgical techniques that may affect surgical risk are also discussed.

Results

It is found that, when candidates are carefully screened, DBS is a relatively low-risk procedure, but rate of hospitalization is somewhat increased for DBS patients.

Discussion

More research is needed to determine the relative influence of more advanced disease vs. DBS itself in increased rate of hospitalization, but education about DBS and PD is important to insure effective patient care within the hospital.

Unlocking potential: low frequency subthalamic nucleus stimulation enhances executive function in Parkinson's disease patients with postural instability/gait disturbance

Postural instability/gait disturbance (PIGD) is very common in advanced Parkinson's disease, and associated with cognitive dysfunction. Research suggests that low frequency (5-12 Hz) subthalamic nucleus-deep brain stimulation (STN-DBS) could improve cognition in patients with Parkinson's disease (PD). However, the clinical effectiveness of low frequency stimulation in PIGD patients has not been explored. This study was designed in a double-blinded randomized cross-over manner, aimed to verify the effect of low frequency STN-DBS on cognition of PIGD patients. Twenty-nine PIGD patients with STN-DBS were tested for cognitive at off (no stimulation), low frequency (5 Hz), and high frequency (130 Hz) stimulation. Neuropsychological tests included the Stroop Color-Word Test (SCWT), Verbal fluency test, Symbol Digital Switch Test, Digital Span Test, and Benton Judgment of Line Orientation test. For conflict resolution of executive function, low frequency stimulation significantly decreased the completion time of SCWT-C (p = 0.001) and Stroop interference effect (p < 0.001) compared to high frequency stimulation. However, no significant differences among stimulation states were found for other cognitive tests. Here we show, low frequency STN-DBS improved conflict resolution of executive function compared to high frequency. Our results demonstrated the possibility of expanding the treatment coverage of DBS to cognitive function in PIGD, which will facilitate integration of low frequency stimulation into future DBS programming.

Patients with Cognitive Impairment in Parkinson's Disease Benefit from Deep Brain Stimulation: A Case-Control Study

Background

Deep brain stimulation (DBS) for Parkinson's disease (PD) is generally contraindicated in persons with dementia but it is frequently performed in people with mild cognitive impairment or normal cognition, and current clinical guidelines are primarily based on these cohorts.

Objectives

To determine if moderately cognitive impaired individuals including those with mild dementia could meaningfully benefit from DBS in terms of motor and non-motor outcomes.

Methods

In this retrospective case-control study, we identified a cohort of 40 patients with PD who exhibited moderate (two or more standard deviations below normative scores) cognitive impairment (CI) during presurgical workup and compared their 1-year clinical outcomes to a cohort of 40 matched patients with normal cognition (NC). The surgery targeted subthalamus, pallidus or motor thalamus, in a unilateral, bilateral or staged approach.

Results

At preoperative baseline, the CI cohort had higher Unified Parkinson's Disease Rating Scale (UPDRS) subscores, but similar levodopa responsiveness compared to the NC cohort. The NC and CI cohorts demonstrated comparable degrees of postoperative improvement in the OFF-medication motor scores, motor fluctuations, and medication reduction. There was no difference in adverse event rates between the two cohorts. Outcomes in the CI cohort did not depend on the target, surgical staging, or impaired cognitive domain.

Conclusions

Moderately cognitively impaired patients with PD can experience meaningful motor benefit and medication reduction with DBS.

Radiomic features of amygdala nuclei and hippocampus subfields help to predict subthalamic deep brain stimulation motor outcomes for Parkinson‘s disease patients

Background and purpose

The aim of the study is to predict the subthalamic nucleus (STN) deep brain stimulation (DBS) outcomes for Parkinson’s disease (PD) patients using the radiomic features extracted from pre-operative magnetic resonance images (MRI).

Methods

The study included 34 PD patients who underwent DBS implantation in the STN. Five patients (15%) showed poor DBS motor outcome. All together 9 amygdalar nuclei and 12 hippocampus subfields were segmented using Freesurfer 7.0 pipeline from pre-operative MRI images. Furthermore, PyRadiomics platform was used to extract 120 radiomic features for each nuclei and subfield resulting in 5,040 features. Minimum Redundancy Maximum Relevance (mRMR) feature selection method was employed to reduce the number of features to 20, and 8 machine learning methods (regularized binary logistic regression (LR), decision tree classifier (DT), linear discriminant analysis (LDA), naive Bayes classifier (NB), kernel support vector machine (SVM), deep feed-forward neural network (DNN), one-class support vector machine (OC-SVM), feed-forward neural network-based autoencoder for anomaly detection (DNN-A)) were applied to build the models for poor vs. good and very good STN-DBS motor outcome prediction.

Results

The highest mean prediction accuracy was obtained using regularized LR (96.65 ± 7.24%, AUC 0.98 ± 0.06) and DNN (87.25 ± 14.80%, AUC 0.87 ± 0.18).

Conclusion

The results show the potential power of the radiomic features extracted from hippocampus and amygdala MRI in the prediction of STN-DBS motor outcomes for PD patients.

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.

Heterogeneity of PD-MCI in Candidates to Subthalamic Deep Brain Stimulation: Associated Cortical and Subcortical Modifications

BACKGROUND

Parkinson's disease mild cognitive impairment (PD-MCI) is frequent and heterogenous. There is no consensus about its influence on subthalamic deep brain stimulation (STN-DBS) outcomes.

OBJECTIVE

To determine the prevalence of PD-MCI and its subtypes in candidates to STN-DBS. Secondarily, we sought to identify MRI structural markers associated with cognitive impairment in these subgroups.

METHODS

Baseline data from the French multicentric PREDISTIM cohort were used. Candidates to STN-DBS were classified according to their cognitive performance in normal cognition (PD-NC) or PD-MCI. The latter included frontostriatal (PD-FS) and posterior cortical (PD-PC) subtypes. Between-group comparisons were performed on demographical and clinical variables as well as on T1-weighted MRI sequences at the cortical and subcortical levels.

RESULTS

320 patients were included: 167 (52%) PD-NC and 153 (48%) PD-MCI patients. The latter group included 123 (80%) PD-FS and 30 (20%) PD-PC patients. There was no between-group difference regarding demographic and clinical variables. PD-PC patients had significantly lower global efficiency than PD-FS patients and significantly worse performance on visuospatial functions, episodic memory, and language. Compared to PD-NC, PD-MCI patients had cortical thinning and radiomic-based changes in the left caudate nucleus and hippocampus. There were no significant differences between the PD-MCI subtypes.

CONCLUSION

Among the candidates to STN-DBS, a significant proportion has PD-MCI which is associated with cortical and subcortical alterations. Some PD-MCI patients have posterior cortical deficits, a subtype known to be at higher risk of dementia.

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.

Nucleus basalis of Meynert predicts cognition after deep brain stimulation in Parkinson's disease

INTRODUCTION

Subthalamic DBS in Parkinson's disease has been associated with cognitive decline in few cases. Volume reduction of the nucleus basalis of Meynert (NBM) seems to precede cognitive impairment in Parkinson's disease. In this retrospective study, we evaluated NBM volume as a predictor of cognitive outcome 1 year after subthalamic DBS.

METHODS

NBM volumes were calculated from preoperative MRIs using voxel-based morphometry. Cognitive outcome was defined as the relative change of MMSE or DemTect scores from pre-to 1 year postoperatively. A multiple linear regression analysis adjusted for the number of cognitive domains affected in the preoperative neuropsychological testing and UPDRS III was conducted. To account for other variables and potential non-linear effects, an additional machine learning analysis using random forests was applied.

RESULTS

55 patients with Parkinson's disease (39 male, age 61.4 ± 7.5 years, disease duration 10.8 ± 4.7 years) who received bilateral subthalamic DBS electrodes at our center were included. Although overall cognition did not change significantly, individual change in cognitive abilities was variable. Cognitive outcome could be predicted based on NBM size (B = 208.98, p = 0.022*) in the regression model (F(3,49) = 2.869; R² of 0.149; p = 0.046*). Using random forests with more variables, cognitive outcome could also be predicted (average root mean squared error between predicted and true cognitive change 11.28 ± 9.51, p = 0.039*). Also in this model, NBM volume was the most predictive variable.

CONCLUSION

NBM volume can be used as a simple non-invasive predictor for cognitive outcome after DBS in Parkinson's disease, especially when combined with other clinical parameters that are prognostically relevant.

Correlates of deep brain stimulation consensus conference decision to treat primary dystonia

BACKGROUND

Deep brain stimulation (DBS) is an effective treatment for motor disturbance in people with primary dystonia (PWD). Numerous factors are considered by an interdisciplinary consensus conference before deciding candidacy for DBS surgery (e.g., demographic, medical, cognitive, and behavioral factors). However, little is known about which of these factors are associated with PWD DBS surgery consensus conference decisions.

OBJECTIVE

Our goal was to examine whether pre-operative demographic, medical, and cognitive/behavioral variables are associated DBS consensus conference decisions in patients with dystonia.

METHODS

Thirty-two PWD completed comprehensive presurgery workup included neurological and neuropsychological exams, and neuroimaging in consideration for DBS surgery. An interdisciplinary conference committee either recommended or did not recommend DBS surgery based upon these data. Demographic and medical data (e.g., dystonia disease characteristics, medical comorbidities, medications) were also collected. We also examined impact from cardiovascular disease factors, using a Revised Cardiac Risk Index. PWD were grouped based on DBS conference decision (eligible: n = 21, ineligible: n = 11) and compared across demographic, medical, and cognitive/behavioral variables.

RESULTS

Across clinical variables, PWD who were deemed ineligible for DBS surgery had a higher Revised Cardiac Risk Index. PWD who were classified as ineligible displayed lower global cognitive functioning, working memory, phonemic fluency, memory retrieval, and cognitive flexibility.

CONCLUSIONS

Consensus decision making regarding DBS surgery eligibility involves a multifactorial process. We found that deficits in executive functioning were associated with the DBS consensus committee decision. We also observed elevated cardiac risk among these individuals, likely reflecting the relation between vascular health and cognition. Implications, and clinical and scientific applications of these findings are discussed.

Predicting Neurocognitive Change after Bilateral Deep Brain Stimulation of Subthalamic Nucleus for Parkinson's Disease

OBJECTIVE

Deep brain stimulation (DBS) of the bilateral subthalamic nucleus (STN) is a standard surgical treatment option in patients with advanced Parkinson's disease. Adverse effects on cognitive function have been reported, impacting the quality of life of patients and caregivers. We aimed to investigate a quantitative predictive preexisting cognitive factor for predicting postoperative cognitive changes.

METHODS

Thirty-five patients underwent STN-DBS. A battery of neuropsychological tests were used to examine executive function, processing speed, and visuospatial function both preoperatively and 1 year postoperatively. A multiple logistic regression analysis was performed to investigate the relationships between preoperative factors and cognitive outcomes. The predictive value of the preoperative factors for global cognitive decline during long-term follow-up were evaluated.

RESULTS

The patients exhibited significant changes in processing speed and visuospatial function after surgery. Using reliable change index values, lower preoperative scores on the Similarities and Object Assembly subtests of the Wechsler Adult Intelligence Scale III were associated with decreases in visuospatial function at 1 year after DBS. The odds ratios were 10.2 for Similarities and 9.53 for Object Assembly. The proportion of Mini Mental State Examination-maintained patients with low scores on the Similarities subtest was significantly lower than that of patients with high scores at 3 and 5 years. No factors were found to be related to decreases in processing speed.

CONCLUSIONS

Preoperative evaluation of the Similarities and Object Assembly subtests may be useful to identify patients who are at a greater risk of experiencing decreases in visuospatial functioning after STN-DBS. Furthermore, a low score on the Similarities subtest may predict future global cognitive deterioration.

Factors Associated With Postoperative Confusion and Prolonged Hospital Stay Following Deep Brain Stimulation Surgery for Parkinson Disease

BACKGROUND

Several patient and disease characteristics are thought to influence DBS outcomes; however, most previous studies have focused on long-term outcomes with only a few addressing immediate postoperative course.

OBJECTIVE

To evaluate predictors of immediate outcomes (postoperative confusion and length of postoperative hospitalization) following deep brain stimulation surgery (DBS) in Parkinson disease (PD) patients.

METHODS

We conducted a retrospective study of PD patients who underwent DBS at our institution from 2006 to 2011. We computed the proportion of patients with postoperative confusion and those with postoperative hospitalization longer than 2 d. To look for associations, Fisher's exact tests were used for categorical predictors and logistic regression for continuous predictors.

RESULTS

We identified 130 patients [71% male, mean age: 63 ± 9.1, mean PD duration: 10.7 ± 5.1]. There were 7 cases of postoperative confusion and 19 of prolonged postoperative hospitalization. Of the 48 patients with tremors, none had postoperative confusion, whereas 10.1% of patients without tremors had confusion (P = .0425). Also, 10.2% of patients with preoperative falls/balance-dysfunction had postoperative confusion, whereas only 1.6% of patients without falls/balance-dysfunction had postoperative confusion (P = .0575). For every one-unit increase in score on the preoperative on-UPDRS III/MDS-UPDRS III score, the odds of having postoperative confusion increased by 10% (P = .0420). The following factors were noninfluential: age, disease duration, dyskinesia, gait freezing, preoperative levodopa-equivalent dose, number of intraoperative microelectrode passes, and laterality/side of surgery.

CONCLUSION

Absence of tremors and higher preoperative UPDRS III predicted postoperative confusion after DBS in PD patients. Clinicians' awareness of these predictors can guide their decision making regarding patient selection and surgical planning.

Biological Sex and Sex Hormone Impacts on Deficits in Episodic-Like Memory in a Rat Model of Early, Pre-motor Stages of Parkinson's Disease

Episodic memory deficits are among the earliest appearing and most commonly occurring examples of cognitive impairment in Parkinson's disease (PD). These enduring features can also predict a clinical course of rapid motor decline, significant cognitive deterioration, and the development of PD-related dementia. The lack of effective means to treat these deficits underscores the need to better understand their neurobiological bases. The prominent sex differences that characterize episodic memory in health, aging and in schizophrenia and Alzheimer's disease suggest that neuroendocrine factors may also influence episodic memory dysfunction in PD. However, while sex differences have been well-documented for many facets of PD, sex differences in, and sex hormone influences on associated episodic memory impairments have been less extensively studied and have never been examined in preclinical PD models. Accordingly, we paired bilateral neostriatal 6-hydroxydopamine (6-OHDA) lesions with behavioral testing using the What-Where-When Episodic-Like Memory (ELM) Task in adult rats to first determine whether episodic-like memory is impaired in this model. We further compared outcomes in gonadally intact female and male subjects, and in male rats that had undergone gonadectomy—with and without hormone replacement, to determine whether biological sex and/or sex hormones influenced the expression of dopamine lesioned-induced memory deficits. These studies showed that 6-OHDA lesions profoundly impaired recall for all memory domains in male and female rats. They also showed that in males, circulating gonadal hormones powerfully modulated the negative impacts of 6-OHDA lesions on What, Where, and When discriminations in domain-specific ways. Specifically, the absence of androgens was shown to fully attenuate 6-OHDA lesion-induced deficits in ELM for “Where” and to partially protect against lesion-induced deficits in ELM for “What.” In sum, these findings show that 6-OHDA lesions in rats recapitulate the vulnerability of episodic memory seen in early PD. Together with similar evidence recently obtained for spatial working memory, the present findings also showed that diminished androgen levels provide powerful, highly selective protections against the harmful effects that 6-OHDA lesions have on memory functions in male rats.

Activities of Daily Living and Their Relationship to Health-Related Quality of Life in Patients with Parkinson Disease After Subthalamic Nucleus Deep Brain Stimulation

BACKGROUND

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) can reduce motor symptoms in patients with Parkinson disease (PD) and improve their health-related quality of life (HRQoL). The effect of STN DBS on activities of daily living (ADL), an important component of quality of life, is poorly understood. We aimed to investigate effects of STN DBS on HRQoL and ADL in patients with PD.

METHODS

HRQoL and ADL were assessed using the following disease-specific and generic questionnaires at baseline and 3, 6, and 12 months after surgery: the Parkinson's Disease Questionnaire 39 (PDQ-39), the Short-Form 36 health survey questionnaire, the World Health Organization Quality of Life Scale-Brief version, the Unified Parkinson's Disease Rating Scale part II, the ADL scale, and the Instrumental Activities of Daily Living scale.

RESULTS

We reported significant early improvements (3 months) in the HRQoL and ADL, and these benefits increased over time (6 months); however, further improvement between 6 and 12 months was nonsignificant. Two PDQ-39 subdomains (social support and communications) and a Short-Form 36 health survey questionnaire subdomain (social functioning) showed declines after surgery. Changes in the Instrumental Activities of Daily Living scale were significantly correlated with changes in the PDQ-39 summary index and other PDQ-39 subdomains, including mobility, emotional well-being, social support, and cognition, at all follow-up points.

CONCLUSIONS

STN DBS caused a marked improvement in HRQoL at 3 and 6 months; however, HRQoL remained stable at the 12-month postoperative follow-up. Moreover, we have shown a significant correlation between ADL performance and HRQoL after STN DBS.

Comparative sensitivity of the MoCA and Mattis Dementia Rating Scale-2 in Parkinson's disease

BACKGROUND

Clinicians and researchers commonly use global cognitive assessments to screen for impairment. Currently there are no published studies directly comparing the sensitivity and specificity of the Montreal Cognitive Assessment and Mattis Dementia Rating Scale-2 in PD. The objective of this study was to identify the relative sensitivity and specificity of the Montreal Cognitive Assessment and Mattis Dementia Rating Scale-2 in PD.

METHODS

The Montreal Cognitive Assessment and Mattis Dementia Rating Scale-2 were administered to training and validation cohorts. Cutoff scores were determined within the training cohort (n = 85) to optimize sensitivity and specificity for cognitive impairment and were applied to an independent validation cohort (n = 521).

RESULTS

The Montreal Cognitive Assessment was consistently sensitive across training and validation cohorts (90.0% and 80.3%, respectively), whereas the Mattis Dementia Rating Scale-2 was not (87.5% and 60.3%, respectively). In individual domains, the Montreal Cognitive Assessment remained sensitive to memory and visuospatial impairments (91.9% and 87.8%, respectively), whereas the Mattis Dementia Rating Scale-2 was sensitive to executive impairments (86.2%).

CONCLUSION

The Montreal Cognitive Assessment and Mattis Dementia Rating Scale-2 demonstrated individual strengths. Future work should focus on developing domain-specific cognitive screening tools for PD. © 2018 International Parkinson and Movement Disorder Society.

Association of MRI Measurements with Cognitive Outcomes After STN-DBS in Parkinson's Disease

Objectives

Subthalamic nucleus deep brain stimulation (STN-DBS) is an effective treatment for improving the motor symptoms of Parkinson's disease (PD). Overall, cognitive function remains stable after STN-DBS in most patients. However, cognitive decline, specifically in the verbal fluency domain, is seen in a subset of STN-DBS patients. Currently, predictors of cognitive decline in PD patients treated with STN-DBS are not well known. Thus, identification of presurgical predictors might provide an important clinical tool for better risk-to-benefit assessment. This study explores whether whole brain white matter lesion (WML) volume, or hippocampal and forebrain volumes, measured quantitatively on MRI, are associated with cognitive changes following STN-DBS in PD patients.

Methods

We conducted a retrospective study using presurgical, and ≥ 6-month postsurgical neuropsychological (NP) evaluation scores from 43 PD patients with STN-DBS. Mean pre/post NP test scores for measures of executive function, attention, verbal fluency, memory, and visuospatial function were analyzed and correlated with WML volume, and brain volumetric data.

Results

Although cognitive measures of verbal fluency, executive function, attention, memory, and visuospatial function showed declines following STN-DBS, we observed limited evidence that white matter lesion burden or cortical atrophy contributed to cognitive change following STN-DBS.

Conclusions

These results suggest that post-STN-DBS cognitive changes may be unrelated to presurgical WML burden and presence of cortical atrophy.

Cognitive and Neuropsychiatric Features of Early Parkinson's Disease

The clinical definition of Parkinson's disease (PD) is based on cardinal motor features including bradykinesia as well as an additional symptom of tremor, postural instability, or rigidity. Evidence from neuropathological, imaging, and clinical research suggests a premotor, early phase of PD pathology. Further understanding of the earliest biomarkers of PD is crucial for the development of neuroprotective, disease modifying, cognitive, and psychiatric interventions. Recent research has explored early non-motor markers of PD pathology. This issue is especially timely as the International Parkinson and Movement Disorder Society has recently provided a research definition for prodromal PD which includes combinations of prodromal markers and risk factors aimed at identifying target populations for disease-prevention trials. In this review of early PD, we will outline early non-motor symptoms, early cognitive and neuropsychiatric features, neuropsychological assessment strategies, emerging evidence for early biomarkers, and treatment recommendations.

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.

The Role of a Neuropsychologist on a Movement Disorders Deep Brain Stimulation Team

The term movement disorders is misleading in the implication that the symptoms are limited to motor problems. Most movement disorders include a variety of neurobehavioral and neurocognitive symptoms that require neuropsychological expertise. The goal of this paper is to provide a rationale and practical roadmap for neuropsychologists' involvement in a Movement Disorders team with a specific focus on pre-operative deep brain stimulation (DBS) evaluations. Pragmatic recommendations regarding requisite skills, clinical practice, recommendations, communication, and benefits are outlined.

Association between baseline cognitive impairment and postoperative delirium in elderly patients undergoing surgery for adult spinal deformity

OBJECTIVE Postoperative delirium is common in elderly patients undergoing spine surgery and is associated with a longer and more costly hospital course, functional decline, postoperative institutionalization, and higher likelihood of death within 6 months of discharge. Preoperative cognitive impairment may be a risk factor for the development of postoperative delirium. The aim of this study was to investigate the relationship between baseline cognitive impairment and postoperative delirium in geriatric patients undergoing surgery for degenerative scoliosis. METHODS Elderly patients 65 years and older undergoing a planned elective spinal surgery for correction of adult degenerative scoliosis were enrolled in this study. Preoperative cognition was assessed using the validated Saint Louis University Mental Status (SLUMS) examination. SLUMS comprises 11 questions, with a maximum score of 30 points. Mild cognitive impairment was defined as a SLUMS score between 21 and 26 points, while severe cognitive impairment was defined as a SLUMS score of ≤ 20 points. Normal cognition was defined as a SLUMS score of ≥ 27 points. Delirium was assessed daily using the Confusion Assessment Method (CAM) and rated as absent or present on the basis of CAM. The incidence of delirium was compared in patients with and without baseline cognitive impairment. RESULTS Twenty-two patients (18%) developed delirium postoperatively. Baseline demographics, including age, sex, comorbidities, and perioperative variables, were similar in patients with and without delirium. The length of in-hospital stay (mean 5.33 days vs 5.48 days) and 30-day hospital readmission rates (12.28% vs 12%) were similar between patients with and without delirium, respectively. Patients with preoperative cognitive impairment (i.e., a lower SLUMS score) had a higher incidence of postoperative delirium. One- and 2-year patient reported outcomes scores were similar in patients with and without delirium. CONCLUSIONS Cognitive impairment is a risk factor for the development of postoperative delirium. Postoperative delirium may be associated with decreased preoperative cognitive reserve. Cognitive impairment assessments should be considered in the preoperative evaluations of elderly patients prior to surgery.

Clinical Ethics in the Context of Deep Brain Stimulation for Movement Disorders

OBJECTIVE

Discuss common clinical ethical challenges encountered in working with patients who are candidates for deep brain stimulation (DBS) for the treatment of motor symptoms of Parkinson's disease (PD).

METHOD

The relevant literature is reviewed and supplemented by descriptive, ethically challenging cases stemming from decades of combined experience working on DBS teams. We outline ethical arguments and provide pragmatic recommendations to assist neuropsychologists working in movement disorder teams.

RESULTS

The goals of the pre-operative neuropsychological DBS assessment include: (1) identification of potential cognitive risk factors; (2) identification of relevant neuropsychiatric or neurobehavioral factors; (3) assessment of level of family support; and (4) systematic assessment of patient's and family member's goals or expectations for DBS. The information gleaned from the pre-operative neuropsychological assessment is highly relevant to the most commonly studied clinical ethics challenges encountered in DBS: (1) assessment of risk/benefit; (2) determinations regarding inclusion/exclusion; (3) autonomy; and (4) patient's perception of benefit and quality of life.

CONCLUSIONS

Neuropsychologists are particularly well poised to provide unique and important insights to assist with developing the most ethically sound practices that take into account patient's values as well as fiduciary responsibilities to the patient, the team, the profession, and the broader community.

Predictors of Functional and Quality of Life Outcomes following Deep Brain Stimulation Surgery in Parkinson's Disease Patients: Disease, Patient, and Surgical Factors

Objective

The primary objective was to evaluate predictors of quality of life (QOL) and functional outcomes following deep brain stimulation (DBS) in Parkinson's disease (PD) patients. The secondary objective was to identify predictors of global improvement.

Methods

PD patients who underwent DBS at our Center from 2006 to 2011 were evaluated by chart review and email/phone survey. Postoperative UPDRS II and EQ-5D were analyzed using simple linear regression adjusting for preoperative score. For global outcomes, we utilized the Patient Global Impression of Change Scale (PGIS) and the Clinician Global Impression of Change Scale (CGIS).

Results

There were 130 patients in the dataset. Preoperative and postoperative UPDRS II and EQ-5D were available for 45 patients, PGIS for 67 patients, and CGIS for 116 patients. Patients with falls/postural instability had 6-month functional scores and 1-year QOL scores that were significantly worse than patients without falls/postural instability. For every 1-point increase in preoperative UPDRS III and for every 1-unit increase in body mass index (BMI), the 6-month functional scores significantly worsened. Patients with tremors, without dyskinesia, and without gait-freezing were more likely to have “much” or “very much” improved CGIS.

Conclusions

Presence of postural instability, high BMI, and worse baseline motor scores were the greatest predictors of poorer functional and QOL outcomes after DBS.

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.

Is Decompressive Surgery for Cervical Spondylotic Myelopathy Effective in Patients Suffering from Concomitant Multiple Sclerosis or Parkinson's Disease?

A subset of patients with a demyelinating disease suffer from concurrent cervical spondylotic myelopathy, both of which evince similar symptomatology. Differentiating the cause of these symptoms is challenging, and little research has been done on patients with coexisting diseases. This review explores the current literature on the appropriate surgical management of patients with concurrent multiple sclerosis (MS) and cervical spondylotic myelopathy (CSM), and those with both Parkinson’s disease (PD) and CSM. MS and CSM patients may benefit from surgery to reduce pain and radiculopathy. Surgical management in PD and CSM patients has shown minimal quality-of-life improvement. Future studies are needed to better characterize demyelinating disease patients with concurrent disease and to determine ideal medical or surgical treatment.

Assessing Visuospatial Skills in Parkinson's: Comparison of Neuropsychological Assessment Battery Visual Discrimination to the Judgment of Line Orientation

OBJECTIVE

Judgment of Line Orientation (JOLO) test is widely used in assessing visuospatial deficits in Parkinson's disease (PD). The neuropsychological assessment battery (NAB) offers the Visual Discrimination test, with age and education correction, parallel forms, and co-normed standardization sample for comparisons within and between domains. However, NAB Visual Discrimination has not been validated in PD, and may not measure the same construct as JOLO.

METHOD

A heterogeneous sample of 47 PD patients completed the JOLO and NAB Visual Discrimination within a broader neuropsychological evaluation. Pearson correlations assessed relationships between JOLO and NAB Visual Discrimination performances.

RESULTS

Raw and demographically corrected scores from JOLO and Visual Discrimination were only weakly correlated. NAB Visual Discrimination subtest was moderately correlated with overall cognitive functioning, whereas the JOLO was not.

CONCLUSIONS

Despite apparent virtues, results do not support NAB Visual Discrimination as an alternative to JOLO in assessing visuospatial functioning in PD.

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.

Quality of life outcomes following cervical decompression for coexisting Parkinson's disease and cervical spondylotic myelopathy

BACKGROUND CONTEXT

Coexisting Parkinson's disease (PD) and cervical spondylotic myelopathy (CSM) presents a diagnostic and therapeutic challenge due to symptomatic similarities between the diseases. Whereas CSM patients are routinely treated with surgery, PD patients face poorer outcomes following spine surgery. No studies have investigated the quality of life (QOL) outcomes following decompression in coexisting PD and CSM.

PURPOSE

The purpose of the present study was to characterize QOL outcomes for patients with coexisting PD and CSM following cervical decompression.

STUDY DESIGN/SETTING

This is a matched cohort study at a single tertiary-care center.

PATIENT SAMPLE

Patients with coexisting PD and CSM undergoing cervical decompression between June 2009 and December 2014 were included. These patients were matched to controls with CSM alone by age, gender, American Society of Anesthesiologists classification, Modified Japanese Orthopaedic Association scores, and operative parameters.

OUTCOME MEASURES

The primary outcome measure was QOL outcomes assessed by change in the EuroQol 5-Dimensions (EQ-5D), Pain Disability Questionnaire (PDQ), and Patient Health Questionnaire-9 (PHQ-9) at last follow-up (LFU). Change in QOL exceeding the minimal clinically important difference (MCID) was secondary.

METHODS

QOL data were collected using the institutional prospectively collected database of patient-reported health status measures. Simple and multivariable regressions were used to assess the impact of PD upon change in QOL.

RESULTS

Eleven PD patients were matched to 44 controls. Control patients experienced QOL improvement across all three measures, whereas PD patients only improved with respect to PDQ(89.9-80.7, p=.03). Despite no significant differences in preoperative QOL, PD patients experienced poorer QOL at LFU in EQ-5D (0.526 vs. 0.707, p=.01) and PDQ (80.7 vs. 51.4, p=.03), and less frequently achieved an EQ-5D MCID (18% vs. 57%, p=.04). However, no differences in the achievement of an MCID in PDQ or PHQ-9 were observed between cohorts. Multivariable regression identified PD as a significant independent predictor of poorer improvement in EQ-5D (β=-0.09, p<.01) and failure to achieve an EQ-5D MCID (odds ratio: 0.08, p<.01).

CONCLUSIONS

This is the first study to characterize QOL outcomes following cervical decompression for patients with coexisting PD and CSM. Although myelopathy may have been less severe among PD patients, a significant reduction in pain-related disability was observed following decompression. However, PD predicted diminished improvement in overall QOL measured by the EQ-5D.

Hypometabolism in Posterior and Temporal Areas of the Brain is Associated with Cognitive Decline in Parkinson's Disease

BACKGROUND

Brain metabolic profiles of patients with Parkinson's disease (PD) and cognitive impairment or dementia are now available. It would be useful if data on brain metabolism were also predictive of the risk of a pejorative cognitive evolution - especially in the multidisciplinary management of advanced PD patients.

OBJECTIVE

The primary objective was to determine whether a specific brain metabolic pattern is associated with cognitive decline in PD.

METHODS

Sixteen advanced PD patients were screened for the absence of cognitive impairment (according to the Mattis dementia rating scale, MDRS) and underwent [18F]-fluorodeoxyglucose positron emission tomography brain imaging in the "off drug" state. The MDRS was scored again about two years later, categorizing patients as having significant cognitive decline (decliners) or not (stables). The two groups were then compared in terms of their brain metabolism at inclusion.

RESULTS

There were six decliners and ten stables. Significant hypometabolism in the two precunei (Brodmann area (BA) 31), the left middle temporal gyrus (BA21) and the left fusiform gyrus (BA37) was found in the decliner group compared withthe stables.

CONCLUSION

In advanced PD, a particular metabolic pattern may be associated with the onset of significant cognitive decline.

Human behavioral assessments in current research of Parkinson's disease

Parkinson's disease (PD) is traditionally classified as a movement disorder because patients mainly complain about motor symptoms. Recently, non-motor symptoms of PD have been recognized by clinicians and scientists as early signs of PD, and they are detrimental factors in the quality of life in advanced PD patients. It is crucial to comprehensively understand the essence of behavioral assessments, from the simplest measurement of certain symptoms to complex neuropsychological tasks. We have recently reviewed behavioral assessments in PD research with animal models (Asakawa et al., 2016). As a companion volume, this article will systematically review the behavioral assessments of motor and non-motor PD symptoms of human patients in current research. The major aims of this article are: (1) promoting a comparative understanding of various behavioral assessments in terms of the principle and measuring indexes; (2) addressing the major strengths and weaknesses of these behavioral assessments for a better selection of tasks/tests in order to avoid biased conclusions due to inappropriate assessments; and (3) presenting new concepts regarding the development of wearable devices and mobile internet in future assessments. In conclusion we emphasize the importance of improving the assessments for non-motor symptoms because of their complex and unique mechanisms in human PD brains.

The impact of biological sex and sex hormones on cognition in a rat model of early, pre-motor Parkinson's disease

Parkinson's disease (PD) is well known for motor deficits such as bradykinesia. However, patients often experience additional deficits in working memory, behavioral selection, decision-making and other executive functions. Like other features of PD, the incidence and severity of these cognitive symptoms differ in males and females. However, preclinical models have not been used to systematically investigate the roles that sex or sex hormones may play in these complex signs. To address this, we used a Barnes maze spatial memory paradigm to compare the effects of a bilateral nigrostriatal dopamine lesion model of early PD on cognitive behaviors in adult male and female rats and in adult male rats that were gonadectomized or gonadectomized and supplemented with testosterone or estradiol. We found that dopamine lesions produced deficits in working memory and other executive operations, albeit only in male rats where circulating androgen levels were physiological. In males where androgen levels were depleted, lesions produced no additional Barnes maze deficits and attenuated those previously linked to androgen deprivation. We also found that while most measures of Barnes maze performance were unaffected by dopamine lesions in the females, lesions did induce dramatic shifts from their preferred use of thigmotactic navigation to the use of spatially guided place strategies similar to those normally preferred by males. These and other sex- and sex hormone-specific differences in the effects of nigrostriatal dopamine lesions on executive function highlight the potential of gonadal steroids as protective and/or therapeutic for the cognitive symptoms of PD. However, their complexity also indicates the need for a more thorough understanding of androgen and estrogen effects in guiding the development of hormone therapies that might effectively address these non-motor signs.

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.