Long-term stability of effects of subthalamic stimulation in Parkinson's disease: Indian Experience

How Long Does Deep Brain Stimulation Give Patients Benefit?

INTRODUCTION

One of the most common questions patients ask when they are contemplating deep brain stimulation (DBS) is how long it will last. To guide physicians in answering this query, we performed a scoping review to assess the current state of the literature and to identify the gaps that need to be addressed.

MATERIALS AND METHODS

The authors performed a MEDLINE search inclusive of articles from January 1987 (advent of DBS literature) to June 2023 including human and modeling studies written in English. For longevity of therapy data, only studies with a mean follow-up of ≥three years were included. Using the Rayyan platform, two reviewers (JP and RM) performed a title screen. Of the 734 articles, 205 were selected by title screen and 109 from abstract review. Ultimately, a total of 122 articles were reviewed. The research questions we explored were 1) how long can the different components of the DBS system maintain functionality? and 2) how long can DBS remain efficacious in treating Parkinson's disease (PD), essential tremor (ET), dystonia, and other disorders?

RESULTS

We showed that patients with PD, ET, and dystonia maintain a considerable long-term benefit in motor scores seven to ten years after implant, although the percentage improvement decreases over time. Stimulation off scores in PD and ET show worsening, consistent with disease progression. Battery life varies by the disease treated and the programming settings used. There remains a paucity of literature after ten years, and the impact of new device technology has not been classified to date.

CONCLUSION

We reviewed existing data on DBS longevity. Overall, outcomes data after ten years of therapy are substantially limited in the current literature. We recommend that physicians who have data for patients with DBS exceeding this duration publish their results.

Stereotatic radiosurgery for the treatment of motor symptoms in Parkinson's disease: A systematic review

BACKGROUND

Stereotaxic Radiosurgery (SRS) is a non-invasive lesioning technique for movement disorders when patients cannot undergo DBS due to medical comorbidities.

OBJECTIVE

To describe and summarize the literature on SRS's application and physical parameters for Parkinson's disease (PD) motor symptoms.

METHODS

The MEDLINE/PUBMED and EMBASE databases were searched in July 2022 following the PRISMA guideline. Two independent reviewers screened data from 425 articles. The level of evidence followed the Oxford Centre for Evidence-Based Medicine. Pertinent details for each study regarding participants, physical parameters, and results were extracted.

RESULTS

Twelve studies reported that 454 PD patients underwent Gamma KnifeⓇ (GK). The mean improvement time of the treated symptoms was three months after GK. Tremor is the most common symptom investigated, with success rates ranging from 47.5% to 93.9%. Few studies were conducted for caudatotomy (GKC) and pallidotomy (GKP), which presented an improvement for dyskinesia and bradykinesia. Physical parameters were similar with doses ranging from 110 to 200 Gy, use of a 4-mm collimator with an advanced imaging locator system, and coordinates were obtained from available stereotactic atlases.

CONCLUSIONS

GK thalamotomy is a good alternative for treating tremor; however, its effects are delayed, and there are cases in which it can regress after years. The outcomes of GKC and GKP seem to be promising. The existing studies are more limited, and effects need to be better investigated.

Unravelling the Parkinson's puzzle, from medications and surgery to stem cells and genes: a comprehensive review of current and future management strategies

Parkinson's disease (PD) is a neurodegenerative disorder, prevalent in the elderly population. Neuropathological hallmarks of PD include loss of dopaminergic cells in the nigro-striatal pathway and deposition of alpha-synuclein protein in the neurons and synaptic terminals, which lead to a complex presentation of motor and non-motor symptoms. This review focuses on various aspects of PD, from clinical diagnosis to currently accepted treatment options, such as pharmacological management through dopamine replacement and surgical techniques such as deep brain stimulation (DBS). The review discusses in detail the potential of emerging stem cell-based therapies and gene therapies to be adopted as a cure, in contrast to the present symptomatic treatment in PD. The potential sources of stem cells for autologous and allogeneic stem cell therapy have been discussed, along with the progress evaluation of pre-clinical and clinical trials. Even though recent techniques hold great potential to improve the lives of PD patients, we present the importance of addressing the safety, efficacy, ethical, cost, and regulatory concerns before scaling them to clinical use.

Long-Term Effects of Subthalamic Stimulation on Motor Symptoms and Quality of Life in Patients with Parkinson's Disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder affecting both motor functions and quality of life (QoL). This study compared motor symptoms and QoL in patients with PD before and at 1 and 5 years after subthalamic nucleus deep brain stimulation (STN-DBS) surgery in Taiwan. This study included 53 patients with PD undergoing STN-DBS. The motor symptoms improved by 39.71 ± 26.52% and 18.83 ± 37.15% in the Unified Parkinson's Disease Rating Scale (UPDRS) part II and by 36.83 ± 22.51% and 22.75 ± 36.32% in the UPDRS part III at 1 and 5 years after STN-DBS in the off-medication/on-stimulation state, respectively. The Hoehn and Yahr stage significantly improved at the 1-year follow-up but declined progressively and returned to the baseline stage 5 years post-surgery. The Schwab and England Activities of Daily Living improved and sustained for 5 years following STN-DBS. Levodopa equivalent daily dose decreased by 35.32 ± 35.87% and 15.26 ± 65.76% at 1 and 5 years post-surgery, respectively. The QoL revealed significant improvement at 1 year post-surgery; however, patients regressed to near baseline levels 5 years post-surgery. The long-term effects of STN-DBS on motor symptoms were maintained over 5 years after STN-DBS surgery. At the same time, STN-DBS had no long-lasting effect on QoL. The study findings will enable clinicians to become more aware of visible and invisible manifestations of PD.

Quality of Life and Motor Outcomes in Patients With Parkinson's Disease 12 Months After Deep Brain Stimulation in China

BACKGROUND

Long-term levodopa use is frequently associated with fluctuations in motor response and can have a serious adverse effect on the quality of life (QoL) of patients with Parkinson's disease (PD). Deep brain stimulation (DBS) is effective in improving symptoms of diminished levodopa responsiveness. QoL improvements with DBS have been shown in several randomized control trials, mostly in Europe and the United States; however, there is a need for evidence from regions around the world.

OBJECTIVE

The study aimed to demonstrate improvement in PD-related QoL in patients undergoing DBS in a prospective, multicenter study conducted in China.

MATERIALS AND METHODS

To evaluate the effect of neurostimulation on the QoL of patients with PD, a Parkinson's Disease Questionnaire (PDQ-8); Unified Parkinson's Disease Rating Scale (UPDRS) I, II, III, and IV; and EuroQol 5-dimension questionnaire (EQ-5D) were administered at baseline and 12 months after DBS implantation. The mean change and percent change from baseline were reported for these clinical outcomes.

RESULTS

Assessments were completed for 85 of the 89 implanted patients. DBS substantially improved patients' QoL and function. Implanted patients showed statistically significant mean improvement in PDQ-8 and UPDRS III (on stimulation/off medication). In the patients who completed the 12-month follow-up visit, the percent change was -22.2% for PDQ-8 and -51.6% for UPDRS III (on stimulation/off medication). Percent change from baseline to 12 months for UPDRS I, II, III, and IV and EQ-5D were -16.8%, -39.4%, -18.5%, and -50.0% and 22.7%, respectively. The overall rate of incidence for adverse events was low at 15.7%. Favorable outcomes were also reported based on patient opinion; 95.3% were satisfied with DBS results.

CONCLUSIONS

These data were comparable to other studies around the world and showed alignment with the ability of DBS to meaningfully improve the QoL of patients with PD. More studies investigating DBS therapy for patients with PD are necessary to accurately characterize clinical outcomes for the global PD population.

CLINICAL TRIAL REGISTRATION

The ClinicalTrials.gov registration number for this study is NCT02937688.

Long-term independence and quality of life after subthalamic stimulation in Parkinson's disease

Background and purpose

Studies on long‐term nonmotor outcomes of subthalamic nucleus stimulation in Parkinson disease (PD) are scarce. This study reports on very long‐term non‐motor and motor outcomes in one of the largest cohorts of people with advanced PD, treated for >10 years with subthalamic nucleus stimulation. The main outcome was to document the evolution of independence in activities of daily living. The secondary outcomes were to measure the change in quality of life, as well as non‐motor and motor outcomes.

Methods

Patients were studied preoperatively, at 1 year, and beyond 10 years after subthalamic stimulation with an established protocol including motor, non‐motor, and neuropsychological assessments.

Results

Eighty‐five people with PD were included. Independence scores in the off‐medication condition (measured with the Schwab & England Activities of Daily Living Scale) as well as quality of life (measured with the Parkinson's Disease Questionnaire [PDQ]‐37) remained improved at longest follow‐up compared to preoperatively (respectively, p < 0.001, p = 0.015). Cognitive scores, measured with the Mattis Dementia Rating Scale, significantly worsened compared to before and 1 year after surgery (p < 0.001), without significant change in depression, measured with the Beck Depression Inventory. Motor fluctuations, dyskinesias, and off dystonia remained improved at longest follow‐up (p < 0.001), with a significant reduction in dopaminergic treatment (45%, p < 0.001).

Conclusions

This study highlights the long‐term improvement of subthalamic stimulation on independence and quality of life, despite the progression of disease and the occurrence of levodopa‐resistant symptoms.

Deep Brain Stimulation in Parkinson Disease: A Meta-analysis of the Long-term Neuropsychological Outcomes

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) or globus pallidum internus (GPi) improves motor functions in patients with Parkinson's disease (PD) but may cause a decline in specific cognitive domains. The aim of this systematic review and meta-analysis was to assess the long-term (1-3 years) effects of STN or GPi DBS on four cognitive functions: (i) memory (delayed recall, working memory, immediate recall), (ii) executive functions including inhibition control (Color-Word Stroop test) and flexibility (phonemic verbal fluency), (iii) language (semantic verbal fluency), and (iv) mood (anxiety and depression). Medline and Web of Science were searched, and studies published before July 2021 investigating long-term changes in PD patients following DBS were included. Random-effects model meta-analyses were performed using the R software to estimate the standardized mean difference (SMD) computed as Hedges' g with 95% CI. 2522 publications were identified, 48 of which satisfied the inclusion criteria. Fourteen meta-analyses were performed including 2039 adults with a clinical diagnosis of PD undergoing DBS surgery and 271 PD controls. Our findings add new information to the existing literature by demonstrating that, at a long follow-up interval (1-3 years), both positive effects, such as a mild improvement in anxiety and depression (STN, Hedges' g = 0,34, p = 0,02), and negative effects, such as a decrease of long-term memory (Hedges' g = -0,40, p = 0,02), verbal fluency such as phonemic fluency (Hedges' g = -0,56, p < 0,0001), and specific subdomains of executive functions such as Color-Word Stroop test (Hedges' g = -0,45, p = 0,003) were observed. The level of evidence as qualified with GRADE varied from low for the pre- verses post-analysis to medium when compared to a control group.

Eight-year follow-up outcome of subthalamic deep brain stimulation for Parkinson's disease: Maintenance of therapeutic efficacy with a relatively low levodopa dosage and stimulation intensity

AIMS

This follow-up study aimed to examine the 8-year efficacy and safety of subthalamic nucleus (STN) deep brain stimulation (DBS) for patients with Parkinson's disease (PD) in southern China.

METHODS

The follow-up data of 10 patients with PD undergoing STN-DBS were analyzed. Motor symptoms were assessed before and 1, 3, 5, and 8 years after the surgery with stimulation-on in both off-medication (off-med) and on-medication (on-med) status using the Unified Parkinson's disease Rating Scale Part III. The quality of life was assessed using the 39-item Parkinson's Disease Questionnaire. The sleep, cognition, and emotion were evaluated using a series of nonmotor scales. Levodopa equivalent daily dose (LEDD) and stimulation parameters were recorded at each follow-up.

RESULTS

The motor symptoms were improved by 50.9%, 37.7%, 36.7%, and 37.3% in 1, 3, 5, and 8 years, respectively, in the off-med / stimulation-on status compared with the baseline. The quality of life improved by 39.7% and 56.1% in 1 and 3 years, respectively, but declined to the preoperative level thereafter. The sleep, cognition, and emotion were mostly unchanged. LEDD reduced from 708.1 ± 172.5 mg to 330 ± 207.8 mg in 8 years. The stimulation parameters, including amplitude, pulse width, and frequency, were 2.77 ± 0.49 V, 71.3 ± 12.8 μs, and 121.5 ± 21 Hz, respectively, in 8 years.

CONCLUSION

Long-term therapeutic efficacy of STN-DBS could be achieved even with relatively low stimulation intensity and medication dosage for PD patients in southern China. Motor improvement and medication reduction were maintained through the 8-year follow-up, but improvement in quality of life lasted for only 3 years. No definite changes was found in nonmotor symptoms after STN-DBS.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

CLASSIFICATION OF EVIDENCE

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

Apraxia of Lid Opening in Subthalamic Nucleus Deep Brain Stimulation for Parkinson's Disease-Frequency, Risk Factors and Response to Treatment

Background

New-onset apraxia of lid opening (ALO) is reported to occur in Parkinson's disease (PD) patients following Deep Brain Stimulation (DBS). There are only few systematic studies on this uncommon disorder of eyelid movements.

Objectives

We aimed to examine the frequency, temporal evolution, predisposing factors and response to treatment, of new-onset ALO in PD patients who underwent bilateral subthalamic nucleus (STN) DBS.

Methods

We retrospectively reviewed the data of patients who underwent STN DBS at our centre between 1999 and 2017, with a minimum of 2 years of follow up after surgery.

Results

New-onset ALO was seen in 17 (9.1%) of the 187 patients after an average of 16.9 months (Range - 6-36 months). Comparison of the groups with and without ALO revealed that ALO occurred more often in older patients, both at the onset of PD symptoms and at surgery and in those with non-tremor dominant subtypes of PD and freezing of gait at baseline. The extent of levodopa dose reduction after surgery and the pre-operative severity of motor symptoms were not risk factors. Response to adjustments of dopaminergic medications and stimulation parameters was ill-sustained or nil. Botulinum toxin therapy resulted in satisfactory improvement in the majority.

Conclusions

New-onset ALO is an uncommon phenomenon that manifests months after STN DBS. Development of ALO is likely to be due to the effects of chronic stimulation of basal ganglia-thalamo-cortical or brain stem circuits controlling lid movements in susceptible patients. Botulinum toxin therapy offers relatively better relief of symptoms than other strategies.

Deep Brain Stimulation of the Subthalamic Nucleus in Parkinson's Disease: A Meta-Analysis of Mood Effects

This meta-analysis examines mood changes after bilateral subthalamic deep brain stimulation (STN-DBS) in patients with Parkinson's disease (PD). Deep brain stimulation improves motor outcomes in Parkinson's disease but there appears to be conflicting reports as to subsequent mood outcomes. Pubmed, PsychINFO and SCOPUS were searched for studies assessing mood outcomes in PD patients who had undergone STN-DBS published between January 2003 and the end of January 2019. Random effects meta-analyses were conducted for all outcome groups with at least two studies homogenous in design and measure. Forty-eight studies, providing data on negative moods (such as depression, anxiety, apathy, and anger) and positive moods (pleasure and euphoria) were assessed. Results of the meta-analysis suggest that post-DBS, depression and anxiety symptoms improve and there is a reduction in negative affect, an increase in apathy, and in energy level. Although there have been reported cases of mania post-DBS surgery, the meta-analysis suggested no significant changes in symptoms of mania in the broader DBS population. Considerable heterogeneity was found and partially addressed through meta-regression and qualitative assessment of the included STN-DBS controlled studies. The major strengths of this meta-analysis, include attention to outcome validity, heterogeneity, independence of samples, and clinical utility, with the potential to improve post-operative safety through comprehensive consideration of mood and psychological adjustment. It appears that STN-DBS is a relatively safe and, in the case of mood symptomatology, an advantageous treatment of Parkinson's disease.

Long term follow-up in advanced Parkinson's disease treated with DBS of the subthalamic nucleus

BACKGROUND

Parkinson's disease (PD) is the second most common neurodegenerative disorder, affecting both motor and non-motor systems. Deep brain stimulation of the subthalamic nucleus (STN-DBS) has been an approved treatment for PD for more than 30 years, but few data are available regarding its long-term effectiveness.

OBJECTIVE

The aim of this study is to evaluate patients' outcome, both from a motor and non-motor perspective, 9 to 14 years after DBS implantation. We have investigated patients with advanced PD and treated with STN-DBS, in relation to key clinical features of PD.

METHODS

18 patients were assessed both retrospectively and prospectively. They underwent motor examination, neuropsychological evaluation and questionnaires on the quality of life, preoperatively, as well as 1, 9 and 14 years after DBS surgery. All patients were implanted with STN-DBS at San Raffaele Hospital between 2004 and 2010.

RESULTS

13 males and five females underwent DBS implantation with a mean PD duration of 11 years. Stimulation significantly improved med-off/stim-on condition up to 9 years, compared to the preoperative off state, and med-on/stim-on condition at 14 years, compared to med-on/stim-off state. Long term improvement specifically involved tremor and rigidity, as well as dopaminergic daily dose. At the same time, STN-DBS had no long-lasting effect on axial symptoms and cognitive functions.

CONCLUSIONS

STN-DBS remains an effective therapy for advanced PD, also over the years. Despite the underlying progression of the disease, this treatment extends the period in which the overall quality of life is still acceptable.

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.

Is Deep Brain Stimulation Associated With Detrimental Effects on Cognitive Functions in Patients of Parkinson's Disease? A Systematic Review

Deep brain stimulation (DBS) is a rapidly evolving procedure with its application in multiple fields of neurology, but it is most prominent in Parkinson's disease (PD). Through electrode implantation in different areas of the brain, it brings a favorable change to the motor symptoms to the magnitude that none of the medications have been able to, but the effect on cognition of the patients is still unknown. We did a comprehensive search through PubMed and Cochrane databases and conducted a systematic review by following the PRISMA guidelines. Inclusion criteria were studies conducted only in PD patients, after the year 2008. The studies published in languages other than English were excluded. Thirteen studies, including randomized and non-randomized controlled trials, observational studies, and meta-analysis, were analyzed in detail. The results showed a declining trend in verbal fluency and attention domains of cognition, while other functions remained unchanged. The decline was significant but not enough to impact the quality index in patients. DBS is associated with worse performance in verbal fluency and attention, and there is a further need for studies focusing on these domains with long-term follow-up. The overall cognitive profile was not affected significantly.

Efforts of subthalamic nucleus deep brain stimulation on cognitive spectrum: From explicit to implicit changes in the patients with Parkinson's disease for 1 year

OBJECTIVE

To evaluate the cognitive function of Chinese patients with Parkinson's disease PD postsubthalamic nucleus deep brain stimulation (STN-DBS).

METHODS

Cognitive function was assessed by neuropsychological methods in PD patients. Twenty matched healthy persons served as normal controls. t test, analysis of variance, and chi-square analysis were used to compare the difference among the groups. Reliable change index was utilized to analyze the changes in cognition from the individual level.

RESULTS

(a) Improvement in motor function was significantly better after STN-DBS (P < .01). (b) Notably, the increase error rates of implicit SRTT (serial reaction time task) was significantly higher after STN-DBS as compared with the conservative therapy group (P = .03). (c) The decline of verbal fluency (explicit) was also significantly higher after STN-DBS than that in the medication therapy group (P = .03). (d) In the explicit clock-drawing test, scores had significantly improved after STN-DBS (P = .04).

CONCLUSIONS

STN-DBS as a neuromodulatory tool in the Chinese PD population not only improves motor symptoms but also cognitive function to a certain extent, such as the decline of executive function and verbal fluency. The explicit cognitive decline was significantly quicker than that in patients on medication therapy. The improvement of visiospatial function was also noted. Implicit memory impairment during the 1-year follow-up period was not observed.

Long-term outcomes of deep brain stimulation in Parkinson disease

The efficacy of deep brain stimulation (DBS) for Parkinson disease (PD) is well established for up to 1 or 2 years, but long-term outcome data are still limited. In this Review, we critically discuss the evidence on the long-term outcomes of DBS and consider the clinical implications. Although many patients are lost to follow-up, the evidence indicates that subthalamic nucleus DBS improves motor function for up to 10 years, although the magnitude of improvement tends to decline over time. Functional scores recorded during on-medication periods worsen more quickly than those recorded in off periods, consistent with the degeneration of non-dopaminergic pathways. Dyskinesia, motor fluctuations and activities of daily living in off periods remain improved at 5 years, but quality-of-life scores have usually fallen below preoperative levels. The incidence and severity of dementia among patients receiving DBS are comparable to those among patients who receive medical treatment. Severe adverse events are rare, but adverse events such as dysarthria are common and probably under-reported. Long-term data on the outcomes of globus pallidus interna DBS are limited and mostly confirm the efficacy for dyskinesia. A trend towards offering DBS in the earlier stages of PD creates a need to identify factors that predict long-term outcomes and to discuss realistic expectations with patients preoperatively.

Predictive potential of preoperative electroencephalogram for neuropsychological change following subthalamic nucleus deep brain stimulation in Parkinson's disease

BACKGROUND

Deep brain stimulation of the bilateral subthalamic nucleus (STN-DBS) improves motor fluctuation and severe dyskinesia in advanced Parkinson's disease (PD). Effects on non-motor symptoms, such as neurocognitive side effects, can also influence the quality of life of both patients with PD and caregivers. Predictive quantitative factors associated with postoperative neurocognitive deterioration therefore warrant further attention. Here, we evaluated preoperative electroencephalogram (EEG) as a predictive marker for changes in neurocognitive functions after surgery.

METHODS

Scalp EEG was recorded preoperatively from 17 patients with PD who underwent bilateral STN-DBS. Global relative power in the theta, alpha, and beta bands was calculated. Cognitive function was assessed with neuropsychological batteries preoperatively and 1 year after STN-DBS.

RESULTS

Performance on the Symbol Search subtest of the WAIS III declined 1 year after DBS. The theta band was chosen for analysis with a 40% cutoff point for increased (≥ 40%) and decreased (< 40%) power. No significant differences between the two groups in baseline performance on most neuropsychological batteries were found, except for the Digit Symbol Coding subtest of the WAIS III. Changes in visual spatial functions were significantly different between groups. The increased theta band power group demonstrated a significant deterioration in performance on the WAIS III Matrix Reasoning subtest and the copy and immediate recall tasks of the Rey-Osterrieth complex figure test.

CONCLUSIONS

These findings suggest that preoperative increases in theta power are related to postoperative deterioration of visuospatial function, which indicates the predictive potential of preoperative quantitative EEG for neurocognitive changes after STN-DBS.

A Review of Cognitive Outcomes Across Movement Disorder Patients Undergoing Deep Brain Stimulation

Introduction: Although the benefit in motor symptoms for well-selected patients with deep brain stimulation (DBS) has been established, cognitive declines associated with DBS can produce suboptimal clinical responses. Small decrements in cognition can lead to profound effects on quality of life. The growth of indications, the expansion of surgical targets, the increasing complexity of devices, and recent changes in stimulation paradigms have all collectively drawn attention to the need for re-evaluation of DBS related cognitive outcomes.

Methods: To address the impact of cognitive changes following DBS, we performed a literature review using PubMed. We searched for articles focused on DBS and cognition. We extracted information about the disease, target, number of patients, assessment of time points, cognitive battery, and clinical outcomes. Diseases included were dystonia, Tourette syndrome (TS), essential tremor (ET), and Parkinson's disease (PD).

Results: DBS was associated with mild cognitive issues even when rigorous patient selection was employed. Dystonia studies reported stable or improved cognitive scores, however one study using reliable change indices indicated decrements in sustained attention. Additionally, DBS outcomes were convoluted with changes in medication dose, alleviation of motor symptoms, and learning effects. In the largest, prospective TS study, an improvement in attentional skills was noted, whereas smaller studies reported variable declines across several cognitive domains. Although, most studies reported stable cognitive outcomes. ET studies largely demonstrated deficits in verbal fluency, which had variable responses depending on stimulation setting. Recently, studies have focused beyond the ventral intermediate nucleus, including the post-subthalamic area and zona incerta. For PD, the cognitive results were heterogeneous, although deficits in verbal fluency were consistent and related to the micro-lesion effect.

Conclusion: Post-DBS cognitive issues can impact both motor and quality of life outcomes. The underlying pathophysiology of cognitive changes post-DBS and the identification of pathways underpinning declines will require further investigation. Future studies should employ careful methodological designs. Patient specific analyses will be helpful to differentiate the effects of medications, DBS and the underlying disease state, including disease progression. Disease progression is often an underappreciated factor that is important to post-DBS cognitive issues.

Sex differences in Parkinson's disease: Features on clinical symptoms, treatment outcome, sexual hormones and genetics

Parkinson's disease (PD) is the second most frequent age-related neurodegenerative disorder. Sex is an important factor in the development of PD, as reflected by the fact that it is more common in men than in women by an approximate ratio of 2:1. Our hypothesis is that differences in PD among men and women are highly determined by sex-dependent differences in the nigrostriatal dopaminergic system, which arise from environmental, hormonal and genetic influences. Sex hormones, specifically estrogens, influence PD pathogenesis and might play an important role in PD differences between men and women. The objective of this review was to discuss the PD physiopathology and point out sex differences in nigrostriatal degeneration, symptoms, genetics, responsiveness to treatments and biochemical and molecular mechanisms among patients suffering from this disease. Finally, we discuss the role estrogens may have on PD sex differences.

Subthalamic beta oscillations are attenuated after withdrawal of chronic high frequency neurostimulation in Parkinson's disease

Subthalamic nucleus (STN) local field potential (LFP) recordings demonstrate beta (13-30Hz) band oscillations in Parkinson's disease (PD) defined as elevations of spectral power. The amount of attenuation of beta band power on therapeutic levels of high frequency (HF) deep brain stimulation (DBS) and/or dopaminergic medication has been correlated with the degree of improvement in bradykinesia and rigidity from the therapy, which has led to the suggestion that elevated beta band power is a marker of PD motor disability. A fundamental question has not been answered: whether there is a prolonged attenuation of beta band power after withdrawal of chronic HF DBS and whether this is related to a lack of progression or even improvement in the underlying motor disability. Until now, in human PD subjects, STN LFP recordings were only attainable in the peri-operative period and after short periods of stimulation. For the first time, using an investigational, implanted sensing neurostimulator (Activa® PC+S, Medtronic, Inc.), STN LFPs and motor disability were recorded/assessed after withdrawal of chronic (6 and 12month) HF DBS in freely moving PD subjects. Beta band power was similar within 14s and 60min after stimulation was withdrawn, suggesting that "off therapy" experiments can be conducted almost immediately after stimulation is turned off. After withdrawal of 6 and 12months of STN DBS, beta band power was significantly lower (P<0.05 at 6 and 12months) and off therapy UPDRS scores were better (P<0.05 at 12months) compared to before DBS was started. The attenuation in beta band power was correlated with improvement in motor disability scores (P<0.05). These findings were supported by evidence of a gradual increase in beta band power in two unstimulated STNs after 24months and could not be explained by changes in lead impedance. This suggests that chronic HF DBS exerts long-term plasticity in the sensorimotor network, which may contribute to a lack of progression in underlying motor disability in PD.

Deep brain stimulation for Parkinson's disease: current status and future outlook

Parkinson's disease is a neurodegenerative condition secondary to loss of dopaminergic neurons in the substantia nigra pars compacta. Surgical therapy serves as an adjunct when unwanted medication side effects become apparent or additional therapy is needed. Deep brain stimulation emerged into the forefront in the 1990s. Studies have demonstrated improvement in all of the cardinal parkinsonian signs with stimulation. Frameless and ‘mini-frame’ stereotactic systems, improved MRI for anatomic visualization, and intraoperative MRI-guided placement are a few of the surgical advances in deep brain stimulation. Other advances include rechargeable pulse generators, voltage- or current-based stimulation, and enhanced abilities to ‘steer’ stimulation. Work is ongoing investigating closed-loop ‘smart’ stimulation in which stimulation is predicated on neuronal feedback.

Research in Parkinson's disease in India: A review

Parkinson's disease (PD) is a common neurodegenerative disorder affecting patients in large numbers throughout the world. In this article, we review all the published data on PD based on studies in Indian population. We have tried to consolidate the contribution of Indian studies in PD research. We found 95 articles, of which 92 were original research papers. This is a relatively less number, but in the last decade, there has been an increase in research on PD from this country. But most of them seem to be restricted to only a few research institutes. The nonmotor symptoms and genetics are the most commonly studied aspects. The systematic review of the articles reveals that the epidemiology in India may be different with relatively lesser incidence here. Most of the genetic mutations found to cause PD in other population are not found in India, revealing that other genetic factors may be involved. Further research needs to be encouraged to understand the disease in Indian patients better, as all the results cannot be extrapolated from the Western literature to this heterogeneous Indian population. There need to be more studies on therapeutic aspects of the disease.

Deep brain stimulation for gait and postural symptoms in Parkinson's disease

In patients with Parkinson's disease, gait and balance difficulties have emerged as some of the main therapeutic concerns. During earlier stages of the disease, the dopamine-responsive aspects of gait disorder can be treated initially with dopaminergic drugs or deep brain stimulation. However, certain temporal aspects of parkinsonian gait disorder remain therapeutically resistant in both the short term and the long term. In this review, we summarize the effects of deep brain stimulation on gait and postural symptoms in the five currently available targets (subthalamic nucleus, globus pallidus, ventralis intermedius thalamic nucleus, pedunculopontine nucleus, and substantia nigra) and describe programming strategies for patients who are mainly disabled by gait problems.

Gender influence on selection and outcome of deep brain stimulation for Parkinson's disease

Background:

Gender differences exist in Parkinson's disease (PD), both in clinical manifestations and response to medical treatment. We investigated whether gender differences occur in the clinical characteristics of patients selected for bilateral subthalamic nucleus deep brain stimulation (STN DBS) or in the outcome when resource limits influence treatment choices made by patients.

Materials and Methods:

Fifty-one consecutive patients were evaluated 1 month before, and 12 months after bilateral STN DBS. All patients were rated using Unified Parkinson's Disease Rating Scale, Parkinson's Disease Quality of Life (PDQL) Scale, Addenbrooke's Cognitive Examination and Beck Depression Inventory.

Results:

Pre-operative characteristics did not differ between the genders except for lower doses of drugs (P = 0.03), worse emotional scores in PDQL (P = 0.01) and worse depression (P = 0.03) in women. There was no gender difference in the surgical outcome, except a lesser reduction of dopaminergic drugs in women. Depression and quality of life (QOL) improved equally well in women and men.

Conclusion:

Bilateral STN DBS is equally efficacious in both genders as a treatment for motor complications of PD and for improving QOL. Women are likely to be undertreated because of more severe dyskinesia and may experience less emotional well-being, and could therefore potentially benefit from earlier surgical treatment.

Influence of deep brain stimulation of the subthalamic nucleus on cognitive function in patients with Parkinson's disease

Deep brain stimulation (DBS) is an effective technique for treating Parkinson's disease (PD) in the middle and advanced stages. The subthalamic nucleus (STN) is the most common target for clinical treatment using DBS. While STN-DBS can significantly improve motor symptoms in PD patients, adverse cognitive effects have also been reported. The specific effects of STN-DBS on cognitive function and the related mechanisms remain unclear. Thus, it is imperative to identify the influence of STN-DBS on cognition and investigate the potential mechanisms to provide a clearer view of the various cognitive sequelae in PD patients. For this review, a literature search was performed using the following inclusion criteria: (1) at least 10 patients followed for a mean of at least 6 months after surgery since the year 2006; (2) pre- and postoperative cognitive data using at least one standardized neuropsychological scale; and (3) adequate reporting of study results using means and standard deviations. Of ∼170 clinical studies identified, 25 cohort studies (including 15 self-controlled studies, nine intergroup controlled studies, and one multi-center, randomized control experiment) and one meta-analysis were eligible for inclusion. The results suggest that the precise mechanism of the changes in cognitive function after STN-DBS remains obscure, but STN-DBS certainly has effects on cognition. In particular, a progressive decrease in verbal fluency after STN-DBS is consistently reported and although executive function is unchanged in the intermediate stage postoperatively, it tends to decline in the early and later stages. However, these changes do not affect the improvements in quality of life. STN-DBS seems to be safe with respect to cognitive effects in carefully-selected patients during a follow-up period from 6 months to 9 years.

Neuropsychological effects of deep brain stimulation for Parkinson's disease

BACKGROUND

Putative changes of cognition after deep brain stimulation (DBS) in patients with Parkinson's disease (PD) are a matter of debate. The aim of this study was to assess cognitive abilities before and following bilateral subthalamic nucleus (STN) DBS and to review the available literature.

METHODS

Twenty patients underwent bilateral DBS of the STN. Cognitive skills were assessed in a standardized fashion before and at least at 12 months after the surgical intervention.

RESULTS

There was a significant decline of both semantic and phonematic verbal fluency and a mild trend for a deterioration of verbal memory after DBS. Mood, general cognitive screening, and visospatial abilities remained unchanged.

CONCLUSION

STN DBS in the treatment of PD has resulted in a significant reduction of motor symptoms and improved independence and quality of life in appropriately selected patients. However, it may have isolatable effects on verbal fluency and related function. Case series in the literature reported similar findings. Potential candidates for DBS should be counseled about the risk of mild cognitive declines.

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

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