Progression and survival in Parkinson's disease with subthalamic nucleus stimulation

Mortality of Deep Brain Stimulation and Risk Factors in Patients With Parkinson's Disease: A National Cohort Study in Korea

BACKGROUND

This study aimed to investigate 1) long-term outcomes of deep brain stimulation (DBS), such as mortality after DBS as well as the causes of death, 2) demographic and socioeconomic factors influencing mortality, and 3) comorbidities affecting mortality after DBS in patients with Parkinson's disease (PD).

METHODS

This study analyzed the National Health Insurance Service-National Health Information Database. Data on patients with PD diagnosis codes from 2002 to 2019 were extracted and analyzed. Data on the causes of death were obtained by linking the causes of death to data from Statistics Korea. The Kaplan-Meier method with the log-rank test was used for survival analysis. Multivariate Cox regression analyses were used to estimate hazard ratios (HRs) and their 95% confidence intervals. Regarding comorbidities such as PD dementia and fracture, which did not satisfy the assumption for the proportional HR, time-dependent Cox analysis with the Mantel-Byar method was used.

RESULTS

From 2005 to 2017, among 156,875 patients diagnosed with PD in Korea, 1,079 patients underwent DBS surgery, and 251 (23.3%) had died by 2019. The most common cause of death (47.1%) was PD. In the multivariate Cox regression analysis, the higher the age at diagnosis and surgery, the higher the mortality rate. The men and medical aid groups had significantly higher mortality rates. PD dementia and fracture were identified as risk factors for mortality.

CONCLUSION

Older age at diagnosis and surgery, being male, the use of medical aid, and the comorbidity of dementia and fractures were associated with a higher risk of mortality after DBS in patients with PD. Neurologists should consider these risk factors in assessing the prognosis of PD patients undergoing DBS.

Axial impairment and falls in Parkinson’s disease: 15 years of subthalamic deep brain stimulation

In this retrospective study, we longitudinally analyzed axial impairment and falls in people with Parkinson’s disease (PD) and subthalamic nucleus deep brain stimulation (STN-DBS). Axial scores and falling frequency were examined at baseline, and 1, 10, and 15 years after surgery. Preoperative demographic and clinical data, including PD duration and severity, phenotype, motor and cognitive scales, medications, and vascular changes on neuroimaging were examined as possible risk factors through Kaplan–Meier and Cox regression analyses. Of 302 individuals examined before and at 1 year after surgery, 102 and 57 were available also at 10 and 15 years of follow-up, respectively. Axial scores were similar at baseline and at 1 year but worsened at 10 and 15 years. The prevalence rate of frequent fallers progressively increased from baseline to 15 years. Preoperative axial scores, frontal dysfunction and age at PD onset were risk factors for axial impairment progression after surgery. Axial scores, akinetic/rigid phenotype, age at disease onset and disease duration at surgery predicted frequent falls. Overall, axial signs progressively worsened over the long-term period following STN-DBS, likely related to the progression of PD, especially in a subgroup of subjects with specific risk factors.

Post-mortem brain histological examination in the substantia nigra and subthalamic nucleus in Parkinson’s disease following deep brain stimulation

Parkinson’s disease (PD) is a progressive neurodegenerative disorder, pathologically hallmarked by the loss of dopamine neurons in the substantia nigra (SN) and alpha-synuclein aggregation. Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is a common target to treat the motor symptoms in PD. However, we have less understanding of the cellular changes in the STN during PD, and the impact of DBS on the STN and SN is limited. We examined cellular changes in the SN and STN in PD patients with and without STN-DBS treatment. Post-mortem brain tissues from 6 PD non-STN-DBS patients, 5 PD STN-DBS patients, and 6 age-matched controls were stained with markers for neurodegeneration (tyrosine hydroxylase, alpha-synuclein, and neuronal loss) and astrogliosis (glial fibrillary acidic protein). Changes were assessed using quantitative and semi-quantitative microscopy techniques. As expected, significant neuronal cell loss, alpha-synuclein pathology, and variable astrogliosis were observed in the SN in PD. No neuronal cell loss or astrogliosis was observed in the STN, although alpha-synuclein deposition was present in the STN in all PD cases. DBS did not alter neuronal loss, astrogliosis, or alpha-synuclein pathology in either the SN or STN. This study reports selective pathology in the STN with deposits of alpha-synuclein in the absence of significant neuronal cell loss or inflammation in PD. Despite being effective for the treatment of PD, this small post-mortem study suggests that DBS of the STN does not appear to modulate histological changes in astrogliosis or neuronal survival, suggesting that the therapeutic effects of DBS mechanism may transiently affect STN neural activity.

Long-Term Outcomes of Bilateral Subthalamic Nucleus Deep Brain Stimulation for Patients With Parkinson's Disease: 10 Years and Beyond

BACKGROUND

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) represents an effective treatment for severe Parkinson's disease (PD), but little is known about the long-term benefit.

OBJECTIVE

To investigate the survival rate and long-term outcome of DBS.

METHODS

We investigated all 81 patients including 37 males and 44 females who underwent bilateral STN DBS from March 2005 to March 2008 at a single institution. The current survival status of the patients was investigated. Preoperative and postoperative follow-up assessments were analyzed.

RESULTS

The mean age at the time of surgery was 62 (range 27-82) years, and the median clinical follow-up duration was 145 months. Thirty-five patients (43%) died during the follow-up period. The mean duration from DBS surgery to death was 110.46 ± 40.8 (range 0-155) months. The cumulative survival rate is as follows: 98.8 ± 1.2% (1 year), 95.1 ± 2.4% (5 years), and 79.0 ± 4.5% (10 years). Of the 81 patients, 33 (40%) were ambulatory up to more than 11 years. The Unified Parkinson's Disease Rating Scale (UPDRS) score was significantly improved until 5 years after surgery although it showed a tendency to increase again after 10 years. The patient group with both electrodes located within the STN showed a higher rate of survival and maintained ambulation.

CONCLUSION

STN DBS is a safe and effective treatment for patients with advanced PD. This study based on the long-term follow-up of large patient populations can be used to elucidate the long-term fate of patients who underwent bilateral STN DBS for PD.

How Does Deep Brain Stimulation Change the Course of Parkinson's Disease?

A robust body of evidence from randomized controlled trials has established the efficacy of deep brain stimulation (DBS) in reducing off time and dyskinesias in levodopa‐treated patients with Parkinson's disease (PD). These effects go along with improvements in on period motor function, activities of daily living, and quality of life. In addition, subthalamic DBS is effective in controlling drug‐refractory PD tremor. Here, we review the available data from long‐term observational and controlled follow‐up studies in DBS‐treated patients to re‐examine the persistence of motor and quality of life benefits and evaluate the effects on disease progression, major disability milestones, and survival. Although there is consistent evidence from observational follow‐up studies in DBS‐treated patients over 5–10 years and beyond showing sustained improvement of motor control, the long‐term impact of DBS on overall progression of disability in PD is less clear. Whether DBS reduces or delays the development of later motor and non‐motor disability milestones in comparison to best medical management strategies is difficult to answer by uncontrolled observational follow‐up, but there are signals from controlled long‐term observational studies suggesting that subthalamic DBS may delay some of the late‐stage disability milestones including psychosis, falls, and institutionalization, and also slightly prolongs survival compared with matched medically managed patients. These observations could be attributable to the sustained improvements in motor function and reduction in medication‐induced side effects, whereas there is no clinical evidence of direct effects of DBS on the underlying disease progression. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society

Deep brain stimulation-induced neuroprotection: A critical appraisal

Over the last two decades deep brain stimulation (DBS) has become a widely used therapeutic alternative for a variety of neurological and psychiatric diseases. The extensive experience in the field of movement disorders has provided valuable knowledge and has led the path to its application to other hard-to-treat conditions. Despite the recognised symptomatic beneficial effects, its capacity to modify the course of a disease has been in constant debate. The ability to demonstrate neuroprotection relies on a thorough understanding of the functioning of both normal and pathological neural structures, as well as their stimulation induced alterations, all of which to this date remain incomplete. Consequently, there is no consensus over the definition of neuroprotection nor its means of quantification or evaluation. Additionally, neuroprotection has been indirectly addressed in most of the literature, challenging the efforts to narrow its interpretation. As such, a broad spectrum of evidence has been considered to demonstrate disease modifying interventions. This paper aims to provide a critical appraisal of the current evidence on potential neuroprotective effects of DBS in neurodegenerative brain disorders.

Lesser-Known Aspects of Deep Brain Stimulation for Parkinson's Disease: Programming Sessions, Hardware Surgeries, Residential Care Admissions, and Deaths

OBJECTIVE

The long-term treatment burden, duration of community living, and survival of patients with Parkinson's disease (PD) after deep brain stimulation (DBS) implantation are unclear. This study aims to determine the frequency of programming, repeat hardware surgeries (of the intracranial electrode, implantable pulse generator [IPG], and extension-cable), and the timings of residential care and death in patients with PD treated with DBS.

MATERIALS AND METHODS

In this cross-sectional, population-based study, individual-level data were collected from the Australian government covering a 15-year period (2002-2016) on 1849 patients with PD followed from DBS implantation.

RESULTS

The mean DBS implantation age was 62.6 years and mean follow-up 5.0 years. Mean annual programming rates were 6.9 in the first year and 2.8 in subsequent years. 51.4% of patients required repeat hardware surgery. 11.3% of patients had repeat intracranial electrode surgery (including an overall 1.1% of patients who were completely explanted). 47.6% of patients had repeat IPG/extension-cable surgery including for presumed battery depletion. 6.2% of patients had early repeat IPG/extension-cable surgery (within one year of any previous such surgery). Thirty-day postoperative mortality was 0.3% after initial DBS implantation and 0.6% after any repeat hardware surgery. 25.3% of patients were admitted into residential care and 17.4% died. The median interval to residential care and death was 10.2 years and 11.4 years, respectively. Age more than 65 years was associated with fewer repeat hardware surgeries for presumed complications (any repeat surgery of electrodes, extension-cables, and early IPG surgery) and greater rates of residential care admission and death.

CONCLUSIONS

Data from a large cohort of patients with PD treated with DBS found that the median life span after surgery is ten years. Repeat hardware surgery, including of the intracranial electrodes, is common. These findings support development of technologies to reduce therapy burden such as enhanced surgical navigation, hardware miniaturization, and improved battery efficiency.

Parkinson's Disease: Can Targeting Inflammation Be an Effective Neuroprotective Strategy?

The reason why dopamine neurons die in Parkinson’s disease remains largely unknown. Emerging evidence points to a role for brain inflammation in neurodegeneration. Essential questions are whether brain inflammation happens sufficiently early so that interfering with this process can be expected to slow down neuronal death and whether the contribution from inflammation is large enough so that anti-inflammatory agents can be expected to work. Here I discuss data from human PD studies indicating that brain inflammation is an early event in PD. I also discuss the role of T-lymphocytes and peripheral inflammation for neurodegeneration. I critically discuss the failure of clinical trials targeting inflammation in PD.

The Queensland Parkinson's Project: An Overview of 20 Years of Mortality from Parkinson's Disease

OBJECTIVE

The consensus is that life expectancy for individuals with Parkinson's disease (PD) is reduced, but estimations vary. We aimed to provide an overview of 20 years of mortality and risk factor data from the Queensland Parkinson's Project.

METHODS

The analysis included 1,334 PD and 1,127 control participants. Preliminary analysis of baseline characteristics (sex, age at onset, family history, smoking status, pesticide exposure, depression and neurosurgery) was conducted, and Kaplan-Meier curves were generated for each potential risk factor. Standardized mortality ratios (SMRs) were calculated comparing this cohort to the general Australian population. Cox proportional hazards regression modeling was used to analyze potential predictors of mortality.

RESULTS

In total, 625 (46.8%) PD and 237 (21.0%) control participants were deceased. Mean disease duration until death was 15.3 ± 7.84 years. Average ages at death were 78.0 ± 7.4 years and 80.4 ± 8.4 years for the deceased PD and control participants, respectively. Mortality was significantly increased for PD in general {SMR = 2.75 [95% confidence interval (CI): 2.53-2.96]; p = 0.001}. SMRs were slightly higher for women and those with an age of onset before 60 years. Multivariate analysis showed that deep brain stimulation (DBS) treatment was associated with lower mortality [hazard ratio (HR) = 0.76; 95% CI: 0.59-0.98], while occasional pesticide exposure increased mortality risk (HR = 1.48; 95% CI: 1.17-1.88). Family history of PD, smoking and depression were not independent predictors of mortality.

CONCLUSION

Mortality in PD is increased. Sex, age at onset and occasional pesticide exposure were independent determinants of increased mortality, while DBS treatment was associated with reduced mortality.

Has Deep Brain Stimulation Changed the Very Long-Term Outcome of Parkinson's Disease? A Controlled Longitudinal Study

BACKGROUND

The long-term impact of deep brain stimulation (DBS) on Parkinson's disease (PD) is difficult to assess and has not yet been rigorously evaluated in comparison to its natural history.

OBJECTIVE

Comparison of key disability milestones (recurrent falls, psychosis, dementia, and institutionalization) and death in patients with PD with versus without DBS.

METHODS

We collected retrospective information from clinical notes of patients with PD at our center that were implanted with subthalamic DBS >8 years ago (1999-2010) and a control group of PD patients without DBS similar in age at onset, age at baseline, sex distribution, and number of comorbidities at baseline (extracted from a registry study performed in 2004). Cox regression models were used to calculate hazard ratios, adjusted for potential baseline confounding variables (age, sex, disease duration, disease severity, and number of comorbidities).

RESULTS

A total of 74 DBS-treated and 61 control patients with PD were included. For a median observational period of 14 years, patients treated with DBS were at lower risk of experiencing recurrent falls (hazard ratio = 0.57; 95% confidence interval, 0.37-0.90; P = 0.015) and psychosis (hazard ratio = 0.26; 95% confidence interval, 0.12-0.59; P = 0.001) compared with control patients. There was no significant difference in risk for dementia, institutionalization, or death. Disease progression as assessed by Hoehn and Yahr scores was not slower in DBS-treated patients.

CONCLUSIONS

Treatment with chronic subthalamic DBS was associated with lower risk for recurrent falls and psychotic symptoms, effects that may be mediated through improved motor symptom control and reduction in dopaminergic therapies, respectively. There was no evidence for DBS effects on underlying disease progression.

Survival and Health Care Use After Deep Brain Stimulation for Parkinson's Disease

OBJECTIVES

To compare long-term survival of Parkinson's disease (PD) patients with deep brain stimulation (DBS) to matched controls, and examine whether DBS was associated with differences in injurious falls, long-term care, and home care.

METHODS

Using administrative health data (Ontario, Canada), we examined DBS outcomes within a cohort of individuals diagnosed with PD between 1997 and 2012. Patients receiving DBS were matched with non-DBS controls by age, sex, PD diagnosis date, time with PD, and a propensity score. Survival between groups was compared using the log-rank test and marginal Cox proportional hazards regression. Cumulative incidence function curves and marginal subdistribution hazard models were used to assess effects of DBS on falls, long-term care admission, and home care use, with death as a competing risk.

RESULTS

There were 260 DBS recipients matched with 551 controls. Patients undergoing DBS did not experience a significant survival advantage compared to controls (log-rank test p = 0.50; HR: 0.89, 95% CI: 0.65-1.22). Among patients <65 years of age, DBS recipients had a significantly reduced risk of death (HR: 0.49, 95% CI: 0.28-0.84). Patients receiving DBS were more likely than controls to receive care for falls (HR: 1.56, 95% CI: 1.19-2.05) and home care (HR: 1.59, 95% CI: 1.32-1.90), while long-term care admission was similar between groups.

CONCLUSIONS

Receiving DBS may increase survival for younger PD patients who undergo DBS. Future studies should examine whether survival benefits may be attributed to effects on PD or the absence of comorbidities that influence mortality.

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.

Deep brain stimulation in Parkinson's disease: A multicentric, long-term, observational pilot study

BACKGROUND

The impact of deep brain stimulation (DBS) on cognitive and urinary disorders, falls, and eventually hospitalizations and mortality in Parkinson's disease (PD) is still debated.

OBJECTIVE

We compared the rates of dementia, mild cognitive impairment (MCI), urinary incontinence, nocturia, falls, hospitalizations, and mortality in a cohort of PD patients undergoing DBS with a cohort of medically-treated patients chosen as controls.

METHODS

We conducted a retrospective pilot study in six Italian DBS centers. 91 PD patients receiving DBS and 91 age- and gender-matched controls receiving the best medical treatment alone with a minimum follow-up of one year were enrolled. Clinical data were collected from baseline to the last follow-up visit using an ad-hoc developed web-based system.

RESULTS

The risk of dementia was similar in the two groups while patients in the surgical cohort had lower rates of MCI, urinary incontinence, nocturia, and falls. In contrast, the risk of hospital admissions related to PD was higher in the surgical cohort. However, when excluding hospitalizations related to DBS surgery, the difference between the two cohorts was not significant. The surgical cohort had a lower number of hospitalizations not related to PD. The risk of death was similar in the two groups.

CONCLUSION

Despite a higher risk of hospitalization, patients receiving DBS had a lower rate of MCI, urinary incontinence, nocturia and falls, without evidence of an increased risk of dementia and mortality. Although these findings need to be confirmed in prospective studies, they seem to suggest that DBS may play a significant role in the management of non-motor symptoms and common complications of advanced PD.

Axial symptoms predict mortality in patients with Parkinson disease and subthalamic stimulation

Objective

To characterize how disease progression is associated with mortality in a large cohort of patients with Parkinson disease (PD) with long-term follow-up after subthalamic nucleus deep brain stimulation (STN-DBS).

Methods

Motor and cognitive disabilities were assessed before and 1, 2, 5, and 10 years after STN-DBS in 143 consecutive patients with PD. We measured motor symptoms “off” and “on” levodopa and STN-DBS and recorded causes of death. We used linear mixed models to characterize symptom progression, including interactions between treatment conditions and time to determine how treatments changed efficacy. We used joint models to link symptom progression to mortality.

Results

Median observation time was 12 years after surgery, during which akinesia, rigidity, and axial symptoms worsened, with mean increases of 8.8 (SD 6.5), 1.8 (3.1), and 5.4 (4.1) points from year 1–10 after surgery (“on” dopamine/“on” STN-DBS), respectively. Responses to dopaminergic medication and STN-DBS were attenuated with time, but remained effective for all except axial symptoms, for which both treatments and their combination were predicted to be ineffective 20 years after surgery. Cognitive status significantly declined. Forty-one patients died, with a median time to death of 9 years after surgery. The current level of axial disability was the only symptom that significantly predicted death (hazard ratio 4.30 [SE 1.50] per unit of square-root transformed axial score).

Conclusions

We quantified long-term symptom progression and attenuation of dopaminergic medication and STN-DBS treatment efficacy in patients with PD and linked symptom progression to mortality. Axial disability significantly predicts individual risk of death after surgery, which may be useful for planning therapeutic strategies in PD.

Deep brain stimulation: potential for neuroprotection

Over the last two decades there has been an exponential rise in the number of patients receiving deep brain stimulation (DBS) to manage debilitating neurological symptoms in conditions such as Parkinson's disease, essential tremor, and dystonia. Novel applications of DBS continue to emerge including treatment of various psychiatric conditions (e.g. obsessive-compulsive disorder, major depression) and cognitive disorders such as Alzheimer's disease. Despite widening therapeutic applications, our understanding of the mechanisms underlying DBS remains limited. In addition to modulation of local and network-wide neuronal activity, growing evidence suggests that DBS may also have important neuroprotective effects in the brain by limiting synaptic dysfunction and neuronal loss in neurodegenerative disorders. In this review, we consider evidence from preclinical and clinical studies of DBS in Parkinson's disease, Alzheimer's disease, and epilepsy that suggest chronic stimulation has the potential to mitigate neuronal loss and disease progression.

BDNF provides many routes toward STN DBS-mediated disease modification

The concept that subthalamic nucleus deep brain stimulation (STN DBS) may be disease modifying in Parkinson's disease (PD) is controversial. Several clinical trials that enrolled subjects with late‐stage PD have come to disparate conclusions on this matter. In contrast, some clinical studies in early‐ to midstage subjects have suggested a disease‐modifying effect. Dopaminergic innervation of the putamen is essentially absent in PD subjects within 4 years after diagnosis, indicating that any neuroprotective therapy, including STN DBS, will require intervention within the immediate postdiagnosis interval. Preclinical prevention and early intervention paradigms support a neuroprotective effect of STN DBS on the nigrostriatal system via increased brain‐derived neurotrophic factor (BDNF). STN DBS‐induced increases in BDNF provide a multitude of mechanisms capable of ameliorating dysfunction and degeneration in the parkinsonian brain. A biomarker for measuring brain‐derived neurotrophic factor‐trkB signaling, though, is not available for clinical research. If a prospective clinical trial were to examine whether STN DBS is disease modifying, we contend the strongest rationale is not dependent on a preclinical neuroprotective effect per se, but on the myriad potential mechanisms whereby STN DBS‐elicited brain‐derived neurotrophic factor‐trkB signaling could provide disease modification. © 2018 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Survival in patients with Parkinson's disease after deep brain stimulation or medical management

OBJECTIVE

Deep brain stimulation has been shown to have a significant long-term beneficial effect on motor function. However, whether it affects survival is not clear. In this study, we compared survival rates for Parkinson's disease (PD) patients who underwent deep brain stimulation (DBS) with those who were medically managed.

METHODS

A retrospective analysis of Veterans Affairs and Medicare administrative data of veterans with PD who received DBS and were propensity score matched to a cohort of veterans with PD who did not receive DBS between 2007-2013.

RESULTS

Veterans with PD who received DBS had a longer survival measured in days than a matched group of veterans who did not undergo DBS (mean = 2291.1 [standard error = 46.4] days [6.3 years] vs 2063.8 [standard error = 47.7] days [5.7 years]; P = .006; hazard ratio = 0.69 [95% confidence interval 0.56-0.85]). Mean age at death was similar for both groups (76.5 [standard deviation = 7.2] vs 75.9 [standard deviation = 8.4] years, P = .67), respectively, and the most common cause of death was PD.

CONCLUSIONS

DBS is associated with a modest survival advantage when compared with a matched group of patients who did not undergo DBS. Whether the survival advantage reflects a moderating influence of DBS on PD or on comorbidities that might shorten life or whether differences may be a result of unmeasured differences between groups is not known. © 2017 International Parkinson and Movement Disorder Society.

Neuroprotective Surgical Strategies in Parkinson's Disease: Role of Preclinical Data

Although there have been many pharmacological agents considered to be neuroprotective therapy in Parkinson's disease (PD) patients, neurosurgical approaches aimed to neuroprotect or restore the degenerative nigrostriatal system have rarely been the focus of in depth reviews. Here, we explore the neuroprotective strategies involving invasive surgical approaches (NSI) using neurotoxic models 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 6-hydroxydopamine (6-OHDA), which have led to clinical trials. We focus on several NSI approaches, namely deep brain stimulation of the subthalamic nucleus, glial neurotrophic derived factor (GDNF) administration and cell grafting methods. Although most of these interventions have produced positive results in preclinical animal models, either from behavioral or histological studies, they have generally failed to pass randomized clinical trials to validate each approach. We argue that NSI are promising approaches for neurorestoration in PD, but preclinical studies should be planned carefully in order not only to detect benefits but also to detect potential adverse effects. Further, clinical trials should be designed to be able to detect and disentangle neuroprotection from symptomatic effects. In summary, our review study evaluates the pertinence of preclinical models to study NSI for PD and how this affects their efficacy when translated into clinical trials.

Earlier Intervention with Deep Brain Stimulation for Parkinson's Disease

Neuromodulation of subcortical areas of the brain as therapy to reduce Parkinsonian motor symptoms was developed in the mid-twentieth century and went through many technical and scientific advances that established specific targets and stimulation parameters. Deep Brain Stimulation (DBS) was approved by the FDA in 2002 as neuromodulation therapy for advanced Parkinson's disease, prompting several randomized controlled trials that confirmed its safety and effectiveness. The implantation of tens of thousands of patients in North America and Europe ignited research into its potential role in early disease stages and the therapeutic benefit of DBS compared to best medical therapy. In 2013 the EARLY-STIM trial provided Class I evidence for the use of DBS earlier in Parkinson's disease. This finding led to the most recent FDA approval in patients with at least 4 years of disease duration and 4 months of motor complications as an adjunct therapy for patients not adequately controlled with medications. This following review highlights the historical development and advances made overtime in DBS implantation, the current application, and the challenges that come with it.

Deep brain stimulation with a pre-existing cochlear implant: Surgical technique and outcome

Background:

Patients with previously implanted cranial devices pose a special challenge in deep brain stimulation (DBS) surgery. We report the implantation of bilateral DBS leads in a patient with a cochlear implant. Technical nuances and long-term interdevice functionality are presented.

Case Description:

A 70-year-old patient with advancing Parkinson's disease and a previously placed cochlear implant for sensorineural hearing loss was referred for placement of bilateral DBS in the subthalamic nucleus (STN). Prior to DBS, the patient underwent surgical removal of the subgaleal cochlear magnet, followed by stereotactic MRI, frame placement, stereotactic computed tomography (CT), and merging of imaging studies. This technique allowed for successful computational merging, MRI-guided targeting, and lead implantation with acceptable accuracy. Formal testing and programming of both the devices were successful without electrical interference.

Conclusion:

Successful DBS implantation with high resolution MRI-guided targeting is technically feasible in patients with previously implanted cochlear implants by following proper precautions.

Comparison of neuropathology in Parkinson's disease subjects with and without deep brain stimulation

BACKGROUND

The aim of this postmortem study was to compare, in Parkinson's disease subjects with and without bilateral subthalamic nucleus deep brain stimulation (STN-DBS), the loss of pigmented neurons within the substantia nigra and pathological alpha-synuclein density within the SN and other brain regions.

METHODS

PD subjects were identified from the Arizona Study of Aging and Neurodegenerative Disorders database (STN-DBS = 11, non-DBS = 156). Pigmented neuron loss scores within the substantia nigra as well as alpha-synuclein density scores within the substantia nigra and 9 other brain regions were compared, the latter individually and in summary as the Lewy body brain load score.

RESULTS

DBS subjects had higher alpha-synuclein density scores within the substantia nigra, olfactory bulb, and locus ceruleus, as well as higher total Lewy body brain load scores when compared with non-DBS subjects. No differences in substantia nigra pigmented neuron loss scores were found.

CONCLUSIONS

STN-DBS subjects tend to have higher alpha-synuclein density scores, but do not have a differential loss of substantia nigra pigmented neurons. © 2016 International Parkinson and Movement Disorder Society.

Current Topics in Deep Brain Stimulation for Parkinson Disease

There is a long history of surgical treatment for Parkinson disease (PD). After pioneering trials and errors, the current primary surgical treatment for PD is deep brain stimulation (DBS). DBS is a promising treatment option for patients with medically refractory PD. However, there are still many problems and controversies associated with DBS. In this review, we discuss current issues in DBS for PD, including patient selection, clinical outcomes, complications, target selection, long-term outcomes, management of axial symptoms, timing of surgery, surgical procedures, cost-effectiveness, and new technology.

Mechanisms of deep brain stimulation

Deep brain stimulation (DBS) is widely used for the treatment of movement disorders including Parkinson's disease, essential tremor, and dystonia and, to a lesser extent, certain treatment-resistant neuropsychiatric disorders including obsessive-compulsive disorder. Rather than a single unifying mechanism, DBS likely acts via several, nonexclusive mechanisms including local and network-wide electrical and neurochemical effects of stimulation, modulation of oscillatory activity, synaptic plasticity, and, potentially, neuroprotection and neurogenesis. These different mechanisms vary in importance depending on the condition being treated and the target being stimulated. Here we review each of these in turn and illustrate how an understanding of these mechanisms is inspiring next-generation approaches to DBS.

The long-term development of non-motor problems after STN-DBS

OBJECTIVES

Stimulation of the subthalamic nucleus (STN-DBS) is an established treatment with long-term beneficial effects on motor symptoms in patients with Parkinson's disease (PD). The long-term development of non-motor problems after STN-DBS is not fully understood. In this study, we have studied how non-motor problems develop in patients with and without STN-DBS.

MATERIALS AND METHODS

We collected data from a prospectively followed cohort of patients that had been operated with STN-DBS 6-9 years before final examination and compared our findings to the longitudinal development of non-motor problems in a non-operated, comparable reference population.

RESULTS

In general, the non-motor problems of advanced PD seem to develop independently of treatment with STN-DBS. We found that depressions do not worsen after STN-DBS, and the Montgomery and Aasberg Depression Rating Scale score in operated patients was substantially reduced from pre-operatively to post-operatively. Further, fatigue may represent an important unrecognized side effect of long-term stimulation, as fatigue was found to increase rapidly in operated patients already a year after surgery and continued to increase trough the 6- to 9-year follow-up.

CONCLUSIONS

The non-motor problems of advanced PD seem to develop independently of treatment with STN-DBS. This may influence the strategy for choice of when to perform this therapy for eligible patients.

Motor symptoms after deep brain stimulation of the subthalamic nucleus

OBJECTIVES

Stimulation of the subthalamic nucleus (STN-DBS) is an established treatment with long-term beneficial effects on motor symptoms in patients with Parkinson's disease (PD). The efficacy of STN-DBS on non-dopaminergic motor symptoms remains less elucidated. In this study, we have examined short- and long-term impacts of STN-DBS on the development of the postural instability and gait difficulties (PIGD) phenotype, freezing of gait (FOG), and falls.

MATERIALS AND METHODS

We collected data from a prospectively followed cohort of patients that had been operated with STN-DBS 6-9 years before final examination and compared our findings to the longitudinal development of the same symptoms in a non-operated, historical reference population.

RESULTS

During short-term follow-up after surgery, we observed a marked improvement in mean UPDRS-motor score from 27 to 18. We also found clear improvements in tremor, bradykinesia, rigidity, and PIGD scores. However, 6-9 years after surgery, all patients had a dominating PIGD pattern of parkinsonism and 50% of the patients had developed FOG and/or had become recurrent fallers. The disease development in a group of patients with PD from the presurgery period had a similar trajectory as among the operated patients. In addition, mean annual change of both bradykinesia and PIGD scores was nearly identical in both study groups while tremor and rigidity had a significant better development in the operated patients.

CONCLUSIONS

We found that STN-DBS induces an acute improvement of PIGD symptoms. The following long-term development was however characterized by a marked progression of non-dopaminergic symptoms.

Preserving cortico-striatal function: deep brain stimulation in Huntington's disease

Huntington's disease (HD) is an incurable neurodegenerative disease characterized by the triad of chorea, cognitive dysfunction and psychiatric disturbances. Since the discovery of the HD gene, the pathogenesis has been outlined, but to date a cure has not been found. Disease modifying therapies are needed desperately to improve function, alleviate suffering, and provide hope for symptomatic patients. Deep brain stimulation (DBS), a proven therapy for managing the symptoms of some neurodegenerative movement disorders, including Parkinson's disease, has been reported as a palliative treatment in select cases of HD with debilitating chorea with variable success. New insights into the mechanism of action of DBS suggest it may have the potential to circumvent other manifestations of HD including cognitive deterioration. Furthermore, because DBS is already widely used, reversible, and has a risk profile that is relatively low, new studies can be initiated. In this article we contend that new clinical trials be considered to test the effects of DBS for HD.