The long-term efficacy of STN vs GPi deep brain stimulation for Parkinson disease: A meta-analysis

Cost Effectiveness of Deep Brain Stimulation for Parkinson's Disease: A Systematic Review

BACKGROUND AND OBJECTIVE

Deep brain stimulation (DBS) is an established treatment for Parkinson's disease (PD) in patients with advanced motor symptoms with an inadequate response to pharmacotherapies. Despite its effectiveness, the cost effectiveness of DBS remains a subject of debate. This systematic review aims to update and synthesize evidence on the cost effectiveness of DBS for PD.

METHODS

To identify full economic evaluations that compared the cost effectiveness of DBS with other best medical treatments, a comprehensive search was conducted of the PubMed, Embase, Scopus, and Tufts Cost-Effective Analysis registry databases. The selected papers were systematically reviewed, and the results were summarized. For the quality appraisal, we used the modified economic evaluations bias checklist. The review protocol was a priori registered with PROSPERO, CRD42022345508.

RESULTS

Sixteen identified cost-utility analyses that reported 19 comparisons on the use of DBS for PD were systematically reviewed. The studies were primarily conducted in high-income countries and employed Markov models. The costs considered were direct costs: surgical expenses, calibration, pulse generator replacement, and annual drug expenses. The majority of studies used country-specific thresholds. Fourteen comparisons from 12 studies reported on the cost effectiveness of DBS compared to best medical treatments. Eleven comparisons reported DBS as cost effective based on incremental cost-utility ratio results.

CONCLUSIONS

The cost effectiveness of DBS for PD varies by time horizon, costs considered, threshold utilized, and stage of PD progression. Standardizing approaches and comparing DBS with other treatments are needed for future research on effective PD management.

White matter fiber integrity and structural brain network topology: implications for balance function in postischemic stroke patients

Previous studies have suggested that ischemic stroke can result in white matter fiber injury and modifications in the structural brain network. However, the relationship with balance function scores remains insufficiently explored. Therefore, this study aims to explore the alterations in the microstructural properties of brain white matter and the topological characteristics of the structural brain network in postischemic stroke patients and their potential correlations with balance function. We enrolled 21 postischemic stroke patients and 21 age, sex, and education-matched healthy controls (HC). All participants underwent balance function assessment and brain diffusion tensor imaging. Tract-based spatial statistics (TBSS) were used to compare the fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity of white matter fibers between the two groups. The white matter structural brain network was constructed based on the automated anatomical labeling atlas, and we conducted a graph theory-based analysis of its topological properties, including global network properties and local node properties. Additionally, the correlation between the significant structural differences and balance function score was analyzed. The TBSS results showed that in comparison to the HC, postischemic stroke patients exhibited extensive damage to their whole-brain white matter fiber tracts (P < 0.05). Graph theory analysis showed that in comparison to the HC, postischemic stroke patients exhibited statistically significant reductions in the values of global efficiency, local efficiency, and clustering coefficient, as well as an increase in characteristic path length (P < 0.05). In addition, the degree centrality and nodal efficiency of some nodes in postischemic stroke patients were significantly reduced (P < 0.05). The white matter fibers of the entire brain in postischemic stroke patients are extensively damaged, and the topological properties of the structural brain network are altered, which are closely related to balance function. This study is helpful in further understanding the neural mechanism of balance function after ischemic stroke from the white matter fiber and structural brain network topological properties.

Deep Brain Stimulation for the Management of Refractory Neurological Disorders: A Comprehensive Review

In recent decades, deep brain stimulation (DBS) has been extensively studied due to its reversibility and significantly fewer side effects. DBS is mainly a symptomatic therapy, but the stimulation of subcortical areas by DBS is believed to affect the cytoarchitecture of the brain, leading to adaptability and neurogenesis. The neurological disorders most commonly studied with DBS were Parkinson's disease, essential tremor, obsessive-compulsive disorder, and major depressive disorder. The most precise approach to evaluating the location of the leads still relies on the stimulus-induced side effects reported by the patients. Moreover, the adequate voltage and DBS current field could correlate with the patient's symptoms. Implantable pulse generators are the main parts of the DBS, and their main characteristics, such as rechargeable capability, magnetic resonance imaging (MRI) safety, and device size, should always be discussed with patients. The safety of MRI will depend on several parameters: the part of the body where the device is implanted, the part of the body scanned, and the MRI-tesla magnetic field. It is worth mentioning that drug-resistant individuals may have different pathophysiological explanations for their resistance to medications, which could affect the efficacy of DBS therapy. Therefore, this could explain the significant difference in the outcomes of studies with DBS in individuals with drug-resistant neurological conditions.

Voice-Related Outcomes in Deep Brain Stimulation in Patients with Vocal Tremor: A Systematic Review and Meta-Analysis

OBJECTIVES

The effectiveness of deep brain stimulation (DBS) in treating vocal tremors is currently a subject of debate. To assess the efficacy of DBS therapy in adults with vocal tremors (VT), we analyzed its impact on voice tremor severity, voice-related quality of life, fundamental frequency, voice intensity, and emotional state.

METHODS

We conducted a systematic review with meta-analysis to investigate the impact of DBS therapy on voice tremor severity, voice-related quality of life, fundamental frequency, voice intensity, and emotional state in adults with vocal tremors (PROSPERO/CRD42023420272). The PubMed, Embase, Cochrane Library, Cochrane Central Register of Controlled Trials databases were searched up to September 20, 2022. Primary outcome measures included voice tremor severity and voice-related quality of life (V-RQOL), while fundamental frequency (F0) and voice intensity, along with emotional state, were selected as secondary outcome indicators. We employed the Cochrane Collaboration's tool for assessing bias risk in randomized trials. Meta-analysis (standardized difference of means and weighted mean differences) and heterogeneity analysis (I2) were performed.

RESULTS

Our search identified 1186 studies, of which nine studies involving 61 patients met the inclusion criteria. The severity of voice tremor (SMD = -1.08; 95% CI: -1.80 to 0.35; P = 0.02) and V-RQOL (SMD = -1.39; 95% CI: -2.68 to -0.09; P = 0.04) in patients with vocal tremor significantly improved after DBS "on". Subgroup analyses revealed that the stimulation site may contribute to high heterogeneity. Specifically, Vim DBS showed significant improvement in voice tremor severity (SMD = -0.97; 95% CI: -1.84 to -0.09; I2 = 51.01%), while STN DBS did not demonstrate a clear benefit in addressing vocal tremor. There was no significant difference between DBS "on" and DBS "off" in terms of F0, voice intensity, or emotional status.

CONCLUSION

DBS therapy is effective in enhancing voice quality and voice-related quality of life in patients with vocal tremors. Notably, Vim DBS demonstrates a significant improvement in voice tremor severity, particularly in VT patients with ET and SD.

Stereotactic Staged Asymmetric Bilateral Radiofrequency Lesioning for Parkinson's Disease

INTRODUCTION

Parkinson's disease (PD) is one of the most common neurodegenerative progressive disorders. Despite the dominance of neurostimulation technology, stereotactic lesioning operations play a significant role in the treatment of PD. The aim of the study was to evaluate the effectiveness and safety of staged bilateral asymmetric radiofrequency (RF) stereotactic lesioning in a highly selected group of PD patients.

MATERIAL AND METHODS

A retrospective review of 418 consecutive patients undergoing stereotactic ablation for advanced PD at our institution revealed 28 patients who underwent staged asymmetric bilateral ablation. In this subset, after initial RF thalamotomy, contralateral pallidotomy was performed in 16 (57.1%) patients (group Vim-GPi), and contralateral lesion of the subthalamic nucleus (STN) was performed in 12 (32.9%) patients (group Vim-STN). The mean duration of disease before the first surgery was 9.9 ± 0.8 years. The mean interval between the two operations was 3.5 ± 0.4 years (range, 1-10 years); in the Vim-GPi group, it was 3.1 ± 0.4 years; and in the Vim-STN group, it was 4.3 ± 0.1 years. After the second operation, the long-term follow-up lasted from 1 to 8 years (mean 4.8 ± 0.5 years). All patients were evaluated 1 year after the second operation.

RESULTS

One year after staged bilateral lesioning, the mean tremor score improved from baseline, prior to the first operation, from 19.8 to 3.8 (improvement of 81%), the overall mean rigidity score improved from 11.0 to 3.7 (improvement of 66%), and hypokinesia improved from 14.8 to 8.9 (improvement of 40%). One year after staged bilateral lesioning, the total UPDRS score improved in the Vim-GPi group by 47% in the OFF and 45.9% in the ON states. In the Vim-STN group, the total UPDRS score improved from baseline, prior to the first operation, by 44.8% in the OFF and 51.6% in the ON states. Overall, levodopa dose was reduced by 43.4%. Neurological complications were observed in 4 (14.3%) cases; among them, 1 (3.6%) patient had permanent events related to local ischemia after pallidotomy.

CONCLUSION

Staged asymmetric bilateral stereotactic RF lesioning can be a safe and effective method in highly selected patients with advanced PD, particularly where deep brain stimulation is not available or desirable. Careful identification and selection of patients for ablative surgery allow achieving optimal results in the treatment of PD with bilateral symptoms.

The Effects of Deep Brain Stimulation on Mood and Quality of Life in Parkinson's Disease: A Systematic Review and Meta-Analysis

Deep brain stimulation (DBS) is extensively used to treat motor and non-motor symptoms in Parkinson's disease (PD). The aim of this study was to investigate the difference between subthalamic (STN) and globus pallidus internus (GPi) DBS on mood and quality of life with reference to minimal clinically important differences (MCID). A systematic literature search for articles published until November 2022 yielded 14 studies meeting the eligibility criteria, with a total of 1,088 patients undergoing STN (n=571) or GPi (n=517) stimulation. Baseline patient and clinical characteristics were comparable between the two groups. Results showed that GPi stimulation demonstrated a greater reduction in the Beck depression inventory (mean difference (MD)=1.68) than STN stimulation (MD=0.84). Hospital anxiety and depression scale showed a 2.69- and 3.48-point decrease by the GPi group in the depression and anxiety categories, respectively. The summary index (SI) of the PD questionnaire depicted a greater improvement in the GPi group from baseline (mean=41.01, 95% CI 34.89, 47.13) to follow-up (mean=30.85, 95% CI 22.08, 39.63) when compared to the STN group (baseline mean=42.43, 95% CI 34.50, 50.37; follow-up mean=34.21, 95% CI 25.43, 42.99). The emotions category also demonstrated a similar trend. However, STN stimulation showed greater reductions in motor symptoms and medication than GPi stimulation. This meta-analysis demonstrated that GPi stimulation seems to offer an advantage over STN stimulation in improving mood and quality of life in PD, but those effects must be further validated by larger studies.

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 motor outcomes of deep brain stimulation of the globus pallidus interna in Parkinson's disease patients: Five-year follow-up

BACKGROUND

Deep brain stimulation (DBS) of globus pallidus interna (GPi) is an established treatment for advanced Parkinson's disease (PD). However, in contrast to subthalamic nucleus (STN)-DBS, long-term outcomes of GPi-DBS have rarely been studied.

OBJECTIVE

We investigated the long-term motor outcomes in PD patients at 5 years after GPi-DBS.

METHODS

We retrospectively analyzed the clinical data for PD patients who underwent GPi-DBS. Longitudinal changes of UPDRS scores from baseline to 5 years after surgery were assessed.

RESULTS

Forty PD patients with a mean age of 59.5 ± 7.9 years at DBS surgery (mean duration of PD: 11.4 ± 3.4 years) were included at baseline and 25 patients were included in 5-year evaluation after DBS. Compared to baseline, sub-scores for tremor, levodopa-induced dyskinesia (LID), and motor fluctuation indicated improved states up to 5 years after surgery (p < 0.001). However, UPDRS Part 3 total score and sub-score for postural instability and gait disturbance (PIGD) gradually worsened over time until 5 years after surgery (p > 0.017 after Bonferroni correction). In a logistic regression model, only preoperative levodopa response was associated with the long-term benefits on UPDRS Part 3 total score and PIGD sub-score (OR = 1.20; 95% CI = 1.04-1.39; p = 0.015 and OR = 4.99; 95% CI = 1.39-17.89; p = 0.014, respectively).

CONCLUSIONS

GPi-DBS provides long-term beneficial effects against tremor, motor fluctuation and LID, but PIGD symptoms gradually worsen. This selective long-term benefit has implications for the optimal application of DBS in PD patients.

Effects of deep brain stimulation target on the activation and suppression of action impulses

OBJECTIVE

Deep brain stimulation (DBS) is an effective treatment to improve motor symptoms in Parkinson's disease (PD). The Globus Pallidus (GPi) and the Subthalamic Nucleus (STN) are the most targeted brain regions for stimulation and produce similar improvements in PD motor symptoms. However, our understanding of stimulation effects across targets on inhibitory action control processes is limited. We compared the effects of STN (n = 20) and GPi (n = 13) DBS on inhibitory control in PD patients.

METHODS

We recruited PD patients undergoing DBS at the Vanderbilt Movement Disorders Clinic and measured their performance on an inhibitory action control task (Simon task) before surgery (optimally treated medication state) and after surgery in their optimally treated state (medication plus their DBS device turned on).

RESULTS

DBS to both STN and GPi targets induced an increase in fast impulsive errors while simultaneously producing more proficient reactive suppression of interference from action impulses.

CONCLUSIONS

Stimulation in GPi produced similar effects as STN DBS, indicating that stimulation to either target increases the initial susceptibility to act on strong action impulses while concomitantly improving the ability to suppress ongoing interference from activated impulses.

SIGNIFICANCE

Action impulse control processes are similarly impacted by stimulating dissociable nodes in frontal-basal ganglia circuitry.

Deep Brain Stimulation in the Treatment of Parkinson’s Disease

Parkinson’s disease (PD) is a common progressive neurodegenerative movement disorder. The cardinal feature of Parkinson's is neuronal degeneration causing a dopamine deficit in the brain which leads to a host of clinical features in the patient. However, consensus over specific clinical criteria for diagnosis remains to be established. Parkinson’s does not have a cure yet, but a variety of diagnostic and treatment protocols have been developed over the years with a primary focus on pharmacological therapy. Anti-parkinsonian drugs such as levodopa lose their efficacy over time and are needed in higher doses as the disease inevitably progresses. An alternative to pharmacological therapy is deep brain stimulation (DBS). Deep brain stimulation involves transcranial placement of unilateral or bilateral leads (wires) most commonly in the sub-thalamic nucleus or the globus pallidus interna of the brain by stereotactic surgery. Given the multiple hypotheses explaining the different effects of DBS with sometimes conflicting mechanisms, it is difficult to pinpoint the exact way in which DBS operates. Nevertheless, it has proven to be significantly effective. DBS, although being a cost-effective treatment measure for Parkinson's patients, is not without limitations. A careful selection of patients is required preoperatively that determines the response and tolerance to the therapy in patients. This review aims to summarize the current literature on DBS in Parkinson's with a focus on the hypothesized mechanisms, selection criteria, advantages and its limitations.

Quality of life of patients with Parkinson's disease: a comparison between preoperative and postoperative states among those who were treated with deep brain stimulation

BACKGROUND

Deep brain stimulation (DBS) is a well-established procedure for treating Parkinson's disease (PD). Although its mechanisms of action are still unclear, improvements in motor symptoms and reductions in medication side effects can be achieved for a significant proportion of patients, with consequent enhancement of quality of life.

OBJECTIVE

To investigate the impact of DBS on the quality of life of PD patients.

METHODS

This was a retrospective longitudinal study with collection of historical data in a neurosurgery center, from June 2019 to December 2020. The sample was obtained according to convenience, and the Parkinson's Disease Questionnaire (PDQ-39), Unified Parkinson's Disease Rating Scale (UPDRS) III and IV, Trail-Making Test and Verbal Fluency Test were used.

RESULTS

Data were collected from 17 patients (13 with subthalamic nucleus DBS and 4 with globus pallidus pars interna DBS). Significant improvement (p=0.008) on the UPDRS III was observed in comparing the preoperative without DBS with the postoperative with DBS. About 47.0% of the patients showed post-surgical improvement in QoL (p=0.29). Thirteen patients were able to complete part A of the Trail-Making Test and four of these also completed part B. Almost 60% of the patients scored sufficiently on the semantic test, whereas only 11.8% scored sufficiently on the orthographic evaluation. No association between implant site and test performance could be traced.

CONCLUSIONS

Improvements in quality of life and motor function were observed in the majority of the patients enrolled. Despite the limitations of this study, DBS strongly benefits a significant proportion of PD patients when well indicated.

Voice handicap Index in Parkinson's patients: Subthalamic versus globus pallidus deep brain stimulation

PURPOSE

Subthalamic nucleus (STN) and globus pallidus interna (GPI) are the two most common sites for deep brain stimulation (DBS) in people with Parkinson's disease (PWP). Voice impairments are a common symptom of Parkinson's disease and information about voice outcomes with DBS is limited. Most studies in speech-language pathology have focused on STN-DBS and few have examined the effects of GPI-DBS. This was an initial effort to examine the impact of DBS location on Vocal Handicap Index (VHI) scores, which assess the impact of a voice disorder on an individual.

METHOD

Twenty-four gender-matched PWP (12 STN-DBS and 12 GPI-DBS) completed the VHI post-DBS implantation. Two-tailed independent samples t-tests were used to compare each VHI scale score (physical, functional, emotional, total) and patient factors between the two groups.

RESULTS

No significant differences in total or subscale VHI scores were identified between the two DBS groups. A trend toward greater impairment in PWP with GPI-DBS was noted. An association between higher VHI scores and DBS settings was found.

CONCLUSIONS

Studies directly comparing speech outcomes for different DBS targets are lacking. The current findings provide new insights concerning voice outcomes following DBS by adding to the limited literature directly comparing speech outcomes in multiple DBS targets. Limitations and directions for future research are discussed.

Deep brain stimulation for parkinson's disease induces spontaneous cortical hypersynchrony in extended motor and cognitive networks

The mechanism of action of deep brain stimulation (DBS) to the basal ganglia for Parkinson's disease remains unclear. Studies have shown that DBS decreases pathological beta hypersynchrony between the basal ganglia and motor cortex. However, little is known about DBS's effects on long range corticocortical synchronization. Here, we use machine learning combined with graph theory to compare resting-state cortical connectivity between the off and on-stimulation states and to healthy controls. We found that turning DBS on increased high beta and gamma band synchrony (26 to 50 Hz) in a cortical circuit spanning the motor, occipitoparietal, middle temporal, and prefrontal cortices. The synchrony in this network was greater in DBS on relative to both DBS off and controls, with no significant difference between DBS off and controls. Turning DBS on also increased network efficiency and strength and subnetwork modularity relative to both DBS off and controls in the beta and gamma band. Thus, unlike DBS's subcortical normalization of pathological basal ganglia activity, it introduces greater synchrony relative to healthy controls in cortical circuitry that includes both motor and non-motor systems. This increased high beta/gamma synchronization may reflect compensatory mechanisms related to DBS's clinical benefits, as well as undesirable non-motor side effects.

Adaptive deep brain stimulation: Retuning Parkinson's disease

A brain-machine interface represents a promising therapeutic avenue for the treatment of many neurologic conditions. Deep brain stimulation (DBS) is an invasive, neuro-modulatory tool that can improve different neurologic disorders by delivering electric stimulation to selected brain areas. DBS is particularly successful in advanced Parkinson's disease (PD), where it allows sustained improvement of motor symptoms. However, this approach is still poorly standardized, with variable clinical outcomes. To achieve an optimal therapeutic effect, novel adaptive DBS (aDBS) systems are being developed. These devices operate by adapting stimulation parameters in response to an input signal that can represent symptoms, motor activity, or other behavioral features. Emerging evidence suggests greater efficacy with fewer adverse effects during aDBS compared with conventional DBS. We address this topic by discussing the basics principles of aDBS, reviewing current evidence, and tackling the many challenges posed by aDBS for PD.

Brain stimulation: a therapeutic approach for the treatment of neurological disorders

Brain stimulation has become one of the most acceptable therapeutic approaches in recent years and a powerful tool in the remedy against neurological diseases. Brain stimulation is achieved through the application of electric currents using non-invasive as well as invasive techniques. Recent technological advancements have evolved into the development of precise devices with capacity to produce well-controlled and effective brain stimulation. Currently, most used non-invasive techniques are repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS), whereas the most common invasive technique is deep brain stimulation (DBS). In last decade, application of these brain stimulation techniques has not only exploded but also expanded to wide variety of neurological disorders. Therefore, in the current review, we will provide an overview of the potential of both non-invasive (rTMS and tDCS) and invasive (DBS) brain stimulation techniques in the treatment of such brain diseases.

Approach to Tremor Disorders

Tremor disorders are diverse and complex. Historical clues and examination features play a major role in diagnosing these disorders, but diagnosis can be challenging due to phenotypic overlap. Ancillary testing, such as neuroimaging or laboratory testing, is driven by the history and examination, and should be performed particularly when there are other neurological or systemic manifestations. The pathophysiology of tremor is not entirely understood, but likely involves multiple networks along with the cerebello-thalamo-cortical pathways. Treatment options include medications, botulinum toxin, surgery, and nonpharmacologic interventions utilizing physical and occupational therapies and assistive devices. Further work is needed in developing accurate diagnostic tests and better treatment options for tremor disorders.

Brain MRI-guided focused ultrasound conceptualised as a tool for brain network intervention

Magnetic resonance imaging guided high intensity focused ultrasound (HIFU) has emerged as a tool offering incisionless intervention on brain tissue. The low risk and rapid recovery from this procedure, in addition to the ability to assess for clinical benefit and adverse events intraprocedurally, makes it an ideal tool for intervention upon brain networks both for clinical and research applications. This review article proposes that conceptualising brain focused ultrasound as a tool for brain network intervention and adoption of methodology to complement this approach may result in better clinical outcomes, fewer adverse events and may unveil or allow treatment opportunities not otherwise possible. A brief introduction to network neuroscience is discussed before a description of pathological brain networks is provided for a number of conditions for which MRI-guided brain HIFU intervention has been implemented. Essential Tremor is discussed as the most advanced example of MRI-guided brain HIFU intervention adoption along with the issues that present with this treatment modality compared to alternatives. The brain network intervention paradigm is proposed to overcome these issues and a number of examples of implementation of this are discussed. The ability of low intensity MRI guided focussed ultrasound to neuromoduate brain tissue without lesioning is introduced. This tool is discussed with regards to its potential clinical application as well as its potential to further our understanding of network neuroscience via its ability to interrogate brain networks without damaging tissue. Finally, a number of current clinical trials utilising brain focused ultrasound are discussed, along with the additional applications available from the utilisation of low intensity focused ultrasound.

Fundamentals of Neuromodulation and Pathophysiology of Neural Networks in Health and Disease

Neuromodulation involves altering neuronal circuitry and subsequent physiological changes with the aim to ameliorate neurological symptoms. Over the years several techniques have been used to obtain neuromodulatory effects for treatment of conditions including Parkinson disease, essential tremor, dystonia or seizures. We provide brief description of the various therapeutics that have been used and mechanisms involved in pathophysiology of these disorders as well as the therapeutic mechanisms of the treatment modalities.

Effects of bilateral subthalamic nucleus deep brain stimulation on motor symptoms in Parkinson's disease: a retrospective cohort study

Deep brain stimulation of the bilateral subthalamic nucleus (STN) is a therapeutic option for patients with Parkinson's disease (PD) in whom medical therapies have been ineffective. This retrospective cohort study analyzed the motor function of 27 patients with advanced PD, from the First Affiliated Hospital of Guangzhou Medical University, China, who received deep brain stimulation of the bilateral subthalamic nucleus and evaluated its therapeutic effects. The 10-year follow-up data of patients was analyzed in Qingyuan People's Hospital, Sixth Affiliated Hospital of Guangzhou Medical University, China. The follow-up data were divided into two categories based on patients during levodopa treatment (on-medication) and without levodopa treatment (off-medication). Compared with baseline, the motor function of on-medication PD patients improved after deep brain stimulation of the bilateral subthalamic nucleus. Even 2 years later, the motor function of off-medication PD patients had improved. On-medication PD patients exhibited better therapeutic effects over the 5 years than off-medication PD patients. On-medication patients' akinesia, speech, postural stability, gait, and cognitive function worsened only after 5 years. These results suggest that the motor function of patients with advanced PD benefitted from treatment with deep brain stimulation of the bilateral subthalamic nucleus over a period up to 5 years. The overall therapeutic effects were more pronounced when levodopa treatment was combined with deep brain stimulation of the bilateral subthalamic nucleus. This study was approved by Institutional Review Board of Qingyuan People's Hospital, The Sixth Affiliated Hospital of Guangzhou Medical University, China (approval No. QPH-IRB-A0140) on January 11, 2018.

The Impact of Deep Brain Stimulation on the Sexual Function of Patients With Parkinson's Disease

BACKGROUND

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is used in the treatment of advanced Parkinson's disease (PD) with well-established benefits over motor complications. However, few studies addressing the impact of DBS on nonmotor dimensions such as sexual function have been conducted. This study aims to determine the effect of DBS-STN on the sexual activity of patients with PD and to establish predictive factors for sexual function decline after surgery.

MATERIALS AND METHODS

Twenty-one patients with PD submitted to DBS-STN were compared with 19 eligible surgery candidates. Clinical measures included disease progression (Hoehn and Yahr scale), sexual function evaluation (Female Sexual Function Index and International Index of Erectile Function), severity of depressive symptoms (Beck Depressive Inventory-II), motor symptoms (Movement Disorders Society-Unified Parkinson's Disease Rating Scale Part III), and quality of life (39-item Parkinson's Disease Questionnaire). The primary outcomes were the development of sexual dysfunction in women and erectile dysfunction in men. Regression analysis was performed to outline risk factors for developing sexual function deterioration.

RESULTS

Erectile dysfunction was present in 83.3% of men and sexual dysfunction in 77.8% of women treated with DBS-STN. Women with sexual dysfunction had higher emotional well-being 39-item Parkinson's Disease Questionnaire scores (P=0.017) and a higher prevalence of cardiovascular diseases (P=0.012) comparing with women without sexual dysfunction. Age was an independent predictive factor for developing erectile dysfunction in men (relative risk=1.26; P=0.033) and sexual dysfunction in women (relative risk =1.30; P=0.039), regardless of DBS-STN submission.

CONCLUSIONS

Sexual function in both sexes of patients with PD does not seem to be influenced by DBS-STN itself, but by psychological and clinical features.

Comparison of Subthalamic Nucleus and Globus Pallidus Internus Deep Brain Stimulation Surgery on Parkinson Disease-Related Pain

OBJECTIVE

To analyze and compare the effects of subthalamic nucleus (STN) deep brain stimulation (DBS) and globus pallidus internus (GPi)-DBS on Parkinson disease (PD)-related pain.

METHODS

A retrospective study was performed of 64 patients (28 who underwent GPi-DBS and 36 who underwent STN-DBS) with PD-related pain in our hospital between January 2017 and July 2019. A numerical rating scale (NRS) was used to evaluate the degree of pain preoperatively and 4 months after operation, and the unified PD scale III (UPDRS-III) was completed simultaneously to assess motor symptoms.

RESULTS

The average NRS score of all 64 patients after surgery was 1.09 ± 1.39, which was significantly lower than that before operation (4.44 ± 1.67; P < 0.0001). The improvement rate of NRS was 75 ± 27% in the 28 GPi-DBS patients and 79 ± 27% in the 36 STN-DBS patients, with no significant difference (P = 0.577). The improvements in NRS and UPDRS-III were significantly correlated in the STN-DBS group (r = 0.3707, P = 0.026) but not significantly correlated in the GPi-DBS group (P = 0.516).

CONCLUSIONS

Both GPi-DBS and STN-DBS were effective for analyzing PD-related pain and seemed to have similar efficacy. This study provides an important first-step toward determining different DBS targets for controlling PD-related pain. Follow-up prospective research is an appropriate next step on the path to multicenter clinical trials.

Neurofeedback: Principles, appraisal, and outstanding issues

Neurofeedback is a form of brain training in which subjects are fed back information about some measure of their brain activity which they are instructed to modify in a way thought to be functionally advantageous. Over the last 20 years, neurofeedback has been used to treat various neurological and psychiatric conditions, and to improve cognitive function in various contexts. However, in spite of a growing popularity, neurofeedback protocols typically make (often covert) assumptions on what aspects of brain activity to target, where in the brain to act and how, which have far-reaching implications for the assessment of its potential and efficacy. Here we critically examine some conceptual and methodological issues associated with the way neurofeedback's general objectives and neural targets are defined. The neural mechanisms through which neurofeedback may act at various spatial and temporal scales, and the way its efficacy is appraised are reviewed, and the extent to which neurofeedback may be used to control functional brain activity discussed. Finally, it is proposed that gauging neurofeedback's potential, as well as assessing and improving its efficacy will require better understanding of various fundamental aspects of brain dynamics and a more precise definition of functional brain activity and brain-behaviour relationships.