Advancements in the Clinical Outcomes of Functional Neurosurgery With Deep Brain Stimulation for Movement Disorders: A Literature Review

This literature review explores recent advancements in deep brain stimulation (DBS) surgery for movement disorders. It highlights notable improvements, including closed-loop stimulation techniques, optogenetics, and improved surgical targeting. Positive clinical outcomes with low complication rates and improved motor symptoms are consistently reported. The review emphasizes the importance of minimizing risks through meticulous surgical practices and discusses potential complications associated with DBS surgery. Future prospects focus on enhancing technology, refining surgical techniques, and conducting further research. Closed-loop stimulation optimizes DBS efficacy by tailoring stimulation parameters to individual patient needs. Optogenetics offers precise modulation of neural activity with light-sensitive proteins, enabling more targeted treatments. Cybersecurity measures are essential due to the integration of wireless and digital technologies in DBS systems. DBS surgery has significantly improved the management of movement disorders with its safety and effectiveness. Ongoing research in closed-loop stimulation, optogenetics, and cybersecurity is expected to further enhance DBS technology and outcomes, benefiting patients with treatment-resistant movement disorders.


Introduction And Background
Deep brain stimulation (DBS) is a well-established and effective treatment option for patients with movement disorders [1][2][3][4]. It involves the implantation of electrodes in specific brain regions to modulate neural activity and alleviate symptoms [5]. Over the years, advancements in surgical techniques and technology have led to improved outcomes and expanded applications of DBS [6]. The safety and efficacy of DBS surgery for movement disorders have been a focus of ongoing research [7]. Closed-loop stimulation techniques have allowed real-time monitoring of neural activity and adjustment of stimulation parameters, optimizing therapeutic outcomes [8]. Additionally, optogenetics, a technique utilizing light to control neural activity, has provided a more targeted approach to DBS by focusing on specific neural circuits involved in movement disorders [9,10]. While DBS has demonstrated positive clinical outcomes, including improvements in motor function, tremor severity, and overall quality of life for patients with movement disorders [3,11], potential complications and their impact on cognitive function in Parkinson's disease require further investigation [5]. Therefore, it is important to carefully assess individual patient considerations before considering DBS as a treatment option [3,4]. Future developments in DBS surgery aim to improve technology, techniques, and research in the field [2,5].

Aim and objectives
This literature review aims to provide a comprehensive overview of the existing evidence on the efficacy, safety, and clinical outcomes of DBS in movement disorders. By analyzing the collective findings of the included studies, this review highlights the progress made in understanding the benefits and potential risks associated with DBS therapy. The outcomes of the literature review emphasize the substantial improvement

Review Results
Based on our analysis, deep brain stimulation (DBS) and functional neurosurgery have consistently shown significant clinical benefits in the treatment of Parkinson's disease, essential tremor, and dystonia [10][11][12][13][14][15][16][17][18]. Several studies have reported improvements in motor function, activities of daily living (ADL), and quality of life (QoL) for Parkinson's disease patients who received DBS compared to those on best medical therapy (BMT) [10][11][12][13]. The long-term efficacy of DBS has been observed in managing specific symptoms of Parkinson's disease, including tremor reduction and sustained motor improvement [14][15][16]. DBS has also been effective in improving tremor severity and ADL in essential tremor patients [17]. Furthermore, DBS has shown promising results in improving dystonia severity and motor function [18]. Although DBS has demonstrated positive outcomes, it is important to consider the reported adverse events associated with the procedure. Commonly reported complications include surgery-related issues, such as infection, hardware problems, and lead migration [19]. While the majority of adverse events were of mild to moderate severity and manageable, addressing these potential risks is crucial. The impact of DBS on cognitive function in Parkinson's disease remains uncertain, with varying results reported in different studies [20]. Some studies have indicated declines in specific cognitive domains while others have not reported significant cognitive decline post-DBS [20]. Further research is needed to gain a comprehensive understanding of the cognitive effects of DBS. Studies focusing on the impact of DBS on quality of life (QoL) in essential tremors consistently show significant improvements [21]. However, it is important to acknowledge the limitations of the included studies, such as variations in sample sizes, follow-up durations, and assessment measures, which may affect the generalizability of the results. Future research should aim to standardize outcome measures and study designs to improve the consistency and comparability of findings. Looking ahead, the field of DBS and functional neurosurgery is expected to advance through technological innovations such as closed-loop stimulation and personalized stimulation parameters [22]. Continued research efforts should focus on optimizing outcomes and minimizing adverse events to enhance the overall effectiveness and safety of these procedures [23,24].

Discussion
This literature review provides a comprehensive analysis of studies examining the efficacy, safety, and clinical outcomes of deep brain stimulation (DBS) in the treatment of movement disorders. The main findings of this literature review are summarized in the tables below.            DBS is a well-established treatment option for patients with Parkinson's disease, essential tremor, and dystonia who are refractory to pharmacological therapies. This systematic review and meta-analysis aimed to evaluate the clinical outcomes and adverse events associated with DBS in these patient populations. A total of 23 studies met the inclusion criteria, encompassing a combined sample size of 3,134 patients who underwent DBS surgery. In Parkinson's disease, Table 1  motor improvement following subthalamic nucleus DBS (sample size = 10) [6]. Moving on to essential tremors, Table 2 summarizes the clinical outcomes of DBS in this patient population. The studies included in this review consistently reported improvements in tremor severity and activities of daily living as measured by the Fahn-Tolosa-Marin Tremor Rating Scale (FTMTRS). Sample sizes ranged from 29 to 76 patients, and follow-up durations varied from one to five years. The results indicate that DBS is an effective treatment option for essential tremors, with improvement rates ranging from 47.5% to 68%. Adverse event rates ranged from 16.7% to 30%, and no serious adverse events were reported across these studies [23]. For dystonia, Table 3 provides a summary of the clinical outcomes of DBS. The studies included in this review demonstrated improvements in dystonia severity, as measured by the Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS), in patients with primary generalized and segmental dystonia, cervical dystonia, and myoclonus-dystonia. Improvement rates ranged from 27.8% to 62% across the studies, with sample sizes ranging from 42 patients. Follow-up durations varied from six months to five years. In general, DBS was found to be an effective treatment option for dystonia, with significant reductions in dystonia severity and improvements in motor function [24]. Moving on to adverse events, Table 4 provides an overview of the reported adverse events associated with DBS across the included studies. The most commonly reported adverse events were related to surgery and device-related complications. These included infection, hardware-related issues, and lead migration. The rates of adverse events varied across the studies, ranging from 8.9% to 75%, with infection being the most frequently reported complication. However, it's worth noting that the severity of adverse events varied, with the majority being mild to moderate and manageable.
In terms of cognitive outcomes, Table 5  This literature review highlights the effectiveness of deep brain stimulation (DBS) as a treatment option for patients with Parkinson's disease, essential tremor, and dystonia. It consistently demonstrates significant improvements in motor function, tremor severity, and quality of life. Although adverse events were reported, the majority were manageable and of mild to moderate severity. The impact of DBS on cognitive function in Parkinson's disease remains uncertain and warrants further investigation. Overall, DBS shows promise as a valuable therapeutic option for these neurological disorders, but careful consideration and individual patient assessment are essential before pursuing this treatment.
Based on our analysis, DBS and functional neurosurgery have consistently shown significant clinical benefits in the treatment of Parkinson's disease, essential tremors, and dystonia [10][11][12][13][14][15][16][17][18]. Several studies have reported improvements in motor function, ADL, and QoL for Parkinson's disease patients who received DBS compared to those on the best medical therapy (BMT) [10][11][12][13]. The long-term efficacy of DBS has been observed in managing specific symptoms of Parkinson's disease, including tremor reduction and sustained motor improvement [14][15][16]. DBS has also been effective in improving tremor severity and ADL in essential tremor patients [17]. Furthermore, DBS has shown promising results in improving dystonia severity and motor function [18]. Although DBS has demonstrated positive outcomes, it is important to consider the reported adverse events associated with the procedure. Complications related to surgery and device-related issues, such as infection, hardware problems, and lead migration, have been commonly reported [19]. While the majority of adverse events were of mild to moderate severity and manageable, it is crucial to address these potential risks. The impact of DBS on cognitive function in Parkinson's disease remains uncertain, with varying results reported in different studies [20]. Some studies have indicated declines in specific cognitive domains, while others have not reported significant cognitive decline post-DBS [20]. Further research is needed to gain a comprehensive understanding of the cognitive effects of DBS. Studies focusing on the impact of DBS on QoL in essential tremors consistently show significant improvements [21]. Different measurement scales, such as the QUEST and the SF-36, have been used to assess QoL in these patients [21]. While the findings support the efficacy of DBS as a valuable treatment option, it is important to acknowledge the limitations of the included studies, such as variations in sample sizes, follow-up durations, and assessment measures, which may affect the generalizability of the results. Future research should aim to standardize outcome measures and study designs to improve the consistency and comparability of findings. Looking ahead, the field of DBS and functional neurosurgery is expected to advance through technological innovations such as closed-loop stimulation and personalized stimulation parameters [22]. Continued research efforts should focus on optimizing outcomes and minimizing adverse events to enhance the overall effectiveness and safety of these procedures [23,24].

Conclusions
The systematic review showed that functional neurosurgery with DBS is an effective treatment for movement disorders. The use of DBS has been on the rise, and it has been shown to be an ever-evolving field with new targets and techniques being developed. The results of this study will help clinicians and researchers understand the progress of functional neurosurgery with DBS outcomes in treating movement disorders. It is important to acknowledge the limitations of the included studies, such as variations in sample sizes, follow-up durations, and assessment measures, which may affect the generalizability of the results. Further research is needed to compare the efficacy of different targets and to identify predictors of response to DBS.

Conflicts of interest:
In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work. played a role in assisting with the literature review and references; Hajar Alharbi: has made substantial contributions to the research by actively participating in the drafting and reviewing of the manuscript. Their feedback and suggestions have been valuable in shaping the content. Hajar has also given their final approval, highlighting their accountability; Abdulaziz Alhuthayli: has made substantial contributions to the research, actively participating in the drafting and reviewing of the manuscript. Their final approval demonstrates their accountability. Abdulaziz has also provided assistance in data interpretation; Zainb M. Al Rebih: has made substantial contributions to the research, actively participating in the drafting and reviewing of the manuscript. Their final approval underscores their accountability. Zainb has also provided assistance in editing and proofreading; Nidaa Alhumaidi: has made substantial contributions to the research by actively participating in the drafting and reviewing of the manuscript. Their data analysis and visualization skills have been instrumental. Nidaa has given their final approval, reflecting their accountability; Wihad Albashrawi: has made substantial contributions to the research, actively participating in the drafting and reviewing of the manuscript. Their support in manuscript formatting has been invaluable. Wihad has provided their final approval, demonstrating their accountability; Razan S. Bazarah: has made substantial contributions to the research, actively participating in the drafting and reviewing of the manuscript. Their assistance in literature search and review has greatly contributed to the quality of the content. Razan has given their final approval, emphasizing their accountability; Anas Alharbi: has made substantial contributions to the research, actively participating in the drafting and reviewing of the manuscript. Their involvement in data collection and analysis has been crucial. Anas has provided their final approval, highlighting their accountability; Ahmed H. Alhejji: has made substantial contributions to the research, actively participating in the drafting and reviewing of the manuscript. Their feedback and suggestions have been valuable. Ahmed has given their final approval, demonstrating their accountability; Hassan A. Aldawood: has made a minor contribution to the research by assisting with data interpretation; Osama AlHumud: has made substantial contributions to the research, actively participating in the drafting and reviewing of the manuscript. Their assistance in editing and proofreading has been instrumental. Osama has provided their final approval, signifying their accountability; Jafar A. Alkathem: has made substantial contributions to the research, actively participating in the drafting and reviewing of the manuscript. Their assistance in literature search and review has been significant. Jafar has given their final approval, demonstrating their accountability; Sami Almalki: has made substantial contributions to the research, actively participating in the drafting and reviewing of the manuscript. They have played a crucial role in supporting manuscript formatting. Furthermore, Sami is the principal investigator of the research, providing overall guidance and leadership. Sami has given their final approval, underscoring their accountability.