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.

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.

Development of Clinical Milestones in Parkinson's Disease After Bilateral Subthalamic Deep Brain Stimulation.

OBJECTIVE: Deep brain stimulation of the subthalamic nucleus (STN-DBS) in Parkinson's disease (PD) patients does not halt disease progression, as these patients will progress and develop disabling non-levodopa responsive symptoms. These features may act as milestones that represent the overall functionality of patients after DBS. The objective of this study was to investigate the development of clinical milestones in advanced PD patients who underwent bilateral STN-DBS. METHODS: The study evaluated PD patients who underwent STN-DBS at baseline up to their last follow-up using the Unified Parkinson's Disease Rating Scale and Hoehn and Yahr scale. The symptoms of hallucinations, dysarthria, dysphagia, frequent falls, difficulty walking, cognitive impairment and the loss of autonomy were chosen as the clinical milestones. RESULTS: A total of 106 patients with a mean age of 47.21 ± 10.52 years at disease onset, a mean age of 58.72 ± 8.74 years at surgery and a mean disease duration of 11.51 ± 4.4 years before surgery were included. Initial improvement of motor symptoms was seen after the surgery with the appearance of clinical milestones over time. Using the moderately disabling criteria, 81 patients (76.41%) developed at least one clinical milestone, while 48 patients (45.28%) developed a milestone when using the severely disabling criteria. CONCLUSION: STN-DBS has a limited effect on axial and nonmotor symptoms of the PD patients, in contrast to the effect on motor symptoms. These symptoms may serve as clinical milestones that can convey the status of PD patients and its impact on the patients and their caregivers. Therefore, advanced PD patients, even those treated with bilateral STN-DBS, will still require assistance and cannot live independently in the long run.

High preoperative gait variability is a prognostic predictor of gait and balance in Parkinson disease patients with deep brain stimulation.

INTRODUCTION: The objective biomarker for prediction of gait and balance in the long-term follow-up of Parkinson's disease(PD) patients with subthalamic nucleus deep brain stimulation(STN-DBS) has not yet been elucidated. We investigated the value of pre-operative quantitative gait parameters for the prediction of long-term prognosis of gait in PD patients with DBS. METHODS: We retrospectively collected gait videos(both medication ON/OFF states) of PD patients recorded as preoperative evaluation before STN DBS. We enrolled patients who were followed-up for more than 5 years after the surgery from 2006 to 2014. We derived objective gait parameters from video-based gait analysis algorithm. We defined the clinical milestones of frequent falling, impaired walking, and loss of autonomy based on the Unified Parkinson's disease rating scale and Hoehn and Yahr stage, which were regularly followed up to 156 months after surgery. We calculated hazard ratios(HRs) of baseline gait parameters for predicting the clinical milestones. RESULTS: A total of 96 gait videos from 63 PD patients were analyzed. The mean follow-up duration(standard deviation) was 88.0(34.2) months after surgery. Relatively high (>mean + 1 standard deviation) variability for step length, step time and stride time (HR = 2.92[1.02-8.33], 3.91[1.38-11.11] and 7.16[2.09-24.52],respectively) in medication-ON state significantly predicted reaching any of the three clinical milestones of frequent falling, impaired walking and loss of autonomy. Gait parameters from the medication-OFF state did not predict any clinical milestone. CONCLUSIONS: High preoperative gait variability from the medication-ON state predicts long-term outcomes for gait and balance in PD patients with STN DBS.

Serum Inflammatory Markers and Progression of Nonmotor Symptoms in Early Parkinson's Disease.

BACKGROUND: The influence of peripheral inflammation on nonmotor symptoms (NMSs) in Parkinson's disease (PD) remains unclear. OBJECTIVE: The aim of this study was to explore whether serum inflammatory marker profiles are associated with the progression of NMSs in early PD. METHODS: We included 45 patients with early PD and 20 healthy control subjects. Six inflammatory markers, including interleukin (IL)-1ß, IL-2, IL-6, IL-10, tumor necrosis factor-α, and high-sensitivity C-reactive protein, were measured. NMSs were assessed using the Non-Motor Symptoms Scale, Montreal Cognitive Assessment, and Composite Autonomic Symptom Score-31 at baseline and after 3 years. RESULTS: Principal component (PC) analysis showed that only PC3 scores, mainly loaded by IL-2 and IL-6, were significantly elevated in the PD group compared with the control group. Higher PC3 scores in the PD group were associated with faster progression of Non-Motor Symptoms Scale total and mood/apathy domain scores. There were no significant associations of PC scores with Montreal Cognitive Assessment and Composite Autonomic Symptom Score-31 score changes. CONCLUSIONS: Peripheral inflammation may be related to the evolution of NMSs, particularly mood symptoms, in the early stages of PD. © 2022 International Parkinson and Movement Disorder Society.

The mortality of patients with Parkinson's disease with deep brain stimulation.

Background: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is effective in improving motor function in patients with Parkinson's disease (PD). This study aimed to investigate mortality associated with bilateral STN DBS in patients with PD and to assess the factors associated with mortality and causes of death after DBS. Methods: We reviewed the medical records of 257 patients with PD who underwent bilateral STN DBS at the Movement Disorder Center at Seoul National University Hospital between March 2005 and November 2018. Patients were evaluated preoperatively, at 3, 6, and 12 months after surgery and annually thereafter. The cause and date of death were obtained from interviews with caregivers or from medical certificates at the last follow-up. Results: Of the 257 patients with PD, 48 patients (18.7%) died, with a median time of death of 11.2 years after surgery. Pneumonia was the most common cause of death. Older age of disease onset, preoperative falling score while on medication, and higher preoperative total levodopa equivalent daily dose were associated with a higher risk of mortality in time-dependent Cox regression analysis. Conclusion: These results confirm the mortality outcome of STN DBS in patients with advanced PD.

Arching deep brain stimulation in dystonia types.

Although medical treatment including botulinum toxic injection is the first-line treatment for dystonia, response is insufficient in many patients. In these patients, deep brain stimulation (DBS) can provide significant clinical improvement. Mounting evidence indicates that DBS is an effective and safe treatment for dystonia, especially for idiopathic and inherited isolated generalized/segmental dystonia, including DYT-TOR1A. Other inherited dystonia and acquired dystonia also respond to DBS to varying degrees. For Meige syndrome (craniofacial dystonia), other focal dystonia, and some rare inherited dystonia, further evidences are still needed to evaluate the role of DBS. Because short disease duration at DBS surgery and absence of fixed musculoskeletal deformity are associated with better outcome, DBS should be considered as early as possible when indicated after careful evaluation including genetic work-up. This review will focus on the factors to be considered in DBS for patients with dystonia and the outcome of DBS in the different types of dystonia.

Clinical outcome prediction from analysis of microelectrode recordings using deep learning in subthalamic deep brain stimulation for Parkinson`s disease.

BACKGROUND: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an effective treatment for improving the motor symptoms of advanced Parkinson's disease (PD). Accurate positioning of the stimulation electrodes is necessary for better clinical outcomes. OBJECTIVE: We applied deep learning techniques to microelectrode recording (MER) signals to better predict motor function improvement, represented by the UPDRS part III scores, after bilateral STN DBS in patients with advanced PD. If we find the optimal stimulation point with MER by deep learning, we can improve the clinical outcome of STN DBS even under restrictions such as general anesthesia or non-cooperation of the patients. METHODS: In total, 696 4-second left-side MER segments from 34 patients with advanced PD who underwent bilateral STN DBS surgery under general anesthesia were included. We transformed the original signal into three wavelets of 1-50 Hz, 50-500 Hz, and 500-5,000 Hz. The wavelet-transformed MER was used for input data of the deep learning. The patients were divided into two groups, good response and moderate response groups, according to DBS on to off ratio of UPDRS part III score for the off-medication state, 6 months postoperatively. The ratio were used for output data in deep learning. The Visual Geometry Group (VGG)-16 model with a multitask learning algorithm was used to estimate the bilateral effect of DBS. Different ratios of the loss function in the task-specific layer were applied considering that DBS affects both sides differently. RESULTS: When we divided the MER signals according to the frequency, the maximal accuracy was higher in the 50-500 Hz group than in the 1-50 Hz and 500-5,000 Hz groups. In addition, when the multitask learning method was applied, the stability of the model was improved in comparison with single task learning. The maximal accuracy (80.21%) occurred when the right-to-left loss ratio was 5:1 or 6:1. The area under the curve (AUC) was 0.88 in the receiver operating characteristic (ROC) curve. CONCLUSION: Clinical improvements in PD patients who underwent bilateral STN DBS could be predicted based on a multitask deep learning-based MER analysis.

Bilateral subthalamic nucleus deep brain stimulation is an effective treatment for diphasic dyskinesia.

BACKGROUND AND PURPOSE: The purpose was to assess the effect of bilateral subthalamic nucleus deep brain stimulation (STN DBS) on diphasic dyskinesia in patients with Parkinson disease (PD) and to assess the factors associated with the remission of diphasic dyskinesia. METHODS: Medical records for PD patients who underwent bilateral STN DBS at the Movement Disorder Center of Seoul National University Hospital from March 2005 to November 2016 were reviewed. Patients were evaluated preoperatively and at 3, 6 and 12 months after surgery, and annually thereafter. The presence of peak-dose dyskinesia and diphasic dyskinesia is based on the interview and examination of patients at baseline and at each follow-up. RESULTS: Amongst 202 patients who underwent STN DBS, 66 patients who had diphasic dyskinesia preoperatively were included in the analysis. Diphasic dyskinesia disappeared in 49 (74%) after surgery. In 27 (55.1%) patients whose diphasic dyskinesia disappeared after DBS, peak-dose and diphasic dyskinesia disappeared persistently from as early as 3 months postoperatively. Age at onset was younger and disease duration at surgery was longer in patients whose diphasic dyskinesia persisted compared with patients whose diphasic dyskinesia disappeared. Multivariate Cox regression analysis demonstrated that patients with greater postoperative decrease of dopaminergic medications were more likely to have remission of diphasic dyskinesia. CONCLUSION: This study showed that bilateral STN DBS is effective in controlling diphasic dyskinesia and should be considered in PD patients with diphasic dyskinesia.

Negative α-synuclein pathology in the submandibular gland of patients carrying PRKN pathogenic variants.

INTRODUCTION: Alpha-synuclein (AS) pathology in the peripheral nervous tissue is a potential pathological biomarker in Parkinson disease (PD). Several studies reported the excellent specificity of the AS pathology of the submandibular gland (SMG) biopsy in PD. PRKN pathogenic variant is one of the major genetic causes of young-onset PD without Lewy pathology in the brain. In this study, we evaluated peripheral AS pathology in the SMG biopsy of patients with PRKN pathogenic variants. METHODS: We enrolled three young-onset PD patients with PRKN pathogenic variants. Two patients were compound heterozygous for trans-exon 3 and 4 deletions and one patient was heterozygous for an exon 2 duplication. We obtained two submandibular gland tissues with core needle biopsy (18G). The neural structures were identified using neurofilament (NF) immunostaining and the neural tissue in the adjacent section were stained with 129 phophorylated α-synuclein (pAS) antibody. RESULTS: pAS staining in the SMG was negative in all cases with the PRKN pathogenic variants. CONCLUSIONS: Our data may support the high specificity of the AS pathology of SMG in α-synuclein associated parkinsonism. Future studies evaluating peripheral neural tissue including the SMG in the elderly healthy population are required to validate the role of peripheral AS pathology as a biomarker in PD.

Serum TNF-α and neurodegeneration in isolated REM sleep behavior disorder.

OBJECTIVE: To investigate serum inflammatory cytokine profiles in patients with isolated REM sleep behavior disorder (iRBD) and to explore whether these markers are associated with phenoconversion risk to α-synucleinopathies. METHODS: In this prospective cohort study, we analyzed serum samples from patients with polysomnography-confirmed iRBD (n = 30) and healthy controls (n = 12). We measured the following cytokines: interleukin (IL)-1ß, IL-2, IL-6, IL-10, and tumor necrosis factor-α (TNF-α). All patients underwent motor and non-motor evaluations and dopamine transporter imaging at baseline for predicting the phenoconversion risk. We followed the patients quarterly over up to 6 years to identify disease conversion. We also assessed longitudinal changes in cytokine levels from baseline at the 2- and 4-year follow-up visits. RESULTS: The baseline cytokine levels did not differ between the patients and controls. However, the TNF-α levels were significantly increased in a subgroup of the patients with multiple markers (≥3) for phenoconversion risk compared to those without (p = 0.008) and controls (p = 0.003). At longitudinal analyses, patients with TNF-α levels above the median showed a higher incidence of phenoconversion than those with lower TNF-α levels (47% vs. 7%; p = 0.008), and this significant association persisted after adjusting for covariates (p = 0.026). The cytokine levels over 4 years of follow-up period did not change significantly. CONCLUSIONS: Our data suggest a possible link between serum TNF-α and phenoconversion risk in iRBD. Further studies are warranted to confirm the role of peripheral TNF-α in the pathogenesis of neurodegeneration in this disorder.

Alternating Hemiplegia of Childhood in Korea: a Case Report.

Alternating hemiplegia of childhood (AHC) is a rare neurodevelopmental disorder characterized by recurrent paroxysmal hemiplegic attacks that affect one or the other side of the body. Up to 74% of patients with AHC have a pathologic variant in the ATP1A3 gene. After the introduction of next-generation sequencing, intermediate cases and atypical cases have expanded the clinical spectrum of ATP1A3-related disorders. Herein, we report the first case of AHC in Korea. A 33-year-old man visited our hospital with recurrent hemiplegic and dystonic episode after his first birthday. He was completely normal between episodes and did not have any ataxia, but brain magnetic resonance imaging showed cerebellar atrophy. He also had pes planovalgus deformity. Whole exome sequencing revealed a heterozygous G947R variant in the ATP1A3 gene (c.2839G > C, rs398122887), which is a known pathologic variant. This atypical case of AHC demonstrates the importance of the clinical approach in diagnosing ATP1A3-related disorders.

Patient selected goals and satisfaction after bilateral subthalamic nucleus deep brain stimulation in Parkinson's disease.

Assessing patient goals is crucial in understanding patient centered outcomes and satisfaction. However, patient goals may change throughout treatment. Our objective is to identify the changes in patient-selected goals of Parkinson's disease (PD) patients undergoing bilateral subthalamic nucleus deep brain stimulation (STN-DBS) and examine the relationship among patient-selected goal achievement, standard DBS outcome measures, and overall patient satisfaction. Seventy-five patients undergoing bilateral STN-DBS listed three patient-selected goals before surgery. After six months, patients were asked to restate the three goals and to rate the degree of goal achievement and the overall satisfaction of surgery. The three most frequently selected goals were "dyskinesia", "gait disorder", and "medication off duration". After six months, 80.0% of patients could not accurately recall their pre-DBS goals. "Dyskinesia" was the most consistently selected goal, more patients selected "tremor" and "less medication" at post-DBS compared to pre-DBS, and less patients selected "gait disorder" at post-DBS compared to pre-DBS. 74.7% of patients reported overall satisfaction by stating they were "very much" or "much better after surgery". Patient satisfaction significantly correlated with goal achievement (r = 0.640; p < 0.001). Interestingly, change in UPDRS motor scores did not correlate with patient satisfaction (r = 0.100; p = 0.395). Although recalled goals do not accurately represent the pre-surgical goals, the achievement score for recalled goals significantly correlated with patient satisfaction. Patient goals change due to many reasons. Therefore, follow-up patient counseling to discuss goals and outcomes is important in improving patient satisfaction after STN-DBS.

Urinary Symptoms and Urodynamic Findings in Patients with Spinocerebellar Ataxia.

Urinary dysfunctions are not considered symptoms of spinocerebellar ataxias (SCAs). However, given that a patient with SCAs without a family history might be misdiagnosed as MSA-C when having urinary dysfunctions, characterization of urinary dysfunctions in SCAs is needed not only to understand SCAs but also to correctly diagnosis patients with ataxia. We retrospectively reviewed medical records of 143 patients with genetically confirmed SCA1, 2, 3, 6, 7, 17, and DRPLA. Twenty-two patients (men n = 9; age 62.1 ± 10.9; disease duration 8.2 ± 2.9 years) who had lower urinary track symptoms (LUTS) were included in this study. Six patients underwent urodynamic study (UDS), and 2 underwent uroflowmetry. LUTS was present in 1 of 11 patients with SCA1, in 4 of 51 with SCA2, in 2 of 26 with SCA3, in 3 of 20 with SCA6, in 2 of 4 with SCA7, in 8 of 26 with SCA17, and in 2 of 5 with DRPLA. Overall, urinary frequency was the most common symptom (16 patients, 72.7%) followed by voiding difficulty. In three of the 6 patients with UDS, post-micturition residuals were > 100 ml. Detrusor overactivity was noted in three patients. Detrusor areflexia was observed in one. Four patients were diagnosed with a neurogenic bladder, 3 with a storage problem, and 1 with both storage and voiding problems. Fifteen percent of the patients with SCAs had LUTS, and LUTS occurred in various types of SCAs. Our results indicate that SCAs should be considered in patients with progressive cerebellar ataxia and urinary dysfunctions.

A 3-year observation of excessive daytime sleepiness after subthalamic deep brain stimulation in patients with Parkinson's disease.

OBJECTIVE: Subthalamic nucleus deep brain stimulation (STN DBS) has a positive effect on sleep quality, but its effect on wake functions is controversial. This study evaluated the longitudinal changes of the quality of sleep and excessive daytime sleepiness (EDS) in Parkinson's disease (PD) patients undergoing STN DBS and identify which factors are associated with the presence of EDS before and after STN DBS. PATIENT AND METHODS: A total of 33 PD patients who underwent bilateral STN DBS between July 2011 and October 2015 were recruited. We evaluated subjective sleep quality assessed by Parkinson's Disease Sleep Scale (PDSS) and EDS using Epworth Sleepiness Scale (ESS) preoperatively and 6 months, 1 year, and 3 years postoperatively. RESULTS: There is a significant improvement in PDSS, and a noticeable change occurs immediately after the surgery. After DBS, the number of patients with persistent EDS gradually decreased, but patients with newly developed EDS were added. Baseline ESS score was highly correlated with EDS at 6 months and 1 year postoperatively, and older age of PD onset was highly associated with EDS at 1 year after DBS. At 3 years after DBS, the total PDSS score is a main contributing factor for EDS. There was no significant difference in dopamine agonist dose (agonist LED) and levodopa equivalent daily dose (LEDD) between groups with and without EDS at any time points. CONCLUSION: Bilateral STN DBS improves the subjective sleep quality, but EDS may improve or worsen. The risk factors for EDS change over time after STN DBS. Interestingly, dopaminergic medication did not affect EDS in DBS-treated PD patients.

Peripheral Blood Inflammatory Cytokines in Idiopathic REM Sleep Behavior Disorder.

BACKGROUND: Although previous research provides insight into the role of neuroinflammation in idiopathic REM sleep behavior disorder, the association of this disorder with peripheral blood inflammatory markers remains unclear. OBJECTIVE: To investigate inflammatory cytokines in plasma samples in patients with idiopathic rapid eye movement sleep behavior disorder and to explore whether these markers are associated with prodromal symptoms of α-synucleinopathies. METHODS: We collected plasma from patients with polysomnographically confirmed idiopathic rapid eye movement sleep behavior disorder without parkinsonism or dementia (n = 54) and from healthy controls (n = 56). The following cytokines were measured: interleukin-1ß, interleukin-2, interleukin-6, interleukin-10, and tumor necrosis factor-α. The idiopathic REM sleep behavior disorder patients underwent sleep, motor, cognitive, olfactory, and autonomic testing. RESULTS: The anti-inflammatory cytokine, interleukin-10, levels in the idiopathic rapid eye movement sleep behavior disorder group were significantly upregulated compared to the control group (P = 0.022), but this difference did not withstand Bonferroni correction. The other proinflammatory cytokine levels did not differ between the groups. No correlation was found between the cytokine levels and any clinical variable. CONCLUSIONS: Our data do not provide evidence supporting the role of peripheral inflammation in idiopathic rapid eye movement sleep behavior disorder. However, considering the limited statistical power because of the small sample size, further large-scale longitudinal studies with a broader spectrum of cytokines are needed to clarify this issue. © 2019 International Parkinson and Movement Disorder Society.

Decision under risk: Argument against early deep brain stimulation in Parkinson's disease.

Deep brain stimulation (DBS) typically has been delayed until late stage of Parkinson's disease (PD), a mean of 14-15 years after diagnosis. EARLYSTIM study applied DBS in patients with PD presenting motor complications for less than three years, and showed that early stimulation offered greater benefit than best medical therapy in all primary and major secondary end points. Based on the results of EARLYSTIM study, the U.S. Food and Drug Administration recently approved DBS for use in people with PD of at least four years duration and with recent onset of motor complications. However, despite of more benefit from DBS surgery than best medical therapy in early stage of PD, we need to consider the risks of surgery and human nature of risk aversion. Here, we make arguments against early DBS stimulation based on the prospect theory.

Determinants of Functional Independence or Its Loss following Subthalamic Nucleus Stimulation in Parkinson's Disease.

OBJECTIVE: This study aimed to describe the change in functional status following bilateral subthalamic nucleus stimulation (STN-DBS) in Parkinson's disease (PD) and to identify predictors of postoperative functional dependence. METHODS: We included PD patients with bilateral STN-DBS who had complete Schwab & England Activities of Daily Living (S&E ADL) Scale data at baseline and 6 months after surgery from our prospective registry. Functional dependence was defined as an S&E ADL score of less than 80%. All data were collected from the on-medication state and on-stimulation state (after surgery). Logistic regression analyses were performed to determine the factors predictive of functional dependence after surgery. RESULTS: A total of 196 patients were included. At baseline, 41 patients were functionally dependent and the other 155 were functionally independent. Among the patients with preoperative dependence, 32 (78%) became functionally independent after surgery, and this conversion was associated with a lower baseline axial score (p = 0.012). Among the patients with preoperative independence, 21 (14%) developed postoperative dependence, and this conversion was associated with a higher baseline axial score (p = 0.013) and its smaller improvement (p < 0.001). Female sex (odds ratio [OR] 3.214; 95% confidence interval [CI] 1.210-8.542; p = 0.019) and a higher baseline axial score (OR 1.184; 95% CI 1.056-1.327; p = 0.004) significantly predicted the risk of postoperative functional dependence. CONCLUSIONS: We found that functional status following bilateral STN-DBS is closely related to preoperative axial symptoms. When loss of independence is a potential target for STN-DBS, clinicians should take into consideration the severity of axial impairment before surgery.