Candidates For Deep Brain Stimulation Research Articles

The role of neuropsychologist in qualifying patients with movement disorders for deep brain stimulation

The appropriate selection of candidates with movement disorders for deep brain stimulation requires the engagement of a multidisciplinary team, including a movement disorders specialist, neurosurgeon, psychiatrist, neuroradiologist, neurological nurse and a neuropsychologist. The neuropsychological assessment should address not only the cognitive function but also include an interview on the emotional functioning, coping mechanisms, social support, and the adequacy of expectations with regards to deep brain stimulation. Neuropsychiatric interview with the patient and – if possible – his/her proxy, should be supported, but not replaced, by questionnaire assessment. Also, if surgery under local anesthesia is considered, the neuropsychological evaluation can help to establish if the patient is cognitively and emotionally capable of enduring it. In this paper, all the important aspects of neuropsychological evaluation are presented, with special emphasis on dealing with motor limitations during cognitive assessment, conducting the behavioral assessment and addressing the patient’s expectations concerning deep brain stimulation efficacy. Neuropsychiatric evaluation should cover not only the presence and severity of affective symptoms, but also the relationship between motor and emotional state, suicidal ideations, psychosocial stability, and a variety of behavioral problems, including pseudobulbar affect, irritability, and psychotic symptoms. Overall, the comprehensive neuropsychological evaluation for deep brain stimulation candidates extends far beyond cognitive assessment.

Deep Brain Stimulation and Treatment Outcomes of Young- and Late-Onset (≤55 Years) Parkinson's Disease: A Population-Based Study.

Background: No studies have reported the rate of motor complications (MC) and response to medical and surgical treatment in a population-based cohort of young-onset Parkinson's Disease (YOPD) patients and a cohort of sex-matched late-onset Parkinson's Disease (LOPD).Objective: To assess the outcomes of dopaminergic treatment in YOPD and LOPD, explore treatment-induced MC, medical adjustment, and rate of deep brain stimulation (DBS).Methods: We used the expanded Rochester Epidemiology Project (eREP) to investigate a population-based cohort of YOPD between 2010 and 2015 in 7 counties in Minnesota. Cases with onset ≤55 years of age were included as YOPD. An additional sex-matched cohort of LOPD (onset at ≥56 years of age) was included for comparison. All medical records were reviewed to confirm the diagnoses.Results: In the seven counties 2010–15, there were 28 YOPD patients, which were matched with a LOPD cohort. Sixteen (57%) YOPD had MC, as compared to 9 (32%) LOPD. In YOPD, 9 had motor fluctuations (MF) and Levodopa-induced dyskinesia (LID) together, whereas 3 had LID only and 4 MF only. In LOPD, 3 had MF and LID, 3 MF only, and 3 LID only. Following medical treatment for MC, 6/16 YOPD (38%) and 3/9 (33%) LOPD had symptoms resolution. In YOPD, 11/16 (69%) were considered for DBS implantation, in LOPD they were 2/9 (22%), but only 7 (6 YOPD and 1 LOPD) underwent the procedure. YOPD had significantly higher rates in both DBS candidacy and DBS surgery (respectively, p = 0.03 and p = 0.04). Among DBS-YOPD, 5/6 (83%) had positive motor response to the surgery; the LOPD case had a poor response. We report the population-based incidence of both YOPD with motor complications and YOPD undergoing DBS, which were 1.17 and 0.44 cases per 100,000 person-years, respectively.Conclusion: Fifty-seven percent of our YOPD patients and 32% of the LOPD had motor complications. Roughly half of both YOPD and LOPD were treatment resistant. YOPD had higher rates of DBS candidacy and surgery. Six YOPD and 1 LOPD underwent DBS implantation and most of them had a positive motor response after the surgery.

Deep brain stimulation in patients on chronic antiplatelet or anticoagulation treatment

BackgroundIn the aging society, many patients with movement disorders, pain syndromes, or psychiatric disorders who are candidates for deep brain stimulation (DBS) surgery suffer also from cardiovascular co-morbidities that require chronic antiplatelet or anticoagulation treatment. Because of a presumed increased risk of intracranial hemorrhage during or after surgery and limited knowledge about perioperative management, chronic antiplatelet or anticoagulation treatment often has been considered a relative contraindication for DBS. Here, we evaluate whether or not there is an increased risk for intracranial hemorrhage or thromboembolic complications in patients on chronic treatment (paused for surgery or bridged with subcutaneous heparin) as compared to those without.MethodsOut of a series of 465 patients undergoing functional stereotactic neurosurgery, 34 patients were identified who were on chronic treatment before and after receiving DBS. In patients with antiplatelet treatment, medication was stopped in the perioperative period. In patients with vitamin K antagonists or novel oral anticoagulants (NOACs), heparin was used for bridging. All patients had postoperative stereotactic CT scans, and were followed up for 1 year after surgery.ResultsIn patients on chronic antiplatelet or anticoagulation treatment, intracranial hemorrhage occurred in 2/34 (5.9%) DBS surgeries, whereas the rate of intracranial hemorrhage was 15/431 (3.5%) in those without, which was statistically not significant. Implantable pulse generator pocket hematomas were seen in 2/34 (5.9%) surgeries in patients on chronic treatment and in 4/426 (0.9%) without. There were only 2 instances of thromboembolic complications which both occurred in patients without chronic treatment. There were no hemorrhagic complications during follow-up for 1 year.ConclusionsDBS surgery in patients on chronic antiplatelet or anticoagulation treatment is feasible. Also, there was no increased risk of hemorrhage in the first year of follow-up after DBS surgery. Appropriate patient selection and standardized perioperative management are necessary to reduce the risk of intracranial hemorrhage and thromboembolic complications.

Sleep apnea syndrome and subthalamic stimulation in Parkinson's disease

ObjectivesΤhe association between Parkinson's disease (PD) and sleep apnea syndrome (SAS) is not fully elucidated and very few studies reported on SAS outcome after deep brain stimulation (DBS). Here, we compare the clinical profile of PD patients with and without SAS and assess, for the first time, the value of pre-DBS SAS as predictor of post-DBS outcome in PD. MethodsFifty patients were grouped into PD with SAS (PD-SAS+,n = 22) and without (PD-SAS-,n = 28), based on the Apnea-Hypopnea-Index (AHI≥5) in polysomnography. We used novel multivariate statistical models to compare pre-DBS profiles and assess post-DBS motor, non-motor and quality of life (QoL) changes in both groups. ResultsIn the entire cohort, 44% of patients had at least mild SAS (AHI≥5), while 22% had at least moderate (AHI≥15). Mean AHI was 11/h (NREM-AHI = 10.2/h and REM-AHI = 13.5/h). The two groups had equal demographics and PD characteristics, and did not differ in respect to unified Parkinson's disease rating scale (UPDRS)-IIOFF, Body-Mass-Index, polysomnographic features, RBD, depression, sleepiness and QoL scores. The PD-SAS+ group had significantly higher scores in UPDRS-IIIOFF (41.1 ± 17.7 vs. 30.9 ± 11.7,p < 0.05) compared to PD-SAS- group.The groups did not differ in respect to post-DBS change in UPDRS-II, UPDRS-III, Epworth sleepiness scale, Hamilton depression rating scale and PDQ39 scores. Positive airway pressure therapy had no impact on post-DBS outcome. ConclusionsIn patients with PD and candidates for DBS, the presence of SAS is associated with increased motor signs, but not with a specific non-motor, QoL or sleep-wake profile. The presence of SAS prior to STN-DBS is not associated with worse outcome after surgery.

Optimizing the selection of Parkinson's disease patients for neuromodulation using the levodopa challenge test.

In Parkinson's disease (PD), early stages are associated with a good long-duration response and as the disease advances, the short-duration response predominates. The transition between the long-duration and short-duration responses may be an important and measurable intermediate stage. A critical criterion in determining the candidature for neuromodulation is a beneficial response to an 'off-on' levodopa challenge test. This test is usually reserved for those that have already developed marked short-duration response and are candidates for deep brain stimulation (DBS) surgery. However, identifying those that are in transition may allow DBS to be offered earlier. The objective of the study was to determine if the transition from a long-duration to a short-duration response can be assessed on a levodopa challenge test. An 'off-on" levodopa challenge test was done in sixty-five PD patients divided into four groups based on the disease duration. OFF motor scores increased in all groups [Mean ± STD; 22.94 ± 8.52, 31.53 ± 9.87, 34.05 ± 9.50, and 33.92 ± 10.15 in groups 1-4, respectively] while a significant response to medication was maintained on 'off-on' testing. The mean levodopa equivalency dose in groups 1 and 2 was significantly less than in groups 3 and 4. This transition occurred between years 7 and 9 of disease duration. Performing a regular levodopa challenge test, when levodopa dose increases substantially, should be considered to determine the ideal time for DBS in patients with Parkinson's disease.

Assessment of deep brain stimulation candidacy during the COVID-19 pandemic: Lessons learned and future directions for neuropsychologists

Objective Neuropsychological assessment is integral to the pre-surgical deep brain stimulation (DBS) workup for patients with movement disorders. The COVID-19 pandemic quickly affected care access and shifted healthcare delivery, and neuropsychology has adapted successfully to provide tele-neuropsychological (teleNP) DBS evaluations during this time, thus permanently changing the landscape of neuropsychological practice. Method: In this paper, we discuss the lessons learned from the pandemic and we offer care management guidelines for teleNP and in-person evaluations of pre-DBS populations, with exploration of the feasibility of the different approaches for uninterrupted care access. Results: We summarize the strengths and weaknesses of these care models and we provide future directions for the state of clinical neuropsychological practice for DBS programs, with implications for broader patient populations. Conclusions: A better understanding of these dynamics will inform and educate the DBS team and community regarding the complexities of performing DBS neuropsychological evaluations during COVID-19 and beyond.

The global pandemic has permanently changed the state of practice for pre-DBS neuropsychological evaluations

The evaluation and management of patients with movement disorders has evolved considerably due to the COVID-19 pandemic, including the assessment of candidates for deep brain stimulation (DBS) therapy. Members of the Neuropsychology Focus Group from the Parkinson Study Group Functional Neurosurgical Working Group met virtually to discuss current practices and solutions, build consensus, and to inform the DBS team and community regarding the complexities of performing DBS neuropsychological evaluations during COVID-19. It is our viewpoint that the practice of neuropsychology has adapted successfully to provide tele-neuropsychological pre-DBS evaluations during the global pandemic, thus permanently changing the landscape of neuropsychological services.

Acute State Effects of Dopamine Replacement Therapy are Relevant to Motivated Behaviors in Deep Brain Stimulation Candidates

Among neuropsychiatric disorders, Parkinson’s Disease (PD) has an especially broad range of cognitive and behavioral manifestations, which may reflect the multifaceted impact of dopaminergic neuron loss. Analogous to the well-known motor symptom fluctuations on and off dopamine substitution, we examined medication related non-motor fluctuations in transdiagnostic measures of apathy, impulsivity, anhedonia, and mood.

The Role of Focused Ultrasound in the Management of Movement Disorders: Insights after 5 Years of Experience.

The Role of Focused Ultrasound in the Management of Movement Disorders: Insights after 5 Years of Experience.

The Decline of Deep Brain Stimulation for Obsessive-Compulsive Disorder Following FDA Humanitarian Device Exemption Approval.

Background: In February 2009, the US Food and Drug Administration (FDA) granted Humanitarian Device Exemption (HDE) for deep brain stimulation (DBS) in the anterior limb of the internal capsule (ALIC) for the treatment of severely debilitating, treatment refractory obsessive–compulsive disorder (OCD). Despite its promise as a life altering treatment for patients with otherwise refractory, severely debilitating OCD, the use of DBS for the treatment of OCD has diminished since the FDA HDE endorsement and is now rarely performed even at busy referral centers. We sought to identify factors hindering OCD patients from receiving DBS therapy.Materials and Methods: University of Florida (UF) clinical research databases were queried to identify patients evaluated as potential candidates for OCD DBS from January 1, 2002 to July 30, 2020. A retrospective review of these patients' medical records was performed to obtain demographic information, data related to their OCD, and details relevant to payment such as third-party payer, study participation, evaluation prior to or after HDE approval, and any stated factors prohibiting surgical intervention.Results: Out of 25 patients with severe OCD identified as candidates for DBS surgery during the past 18 years, 15 underwent surgery. Prior to FDA HDE approval, 6 out of 7 identified candidates were treated. After the HDE, only 9 out of 18 identified candidates were treated. Seven of the 9 were funded by Medicare, 1 paid out of pocket, and 1 had “pre-authorization” from her private insurer who ultimately refused to pay after the procedure. Among the 10 identified OCD DBS candidates who were ultimately not treated, 7 patients—all with private health insurance—were approved for surgery by the interdisciplinary team but were unable to proceed with surgery due to lack of insurance coverage, 1 decided against surgical intervention, 1 was excluded due to medical comorbidities and excessive perceived surgical risk, and no clear reason was identified for 1 patient evaluated in 2004 during our initial NIH OCD DBS trial.Conclusion: Based on compelling evidence that DBS provides substantial improvement of OCD symptoms and markedly improved functional capacity in 2 out of 3 patients with severely debilitating, treatment refractory OCD, the FDA approved this procedure under a Humanitarian Device Exemption in 2009, offering new hope to this unfortunate patient population. A careful review of our experience with OCD DBS at the University of Florida shows that since the HDE approval, only 50% of the severe OCD patients (9 of 18) identified as candidates for this potentially life altering treatment have been able to access the therapy. We found the most common limiting factor to be failure of private insurance policies to cover DBS for OCD, despite readily covering DBS for Parkinson's disease, essential tremor, and even dystonia—another HDE approved indication for DBS. We have identified an inherent discrimination in the US healthcare system against patients with medication-refractory OCD who are economically challenged and do not qualify for Medicare. We urge policy makers, insurance companies, and hospital administrations to recognize this health care disparity and seek to rectify it.

Recruitment Challenges for Studies of Deep Brain Stimulation for Treatment-Resistant Depression.

IntroductionDeep brain stimulation (DBS) is currently an investigational treatment for treatment-resistant depression (TRD). There is a need for more DBS trials to strengthen existing evidence of its efficacy for both regulatory and clinical reasons. Recruitment for DBS trials remains challenging due to unproven efficacy in sham-controlled DBS trials, invasive nature of the intervention and stringent eligibility criteria in patient selection. Here, we examined the referral patterns and reasons for exclusion of subjects in our DBS trial.MethodsData were collected from all patients who expressed interest in participating in a DBS study involving subcallosal cingulate region from 2014 to 2016. Referral sources were categorized as either self-referral or professional referral. Evaluation for eligibility was performed in three stages; initial contact, brief telephone assessment, and in-person psychiatric evaluation. The reasons for exclusion were documented. Descriptive and inferential statistics were used for analysis.ResultsOf the 225 patients who contacted us initially, 22 (9.2%) underwent DBS surgery. Self-referral was higher than the referral from professionals (72% versus 28%, P<0.0001). However, the acceptance rate for surgery was higher among the professional referrals than from self-referrals (40% versus 15%, P=0.03). The common reasons for exclusion were self-withdrawal (38.4%), residing out of province or country (26.1%) and psychiatric/medical comorbidity (21.7%).ConclusionThese findings provide insight into DBS candidacy for future TRD trials. It suggests a need for comprehensive recruitment strategies including active engagement of patients and professionals throughout trials, and effective referral communication with education to optimize recruitment for future DBS trials.

Does the Personality of Patients with Parkinson's Disease Affect the Decision to Perform Deep Brain Stimulation Surgery? A Cross-Sectional Study in a Chinese Cohort.

We investigated whether the personality of patients with Parkinson's disease (PD) before subthalamic brain stimulation differed from patients receiving drug treatments and whether the personality of patients affected surgical decisions. We recruited 38 patients with advanced PD scheduled for deep brain stimulation (DBS), 40 patients with PD receiving the very best medical treatment, and 51 healthy control subjects. All participants were evaluated by the Minnesota multiphasic personality inventory-1 (MMPI-1). PD patients who were candidates for DBS did not exhibit any significant differences in personality when compared with PD patients who were treated with drugs. Compared with healthy controls, patients with PD had remarkably higher MMPI-1 scores for spiritual quality, neuroticism, and introversion, but significantly lower scores for socialization. In addition, patients with PD were more submissive, more dependent on others, and less active in social activities. Our data indicated that the main deciding factor relating to whether to undergo DBS was the disease itself and not the pathological personality. However, neurotic and psychotic symptoms accompanying PD may influence the effect of DBS. We found that greater benefit is obtained by surgical or medical interventions if abnormal neurotic characteristics are considered early in the course of PD.

Depression and dopamine dysregulation syndrome as risk factor for suicide after deep brain stimulation in Parkinson's disease

Modern approaches to the management of advanced stages of Parkinson's disease include deep brain stimulation (DBS). Adequate selection of candidates for DBS is a key factor for the effectiveness and safety of this method. Selection criteria are mainly based on data from large multicenter studies. It is known that the use of DBS can be accompanied by the development of side effects, the most common of which is neuropsychiatric disorders. Suicide is an extreme manifestation of neuropsychiatric disorders and a potentially reversible cause of death in patients with Parkinson's disease. Patients with chronic diseases, including neurological diseases, have an increased risk of suicide or suicide attempts. Depression and impulse control disorders following DBS are likely key contributors to suicidal behavior in patients. The authors present a clinical case – an attempt to commit suicide after DBS with the use of levodopa with an analysis of the factors contributing the development of suicidal behavior and an analysis of the management of neuropsychiatric disorders.

Development and Initial Validation of the Chinese Version of the Florida Surgical Questionnaire for Parkinson's Disease.

Background Deep brain stimulation (DBS) for Parkinson's disease (PD) has evolved as a well-established treatment in neurosurgery, and identifying appropriate surgical candidates could contribute to better DBS outcomes. The Florida Surgical Questionnaire for Parkinson Disease (FLASQ-PD) is a reasonable screening tool for assessing DBS candidacy in PD patients; however, a Chinese version of FLASQ-PD is needed for functional neurosurgery units in China. In this study, we translated the FLASQ-PD to Chinese and assessed its reliability and validity for Chinese PD patients. Methods The FLASQ-PD was translated before the study formally started. A single-center retrospective analysis of FLASQ-PD was performed at the Ruijin Hospital, affiliated with Shanghai Jiaotong University School of Medicine, between July and December 2019. The Unified Parkinson Disease Rating Scale III (UPDRS-III) was also used to assess PD patients on and off medication. All patients were evaluated for surgical candidacy by specialists. Results Overall, 115 PD patients, 25 with parkinsonism and six with multiple system atrophy were consecutively included. Internal consistency of the Chinese FLASQ-PD was roughly adequate (Cronbach's alpha = 0.664). There were significant differences in mean total scores of the Chinese FLASQ-PD between the diagnostic (Kruskal–Wallis H value = 37.450, p ≤ 0.001) and surgery-candidacy groups (H = 48.352, p ≤ 0.001). Drug improvements in UPDRS-III scores were mildly correlated with the Chinese FLASQ-PD scores in the surgery-ready group (Pearson correlation = 0.399, p=0.001). Conclusions The Chinese FLASQ-PD, which is a simple and efficient screening tool for clinicians, was developed and initially validated in this retrospective single-center study.

Patient-Reported Outcomes Measurement Information System (PROMIS) Assessment of Non-Motor Features in Deep Brain Stimulation Candidates: Relationship to the Beck Depression and Anxiety Inventories.

To compare Patient-Reported Outcomes Measurement Information System (PROMIS) measures of depression and anxiety to the Beck Depression Inventory-II (BDI-II), Beck Anxiety Inventory (BAI), and explore patterns of selected PROMIS measures in patients undergoing evaluation for Deep Brain Stimulation (DBS). BDI-II, BAI, and seven PROMIS measures were administered to 163 DBS candidates with diagnoses of Parkinson Disease (PD, n=102), Essential Tremor (ET, n=45), or Dystonia (n=16). Elevated PROMIS Depression using BDI-II Crosswalk equivalents predicted elevated BDI-II with 63% sensitivity and 94% specificity. On other PROMIS measures, 69 patients (42%) reported low Physical Function (T≤40) with Pain Interference being the next most frequent abnormal score (n=51, 31%). Group differences were present for PROMIS Physical Function, Sleep Disturbance, and Pain. These preliminary findings provide initial support for PROMIS Depression to assess mood disturbance in DBS candidates, and characterize other PROMIS measures in DBS candidates including group differences reflecting disease specific contribution to Quality of Life.

Current Management of Tics and Tourette Syndrome: Behavioral, Pharmacologic, and Surgical Treatments.

Tourette syndrome is a heterogeneous neurobehavioral disorder manifested by childhood-onset motor and phonic tics, often accompanied by a variety of behavioral comorbidities, including attention deficit and obsessive compulsive disorder. Treatment must be tailored to the needs and goals of the individual patients and their families. All patients should receive education on the condition and, if possible, engage behavioral therapy targeted towards tics and/or comorbidities. Pharmacological therapies, such as alpha agonists, topiramate, and vesicular monoamine transport type 2 inhibitors, are generally used as first-line therapies in patients with troublesome tics that are not controlled by behavioral therapy or when the latter is not available or accessible. Botulinum toxin injections can be used in patients with bothersome focal tics. Second-line therapy includes antipsychotics, such as fluphenazine, aripiprazole, risperidone, and ziprasidone. These medications are generally efficacious but carry the risk of metabolic syndrome, tardive dyskinesia, and other side effects. Much more research is needed before novel therapies such as cannabis-derived products or transcranial magnetic stimulation can be recommended. There is promise in ongoing clinical trials with D1 receptor antagonist ecopipam and other experimental therapeutics. Patients with tics that are refractory to conventional treatments may be candidates for deep brain stimulation, but further studies are needed to determine the optimal target selection.

Difficulties in activities of daily living are associated with stigma in patients with Parkinson's disease who are candidates for deep brain stimulation.

Objective:Parkinson’s disease (PD) is often accompanied by stigma, which could contribute to a worse prognosis. The objective of this study is to identify the variables associated with stigma in PD patients who are candidates for deep brain stimulation (DBS).Methods:We investigated sociodemographic and clinical variables associated with stigma in a sample of 54 PD patients indicated for DBS. The independent variables were motor symptoms assessed by the Movement Disorder Society‐sponsored revision of the Unified Parkinson Disease Rating Scale (MDS-UPDRS III), depressive symptoms measured by the Hospital Anxiety and Depression Scale, age, disease duration and the presence of a general medical condition. The Mobility, Activities of daily living and Emotional well-being domains of the 39-item Parkinson’s Disease Questionnaire (PDQ-39) were also investigated as independent variables, and the Stigma domain of the PDQ-39 scale was considered the outcome variable.Results:After multiple linear regression analysis, activities of daily living remained associated with the Stigma domain (B = 0.42 [95%CI 0.003-0.83], p = 0.048). The full model accounted for 15% of the variance in the Stigma domain (p = 0.03).Conclusions:Although causal assumptions are not appropriate for cross-sectional studies, the results suggest that ADL difficulties could contribute to greater stigma in PD patients with refractory motor symptoms who are candidates for DBS.

Experts Debate What's Next for DBS for Depression

Experts Debate What's Next for DBS for Depression

Subthalamic Gamma Knife Radiosurgery in Parkinson’s Disease: A Cautionary Tale

Introduction: Deep brain stimulation (DBS) targeting the subthalamic nucleus (STN) has been shown to reliably improve several symptoms of Parkinson’s disease (PD) in appropriately selected patients. Various factors may preclude patients from undergoing DBS and for them, non-invasive lesion-based therapies such as focused ultrasound and Gamma Knife (GK) radiosurgery may present a safer alternative. Materials and Methods: Based on preliminary positive reports of STN GK for PD, we conducted a prospective, open-label, single-center, pilot study in PD patients deemed potential candidates for unilateral DBS based on their disease characteristics, but contraindicated due to age >74, an irreversible bleeding diathesis, or significant comorbid medical disease. Stereotactic MRI-guided GK radiosurgery was performed using a single 110- or 120-Gy dose targeting the STN contralateral to the more symptomatic extremity. Clinical follow-up and imaging assessed the safety and efficacy of the procedure over a 12-month period. Results: Four PD patients with medication-refractory tremors and disabling dyskinesias underwent unilateral STN GK radiosurgery. Contraindications to DBS included high-risk comorbid cardiovas­cular disease in 3 patients and an irreversible bleeding diathesis in 1. There were no immediate post-procedural adverse events. One patient who underwent left STN GK radiosurgery developed right hemiparesis and dysarthria 7 months post-procedure followed by hospitalization at 9 months for bacterial endocarditis and liver failure from which he died. The remaining 3 patients were free of adverse events up to 12 months post-procedure and experienced a reduction in contralateral rigidity, bradykinesia, and tremor. Upon extended follow-up, 2 patients developed subacute worsening of gait. One died at 16 months due to complications of a fall whereas the other saw no change in gait up to 42 months post-procedure. All 3 patients with adverse events demonstrated a hyper-response in the targeted area on follow-up neuroimaging. Discussion/Conclusion: Despite the potential for clinical improvement, our results suggest that unilateral STN GK radiosurgery should be approached cautiously in medically frail PD patients who may be at higher risk of GK hyper-response and neurologic complications.

Gamma Knife Thalamotomy of Medication Refractory Tremor Disorders

To Investigate the effectiveness and safety of use of Gamma Knife radiosurgery for lesioning the Ventral Intermediate Thalamic Nucleus (VIM) for management of medication refractory tremor disorders. Patients with medication refractory tremor disorders were treated utilizing Gamma Knife radiosurgery. Patients received 130 Gy targeting the VIM nucleus utilizing a single 4 mm collimator shot. Plugs were customized to limit dose to the adjacent internal capsule. Patients were then followed for 2 years with serial standardized Fahn-Tolosa-Marin Tremor scale evaluation and any adverse events were recorded. Results from this testing were tabulated with numerical scores in four separate categories including postural, handwriting, drawing, and functioning. From 2/2013 through 8/2018, 18 patients were treated to 20 lesions. Median age was 69 (range 34-87). Sixteen treatments were directed at the left VIM nucleus to treat a right sided tremor. All of these 16 treatments were directed at the dominant hand. Two of the four patients treated to the non-dominant hand (right VIM nucleus) had also been treated previously to the contralateral side 1 year prior. Fahn-Tolosa-Marin testing was performed at 3-6 month intervals. Median follow up was 18 months (range 0-26) with one patient lost to follow up. 17/19 (89.5%)treatments demonstrated significant improvements on follow up. There were improvements in all assessed scores. Median postural scores improved from 6.0 to 3.0 (p <0.01), handwriting scores from 3.0 to 1.0 ( p<0.01), drawing scores from 9.0 to 3.0 (p<0.01), and functioning scores from 18 to 9.5 (p<0.01). Median time to improvement was 6 months (Range3-24 months). No acute or chronic adverse events were reported in any patient. Gamma Knife Thalamotomy is a safe and effective treatment for tremor disorders. With great care in the delineation of the internal capsule, no adverse events were noted. Treatments can safely be administered in a community setting. Patients who are deemed to be poor candidates for deep brain stimulation including the elderly, patients with pulmonary and cardiac comorbidities, and patients on anticoagulation should be considered for treatment.