Harrison C. Walker

Tourette syndrome deep brain stimulation: A review and updated recommendations

Deep brain stimulation (DBS) may improve disabling tics in severely affected medication and behaviorally resistant Tourette syndrome (TS). Here we review all reported cases of TS DBS and provide updated recommendations for selection, assessment, and management of potential TS DBS cases based on the literature and implantation experience. Candidates should have a Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM V) diagnosis of TS with severe motor and vocal tics, which despite exhaustive medical and behavioral treatment trials result in significant impairment. Deep brain stimulation should be offered to patients only by experienced DBS centers after evaluation by a multidisciplinary team. Rigorous preoperative and postoperative outcome measures of tics and associated comorbidities should be used. Tics and comorbid neuropsychiatric conditions should be optimally treated per current expert standards, and tics should be the major cause of disability. Psychogenic tics, embellishment, and malingering should be recognized and addressed. We have removed the previously suggested 25‐year‐old age limit, with the specification that a multidisciplinary team approach for screening is employed. A local ethics committee or institutional review board should be consulted for consideration of cases involving persons younger than 18 years of age, as well as in cases with urgent indications. Tourette syndrome patients represent a unique and complex population, and studies reveal a higher risk for post‐DBS complications. Successes and failures have been reported for multiple brain targets; however, the optimal surgical approach remains unknown. Tourette syndrome DBS, though still evolving, is a promising approach for a subset of medication refractory and severely affected patients.

A Trial of Scheduled Deep Brain Stimulation for Tourette Syndrome Moving Away From Continuous Deep Brain Stimulation Paradigms

OBJECTIVE To collect the information necessary to design the methods and outcome variables for a larger trial of scheduled deep brain stimulation (DBS) for Tourette syndrome. DESIGN We performed a small National Institutes of Health-sponsored clinical trials planning study of the safety and preliminary efficacy of implanted DBS in the bilateral centromedian thalamic region. The study used a cranially contained constant-current device and a scheduled, rather than the classic continuous, DBS paradigm. Baseline vs 6-month outcomes were collected and analyzed. In addition, we compared acute scheduled vs acute continuous vs off DBS. SETTING A university movement disorders center. PATIENTS Five patients with implanted DBS. MAIN OUTCOME MEASURE A 50% improvement in the Yale Global Tic Severity Scale (YGTSS) total score. RESULTS Participating subjects had a mean age of 34.4 (range, 28-39) years and a mean disease duration of 28.8 years. No significant adverse events or hardware-related issues occurred. Baseline vs 6-month data revealed that reductions in the YGTSS total score did not achieve the prestudy criterion of a 50% improvement in the YGTSS total score on scheduled stimulation settings. However, statistically significant improvements were observed in the YGTSS total score (mean [SD] change, -17.8 [9.4]; P=.01), impairment score (-11.3 [5.0]; P=.007), and motor score (-2.8 [2.2]; P=.045); the Modified Rush Tic Rating Scale Score total score (-5.8 [2.9]; P=.01); and the phonic tic severity score (-2.2 [2.6]; P=.04). Continuous, off, and scheduled stimulation conditions were assessed blindly in an acute experiment at 6 months after implantation. The scores in all 3 conditions showed a trend for improvement. Trends for improvement also occurred with continuous and scheduled conditions performing better than the off condition. Tic suppression was commonly seen at ventral (deep) contacts, and programming settings resulting in tic suppression were commonly associated with a subjective feeling of calmness. CONCLUSIONS This study provides safety and proof of concept that a scheduled DBS approach could improve motor and vocal tics in Tourette syndrome. Refinements in neurostimulator battery life, outcome measure selection, and flexibility in programming settings can be used to enhance outcomes in a future larger study. Scheduled stimulation holds promise as a potential first step for shifting movement and neuropsychiatric disorders toward more responsive neuromodulation approaches. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT01329198.

Design innovations and baseline findings in a long-term parkinson’s trial: The national institute of neurological disorders and stroke exploratory trials in parkinson’s disease long-term study-1

Based on the preclinical data and the results of a phase II futility study, creatine was selected for an efficacy trial in Parkinsons disease (PD). We present the design rationale and a description of the study cohort at baseline. A randomized, multicenter, double‐blind, parallel‐group, placebo‐controlled phase III study of creatine (10 g daily) in participants with early, treated PD, the Long‐term Study–1 (LS‐1), is being conducted by the National Institute of Neurological Disorders and Stroke Exploratory Trials in Parkinsons Disease network. The study utilizes a global statistical test (GST) encompassing five clinical rating scales to provide a multidimensional assessment of disease progression. A total of 1,741 PD participants from 45 sites in the United States and Canada were randomized 1:1 to either 10 g of creatine/day or matching placebo. Participants are being evaluated for a minimum of 5 years. The LS‐1 baseline cohort includes participants treated with dopaminergic therapy and generally mild PD. LS‐1 represents the largest cohort of patients with early treated PD ever enrolled in a clinical trial. The GST approach should provide high power to test the hypothesis that daily administration of creatine (10 g/day) is more effective than placebo in slowing clinical decline in PD between baseline and the 5‐year follow‐up visit against the background of dopaminergic therapy and best PD care.

Bilateral effects of unilateral subthalamic deep brain stimulation on Parkinson's disease at 1 year.

OBJECTIVETo quantify the benefit of unilateral subthalamic nucleus (STN) deep brain stimulation (DBS) on contralateral, ipsilateral, and axial symptoms of advanced Parkinsons disease. METHODSThirty-seven patients received unilateral STN DBS and were rated on the Unified Parkinsons Disease Rating Scale (UPDRS) and timed tests of motor function in the “practically defined off” state at baseline and at 3, 6, and 12 months postoperatively. RESULTSUPDRS motor scores improved significantly at 3, 6, and 12 months relative to the preoperative baseline (P < 0.001, 37.1% at 1 year). There was improvement in the contralateral UPDRS subscores (P < 0.001, 54.6% at 1 year), and although contralateral benefit was larger on all outcome measures, ipsilateral benefit was present at 3 and 6 months on the UPDRS subscore (P = 0.013 and 23.5%, P = 0.005 and 27.7%, respectively). A trend toward ipsilateral benefit was present on the UPDRS subscore at 12 months; however, the effect was not statistically significant. Two timed tests of motor function in the upper extremities showed significant ipsilateral benefit in bradykinesia at 12 months (P < 0.001 and P = 0.014, respectively). Significant benefit was also observed in the UPDRS part 2 “off” medications and the UPDRS part 4 after unilateral STN DBS at 12 months (both P < 0.001). CONCLUSIONConsidering the bilateral effects and tolerability of unilateral STN DBS, unilateral stimulation followed by a contralateral procedure later, if necessary, is a reasonable option for patients with advanced Parkinsons disease, especially with prominent asymmetry.

Short latency activation of cortex during clinically effective subthalamic deep brain stimulation for Parkinson's disease

Subthalamic deep brain stimulation (DBS) is superior to medical therapy for the motor symptoms of advanced Parkinsons disease (PD), and additional evidence suggests that it improves refractory symptoms of essential tremor, primary generalized dystonia, and obsessive‐compulsive disorder. Despite this, its therapeutic mechanism is unknown. We hypothesized that subthalamic stimulation activates the cerebral cortex at short latencies after stimulus onset during clinically effective stimulation for PD. In 5 subjects (six hemispheres), EEG measured the response of cortex to subthalamic stimulation across a range of stimulation voltages and frequencies. Novel analytical techniques reversed the anode and cathode electrode contacts and summed the resulting pair of event‐related potentials to suppress the stimulation artifact. We found that subthalamic brain stimulation at 20 Hz activates the somatosensory cortex at discrete latencies (mean latencies: 1.0 ± 0.4, 5.7 ± 1.1, and 22.2 ± 1.8 ms, denoted as R1, R2, and R3, respectively). The amplitude of the short latency peak (R1) during clinically effective high‐frequency stimulation is nonlinearly dependent on stimulation voltage (P < 0.001; repeated‐measures analysis of variance), and its latency is less variable than that of R3 (1.02 versus 19.46 ms; P < 0.001, Levenes test). We conclude that clinically effective subthalamic brain stimulation in humans with PD activates the cerebral cortex at 1 ms after stimulus onset, most likely by antidromic activation. These findings suggest that alteration of the precise timing of action potentials in cortical neurons with axonal projections to the subthalamic region may be an important component of the therapeutic mechanism of subthalamic brain stimulation.

Adverse events associated with deep brain stimulation for movement disorders: analysis of 510 consecutive cases.

BACKGROUND: Although numerous studies have focused on the efficacy of deep brain stimulation (DBS) for movement disorders, less is known about surgical adverse events, especially over longer time intervals. OBJECTIVE: Here, we analyze adverse events in 510 consecutive cases from a tertiary movement disorders center at up to 10 years postoperatively. METHODS: We conducted a retrospective review of adverse events from craniotomies between January 2003 and March 2013. The adverse events were categorized into 2 broad categories—immediate perioperative and time-dependent postoperative events. RESULTS: Across all targets, perioperative mental status change occurred in 18 (3.5%) cases, and symptomatic intracranial hemorrhage occurred in 4 (0.78%) cases. The most common hardware-related event was skin erosion in 13 (2.5%) cases. The most frequent stimulation-related event was speech disturbance in 16 (3.1%) cases. There were no significant differences among surgical targets with respect to the incidence of these events. Time-dependent postoperative events leading to the revision of a given DBS electrode for any reason occurred in 4.7% ± 1.0%, 9.3% ± 1.4%, and 12.4% ± 1.5% of electrodes at 1, 4, and 7 years postoperatively, respectively. Staged bilateral DBS was associated with approximately twice the risk of repeat surgery for electrode replacement vs unilateral surgery (P = .020). CONCLUSION: These data provide low incidences for adverse events in a large series of DBS surgeries for movement disorders at up to 10 years follow-up. Accurate estimates of adverse events will better inform patients and caregivers about the potential risks and benefits of surgery and provide normative data for process improvement. ABBREVIATIONS: DBS, deep brain stimulation GPI, globus pallidus interna ICH, intracranial hemorrhage IPG, implanted pulse generator MER, microelectrode recording PD, Parkinson disease STN, subthalamic nucleus VIM, ventral intermediate thalamus

Activation of subthalamic neurons by contralateral subthalamic deep brain stimulation in Parkinson disease

Multiple studies have shown bilateral improvement in motor symptoms in Parkinson disease (PD) following unilateral deep brain stimulation (DBS) of the subthalamic nucleus (STN) and internal segment of the globus pallidus, yet the mechanism(s) underlying this phenomenon are poorly understood. We hypothesized that STN neuronal activity is altered by contralateral STN DBS. This hypothesis was tested intraoperatively in humans with advanced PD using microelectrode recordings of the STN during contralateral STN DBS. We demonstrate alterations in the discharge pattern of STN neurons in response to contralateral STN DBS including short latency, temporally precise, stimulation frequency-independent responses consistent with antidromic activation. Furthermore, the total discharge frequency during contralateral high frequency stimulation (160 Hz) was greater than during low frequency stimulation (30 Hz) and the resting state. These findings demonstrate complex responses to DBS and imply that output activation throughout the basal ganglia-thalamic-cortical network rather than local inhibition is a therapeutic mechanism of DBS.

The effects of deep brain stimulation on sleep in Parkinson’s disease

Sleep dysfunction is a common nonmotor symptom experienced by patients with Parkinson’s disease (PD). Symptoms, including excessive daytime sleepiness, sleep fragmentation, rapid eye movement (REM) sleep behavior disorder and others, can significantly affect quality of life and daytime functioning in these patients. Recent studies have evaluated the effects of deep brain stimulation (DBS) at various targets on sleep in patients with advanced PD. Several of these studies have provided evidence that subthalamic nucleus DBS improves subjective and objective measures of sleep, including sleep efficiency, nocturnal mobility, and wake after sleep onset (minutes spent awake after initial sleep onset). Although fewer studies have investigated the effects of bilateral internal globus pallidus and thalamic ventral intermedius DBS on sleep, pallidal stimulation does appear to improve subjective sleep quality. Stimulation of the pedunculopontine nucleus has recently been proposed for selected patients with advanced PD to treat severe gait and postural dysfunction. Owing to the role of the pedunculopontine nucleus in modulating behavioral state, the impact of stimulation at this target on sleep has also been evaluated in a small number of patients, showing that pedunculopontine nucleus DBS increases REM sleep. In this review, we discuss the effects of stimulation at these various targets on sleep in patients with PD. Studying the effects of DBS on sleep can enhance our understanding of the pathophysiology of sleep disorders, provide strategies for optimizing clinical benefit from DBS, and may eventually guide novel therapies for sleep dysfunction.

Unilateral subthalamic nucleus deep brain stimulation improves sleep quality in Parkinson’s disease

BACKGROUND Sleep disturbances are common in Parkinsons disease (PD). Bilateral subthalamic nucleus (STN) deep brain stimulation (DBS) is superior to best medical therapy in the treatment of motor symptoms in advanced PD, and observational studies suggest that bilateral STN DBS improves sleep in these patients as well. Unilateral STN DBS also improves motor function in PD, but its effects on sleep have not been extensively investigated. METHODS We report the effects of unilateral STN DBS on subjective sleep quality as measured by the Pittsburgh Sleep Quality Index (PSQI) in 53 consecutive PD patients. These subjects completed the PSQI prior to surgery and at 3 and 6 months post-operatively. The primary outcome measure was the change in the global PSQI at 6 months post-operatively versus the pre-operative baseline, measured with repeated measures analysis of variance (ANOVA). RESULTS Patients with PD who underwent unilateral STN DBS had a significant improvement in PSQI at 6 months post-operatively (baseline 9.30 ± 0.56 (mean ± SEM), 6 months: 7.93 ± 0.56, p = 0.013). Supplemental analyses showed that subjects selected for STN DBS placed on the right had worse baseline subjective sleep quality and more improvement in PSQI at 6 months compared to patients who received left STN DBS. CONCLUSION This prospective case series study provides evidence that unilateral STN DBS improves subjective sleep quality in patients with PD at up to 6 months post-operatively as measured by the PSQI.

Weight changes associated with unilateral STN DBS and advanced PD

Weight gain following bilateral subthalamic nucleus deep brain stimulation (STN DBS) in Parkinson disease (PD) has been characterized previously, but little is known about changes in weight following unilateral STN DBS. Weight gain of approximately 10 kg at one year after bilateral STN DBS for PD has been noted in previous studies, and PD in the absence of DBS has been associated with weight loss. A case-control comparison evaluated the change in weight following unilateral STN DBS in PD. In 39 patients who underwent unilateral STN DBS for PD, we measured the weight change over 1 year versus both preoperative weight change and the weight change in 40 age- and disease severity-matched PD controls without DBS. Regression analyses incorporating age, gender, baseline weight in case or control were conducted to assess weight changes. At 12 months following surgery, the mean weight of unilateral STN DBS patients increased by 4.3+/-7.2 kg versus the preoperative baseline weight (p<0.001) and this increase was 4.8 kg compared with the controls (p=0.015). Over a 1 year time interval, weight gain occurred in 41% of the preoperative unilateral STN DBS patients and 45% of the PD controls, while 85% of the unilateral STN DBS patients had gained weight at 12 months after surgery (p<0.0001, respectively, chi square test). We conclude that unilateral STN DBS in PD is associated with weight gain, which offsets weight loss associated with advanced PD.