Co-Occurrence of Apathy and Impulse Control Disorders in Parkinson Disease: Variation across Multiple Measures

OBJECTIVE

To determine if the co-occurrence of apathy and impulse control disorders (ICDs) in Parkinson disease is dependent on instrument selection and assess the concurrent validity of three motivation measures by examining interrelationships between them.

METHOD

Ninety-seven cognitively normal individuals with idiopathic Parkinson disease (PD) completed the Questionnaire for Impulsive-Compulsive Disorders in Parkinson Disease-Rating Scale (QUIP-RS) and three apathy measures: the Apathy Scale, Lille Apathy Rating Scale, and Item 4 of the Movement Disorder Society-Unified Parkinson Disease Rating Scale.

RESULTS

Fifty (51.5%) participants were classified as apathetic on at least one measure, and only four individuals (4.3%) obtained clinically elevated scores on all three measures. The co-occurrence of apathy and ICD varied across measures.

CONCLUSIONS

We observed a co-occurrence of apathy and ICDs in PD patients with each apathy instrument; however, limited concurrent validity exists across measures. This is important for future investigations into shared pathophysiology and the design of future clinical trials aimed at improving the early detection and treatment of these debilitating syndromes.

Weight and survival after deep brain stimulation for Parkinson's disease

BACKGROUND

Weight loss in Parkinson's disease (PD) is common and associated with increased mortality. The clinical significance of weight changes following deep brain stimulation (DBS) of the subthalamic nucleus (STN) and globus pallidus internus (GPi) is unclear.

OBJECTIVES

To address (1) whether PD patients exhibit progressive weight loss, (2) whether staged DBS surgery is associated with weight changes, and (3) whether survival after DBS correlates with post-DBS weight.

METHODS

This is a single-center, longitudinal, retrospective cohort study of 1625 PD patients. We examined trends in weight over time and the relationship between weight and years survival after DBS using regression and mixed model analyses.

RESULTS

There was a decline in body weight predating motor symptom onset (n = 756, 0.70 ± 0.03% decrease per year, p < 0.001). Weight decline accelerated in the decade preceding death (n = 456, 2.18 ± 0.31% decrease per year, p < 0.001). DBS patients showed a weight increase of 2.0 ± 0.33% at 1 year following the first DBS lead implant (n = 455) and 2.68 ± 1.1% at 3 years if a contralateral DBS lead was placed (n = 249). The bilateral STN DBS group gained the most weight after surgery during 6 years of follow up (vs bilateral GPi, 3.03 ± 0.45% vs 1.89 ± 0.31%, p < 0.01). An analysis of the DBS cohort with date of death available (n = 72) revealed that post-DBS weight (0-12 months after the first or 0-36 months after the second surgery) was positively associated with survival (R2 = 0.14, p < 0.001).

DISCUSSION

Though PD is associated with significant weight loss, DBS patients gained weight following surgery. Higher post-operative weight was associated with increased survival. These results should be replicated in other cohorts.

Evaluating analgesic medications utilized in the treatment of aneurysmal subarachnoid hemorrhage and association with delayed cerebral ischemia

BACKGROUND

Spontaneous aneurysmal subarachnoid hemorrhage (aSAH) recovery may be hampered by delayed cerebral ischemia (DCI). Herein, we sought to identify whether frequently administered medications in the intensive care unit (ICU) are associated with DCI.

METHODS

In this retrospective study, patients admitted to a tertiary care center neuro-ICU between 2012 and 2019 with aSAH who could verbalize pain intensity scores were included. Medication dosages and clinical characteristics were abstracted from the medical record. Both paired and unpaired analyses were utilized to measure individual DCI risk for a given patient in relation to drug dosages.

RESULTS

119 patients were included; average age was 61.7 ± 15.2 (SD) years, 89 (74.7%) were female, and 32 (26.9%) experienced DCI during admission. Patients with DCI had longer length of stay (19.3 ± 7.4 vs 12.7 ± 5.3 days, p < 0.0001). The combination medication of acetaminophen 325 mg/butalbital 50 mg/caffeine 40 mg (A/B/C) was associated with decreased DCI on paired (2.3 ± 2.0 vs 3.1 ± 1.9 tabs, p = 0.034) and unpaired analysis (1.84 ± 2.4 vs 2.6 ± 2.4 tabs, p < 0.001). No associations were found between DCI and opioids, dexamethasone, levetiracetam, or acetaminophen. Max and mean daily headache pain was not associated with DCI occurrence.

CONCLUSION

We identified an association between a commonly administered analgesic and DCI. A/B/C is associated with decreased DCI in this study, while other medications are not associated with DCI risk.

Course of Impulse Control Disorder Symptoms in Parkinson's Disease: Deep Brain Stimulation Versus Medications

Background

The effect of surgery on impulse control disorders (ICDs) remains unclear in Parkinson's disease (PD) patients undergoing deep brain stimulation (DBS).

Objective

To examine changes in ICD symptoms in PD patients undergoing DBS compared to a medication-only control group.

Methods

The study was a 2-center, 12-month, prospective, observational investigation of PD patients undergoing DBS and a control group matched on age, sex, dopamine agonist use, and baseline presence of ICDs. Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease-Rating Scale (QUIP-RS) and total levodopa equivalent daily dose (LEDD) were collected at baseline, 3, 6, and 12 months. Linear mixed-effects models assessed changes in mean QUIP-RS score (sum of buying, eating, gambling, and hypersexuality items).

Results

The cohort included 54 participants (DBS = 26, controls = 28), mean (SD) age 64.3 (8.1) and PD duration 8.0 (5.2) years. Mean baseline QUIP-RS was higher in the DBS group at baseline (8.6 (10.7) vs. 5.3 (6.9), P = 0.18). However, scores at 12 months follow-up were nearly identical (6.6 (7.3) vs. 6.0 (6.9) P = 0.79). Predictors of change in QUIP-RS score were baseline QUIP-RS score (β = 0.483, P < 0.001) and time-varying LEDD (β = 0.003, P = 0.02). Eight patients (four in each group) developed de novo ICD symptoms during follow-up, although none met diagnostic criteria for an impulse control disorder.

Conclusions

ICD symptoms (including de novo symptoms) at 12 months follow-up were similar between PD patients undergoing DBS and patients treated with pharmacological therapy only. Monitoring for emergence of ICD symptoms is important in both surgically- and medication-only-treated PD patients.

From pleasure to punding: Distinct patterns of anhedonia and impulsivity linked to motivational disturbances in Parkinson disease

INTRODUCTION

Apathy and impulse control disorders (ICD) are common comorbid motivational syndromes in Parkinson disease (PD). This study aimed to determine if patients with these motivational disturbances exhibit different patterns of anhedonia and trait impulsivity.

METHODS

Sixty-four non-demented patients with PD completed questionnaires assessing apathy and ICD symptoms, which were used to classify participants into one of the following groups: apathy only, ICD only, both, and neither. Participants also completed multidimensional measures of anhedonia and trait impulsivity, which were compared across groups defined by motivational status.

RESULTS

Individuals with both apathy and ICD had significantly greater symptoms of positive and negative urgency than all other groups and had significantly greater consummatory anhedonia and lack of premeditation and perseverance than those with ICD only and neither. Patients with apathy only also reported significantly greater anticipatory anhedonia than those with ICD only and the neither group. There were no significant between-group differences in sensation seeking.

CONCLUSION

Distinct patterns of impulsivity and anhedonia characterize unique behavioral phenotypes of motivational disturbances in PD and may reflect important differences in the underlying neurobiological mechanisms. Clinicians should be aware that motivational disturbances may be more severe in cases where apathy co-occurs with one or more ICD.HIGHLIGHTSHighlights are mandatory for all submissions except letters. They consist of a short collection of bullet points that convey the core findings of the article and should be submitted in a separate file in the online submission system. Please use "Highlights" in the file name and include 3-5 bullet points (maximum 85 characters, including spaces, per bullet point). See https://www.elsevier.com/highlights for examples.

Embedded Human Closed-Loop Deep Brain Stimulation for Tourette Syndrome: A Nonrandomized Controlled Trial

Importance

Because Tourette syndrome (TS) is a paroxysmal disorder, symptomatic relief in individuals with TS may be possible through the application of stimulation only during the manifestation of human tic neural signatures. This technique could be capable of suppressing both motor and vocal tics and would have similar effectiveness to conventional continuous deep brain stimulation (DBS).

Objective

To evaluate the feasibility, safety, and clinical effectiveness of bilateral centromedian-parafascicular complex thalamic closed-loop DBS as a treatment for medication-refractory TS.

Design, Setting, and Participants

This single-center double-blinded safety and feasibility trial was conducted between February 2014 and June 2020. Six individuals with TS were screened and recruited from the Norman Fixel Institute at the University of Florida. The primary outcome was measured at 6 months, and participants were followed up for the duration of the neurostimulator battery life. Independent ratings that compared closed-loop and conventional DBS were videotaped. The first 2 of 6 individuals with TS were excluded from the study because the technology for embedded closed-loop capability was not yet available. The date of analysis was August 2020.

Interventions

DBS therapy controlled by an embedded closed-loop stimulation system.

Main Outcomes and Measures

The primary clinical outcome measure was a minimum of a 40% reduction in the YGTSS score at 6 months following DBS. There was also a comparison of conventional DBS with closed-loop DBS using the Modified Rush Videotape Rating Scale for Tic.

Results

The mean (SD) age at TS diagnosis for the cohort was 8.5 (2.9), and the mean (SD) disease duration was 23.7 (5.8) years. Four individuals with TS were analyzed (2 male, 2 female; mean [SD] age, 23.7 [5.8] years). The study showed the closed-loop approach was both feasible and safe. One of the novelties of this study was that a patient-specific closed-loop paradigm was created for each participant. The features and stimulation transition speed were customized based on the signal quality and the tolerance to adverse reactions. The mean (SD) therapeutic outcome with conventional DBS was 33.3% (35.7%) improvement on the YGTSS and 52.8% (21.9%) improvement on the Modified Rush Videotape Rating Scale. Two of 4 participants had a primary outcome variable improvement of 40% meeting the primary efficacy target. When comparing closed-loop DBS with conventional DBS using a Wilcoxon sign-rank test, there was no statistical difference between tic severity score and both approaches revealed a lower tic severity score compared with baseline. The study was feasible in all 4 participants, and there were 25 total reported adverse events with 3 study-related events (12%). The most common adverse events were headache and anxiety.

Conclusions and Relevance

Embedded closed-loop deep DBS was feasible, safe, and had a comparable outcome to conventional TS DBS for the treatment of tics.

Trial Registration

ClinicalTrials.gov Identifier: NCT02056873.

Online vs Face-to-Face Administration of Impulse Control Disorder Questionnaires in Parkinson Disease: Does Method Matter?

Background:

Social desirability bias, the tendency to underreport undesirable behaviors, may be one reason patients with Parkinson disease (PD) underreport symptoms of impulse control disorders (ICDs).

Methods:

We compared rates of ICD endorsement on questionnaires administered face-to-face and online in 60 patients with mild to moderate idiopathic PD. Participants also completed a self-report measure of social desirability.

Results:

We found significantly higher prevalence of any ICD based on online (56.7%) versus in-person (33.3%) administration. Significantly higher endorsement of items related to hypersexuality in men, and compulsive eating and buying in women were found with online administration. Social desirability bias was positively correlated with ICD symptom endorsement across all items and subscales.

Conclusion:

Results highlight the importance of social context/setting and the need for sensitivity and discretion when screening for ICD symptoms. While a higher level of symptom endorsement does not necessarily imply a greater level of accuracy, more work is needed to determine which method of administration is most accurate for clinical and research practice.

Clinical risk factors associated with cerebrospinal fluid leak in facial trauma: A retrospective analysis

OBJECTIVE

Cerebrospinal fluid (CSF) leak occurs most commonly following skull fracture, with a CSF leakage complicating up to 2% of all head traumas. This study aims to identify demographic and injury characteristics correlated with the highest risk of CSF leak in patients with known facial fractures.

METHODS

Retrospective data was collected from a previously described trauma registry from 2010 to 2019. Patients over 18 years old with any type of facial fracture, known CSF leak status, available neuroimaging, and hospital admission were included. Chi-Square analysis for demographic and injury characteristic data were utilized.

RESULTS

A total of 79 patients with CSF leak and 4907 patients without CSF leak were included in the database. Patients with CSF leak tended to be younger than those without CSF leak (38.45 +/- 0.28 vs 44.08 +/- 0.28, M +/- SE, p = 0.0197). CSF leak depended on the mechanism of injury (MOI; X² =27.02, df=2, p = 0.0000013), with CSF leak rates highest in penetrating injuries (4.87%) and motor vehicle accidents (1.78%) compared to blunt injuries (0.95%); age did not significantly differ between the MOI groups (p = 0.11). CSF leak was also more common in patients with a lower Glasgow coma scale (GCS; 7.95 +/- 0.58 vs 12.21 +/- 0.10, p = 10^-15), LeFort type 2&3 and pan-facial fractures compared to all other facial fracture types (8.9% vs 1.2%, p = 10^-15), and radiographic midline shift (29.4% vs 9.1%, p = 10^-15). There was a trend towards a higher proportion of males in those with CSF leak compared to those without (83.3% vs 73.7% males, p = 0.073), and in patients with prolonged loss of consciousness (LOC; 9.43% with LOC > 1 h vs 2.69% LOC < 1 h, p = 0.056).

CONCLUSION

Facial fractures often present with CSF leak, and certain demographic and injury risk factors including younger age, worse GCS score, evidence of midline shift, and certain mechanisms of injury (penetrating and motor vehicle) are correlated with increased risk and warrant close screening and follow-up for CSF leak detection. LeFort type 2&3 and pan-facial fractures are at high risk of CSF leak.

Severe headache trajectory following aneurysmal subarachnoid hemorrhage: the association with lower sodium levels

BACKGROUND

A clinical hallmark of aneurysmal SAH (aSAH) is headache. Little is known about post-aSAH headache factors which may point to underlying mechanisms. In this study, we aimed to characterize the severity and trajectory of headaches in relation to clinical features of patients with aSAH.

METHODS

This is a retrospective longitudinal study of adult patients admitted to an academic tertiary care center between 2012 and 2019 with aSAH who could verbalize pain scores. Factors recorded included demographics, aneurysm characteristics, analgesia, daily morning serum sodium concentration, and occurrence of vasospasm. Group-based trajectory modeling was used to identify headache pain trajectories, and clinical factors were compared between trajectories.

RESULTS

Of 91 patients included in the analysis, mean age was 57 years and 20 (22%) were male. Headache score trajectories clustered into two groups: patients with mild-moderate and moderate-severe pain. Patients in the moderate-severe pain group were younger (P<0.05), received more opioid analgesia (P<0.001), and had lower sodium concentrations (P<0.001) than patients in the mild-moderate pain group.

CONCLUSION

We identified two distinct post-aSAH headache pain trajectory cohorts and identified an association with age, analgesia, and sodium levels. Future prospective studies considering sodium homeostasis and volume status under standardized analgesic regimens are warranted.

Distinct Roles of the Human Subthalamic Nucleus and Dorsal Pallidum in Parkinson's Disease Impulsivity

BACKGROUND

Impulsivity and impulse control disorders are common in Parkinson's disease and lead to increased morbidity and reduced quality of life. Impulsivity is thought to arise from aberrant reward processing and inhibitory control, but it is unclear why deep brain stimulation of either the subthalamic nucleus (STN) or globus pallidus internus (GPi) affects levels of impulsivity. Our aim was to assess the role of the STN and GPi in impulsivity using invasive local field potential (LFP) recordings from deep brain stimulation electrodes.

METHODS

We measured LFPs during a simple rewarding Go/NoGo paradigm in 39 female and male human patients with Parkinson's disease manifesting variable amounts of impulsivity who were undergoing unilateral deep brain stimulation of either the STN (18 nuclei) or GPi (28 nuclei). We identified reward-specific LFP event-related potentials and correlated them to impulsivity severity.

RESULTS

LFPs in both structures modulated during reward-specific Go and NoGo stimulus evaluation, reward feedback, and loss feedback. Motor and limbic functions were anatomically separable in the GPi but not in the STN. Across participants, LFP reward processing responses in the STN and GPi uniquely depended on the severity of impulsivity.

CONCLUSIONS

This study establishes LFP correlates of impulsivity within the STN and GPi regions. We propose a model for basal ganglia reward processing that includes the bottom-up role of the GPi in reward salience and the top-down role of the STN in cognitive control.

Chronic embedded cortico-thalamic closed-loop deep brain stimulation for the treatment of essential tremor

Deep brain stimulation (DBS) is an approved therapy for the treatment of medically refractory and severe movement disorders. However, most existing neurostimulators can only apply continuous stimulation [open-loop DBS (OL-DBS)], ignoring patient behavior and environmental factors, which consequently leads to an inefficient therapy, thus limiting the therapeutic window. Here, we established the feasibility of a self-adjusting therapeutic DBS [closed-loop DBS (CL-DBS)], fully embedded in a chronic investigational neurostimulator (Activa PC + S), for three patients affected by essential tremor (ET) enrolled in a longitudinal (6 months) within-subject crossover protocol (DBS OFF, OL-DBS, and CL-DBS). Most patients with ET experience involuntary limb tremor during goal-directed movements, but not during rest. Hence, the proposed CL-DBS paradigm explored the efficacy of modulating the stimulation amplitude based on patient-specific motor behavior, suppressing the pathological tremor on-demand based on a cortical electrode detecting upper limb motor activity. Here, we demonstrated how the proposed stimulation paradigm was able to achieve clinical efficacy and tremor suppression comparable with OL-DBS in a range of movements (cup reaching, proximal and distal posture, water pouring, and writing) while having a consistent reduction in energy delivery. The proposed paradigm is an important step toward a behaviorally modulated fully embedded DBS system, capable of delivering stimulation only when needed, and potentially mitigating pitfalls of OL-DBS, such as DBS-induced side effects and premature device replacement.

Globus Pallidus Internus (GPi) Deep Brain Stimulation for Parkinson's Disease: Expert Review and Commentary

INTRODUCTION

The globus pallidus internus (GPi) region has evolved as a potential target for deep brain stimulation (DBS) in Parkinson's disease (PD). DBS of the GPi (GPi DBS) is an established, safe and effective method for addressing many of the motor symptoms associated with advanced PD. It is important that clinicians fully understand this target when considering GPi DBS for individual patients.

METHODS

The literature on GPi DBS in PD has been comprehensively reviewed, including the anatomy, physiology and potential pitfalls that may be encountered during surgical targeting and post-operative management. Here, we review and address the implications of lead location on GPi DBS outcomes. Additionally, we provide a summary of randomized controlled clinical trials conducted on DBS in PD, together with expert commentary on potential applications of the GPi as target. Finally, we highlight future technologies that will likely impact GPi DBS, including closed-loop adaptive approaches (e.g. sensing-stimulating capabilities), advanced methods for image-based targeting and advances in DBS programming, including directional leads and pulse shaping.

RESULTS

There are important disease characteristics and factors to consider prior to selecting the GPi as the DBS target of PD surgery. Prior to and during implantation of the leads it is critical to consider the neuroanatomy, which can be defined through the combination of image-based targeting and intraoperative microelectrode recording strategies. There is an increasing body of literature on GPi DBS in patients with PD suggesting both short- and long-term benefits. Understanding the GPi target can be useful in choosing between the subthalamic (STN), GPi and ventralis intermedius nucleus as lead locations to address the motor symptoms and complications of PD.

CONCLUSION

GPi DBS can be effectively used in select cases of PD. As the ongoing DBS target debate continues (GPi vs. STN as DBS target), clinicians should keep in mind that GPi DBS has been shown to be an effective treatment strategy for a variety of symptoms, including bradykinesia, rigidity and tremor control. GPi DBS also has an important, direct anti-dyskinetic effect. GPi DBS is easier to program in the outpatient setting and will allow for more flexibility in medication adjustments (e.g. levodopa). Emerging technologies, including GPi closed-loop systems, advanced tractography-based targeting and enhanced programming strategies, will likely be future areas of GPi DBS expansion. We conclude that although the GPi as DBS target may not be appropriate for all PD patients, it has specific clinical advantages.

Comparative connectivity correlates of dystonic and essential tremor deep brain stimulation

The pathophysiology of dystonic tremor and essential tremor remains partially understood. In patients with medication-refractory dystonic tremor or essential tremor, deep brain stimulation (DBS) targeting the thalamus or posterior subthalamic area has evolved into a promising treatment option. However, the optimal DBS targets for these disorders remains unknown. This retrospective study explored the optimal targets for DBS in essential tremor and dystonic tremor using a combination of volumes of tissue activated estimation and functional and structural connectivity analyses. We included 20 patients with dystonic tremor who underwent unilateral thalamic DBS, along with a matched cohort of 20 patients with essential tremor DBS. Tremor severity was assessed preoperatively and approximately 6 months after DBS implantation using the Fahn-Tolosa-Marin Tremor Rating Scale. The tremor-suppressing effects of DBS were estimated using the percentage improvement in the unilateral tremor-rating scale score contralateral to the side of implantation. The optimal stimulation region, based on the cluster centre of gravity for peak contralateral motor score improvement, for essential tremor was located in the ventral intermediate nucleus region and for dystonic tremor in the ventralis oralis posterior nucleus region along the ventral intermediate nucleus/ventralis oralis posterior nucleus border (4 mm anterior and 3 mm superior to that for essential tremor). Both disorders showed similar functional connectivity patterns: a positive correlation between tremor improvement and involvement of the primary sensorimotor, secondary motor and associative prefrontal regions. Tremor improvement, however, was tightly correlated with the primary sensorimotor regions in essential tremor, whereas in dystonic tremor, the correlation was tighter with the premotor and prefrontal regions. The dentato-rubro-thalamic tract, comprising the decussating and non-decussating fibres, significantly correlated with tremor improvement in both dystonic and essential tremor. In contrast, the pallidothalamic tracts, which primarily project to the ventralis oralis posterior nucleus region, significantly correlated with tremor improvement only in dystonic tremor. Our findings support the hypothesis that the pathophysiology underpinning dystonic tremor involves both the cerebello-thalamo-cortical network and the basal ganglia-thalamo-cortical network. Further our data suggest that the pathophysiology of essential tremor is primarily attributable to the abnormalities within the cerebello-thalamo-cortical network. We conclude that the ventral intermediate nucleus/ventralis oralis posterior nucleus border and ventral intermediate nucleus region may be a reasonable DBS target for patients with medication-refractory dystonic tremor and essential tremor, respectively. Uncovering the pathophysiology of these disorders may in the future aid in further improving DBS outcomes.

A novel local field potential-based functional approach for targeting the centromedian-parafascicular complex for deep brain stimulation

BACKGROUND

The centromedian-parafascicular (Cm-Pf) complex of the thalamus is a common deep brain stimulation (DBS) target for treatment of Tourette syndrome (TS). Currently, there are no standardized functional intraoperative neurosurgical targeting approaches. Collectively, these issues have led to variability in DBS lead placement. Therefore, more defined methods are needed to improve targeting accuracy.

OBJECTIVE

The objective of this observational study was to develop and to verify a functional mapping task capable of differentiating the Cm-Pf region from the nearby ventral intermediate (Vim) nucleus region of the thalamus. The overarching goal was to improve the reproducibility of DBS targeting in the Cm-Pf region.

METHODS

Seven TS patients completed a modified Go/NoGo task (five in the post-operative setting and two in the intra-operative setting). Post-operative neural signals from Cm-Pf region were collected using sensing-enabled implanted neural stimulators, and intraoperative neural signals from the Cm-Pf region were collected using an external amplifier. Event-related potential (ERP) features were identified by using the grand-average of stimulus onset signals derived from the postoperative participants. These features were correlated with anatomical locations for the specific electrode recordings. The same features were extracted from the intraoperative patients in order to verify electrode positions in the operating room environment.

RESULTS

Two features - a positive and a negative deflection - were identified in the average ERP from the post-operative participants. The peak amplitudes of both features were significantly correlated with the electrode depth position (p = 0.025 for positive deflection and p = 0.039 for negative deflection). The same result was reproduced intra-operatively in the two most recent patients, where more ventral electrode contacts revealed stronger peak amplitudes in comparison to the dorsal electrode contacts.

CONCLUSION

This process was used to physiologically confirm accurate lead placement in the operating room setting. The modified Go/NoGo task elicited robust neural responses in the Cm-Pf region however the signal was not present in the Vim nucleus region of thalamus along the DBS electrode trajectory. We conclude that the differences in ERP responses may be a potentially novel LFP based functional approach for future targeting of the Cm-Pf complex for TS DBS.

Closed-Loop Deep Brain Stimulation to Treat Medication-Refractory Freezing of Gait in Parkinson's Disease

Background: Treating medication-refractory freezing of gait (FoG) in Parkinson’s disease (PD) remains challenging despite several trials reporting improvements in motor symptoms using subthalamic nucleus or globus pallidus internus (GPi) deep brain stimulation (DBS). Pedunculopontine nucleus (PPN) region DBS has been used for medication-refractory FoG, with mixed findings. FoG, as a paroxysmal phenomenon, provides an ideal framework for the possibility of closed-loop DBS (CL-DBS).

Methods: In this clinical trial (NCT02318927), five subjects with medication-refractory FoG underwent bilateral GPi DBS implantation to address levodopa-responsive PD symptoms with open-loop stimulation. Additionally, PPN DBS leads were implanted for CL-DBS to treat FoG. The primary outcome of the study was a 40% improvement in medication-refractory FoG in 60% of subjects at 6 months when “on” PPN CL-DBS. Secondary outcomes included device feasibility to gauge the recruitment potential of this four-lead DBS approach for a potentially larger clinical trial. Safety was judged based on adverse events and explantation rate.

Findings: The feasibility of this approach was demonstrated as we recruited five subjects with both “on” and “off” medication freezing. The safety for this population of patients receiving four DBS leads was suboptimal and associated with a high explantation rate of 40%. The primary clinical outcome in three of the five subjects was achieved at 6 months. However, the group analysis of the primary clinical outcome did not reveal any benefit.

Interpretation: This study of a human PPN CL-DBS trial in medication-refractory FoG showed feasibility in recruitment, suboptimal safety, and a heterogeneous clinical effect in FoG outcomes.

STN Versus GPi Deep Brain Stimulation for Action and Rest Tremor in Parkinson's Disease

Objective

To investigate the effects of subthalamic nucleus (STN) and globus pallidus internus (GPi), deep brain stimulation (DBS) on individual action tremor/postural tremor (AT) and rest tremor (RT) in Parkinson’s disease (PD). Randomized DBS studies have reported marked benefit in tremor with both GPi and STN and DBS, however, there is a paucity of information available on AT vs RT when separated by the surgical target.

Methods

We retrospectively reviewed the 1-year clinical outcome of PD patients treated with STN and GPi DBS at the University of Florida. We specifically selected patients with moderate to severe AT. Eighty-eight patients (57 STN and 31 GPi) were evaluated at 6 and 12 months for changes in AT and RT in the OFF-medication/ON stimulation state. A comparison of “response” was performed and defined as greater than or equal to a 2-point decrease in tremor score.

Results

STN and GPi DBS both improved AT at 6- and 12-months post-implantation (p < 0.001 and p < 0.001). The STN DBS group experienced a greater improvement in AT at 6 months compared to the GPi group (p = 0.005) but not at the 12 months follow-up (p = 0.301). Both STN and GPi DBS also improved RT at 6- and 12-months post-implantation (p < 0.001 and p < 0.001). There was no difference in RT scores between the two groups at 6 months (p = 0.23) or 12 months (p = 0.74). The STN group had a larger proportion of patients who achieved a “response” in AT at 6 months (p < 0.01), however, this finding was not present at 12 months (p = 0.23). A sub-analysis revealed that in RT, the STN group had a larger percentage of “responders” when followed through 12 months (p < 0.01).

Conclusion

Both STN and GPi DBS reduced PD associated AT and RT at 12 months follow-up. There was no advantage of either brain target in the management of RT or AT. One nuance of the study was that STN DBS was more effective in suppressing AT in the early postoperative period, however, this effect diminished over time. Clinicians should be aware that it may take longer to achieve a similar tremor outcome when utilizing the GPi target.

Long-term clinical outcomes of bilateral GPi deep brain stimulation in advanced Parkinson's disease: 5 years and beyond

OBJECTIVE

Few studies have reported long-term outcomes of globus pallidus internus (GPi) deep brain stimulation (DBS) in Parkinson's disease (PD). The authors aimed to investigate long-term outcomes of bilateral GPi DBS for 5 years and beyond for PD patients.

METHODS

The authors retrospectively analyzed the clinical outcomes in 65 PD patients treated with bilateral GPi DBS at a single center. The outcome measures of motor symptoms and health-related quality of life (HRQoL) included the Unified Parkinson's Disease Rating Scale (UPDRS) and the Parkinson's Disease Questionnaire (PDQ-39). Scores at baseline were compared with those at 1, 3, 5, and 6-8 years after implantation using Wilcoxon signed-rank tests with α correction.

RESULTS

GPi DBS significantly improved the off-medication UPDRS III total scores, UPDRS IV, and dyskinesia score at 1 year when compared with baseline (all p < 0.001). The off- and on-medication tremor scores, UPDRS IV, and dyskinesia scores showed moderate and sustained improvement (the ranges of the mean percentage improvement at each time point were 61%-75%, 30%-80%, 29%-40%, and 40%-65%, respectively) despite lacking statistical significance at long-term follow-up with diminishing sample sizes. The off-medication UPDRS III total scores did not show significant improvement at 5 years or later, primarily because of worsening in rigidity, akinesia, speech, gait, and postural stability scores. The on-medication UPDRS III total scores also worsened over time, with a significant worsening at 6-8 years when compared with baseline (p = 0.008). The HRQoL analyses based on the PDQ-39 revealed significant improvement in the activities of daily living and discomfort domains at 1 year (p = 0.003 and 0.006, respectively); however, all the domains showed gradual worsening at the later time points without reaching statistical significance. At 3 years, the communication domain showed significant worsening compared with baseline scores (p = 0.002).

CONCLUSIONS

GPi DBS in PD patients in this single-center cohort was associated with sustained long-term benefits in the off- and on-medication tremor score and motor complications. HRQoL and the cardinal motor symptoms other than tremor may worsen gradually in the long term. When counseling patients, it is important to recognize that benefits in tremor and dyskinesia are expected to be most persistent following bilateral GPi DBS implantation.

Co-occurrence of apathy and impulse control disorders in Parkinson disease

OBJECTIVE

To empirically test whether apathy and impulse control disorders (ICDs) represent independent, opposite ends of a motivational spectrum.

METHODS

In this single-center, cross-sectional study, we obtained retrospective demographics and clinical data for 887 patients with idiopathic Parkinson disease (PD) seen at a tertiary care center. Mood and motivation disturbances were classified using recommended cutoff scores from self-reported measures of apathy, ICD, anxiety, and depression.

RESULTS

Prevalence rates included 29.0% of patients with PD with depression, 40.7% with anxiety, 41.3% with apathy, 27.6% with ICDs, and 17.0% with both apathy and ICD. The majority (61.6%) of people reporting clinically significant ICDs also reported clinically significant apathy, and more than a third of patients with apathy (41.3%) also reported elevated ICD. Anxiety and depression were highest in patients with both apathy and ≥1 ICDs. Dopamine agonist use was higher in people with only ICD compared to people with only apathy. Mood significantly interacted with demographic variables to predict motivational disturbances.

CONCLUSIONS

Motivational disturbances are common comorbid conditions in patients with PD. In addition, these complex behavioral syndromes interact with mood in clinically important ways that may influence the design of future clinical trials and the development of novel therapies. This study challenges the concept of apathy and ICD in PD as opposite ends of a spectrum.

Neuroimaging Advances in Deep Brain Stimulation: Review of Indications, Anatomy, and Brain Connectomics

Deep brain stimulation is an established therapy for multiple brain disorders, with rapidly expanding potential indications. Neuroimaging has advanced the field of deep brain stimulation through improvements in delineation of anatomy, and, more recently, application of brain connectomics. Older lesion-derived, localizationist theories of these conditions have evolved to newer, network-based "circuitopathies," aided by the ability to directly assess these brain circuits in vivo through the use of advanced neuroimaging techniques, such as diffusion tractography and fMRI. In this review, we use a combination of ultra-high-field MR imaging and diffusion tractography to highlight relevant anatomy for the currently approved indications for deep brain stimulation in the United States: essential tremor, Parkinson disease, drug-resistant epilepsy, dystonia, and obsessive-compulsive disorder. We also review the literature regarding the use of fMRI and diffusion tractography in understanding the role of deep brain stimulation in these disorders, as well as their potential use in both surgical targeting and device programming.

Pavlovian bias in Parkinson's disease: an objective marker of impulsivity that modulates with deep brain stimulation

Impulsivity is a common symptom in Parkinson's disease (PD). Adaptive behavior is influenced by prepotent action-reward and inaction-avoid loss Pavlovian biases. We aimed to assess the hypothesis that impulsivity in PD is associated with Pavlovian bias, and to assess whether dopaminergic medications and deep brain stimulation (DBS) influence Pavlovian bias. A PD DBS cohort (N = 37) completed a reward-based Go/No-Go task and bias measures were calculated. This DBS cohort completed the task under three conditions: on-med/pre-DBS, off-med/off-DBS, and on-med/on-DBS. Participants also completed self-reported measures of impulsivity. Dopaminergic medication was associated with lower action-reward bias while DBS was associated with higher action-reward bias. Impulsivity was associated with higher action-reward bias but not inaction-avoid loss bias. We furthermore replicated this association in an independent, non-DBS PD cohort (N = 88). Overall we establish an objective behavioral marker of impulsivity and show that DBS affects impulsivity by amplifying automated responding. Our results point to the importance of reward rather than punishment avoidance in driving impulsive behaviors. This work provides insight into the pathophysiological underpinnings of impulsivity and especially medication and DBS-associated impulsivity in PD.

Long-term Parkinson's disease quality of life after staged DBS: STN vs GPi and first vs second lead

Deep brain stimulation (DBS) for Parkinson’s disease (PD) improves quality of life (QoL), but longitudinal follow-up data are scarce. We sought to quantify long-term benefits of subthalamic nucleus (STN) vs globus pallidus internus (GPi), and unilateral vs staged bilateral PD-DBS on postoperative QoL. This is a retrospective, longitudinal, non-randomized study using the PD QoL questionnaire (PDQ)-39 in patients with STN- or GPi-DBS, and with unilateral (N = 191) or staged bilateral (an additional contralateral lead implant) surgery (N = 127 and 156 for the first and second lead, respectively). Changes in PDQ-39 summary index (PDQ-39SI) and subscores throughout 60 months of follow-up were used as the primary analysis. We applied mixed models that included levodopa and covariates that differed at baseline across groups. For unilateral implantation, we observed an initial improvement in PDQ-39SI of 15.55 ± 3.29% (µ ± SE) across both brain targets at 4 months postoperatively. Unilateral STN patients demonstrated greater improvement in PDQ-39SI than GPi patients at 4 and 18 months postoperatively. Analysis of patients with staged bilateral leads revealed an initial 25.34 ± 2.74% (µ ± SE) improvement in PDQ-39SI at 4 months after the first lead with further improvement until 18 months, with no difference across targets. Scores did not improve after the second lead with gradual worsening starting at 18 months postoperatively. STN-DBS provided greater short-term QoL improvement than GPi-DBS for unilateral surgery. For staged bilateral DBS, overall QoL improvement was explained primarily by the first lead. Decision-making for patients considering DBS should include a discussion surrounding the potential risks and benefits from a second DBS lead.

Therapeutic Advances in the Treatment of Holmes Tremor: Systematic Review

OBJECTIVE

We aimed to formulate a practical clinical treatment algorithm for Holmes's tremor (HT) by reviewing currently published clinical data.

MATERIALS AND METHODS

We performed a systematic review of articles discussing the management of HT published between January 1990 and December 2018. We examined data from 89 patients published across 58 studies detailing the effects of pharmacological or surgical interventions on HT severity. Clinical outcomes were measured by a continuous 1-10 ranked scale. The majority of studies addressing treatment response were case series or case reports. No randomized control studies were identified.

RESULTS

Our review included 24 studies focusing on pharmacologic treatments of 25 HT patients and 34 studies focusing on the effect of deep brain stimulation (DBS) in 64 patients. In the medical intervention group, the most commonly used drugs were levetiracetam, trihexyphenidyl, and levodopa. In the surgically treated group, the thalamic ventralis intermedius nucleus (VIM) and globus pallidus internus (GPi) were the most common brain targets for neuromodulation. The two targets accounted for 57.8% and 32.8% of total cases, respectively. Overall, compared to the medically treated group, DBS provided greater tremor suppression (p = 0.025) and was more effective for the management of postural tremor in HT. Moreover, GPi DBS displayed greater benefit in the resting tremor component (p = 0.042) and overall tremor reduction (p = 0.022).

CONCLUSIONS

There is a highly variable response to different medical treatments in HT without randomized clinical trials available to dictate treatment decisions. A variety of medical and surgical treatment options can be considered for the management of HT. Collaborative reseach between different institutions and researchers are warranted and needed to improve our understanding of the pathophysiology and management of this condition. In this review, we propose a practical treatment algorithm for HT based on currently available evidence.

Florida research open-source synchronization tool (FROST) for electrophysiology experiments

BACKGROUND

Accurate interpretation of electrophysiological data in cognitive and behavioral experiments requires the acquisition of time labels, such as marking the exact start of a condition or moment a stimulus is presented to a research subject.

NEW METHOD

Here we present an inexpensive (∼30 USD) device used as a central relay for multiple peripheral devices, such as a computer screen presenting an experiment, a pressure-sensor push button, a multi-button responder, a pulse oximeter sensor, a light-emitting diode trigger for camera synchronization, and more. We refer to this device as the Florida Research Open-source Synchronization Tool (FROST). FROST allows for easy hardware and Arduino-based firmware modifications that enable a standard platform for the integration of novel peripheral sensors.

RESULTS

With two examples, we demonstrate the application of this device during human research experiments: intracranial-electroencephalography (EEG) recordings in a patient with epilepsy and surface-EEG recordings in a healthy participant. We provide an example setup for a rodent experiment as well. We also demonstrate the timing delays of our device.

COMPARISON WITH EXISTING METHODS

There is currently very few existing open-source synchronization tools for electrophysiological research that enable customization with new device compatibility. We developed this tool to enable widespread replication for many applications through an open-source platform.

CONCLUSIONS

FROST can be easily adapted for research experiments beyond the included example cases. All materials are open-source at github.com/Brain-Mapping-Lab/FROST.

Parkinson's disease motor subtypes and bilateral GPi deep brain stimulation: One-year outcomes

OBJECTIVE

We aimed to explore the differences in motor symptoms and quality of life (QOL) outcomes following bilateral globus pallidus internus deep brain stimulation (GPi DBS), across well-defined motor subtypes of Parkinson's disease (PD), to improve clinical decision making.

METHODS

This single-center retrospective study investigated bilateral GPi DBS outcomes in 65 PD patients. Outcome measures included the Unified Parkinson's Disease Rating Scale (UPDRS) and Parkinson's Disease Questionnaire (PDQ-39) before and one year after surgery. Outcomes were compared between the tremor-dominant (TD) and postural instability and gait difficulty (PIGD) subtypes and between the TD and akinetic-rigid (AR) subtypes.

RESULTS

For the entire cohort, motor function (UPDRS III) in the Off-medication state, motor complications (UPDRS IV), activities of daily living (ADL, UPDRS II), and the ADL and discomfort domains of PDQ-39 significantly improved one year following GPi implantation compared to baseline (effect size = 1.32, 1.15, 0.25, 0.45, and 0.34, respectively). GPi DBS improved the Off-medication UPDRS III scores regardless of the motor subtypes. However, compared to the PIGD and AR patients, the TD patients showed greater improvement in overall UPDRS III postoperatively primarily due to greater tremor improvement in the Off-medication state. The outcomes in akinesia, rigidity, axial symptoms and QOL were similar among all subtypes.

CONCLUSION

Bilateral GPi DBS was effective for advanced PD patients regardless of motor subtypes. Greater tremor improvement in the TD patients accounted for greater Off-medication motor improvement. Longer-term GPi DBS outcomes across different motor subtypes and brain targets should be further studied.

Obesity and STING1 genotype associate with 23-valent pneumococcal vaccination efficacy

BACKGROUND

Obesity has been associated with attenuated vaccine responses and an increased risk of contracting pneumococcal pneumonia, but no study to our knowledge has assessed the impact of obesity and genetics on 23-valent pneumococcal vaccine (PPSV23) efficacy. We assessed the relationship of obesity (primary analysis) and stimulator of interferon genes (STING1) genotype (secondary analysis) on PPSV23 efficacy.

METHODS

Nonobese (BMI 22–25 kg/m²) and obese participants (BMI ≥30 kg/m²) were given a single dose of PPSV23. Blood was drawn immediately prior to and 4–6 weeks after vaccination. Serum samples were used to assess PPSV23-specific antibodies. STING1 genotypes were identified using PCR on DNA extracted from peripheral blood samples.

RESULTS

Forty-six participants were categorized as nonobese (n = 23; 56.5% women; mean BMI 23.3 kg/m²) or obese (n = 23; 65.2% women; mean BMI 36.3 kg/m²). Obese participants had an elevated fold change in vaccine-specific responses compared with nonobese participants (P < 0.0001). The WT STING1 group (R232/R232) had a significantly higher PPSV23 response than individuals with a single copy of HAQ-STING1 regardless of BMI (P = 0.0025). When WT was assessed alone, obese participants had a higher fold serotype-specific response compared with nonobese participants (P < 0.0001), but no difference was observed between obese and nonobese individuals with 1 HAQ allele (P = 0.693).

CONCLUSIONS

These observations demonstrate a positive association between obesity and PPSV23 efficacy specifically in participants with the WT STING1 genotype.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02471014.

FUNDING

This research was supported by the NIH and the University of Florida MD-PhD Training Program.

Obesity and a WT STING1 genotype are positively associated with efficacy of the 23-valent pneumococcal vaccine in a small cohort of subjects.

Proceedings of the Seventh Annual Deep Brain Stimulation Think Tank: Advances in Neurophysiology, Adaptive DBS, Virtual Reality, Neuroethics and Technology

The Seventh Annual Deep Brain Stimulation (DBS) Think Tank held on September 8th of 2019 addressed the most current: (1) use and utility of complex neurophysiological signals for development of adaptive neurostimulation to improve clinical outcomes; (2) Advancements in recent neuromodulation techniques to treat neuropsychiatric disorders; (3) New developments in optogenetics and DBS; (4) The use of augmented Virtual reality (VR) and neuromodulation; (5) commercially available technologies; and (6) ethical issues arising in and from research and use of DBS. These advances serve as both "markers of progress" and challenges and opportunities for ongoing address, engagement, and deliberation as we move to improve the functional capabilities and translational value of DBS. It is in this light that these proceedings are presented to inform the field and initiate ongoing discourse. As consistent with the intent, and spirit of this, and prior DBS Think Tanks, the overarching goal is to continue to develop multidisciplinary collaborations to rapidly advance the field and ultimately improve patient outcomes.

Functional and Structural Connectivity Patterns Associated with Clinical Outcomes in Deep Brain Stimulation of the Globus Pallidus Internus for Generalized Dystonia

BACKGROUND AND PURPOSE

Deep brain stimulation is a well-established treatment for generalized dystonia, but outcomes remain variable. Establishment of an imaging marker to guide device targeting and programming could possibly impact the efficacy of deep brain stimulation in dystonia, particularly in the absence of acute clinical markers to indicate benefit. We hypothesize that the stimulation-based functional and structural connectivity using resting-state fMRI and DTI can predict therapeutic outcomes in patients with generalized dystonia and deep brain stimulation.

MATERIALS AND METHODS

We performed a retrospective analysis of 39 patients with inherited or idiopathic-isolated generalized dystonia who underwent bilateral globus pallidus internus deep brain stimulation. After electrode localization, the volumes of tissue activated were modeled and used as seed regions for functional and structural connectivity measures using a normative data base. Resulting connectivity maps were correlated with postoperative improvement in the Unified Dystonia Rating Scale score.

RESULTS

Structural connectivity between the volumes of tissue activated and the primary sensorimotor cortex was correlated with Unified Dystonia Rating Scale improvement, while more anterior prefrontal connectivity was inversely correlated with Unified Dystonia Rating Scale improvement. Functional connectivity between the volumes of tissue activated and primary sensorimotor regions, motor thalamus, and cerebellum was most correlated with Unified Dystonia Rating Scale improvement; however, an inverse correlation with Unified Dystonia Rating Scale improvement was seen in the supplemental motor area and premotor cortex.

CONCLUSIONS

Functional and structural connectivity with multiple nodes of the motor network is associated with motor improvement in patients with generalized dystonia undergoing deep brain stimulation. Results from this study may serve as a basis for future development of clinical markers to guide deep brain stimulation targeting and programming in dystonia.

Three-Year Gait and Axial Outcomes of Bilateral STN and GPi Parkinson's Disease Deep Brain Stimulation

Objective: To examine the short- and long-term clinical outcomes of the bilateral subthalamic nucleus (STN) and globus pallidus internus (GPi) deep brain stimulation (DBS) on gait and axial symptoms in Parkinson's disease (PD) patients. Available data have been inconsistent and mostly short-term regarding the effect of both brain targets on gait and axial symptoms. We aimed to identify potential target specific differences at 3-year follow-up from a large single-center experience. Methods: We retrospectively reviewed short-term (6-month follow-up) and long-term (36-month follow-up) changes in the Unified Parkinson's Disease Rating Scale (UPDRS) Part II and III total scores of 72 PD patients (53 with bilateral STN-DBS and 19 with bilateral GPi-DBS). An interdisciplinary team made target-specific decisions for each DBS patient. We analyzed changes in gait and axial subscores derived from UPDRS II and III. Results: In both the STN- and GPi-DBS cohorts, we observed no significant differences in gait and axial UPDRS derived subscores in the off-med/on stimulation state at long-term follow-up when compared to baseline. On-med axial scores remained similar in the short-term but worsened in both groups (STN, 2.23 ± 3.43, p < 0.001; GPi, 2.53 ± 2.37, p < 0.01) in the long-term possibly due to disease progression. At long-term follow-up, the UPDRS III off-med/on stimulation scores worsened but were persistently improved from baseline in both groups (-9.07 ± 13.9, p < 0.001). Conclusions: The study showed that long-term both STN- and GPi-DBS had a similar effect on gait and axial symptoms in UPDRS derived subscores at 36-month follow-up despite potential baseline differences in criteria for selection of each target. More sophisticated measures of gait and balance beyond the categorical UPDRS score will be needed for future studies.

Pallidal versus subthalamic nucleus deep brain stimulation for levodopa-induced dyskinesia

OBJECTIVE

To compare the efficacy of subthalamic nucleus (STN) and globus pallidus internus (GPi) deep brain stimulation (DBS) on reducing levodopa-induced dyskinesia (LID) in Parkinson's disease, and to explore the potential underlying mechanisms.

METHODS

We retrospectively assessed clinical outcomes in 43 patients with preoperative LID who underwent DBS targeting the STN (20/43) or GPi (23/43). The primary clinical outcome was the change from baseline in the Unified Dyskinesia Rating Scale (UDysRS) and secondary outcomes included changes in the total daily levodopa equivalent dose, the drug-off Unified Parkinson Disease Rating Scale Part Ⅲ at the last follow-up (median, 18 months), adverse effects, and programming settings. Correlation analysis was used to find potential associated factors that could be used to predict the efficacy of DBS for dyskinesia management.

RESULTS

Compared to baseline, both the STN group and the GPi group showed significant improvement in LID with 60.73 ± 40.29% (mean ± standard deviation) and 93.78 ± 14.15% improvement, respectively, according to the UDysRS score. Furthermore, GPi-DBS provided greater clinical benefit in the improvement of dyskinesia (P < 0.05) compared to the STN. Compared to the GPi group, the levodopa equivalent dose reduction was greater in the STN group at the last follow-up (43.81% vs. 13.29%, P < 0.05). For the correlation analysis, the improvement in the UDysRS outcomes were significantly associated with a reduction in levodopa equivalent dose in the STN group (r = 0.543, P = 0.013), but not in the GPi group (r = -0.056, P = 0.801).

INTERPRETATION

Both STN and GPi-DBS have a beneficial effect on LID but GPi-DBS provided greater anti-dyskinetic effects. Dyskinesia suppression for STN-DBS may depend on the reduction of levodopa equivalent dose. Unlike the STN, GPi-DBS might exert a direct and independent anti-dyskinesia effect.

Rescue levodopa-carbidopa intestinal gel (LCIG) therapy in Parkinson's disease patients with suboptimal response to deep brain stimulation

Objective

To evaluate the effectiveness of levodopa‐carbidopa intestinal gel (LCIG) as an add‐on rescue therapy following deep brain stimulation (DBS) for treatment of motor fluctuations.

Background

Both DBS and LCIG are FDA‐approved therapies for treatment of motor fluctuations in advanced PD. Few studies have examined dual therapy for refractory motor fluctuations and it is unknown what the effect on quality of life will be in advanced PD.

Methods

We conducted a retrospective study using a large database of all medical and surgical PD cases at the University of Florida. Six patients were identified with DBS who subsequently received rescue LCIG therapy. The clinical histories, indications for intervention and outcomes were reviewed.

Results

All patients were managed initially with DBS (bilateral STN DBS (n = 3), bilateral GPi DBS (n = 1), unilateral GPI DBS (n = 2)). Patients with well‐placed (n = 3) and suboptimally placed DBS leads (n = 3) had significant reduction in their motor fluctuations with improvement in the off‐medication time after rescue LCIG therapy. Improvement in quality of life scores (PDQ‐39) was appreciated in four DBS patients following the addition of LCIG therapy.

Conclusions

LCIG is a promising add‐on rescue therapy for select patients with existing DBS devices. The LCIG may possibly reduce motor fluctuations and improve quality of life in advanced PD irrespective of the DBS target or the accuracy of lead placement. Dual therapy may also be ideal for patients who are considered high risk for additional DBS surgeries.

Dorsal GPi/GPe Stimulation Induced Dyskinesia in a Patient with Parkinson's Disease

Clinical vignette

A 68-year-old man with Parkinson’s disease (PD) had bilateral GPi DBS placed for management of his motor fluctuations. He developed stimulation-induced dyskinesia (SID) with left dorsal GPi stimulation.

Clinical dilemma

What do we know about SID in PD patients with GPi DBS? What are the potential strategies used to maximize the DBS therapeutic benefit and minimize the side effects of stimulation?

Clinical solution

Avoiding the contact implicated in SID and programming more ventral contacts, using lower voltage, frequency and pulse width and programming in bipolar configuration all appear to help minimize the SID and provide appropriate symptomatic motor control.

Gap in knowledge

Little is known about SID in patients with PD who had GPi DBS therapy. More studies using volume of tissue activated and diffusion tensor imaging MRI are needed to localize specific tracts in or around the GPi that may be implicated in SID.

Gait worsening and the microlesion effect following deep brain stimulation for essential tremor

OBJECTIVE

To investigate the effects of unilateral thalamic deep brain stimulation (DBS) on walking in persons with medication-refractory essential tremor (ET).

METHODS

We performed laboratory-based gait analyses on 24 persons with medication-refractory ET before and after unilateral thalamic DBS implantation. Normal and tandem walking parameters were analysed across sessions (PRE-DBS/DBS OFF/DBS ON) by repeated measures analyses of variance. Pearson's correlations assessed whether changes in walking after DBS were global (ie, related across gait parameters). Baseline characteristics, lead locations and stimulation parameters were analysed as possible contributors to gait effects.

RESULTS

DBS minimally affected gait at the cohort level. However, 25% of participants experienced clinically meaningful gait worsening. Walking speed decreased by >30% in two participants and by >10% in four others. Decreased walking speed correlated with increased gait variability, indicating global gait worsening in affected participants. The worsening persisted even after the stimulation was turned off. Participants with worse baseline tandem walking performance may be more likely to experience post-DBS gait worsening; the percentage of tandem missteps at baseline was nearly three times higher and tandem walking speeds were approximately 30% slower in participants who experienced gait worsening. However, these differences in tandem walking in persons with gait worsening as compared with those without worsening were not statistically significant. Lead locations and stimulation parameters were similar in participants with and without gait worsening.

CONCLUSION

Global gait worsening occurred in 25% of participants with unilateral DBS for medication-refractory ET. The effect was present on and off stimulation, likely indicating a microlesion effect.

Medications, Deep Brain Stimulation, and Other Factors Influencing Impulse Control Disorders in Parkinson's Disease

Impulse control disorders (ICDs) in Parkinson's disease (PD) have a high cumulative incidence and negatively impact quality of life. ICDs are influenced by a complex interaction of multiple factors. Although it is now well-recognized that dopaminergic treatments and especially dopamine agonists underpin many ICDs, medications alone are not the sole cause. Susceptibility to ICD is increased in the setting of PD. While causality can be challenging to ascertain, a wide range of modifiable and non-modifiable risk factors have been linked to ICDs. Common characteristics of PD patients with ICDs have been consistently identified across many studies; for example, males with an early age of PD onset and dopamine agonist use have a higher risk of ICD. However, not all cases of ICDs in PD can be directly attributable to dopamine, and studies have concluded that additional factors such as genetics, smoking, and/or depression may be more predictive. Beyond dopamine, other ICD associations have been described but remain difficult to explain, including deep brain stimulation surgery, especially in the setting of a reduction in dopaminergic medication use. In this review, we will summarize the demographic, genetic, behavioral, and clinical contributions potentially influencing ICD onset in PD. These associations may inspire future preventative or therapeutic strategies.

Against the Overgrowth Hypothesis: Shorter Costal Cartilage Lengths in Pectus Excavatum

BACKGROUND

Pectus excavatum is a common chest wall deformity with no known cause. A common hypothesis is that in patients with pectus excavatum, there is an overgrowth of costal cartilage relative to healthy individuals.

MATERIALS AND METHODS

We obtained radiological curvilinear three-dimensional measurements of the fourth to eighth costal cartilage and associated ribs in 16 patients with pectus excavatum and 16 age- and gender-matched controls between the ages of 6 and 32 y. An analysis of variance was used to compare bone length, cartilage length, and their ratios between patients and controls.

RESULTS

Relative to bone length, patients with pectus excavatum overall had shorter costal cartilage lengths (P < 0.001), especially on the left side (P < 0.05). We were unable to localize this observation to specific ribs during post hoc analysis.

CONCLUSIONS

This is the first study to empirically test the overgrowth hypothesis of pectus excavatum for ribs 4 through 8. Although we and others have found no evidence to support this hypothesis, we surprisingly found the alternate hypothesis to be true: patients with pectus excavatum tend to have shorter costal cartilages. Future studies should expand on these results with larger sample sizes and consider volumetric measurements longitudinally during thoracic development.

A review of basal ganglia circuits and physiology: Application to deep brain stimulation

INTRODUCTION

Drawing on the seminal work of DeLong, Albin, and Young, we have now entered an era of basal ganglia neuromodulation. Understanding, re-evaluating, and leveraging the lessons learned from neuromodulation will be crucial to facilitate an increased and improved application of neuromodulation in human disease.

METHODS

We will focus on deep brain stimulation (DBS) - the most common form of basal ganglia neuromodulation - however, similar principles can apply to other neuromodulation modalities. We start with a brief review of DBS for Parkinson's disease, essential tremor, dystonia, and Tourette syndrome. We then review hallmark studies on basal ganglia circuits and electrophysiology resulting from decades of experience in neuromodulation. The organization and content of this paper follow Dr. Okun's Lecture from the 2018 Parkinsonism and Related Disorders World Congress.

RESULTS

Information gained from neuromodulation has led to an expansion of the basal ganglia rate model, an enhanced understanding of nuclei dynamics, an emerging focus on pathological oscillations, a revision of the tripartite division of the basal ganglia, and a redirected focus toward individualized symptom-specific stimulation. Though there have been many limitations of the basal ganglia "box model," the construct provided the necessary foundation to advance the field. We now understand that information in the basal ganglia is encoded through complex neural responses that can be reliably measured and used to infer disease states for clinical translation.

CONCLUSIONS

Our deepened understanding of basal ganglia physiology will drive new neuromodulation strategies such as adaptive DBS or cell-specific neuromodulation through the use of optogenetics.

Pallidal deep brain stimulation and intraoperative neurophysiology for treatment of poststroke hemiballism

Deep brain stimulation is a recognized and effective treatment for several movement disorders. Nevertheless, the efficacy of this intervention on abnormal movements secondary to structural brain pathologies is less consistent. In this report, we describe a case of hemiballism-hemichorea due to a peripartum ischemic stroke-treated with deep brain stimulation of the globus pallidus internus. Patient observed marked improvement in her symptoms at long-term follow-up. Neurophysiologic data revealed lower globus pallidus internus firing rates compared to other hyperkinetic disorders. Pallidal deep brain stimulation is a plausible option for medically refractory hemiballism-hemichorea and cumulative data from multiple centers may be used to fully evaluate its efficacy.

Non-motor Characterization of the Basal Ganglia: Evidence From Human and Non-human Primate Electrophysiology

Although the basal ganglia have been implicated in a growing list of human behaviors, they include some of the least understood nuclei in the brain. For several decades studies have employed numerous methodologies to uncover evidence pointing to the basal ganglia as a hub of both motor and non-motor function. Recently, new electrophysiological characterization of the basal ganglia in humans has become possible through direct access to these deep structures as part of routine neurosurgery. Electrophysiological approaches for identifying non-motor function have the potential to unlock a deeper understanding of pathways that may inform clinical interventions and particularly neuromodulation. Various electrophysiological modalities can also be combined to reveal functional connections between the basal ganglia and traditional structures throughout the neocortex that have been linked to non-motor behavior. Several reviews have previously summarized evidence for non-motor function in the basal ganglia stemming from behavioral, clinical, computational, imaging, and non-primate animal studies; in this review, instead we turn to electrophysiological studies of non-human primates and humans. We begin by introducing common electrophysiological methodologies for basal ganglia investigation, and then we discuss studies across numerous non-motor domains–emotion, response inhibition, conflict, decision-making, error-detection and surprise, reward processing, language, and time processing. We discuss the limitations of current approaches and highlight the current state of the information.

Impulse control disorders in Parkinson's: Sleep disorders and nondopaminergic associations

OBJECTIVES

Impulse control disorders (ICDs) are common among patients with Parkinson's disease (PD). Risk factors identified for developing ICDs include young age, family history, and impulsive personality traits. However, the association of these potentially disabling disorders with nondopaminergic drugs and sleep disorders has been understudied. Our objective was to examine the association between ICDs and nondopaminergic medications and sleep disorders.

METHODS

We conducted an observational study of 53 patients with PD from the National Institute of Neurology and Neurosurgery. ICDs were diagnosed using the Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease Rating Scale (QUIP-RS). Patients underwent polysomnography screening to diagnose the presence of sleep disorders. We documented the presence of dopaminergic and nondopaminergic medications, including monoamine oxidase type B inhibitors (MAOBIs), antidepressants, sleep inductors, and antipsychotics.

RESULTS

ICDs were reported in 18.9% of the patients (n = 10), and sleep disorders were diagnosed in 81.1% of patients (n = 43). 32.1% of the patients were on antidepressants, 17% on MAOBIs, 15.1% on sleep inductors, and 1.9% on antipsychotics. We observed that QUIP-RS A-D subscore depended on the presence of antidepressants (p = .03) and sleep inductors (p = .02). Sleep disorders were not associated with the total QUIP-RS score (p = .93) or QUIP-RS A-D subscore (p = .81).

CONCLUSION

Antidepressants and sleep inductors were significant predictors for individual QUIP-RS items and subscores. Our results suggest that nondopaminergic drugs commonly used for PD may be associated with impulse control disorders. We did not identify a relationship between ICDs and polysomnography-confirmed sleep disorders in patients with PD. Larger and longitudinal studies are needed to confirm our results.

Evaluating interest in narrative therapy for decision making about pectus excavatum treatment

OBJECTIVES

The decision to proceed with surgical treatment for pectus excavatum (PE) is rarely clear-cut. Patients interested in treatment are referred for evaluation by numerous different specialists, but psychosocial counselling is currently not included in this process. Our objective was to assess whether PE patients would be interested in formal assistance with the decision-making process surrounding PE surgery using narrative therapy principles.

METHODS

Ninety-seven untreated PE patients at 5 different institutions in 4 countries completed a questionnaire consisting of 13 questions, with 3 questions specifically evaluating interest in narrative therapy.

RESULTS

Eighty-two percent of participants were interested in narrative therapy to assist with the decision-making process surrounding PE surgery. Individuals most interested in narrative therapy tend to be more interested in correction (P < 0.05) to improve the way they feel about their body (P < 0.05).

CONCLUSIONS

The majority of PE patients are interested in narrative therapy to aid the decision-making process about treatment. We propose that narrative therapy should be offered to PE patients during the treatment evaluation process to address the psychosocial difficulties associated with PE and the surgical decision-making process overall. Future studies should assess the effectiveness of this interdisciplinary model.

Ventral Intermediate Nucleus Versus Zona Incerta Region Deep Brain Stimulation in Essential Tremor

Background

The ventral intermediate nucleus (VIM) is the target of choice for Essential Tremor (ET) deep brain stimulation (DBS). Renewed interest in caudal zona incerta (cZI) stimulation for tremor control has recently emerged and some groups believe this approach may address long-term reduction of benefit seen with VIM-DBS.

Objectives

To compare clinical outcomes and DBS programming in the long-term between VIM and cZI neurostimulation in ET-DBS patients.

Materials and Methods

A retrospective review of 53 DBS leads from 47 patients was performed. Patients were classified into VIM or cZI groups according to the location of the activated DBS contact. Demographics, DBS settings, and Tremor Rating Scale scores were compared between groups at baseline and yearly follow-up to 4 years after DBS. Student t-tests and analysis of variance (ANOVA) were used to compare variables between groups.

Results

Relative to baseline, an improvement in ON-DBS tremor scores was observed in both groups from 6 months to 4 years post-DBS (p < 0.05). Although improvement was still significant at 4 years, scores from month 6 to 2 years were comparable between groups but at 3 and 4 years post-DBS the outcome was better in the VIM group (p < 0.01). Stimulation settings were similar across groups, although we found a lower voltage in the VIM group at 3 years post-DBS.

Conclusions

More ventral DBS contacts in the cZI region do improve tremor, however, VIM-DBS provided better long-term outcomes. Randomized controlled trials comparing cZI vs VIM targets should confirm these results.

Motor subtype changes in early Parkinson's disease

INTRODUCTION

Distinct motor subtypes of Parkinson's disease (PD) have been described through both clinical observation and through data-driven approaches. However, the extent to which motor subtypes change during disease progression remains unknown. Our objective was to determine motor subtypes of PD using an unsupervised clustering methodology and evaluate subtype changes with disease duration.

METHODS

The Parkinson's Progression Markers Initiative database of 423 newly diagnosed PD patients was utilized to retrospectively identify unique motor subtypes through a data-driven, hierarchical correlational clustering approach. For each patient, we assigned a subtype to each motor assessment at each follow-up visit (time points) and by using published criteria. We examined changes in PD subtype with disease duration using both qualitative and quantitative methods.

RESULTS

Five distinct motor subtypes were identified based on the motor assessment items and these included: Tremor Dominant (TD), Axial Dominant, Appendicular Dominant, Rigidity Dominant, and Postural and Instability Gait Disorder Dominant. About half of the patients had consistent subtypes at all time points. Most patients met criteria for TD subtype soon after diagnosis. For patients with inconsistent subtypes, there was an overall trend to shift away from a TD phenotype with disease duration, as shown by chi-squared test, p < 0.001, and linear regression analysis, p < 0.05.

CONCLUSION

These results strongly suggest that classification of motor subtypes in PD can shift with increasing disease duration. Shifting subtypes is a factor that should be accounted for in clinical practice or in clinical trials.