The Role of Levodopa Challenge in Predicting the Outcome of Subthalamic Deep Brain Stimulation

Background

Deep brain stimulation of the subthalamic nucleus (STN-DBS) is an effective and evidence-based treatment for idiopathic Parkinson's disease (iPD). A minority of patients does not sufficiently benefit from STN-DBS.

Objective

The predictive validity of the levodopa challenge for individual patients is analyzed.

Methods

Data from patients assessed with a preoperative Levodopa-test and a follow-up examination (mean ± standard deviation: 9.15 months ±3.39) from Kiel (n = 253), Berlin (n = 78) and Toronto (n = 98) were studied. Insufficient DBS outcome was defined as an overall UPDRS-III reduction <33% compared to UPDRS-III in med-off at baseline or alternatively if the minimal clinically important improvement of 5 points was not reached. Single UPDRS-items and sub-scores were dichotomized. Following exploratory analysis, we trained supervised regression- and classification models for outcome prediction.

Results

Data analysis confirmed significant correlation between the absolute UPDRS-III reduction during Levodopa challenge and after stimulation. But individual improvement was inaccurately predicted with a large range of up to 30 UPDRS III points. Further analysis identified preoperative UPDRS-III/med-off-scores and preoperative Levodopa-improvement as most influential factors. The models for UPDRS-III and sub-scores improvement achieved comparably low accuracy.

Conclusions

With large prediction intervals, the Levodopa challenge use for patient counseling is limited, though remains important for excluding non-responders to Levodopa. Despite these deficiencies, the current practice of patient selection is highly successful and builds not only on the Levodopa challenge. However, more specific motor tasks and further paraclinical tools for prediction need to be developed.

Modulation of fear generalization by the zona incerta

Fear expressed toward threat-associated stimuli is an adaptive behavioral response. In contrast, the generalization of fear responses toward nonthreatening cues is a maladaptive and debilitating dimension of trauma- and anxiety-related disorders. Expressing fear to appropriate stimuli and suppressing fear generalization require integration of relevant sensory information and motor output. While thalamic and subthalamic brain regions play important roles in sensorimotor integration, very little is known about the contribution of these regions to the phenomenon of fear generalization. In this study, we sought to determine whether fear generalization could be modulated by the zona incerta (ZI), a subthalamic brain region that influences sensory discrimination, defensive responses, and retrieval of fear memories. To do so, we combined differential intensity-based auditory fear conditioning protocols in mice with C-FOS immunohistochemistry and designer receptors exclusively activated by designer drugs (DREADDs)-based manipulation of neuronal activity in the ZI. C-FOS immunohistochemistry revealed an inverse relationship between ZI activation and fear generalization: The ZI was less active in animals that generalized fear. In agreement with this relationship, chemogenetic inhibition of the ZI resulted in fear generalization, while chemogenetic activation of the ZI suppressed fear generalization. Furthermore, targeted stimulation of GABAergic cells in the ZI reduced fear generalization. To conclude, our data suggest that stimulation of the ZI could be used to treat fear generalization in the context of trauma- and anxiety-related disorders.

Long-term effect of subthalamic nucleus deep brain stimulation on freezing of gait in Parkinson's disease

OBJECTIVE

Subthalamic nucleus deep brain stimulation (STN DBS) is effective against freezing of gait (FOG) in Parkinson's disease (PD); however, whether this effect persists over the long term is debated. The aim of the current study was to investigate the long-term effect of STN DBS on FOG in patients with PD.

METHODS

Data on 52 cases in which PD patients received bilateral STN DBS were obtained from a prospective registry. The authors blindly analyzed FOG incidence and its severity from the videotapes of a 5-m walking task at the baseline and at the 1-, 2-, and 5- or 7-year follow-up visits. They also compared the axial score from the Unified Parkinson's Disease Rating Scale (UPDRS) part III, UPDRS part II (UPDRS-II) item 14, and the FOG questionnaire (FOG-Q). Postoperatively, video-based FOG analysis and the axial score were evaluated under 4 conditions (off-medication/off-stimulation, off-medication/on-stimulation, on-medication/off-stimulation, and on-medication/on-stimulation), and UPDRS-II item 14 and the FOG-Q score were evaluated under 2 conditions (off-medication/on-stimulation and on-medication/on-stimulation).

RESULTS

During the off-medication state, the on-stimulation condition improved FOG outcomes, except for video-based FOG severity, up to the last follow-up compared with the baseline. Video-based FOG outcomes and the axial score during the off-medication state were improved with the on-stimulation condition up to the last follow-up compared with the off-stimulation condition. During the on-medication state, the on-stimulation condition did not improve any FOG outcome compared with the baseline; however, it improved video-based FOG outcomes up to the 2-year follow-up and the axial score up to the last follow-up compared with the off-stimulation condition.

CONCLUSIONS

Our findings suggest that STN DBS has a long-term effect on FOG in the off-medication state. However, STN DBS did not show a long-term effect on FOG in the on-medication state, although it had a short-term effect until the 2-year follow-up.

Pulse duration settings in subthalamic stimulation for Parkinson's disease

BACKGROUND

Stimulation parameters in deep brain stimulation (DBS) of the subthalamic nucleus for Parkinson's disease (PD) are rarely tested in double-blind conditions. Evidence-based recommendations on optimal stimulator settings are needed. Results from the CUSTOM-DBS study are reported, comparing 2 pulse durations.

METHODS

A total of 15 patients were programmed using a pulse width of 30 µs (test) or 60 µs (control). Efficacy and side-effect thresholds and unified PD rating scale (UPDRS) III were measured in meds-off (primary outcome). The therapeutic window was the difference between patients' efficacy and side effect thresholds.

RESULTS

The therapeutic window was significantly larger at 30 µs than 60 µs (P = ·0009) and the efficacy (UPDRS III score) was noninferior (P = .00008).

INTERPRETATION

Subthalamic neurostimulation at 30 µs versus 60 µs pulse width is equally effective on PD motor signs, is more energy efficient, and has less likelihood of stimulation-related side effects. © 2017 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Cortical Hemiballism: A Case of Hemiballismus Associated with Parietal Lobe Infarct

CONTEXT

Hemiballismus is characterized by involuntary, irregular, large amplitude, and violent flinging movements of limbs. Stroke (middle and posterior cerebral artery) remains the most common etiology with 2/3 being lacunar. Lesions outside the substantia niagra (STN) can cause hemiballism, and only a minority by STN lesions, unlike the classical belief. Compared to those arising from STN, cortical hemiballismus is usually less severe with a good prognosis.

CASE REPORT

A 61-year-old man presented with sudden onset involuntary flinging movements of his right upper extremity accompanied by numbness and tingling. Past medical history was significant for stroke 2 years back with no residual deficits. Vitals signs were blood pressure of 165/84 mm Hg, and heart rate - 82 beats/min. Irregular, arrhythmic, jerky flinging movement, and decreased sensation to light touch in right upper extremity was noted. Magnetic resonance imaging of the brain revealed acute posterior left parietal lobe infarction. He was treated with aspirin and atorvastatin. Thrombolytic therapy was offered but declined. The movements resolved spontaneously over the next 2 days. No further episodes occurred at 3-month follow-up.

CONCLUSION

Lesions affecting various areas outside the STN can cause hemiballism and usually carries a good prognosis with spontaneous resolution. Acute thrombolytic therapy may be considered on an individual basis. Treatment with antipsychotics can be useful for severe and recurring symptoms.

Comparison of weight changes following unilateral and staged bilateral STN DBS for advanced PD

Unilateral and bilateral subthalamic nucleus deep brain stimulation (STN DBS) in Parkinson's disease (PD) result in weight gain in the initial postoperative months, but little is known about the changes in weight following unilateral and staged bilateral STN DBS over longer time intervals. A case-control comparison evaluated weight changes over 2 years in 43 consecutive unilateral STN DBS patients, among whom 25 elected to undergo staged bilateral STN DBS, and 21 age-matched and disease severity matched PD controls without DBS. Regression analyses incorporating age, gender, and baseline weight in case or control were conducted to assess weight changes 2 years after the initial unilateral surgery. Unilateral STN DBS and staged bilateral STN DBS patients gained 3.9 ± 2.0 kg and 5.6 ± 2.1 kg versus their preoperative baseline weight (P < 0.001, respectively) while PD controls without DBS lost 0.8 ± 1.1 kg. Although bilateral STN DBS patients gained 1.7 kg more than unilateral STN DBS patients at 2 years, this difference was not statistically significant (P = 0.885). Although there was a trend toward greater weight gain in staged bilateral STN DBS patients versus unilateral patients, we found no evidence for an equivalent or synergistic increase in body weight following placement of the second DBS electrode.