Current Topics in Deep Brain Stimulation for Parkinson Disease

Neurologists' Attitudes Toward Use and Timing of Deep Brain Stimulation

OBJECTIVE

We sought to explore current perspectives and attitudes of general neurologists and movement disorder specialists toward deep brain stimulation (DBS) for Parkinson disease (PD), focusing on perspectives on its earlier use in the clinical course of the disease.

METHODS

We designed a 30-question online survey comprised of Likert-type, multiple choice, and rank-order questions, which was distributed to 932 neurologist members of the American Academy of Neurology. We analyzed clinicians' sociodemographic information, treatment patterns used for patients with PD, reasons for and against patient referral for DBS, and general attitudes toward DBS. Data were analyzed using descriptive and inferential statistics.

RESULTS

We received 164/930 completed surveys (completion rate of 18%). Overall, most respondents agreed that DBS was more useful after the appearance of motor complications and that DBS utilization offered better management of PD than medication alone. However, respondents were divided on issues like minimum duration of disease needed to consider DBS as a treatment option and timing of DBS referral relative to disease progression. Specifically, differences between movement disorder specialists and general neurologists were seen in medication management of symptoms and dyskinesia.

CONCLUSIONS

There remains a lack of consensus on several aspects of DBS, including medical management before offering DBS and the appropriate timing of its consideration for patients. Given the effect of such lack of consensus on patients' outcomes and recent evidence on positive DBS results, it is essential to update DBS professional guidelines with a focus on medical management and the timely use of DBS.

Cost-Effectiveness of Device-Aided Therapies in Parkinson's Disease: A Structured Review

BACKGROUND

Despite optimal dopaminergic treatment most patients in moderate to advanced stages of Parkinson's disease (PD) experience progressively increasing disabilities, necessitating a shift from oral medication to device-aided therapies, including deep brain stimulation (DBS), intrajejunal levodopa-carbidopa infusion (IJLI), and continuous subcutaneous apomorphine infusion (CSAI). However, these therapies are costly, limiting their implementation.

OBJECTIVES

To perform a systematic review on cost-effectiveness analyses for device-aided therapies in PD.

METHODS

References were identified by performing a systematic search in the PubMed and Web of Science databases in accordance with the PRISMA statement. In the absence of universal cost-effectiveness definitions, the gross domestic product per capita (GDP) in the country where a study was performed was used as a cut-off for cost-effectiveness based on cost per quality adjusted life year (QALY) gained.

RESULTS

In total 30 studies were retrieved. All device-aided therapies improved quality of life compared to best medical treatment, with improvements in QALYs between 0.88 and 1.26 in the studies with long temporal horizons. For DBS, nearly all studies showed that cost per QALY was below the GDP threshold. For infusion therapies only three studies showed a cost per QALY below this threshold, with several studies with long temporal horizons showing costs below or near the GDP threshold.

CONCLUSION

Of the device-aided therapies, DBS can be considered cost-effective, but the majority of infusion therapy studies showed that these were less cost-effective. However, long-term use of the infusion therapies appears to improve their cost-effectiveness and in addition, several strategies are underway to reduce these high costs.

A new era in electroencephalographic monitoring? Subscalp devices for ultra-long-term recordings

Inaccurate subjective seizure counting poses treatment and diagnostic challenges and thus suboptimal quality in epilepsy management. The limitations of existing hospital- and home-based monitoring solutions are motivating the development of minimally invasive, subscalp, implantable electroencephalography (EEG) systems with accompanying cloud-based software. This new generation of ultra-long-term brain monitoring systems is setting expectations for a sea change in the field of clinical epilepsy. From definitive diagnoses and reliable seizure logs to treatment optimization and presurgical seizure foci localization, the clinical need for continuous monitoring of brain electrophysiological activity in epilepsy patients is evident. This paper presents the converging solutions developed independently by researchers and organizations working at the forefront of next generation EEG monitoring. The immediate value of these devices is discussed as well as the potential drivers and hurdles to adoption. Additionally, this paper discusses what the expected value of ultra-long-term EEG data might be in the future with respect to alarms for especially focal seizures, seizure forecasting, and treatment personalization.

Distance to white matter tracts is associated with deep brain stimulation motor outcome in Parkinson's disease

OBJECTIVE

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) alleviates motor symptoms in patients with Parkinson's disease (PD). However, the underlying mechanism of tremor suppression is not well understood. Stimulation of white matter tracts, such as the dentatorubrothalamic tract (DRT), might be involved. Also, side effects, including dysarthria, might result from (unwanted) stimulation of white matter tracts in proximity to the STN. The aim of this study was to establish an association between stimulation effect on tremor and dysarthria and stimulation location relative to relevant white matter tracts.

METHODS

In 35 PD patients in whom a bilateral STN DBS system was implanted, the authors established clinical outcome measures per electrode contact. The distance from each stimulation location to the center of the DRT, corticopontocerebellar tract, pyramidal tract (PT), and medial lemniscus was determined using diffusion-weighted MRI data. Clinical outcome measures were subsequently related to the distances to the white matter tracts.

RESULTS

Patients with activated contacts closer to the DRT showed increased tremor improvement. Proximity of activated contacts to the PT was associated with dysarthria.

CONCLUSIONS

Proximity to specific white matter tracts is associated with tremor outcome and side effects in DBS. This knowledge can help to optimize both electrode placement and postsurgical electrode contact selection. Presurgical white matter tract visualization may improve targeting and DBS outcome. These findings are of interest not only for treatment in PD, but potentially also for other (movement) disorders.

Sensory Neuromodulation

We describe a model of neurological disease based on dysfunctional brain oscillators. This is not a new model, but it is not one that is widely appreciated by clinicians. The value of this model lies in the predictions it makes and the utility it provides in translational applications, in particular for neuromodulation devices. Specifically, we provide a perspective on devices that provide input to sensory receptors and thus stimulate endogenous sensory networks. Current forms of clinically applied neuromodulation, including devices such as (implanted) deep brain stimulators (DBS) and various, noninvasive methods such as transcranial magnetic stimulation (TMS) and transcranial current methods (tACS, tDCS), have been studied extensively. The potential strength of neuromodulation of a sensory organ is access to the same pathways that natural environmental stimuli use and, importantly, the modulatory signal will be transformed as it travels through the brain, allowing the modulation input to be consistent with regional neuronal dynamics. We present specific examples of devices that rely on sensory neuromodulation and evaluate the translational potential of these approaches. We argue that sensory neuromodulation is well suited to, ideally, repair dysfunctional brain oscillators, thus providing a broad therapeutic approach for neurological diseases.

Cost-Effectiveness of Deep Brain Stimulation With Movement Disorders: A Systematic Review

BACKGROUND

Movement disorders (MDs) are increasingly being managed with deep brain stimulation (DBS). High-quality economic evaluations (EEs) are necessary to evaluate the cost-effectiveness of DBS. We conducted a systematic review of published EEs of the treatment of MDs with DBS. The review compares and contrasts the reported incremental cost-effectiveness ratios (ICERs) and methodology employed by trial-based evaluations (TBEs) and model-based evaluations (MBEs).

METHODS

MeSH and search terms relevant to "MDs," "DBS," and "EEs" were used to search biomedical and economics databases. Studies that used a comparative design to evaluate DBS, including before-after studies, were included. Quality and reporting assessments were conducted independently by 2 authors. Seventeen studies that targeted Parkinson's disease (PD), dystonia, and essential tremor (ET), met our selection criteria.

RESULTS

Mean scores for methodological and reporting quality were 73% and 76%, respectively. The ICERs for DBS compared with best medical therapy to treat PD patients obtained from MBEs had a lower mean and range compared with those obtained from TBEs ($55,461-$735,192 per quality-adjusted life-year [QALY] vs. $9,301-$65,111 per QALY). Pre-post ICER for DBS to treat dystonia was $64,742 per QALY. DBS was not cost-effective in treating ET compared with focused-ultrasound surgery. Cost-effectiveness outcomes were sensitive to assumptions in health utilities, surgical costs, battery life-span, model time horizons, and the discount rate.

CONCLUSIONS

The infrequent use of randomized, controlled trials to evaluate DBS efficacy, the paucity of data reporting the long-term effectiveness and/or utility of DBS, and the uncertainty surrounding cost data limit our ability to report cost-effectiveness summaries that are robust.

Balance and mobility in patients with newly diagnosed Parkinson's disease - a five-year follow-up of a cohort in northern Sweden

Background: The presence of early balance impairment in patients with Parkinson's disease has not been fully investigated.Purpose: The purpose of this study was to examine balance and mobility, self-perceived unsteadiness, self-reported falls, and effects of medication on balance among patients at their first visit to a neurological clinic and during the ensuing five years.Materials and methods: The participants were collected from a prospective longitudinal study. One hundred and forty-five patients with idiopathic Parkinson's disease and 31 healthy controls were included. The outcome measures were the Berg Balance Scale, the Timed Up and Go, the Postural Stability test and a questionnaire.Results: At their first visit to the neurological clinic, the patients performed less well on the Berg Balance Scale (p < 0.001, r = 0.36), the Timed Up and Go (p < 0.001, r = 0.32), and the Postural Stability test (p < 0.001, r = 0.35) compared with the controls. In addition, a higher percentage of the patients reported self-perceived unsteadiness (p < 0.001, phi = 0.47). During the ensuing five years, balance and mobility worsened both with and without medication (p < 0.01, r = 0.24-0.37), although with small median differences.Conclusions: Further studies are needed to confirm that minor balance impairments exist even at the time of diagnosis and worsen during the ensuing five years.IMPLICATIONS FOR REHABILITATIONImpairments in balance and mobility may occur early in Parkinson's disease, especially in the elderly patients, and seem to worsen during the first five years.There is a need to use sensitive outcome measures and to ask the patients about unsteadiness and falls to detect balance impairment in this cohort.Parkinsonian medication has a limited effect on balance and may preferably be complemented with balance exercises to target balance impairment early in Parkinson's disease.

Engineered Axonal Tracts as "Living Electrodes" for Synaptic-Based Modulation of Neural Circuitry

Brain-computer interface and neuromodulation strategies relying on penetrating non-organic electrodes/optrodes are limited by an inflammatory foreign body response that ultimately diminishes performance. A novel "biohybrid" strategy is advanced, whereby living neurons, biomaterials, and microelectrode/optical technology are used together to provide a biologically-based vehicle to probe and modulate nervous-system activity. Microtissue engineering techniques are employed to create axon-based "living electrodes", which are columnar microstructures comprised of neuronal population(s) projecting long axonal tracts within the lumen of a hydrogel designed to chaperone delivery into the brain. Upon microinjection, the axonal segment penetrates to prescribed depth for synaptic integration with local host neurons, with the perikaryal segment remaining externalized below conforming electrical-optical arrays. In this paradigm, only the biological component ultimately remains in the brain, potentially attenuating a chronic foreign-body response. Axon-based living electrodes are constructed using multiple neuronal subtypes, each with differential capacity to stimulate, inhibit, and/or modulate neural circuitry based on specificity uniquely afforded by synaptic integration, yet ultimately computer controlled by optical/electrical components on the brain surface. Current efforts are assessing the efficacy of this biohybrid interface for targeted, synaptic-based neuromodulation, and the specificity, spatial density and long-term fidelity versus conventional microelectronic or optical substrates alone.

The need for non-oral therapy in Parkinson's disease; a potential role for apomorphine

In the course of Parkinson's disease (PD), oral medication may lose its effectiveness due to several reasons, like dysphagia, impaired absorption from the gastro-intestinal tract and delayed emptying of the stomach. If these problems occur, a non-oral therapy should be considered. Examples of non-oral therapies are transdermal patches, (e.g. rotigotine) which may overcome motor and nonmotor nighttime problems, and may serve as well to treat daytime response-fluctuations, if oral therapies fail to do so. Other options are injections with apomorphine to treat early morning dystonia and random off-periods during daytime, as well as continuously infused subcutaneous apomorphine for random fluctuations in PD patients. Low-dose apomorphine infusions also may be useful in the peri-operative phase, when PD patients may not be able to swallow oral medication. Finally, levodopa-carbidopa intestinal gel (LCIG) infusions or DBS have shown to be effective non-oral options to treat PD patients adequately, if they are not properly controlled by oral options.