The evolution of neuromodulation for chronic stroke: From neuroplasticity mechanisms to brain-computer interfaces

Stroke is one of the most common and debilitating neurological conditions worldwide. Those who survive experience motor, sensory, speech, vision, and/or cognitive deficits that severely limit remaining quality of life. While rehabilitation programs can help improve patients' symptoms, recovery is often limited, and patients frequently continue to experience impairments in functional status. In this review, invasive neuromodulation techniques to augment the effects of conventional rehabilitation methods are described, including vagus nerve stimulation (VNS), deep brain stimulation (DBS) and brain-computer interfaces (BCIs). In addition, the evidence base for each of these techniques, pivotal trials, and future directions are explored. Finally, emerging technologies such as functional near-infrared spectroscopy (fNIRS) and the shift to artificial intelligence-enabled implants and wearables are examined. While the field of implantable devices for chronic stroke recovery is still in a nascent stage, the data reviewed are suggestive of immense potential for reducing the impact and impairment from this globally prevalent disorder.

Network Substrates of Centromedian Nucleus Deep Brain Stimulation in Generalized Pharmacoresistant Epilepsy

Deep brain stimulation (DBS), specifically thalamic DBS, has achieved promising results to reduce seizure severity and frequency in pharmacoresistant epilepsies, thereby establishing it for clinical use. The mechanisms of action are, however, still unknown. We evidenced the brain networks directly modulated by centromedian (CM) nucleus-DBS and responsible for clinical outcomes in a cohort of patients uniquely diagnosed with generalized pharmacoresistant epilepsy. Preoperative imaging and long-term (2-11 years) clinical data from ten generalized pharmacoresistant epilepsy patients (mean age at surgery = 30.8 ± 5.9 years, 4 female) were evaluated. Volume of tissue activated (VTA) was included as seeds to reconstruct the targeted network to thalamic DBS from diffusion and functional imaging data. CM-DBS clinical outcome improvement (> 50%) appeared in 80% of patients and was tightly related to VTAs interconnected with a reticular system network encompassing sensorimotor and supplementary motor cortices, together with cerebellum/brainstem. Despite methodological differences, both structural and functional connectomes revealed the same targeted network. Our results demonstrate that CM-DBS outcome in generalized pharmacoresistant epilepsy is highly dependent on the individual connectivity profile, involving the cerebello-thalamo-cortical circuits. The proposed framework could be implemented in future studies to refine stereotactic implantation or the parameters for individualized neuromodulation.

Gene and Cell-Based Therapies for Parkinson's Disease: Where Are We?

Parkinson's disease (PD) is a neurodegenerative disorder that carries large health and socioeconomic burdens. Current therapies for PD are ultimately inadequate, both in terms of symptom control and in modification of disease progression. Deep brain stimulation and infusion therapies are the current mainstay for treatment of motor complications of advanced disease, but these have very significant drawbacks and offer no element of disease modification. In fact, there are currently no agents that are established to modify the course of the disease in clinical use for PD. Gene and cell therapies for PD are now being trialled in the clinic. These treatments are diverse and may have a range of niches in the management of PD. They hold great promise for improved treatment of symptoms as well as possibly slowing progression of the disease in the right patient group. Here, we review the current state of the art for these therapies and look to future strategies in this fast-moving field.

Emerging Targeted Therapeutics for Genetic Subtypes of Parkinsonism

In recent years, a precision medicine approach, which customizes medical treatments based on patients' individual profiles and incorporates variability in genes, the environment, and lifestyle, has transformed medical care in numerous medical fields, most notably oncology. Applying a similar approach to Parkinson's disease (PD) may promote the development of disease-modifying agents that could help slow progression or possibly even avert disease development in a subset of at-risk individuals. The urgent need for such trials partially stems from the negative results of clinical trials where interventions treat all PD patients as a single homogenous group. Here, we review the current obstacles towards the development of precision interventions in PD. We also review and discuss the clinical trials that target genetic forms of PD, i.e., GBA-associated and LRRK2-associated PD.

Consensus Paper: Experimental Neurostimulation of the Cerebellum

The cerebellum is best known for its role in controlling motor behaviors. However, recent work supports the view that it also influences non-motor behaviors. The contribution of the cerebellum towards different brain functions is underscored by its involvement in a diverse and increasing number of neurological and neuropsychiatric conditions including ataxia, dystonia, essential tremor, Parkinson's disease (PD), epilepsy, stroke, multiple sclerosis, autism spectrum disorders, dyslexia, attention deficit hyperactivity disorder (ADHD), and schizophrenia. Although there are no cures for these conditions, cerebellar stimulation is quickly gaining attention for symptomatic alleviation, as cerebellar circuitry has arisen as a promising target for invasive and non-invasive neuromodulation. This consensus paper brings together experts from the fields of neurophysiology, neurology, and neurosurgery to discuss recent efforts in using the cerebellum as a therapeutic intervention. We report on the most advanced techniques for manipulating cerebellar circuits in humans and animal models and define key hurdles and questions for moving forward.

[Deep brain stimulation for movement disorders]

Deep brain stimulation (DBS) is a treatment which uses high-frequency electric stimulation to suppress pathological brain activity. DBS has been applied for over 30 years now, particularly in patients with severe movement disorders, such as Parkinson's disease, dystonia and tremor. Although there is clearly scientific evidence for the effectiveness of DBS in these three movement disorders, the effect size of the treatment remains limited. Furthermore, DBS is not curative and can only be applied in a select subset of patients. In this article, we discuss the key indications and contraindications for DBS, and the outcomes achieved when it is applied in the aforementioned movement disorders. We discuss the most notable controversies and new developments in the field of deep brain stimulation, in order to offer referrers and fellow healthcare professionals an accessible introduction to this mode of therapy.

A Driving-Force Predictor for Estimating Pathway Activation in Patient-Specific Models of Deep Brain Stimulation

OBJECTIVE

Detailed biophysical modeling of deep brain stimulation (DBS) provides a theoretical approach to quantify the cellular response to the applied electric field. However, the most accurate models for performing such analyses, patient-specific field-cable (FC) pathway-activation models (PAMs), are so technically demanding to implement that their use in clinical research is greatly limited. Predictive algorithms can simplify PAM calculations, but they generally fail to reproduce the output of FC models when evaluated over a wide range of clinically relevant stimulation parameters. Therefore, we set out to develop a novel driving-force (DF) predictive algorithm (DF-Howell), customized to the study of DBS, which can better match FC results.

METHODS

We developed the DF-Howell algorithm and compared its predictions to FC PAM results, as well as to the DF-Peterson algorithm, which is currently the most accurate and generalizable DF-based method. Comparison of the various methods was quantified within the context of subthalamic DBS using activation thresholds of axons representing the internal capsule, hyperdirect pathway, and cerebellothalamic tract for various combinations of fiber diameters, stimulus pulse widths, and electrode configurations.

RESULTS

The DF-Howell predictor estimated activation of the three axonal pathways with less than a 6.2% mean error with respect to the FC PAM for all 21 cases tested. In 15 of the 21 cases, DF-Howell outperformed DF-Peterson in estimating pathway activation, reducing mean-errors up to 22.5%.

CONCLUSIONS

DF-Howell represents an accurate predictor for estimating axonal pathway activation in patient-specific DBS models, but errors still exist relative to FC PAM calculations. Nonetheless, the tractability of DF algorithms helps to reduce the technical barriers for performing accurate biophysical modeling in clinical DBS research studies.

A comparison of resting state functional magnetic resonance imaging to invasive electrocortical stimulation for sensorimotor mapping in pediatric patients

Localizing neurologic function within the brain remains a significant challenge in clinical neurosurgery. Invasive mapping with direct electrocortical stimulation currently is the clinical gold standard but is impractical in young or cognitively delayed patients who are unable to reliably perform tasks. Resting state functional magnetic resonance imaging non-invasively identifies resting state networks without the need for task performance, hence, is well suited to pediatric patients. We compared sensorimotor network localization by resting state fMRI to cortical stimulation sensory and motor mapping in 16 pediatric patients aged 3.1 to 18.6 years. All had medically refractory epilepsy that required invasive electrographic monitoring and stimulation mapping. The resting state fMRI data were analyzed using a previously trained machine learning classifier that has previously been evaluated in adults. We report comparable functional localization by resting state fMRI compared to stimulation mapping. These results provide strong evidence for the utility of resting state functional imaging in the localization of sensorimotor cortex across a wide range of pediatric patients.

Headache in mitochondrial disorders

Headache is a prominent feature in mitochondrial disorders (MIDs) but no comprehensive overview is currently available. This review aims at summarising and discussing findings concerning type, frequency, pathogenesis, and treatment of headache in MIDs. The most frequent headache types in MIDs are migraine and migraine-like headache (MLH). MLH is classified as secondary headache. More rarely, tension-type headache, trigemino-autonomic headache, or different secondary headaches can be found. Migraine or MLH may manifest with or without aura. MLH is frequently associated with an ongoing or previous stroke-like episode (SLE) or a seizure but may also occur independently of other neurological features. MLH may be associated with prolonged aura or visual phenomena after headache. Except for MLH, treatment of headache in MIDs is not at variance from other causes of headache. Beyond the broadly accepted subtype-related headache treatment, diet, cofactors, vitamins, and antioxidants may provide a supplementary benefit. Midazolam, l-arginine, or l-citrulline may be beneficial for MLH. The pathogenesis of headache in MIDs largely remains unsolved. However, since migraine and MLH respond both to triptanes, a shared pathomechanism is likely. In conclusion, migraine and MLH are the prominent headache types in MIDs. MLH may or may not be associated with current or previous SLEs. MLH is pathophysiologically different from migraine and requires treatment at variance from that of migraine with aura.

Pallidal and thalamic neural oscillatory patterns in tourette's syndrome

OBJECTIVE

Aberrant oscillatory activity has been hypothesized to play a role in the pathophysiology of Tourette's syndrome (TS). Deep brain stimulation (DBS) has recently been established as an effective treatment for severe TS. Modulation of symptom-specific oscillations may underlie the mechanism of action of DBS and could be used for adaptive neuromodulation to improve therapeutic efficacy. The objective of this study was to demonstrate a pathophysiological association of pallidal and thalamic local field potentials (LFPs) with TS.

METHODS

Nine medication-refractory TS patients were included in the study. Intracerebral LFPs were recorded simultaneously from bilateral pallidal and thalamic DBS electrodes. Spectral and temporal dynamics of pallidal and thalamic oscillations were characterized and correlated with preoperative Yale Global Tic Severity Scale (YGTSS) scores.

RESULTS

Peaks of activity in the theta (3-12Hz) and beta (13-35Hz) were present in pallidal and thalamic recordings from all patients (3 women/6 men; mean age, 29.8 years) and coupled through coherence across targets. Presence of prolonged theta bursts in both targets was associated with preoperative motor tic severity. Total preoperative YGTSS scores (mean, 38.1) were correlated with pallidal and thalamic LFP activity using multivariable linear regression (R² = 0.96; p = 0.02).

INTERPRETATION

Our findings suggest that pallidothalamic oscillations may be implicated in the pathophysiology of TS. Furthermore, our results highlight the utility of multisite and -spectral oscillatory features in severely affected patients for future identification and clinical use of oscillatory physiomarkers for adaptive stimulation in TS. Ann Neurol 2018;84:505-514.

Deep Brain Stimulation in Psychiatry: Mechanisms, Models, and Next-Generation Therapies

Deep brain stimulation has preliminary evidence of clinical efficacy, but has been difficult to develop into a robust therapy, in part because its mechanisms are incompletely understood. We review evidence from movement and psychiatric disorder studies, with an emphasis on how deep brain stimulation changes brain networks. From this, we argue for a network-oriented approach to future deep brain stimulation studies. That network approach requires methods for identifying patients with specific circuit/network deficits. We describe how dimensional approaches to diagnoses may aid that identification. We discuss the use of network/circuit biomarkers to develop self-adjusting "closed loop" systems.

The development of neural stimulators: a review of preclinical safety and efficacy studies

OBJECTIVE

Given the rapid expansion of the field of neural stimulation and the rigorous regulatory approval requirements required before these devices can be applied clinically, it is important that there is clarity around conducting preclinical safety and efficacy studies required for the development of this technology.

APPROACH

The present review examines basic design principles associated with the development of a safe neural stimulator and describes the suite of preclinical safety studies that need to be considered when taking a device to clinical trial.

MAIN RESULTS

Neural stimulators are active implantable devices that provide therapeutic intervention, sensory feedback or improved motor control via electrical stimulation of neural or neuro-muscular tissue in response to trauma or disease. Because of their complexity, regulatory bodies classify these devices in the highest risk category (Class III), and they are therefore required to go through a rigorous regulatory approval process before progressing to market. The successful development of these devices is achieved through close collaboration across disciplines including engineers, scientists and a surgical/clinical team, and the adherence to clear design principles. Preclinical studies form one of several key components in the development pathway from concept to product release of neural stimulators. Importantly, these studies provide iterative feedback in order to optimise the final design of the device. Key components of any preclinical evaluation include: in vitro studies that are focussed on device reliability and include accelerated testing under highly controlled environments; in vivo studies using animal models of the disease or injury in order to assess efficacy and, given an appropriate animal model, the safety of the technology under both passive and electrically active conditions; and human cadaver and ex vivo studies designed to ensure the device's form factor conforms to human anatomy, to optimise the surgical approach and to develop any specialist surgical tooling required.

SIGNIFICANCE

The pipeline from concept to commercialisation of these devices is long and expensive; careful attention to both device design and its preclinical evaluation will have significant impact on the duration and cost associated with taking a device through to commercialisation. Carefully controlled in vitro and in vivo studies together with ex vivo and human cadaver trials are key components of a thorough preclinical evaluation of any new neural stimulator.

Radiofrequency Lesioning Through Deep Brain Stimulation Electrodes in Patients with Generalized Dystonia

BACKGROUND

Deep brain stimulation (DBS) is an established treatment for generalized dystonia. However, the DBS device is sometimes removed owing to hardware complications. We present 4 cases of generalized dystonia treated with radiofrequency lesioning through DBS electrodes.

CASE DESCRIPTION

Four patients, 3 men and 1 woman (age range, 34-44 years), underwent DBS for generalized dystonia and subsequently developed complications, such as infection, necessitating removal of the devices. As stopping the stimulation caused recurrence of uncontrollable symptoms, radiofrequency lesioning was performed through the DBS electrodes under local anesthesia, and the DBS systems were removed under local or generalized anesthesia thereafter. The procedures performed were as follows: 2 patients had bilateral pallidotomy, 1 patient had unilateral pallidotomy, and 1 patient had pallidotomy and ipsilateral thalamotomy. As a result, in 4 patients, the dystonic symptoms did not worsen even after removal of the DBS systems during a follow-up period of 1-12 years. However, 1 patient had a small hemorrhage, and 2 patients showed recurrence of dystonia.

CONCLUSIONS

Radiofrequency lesioning with DBS electrodes is feasible in cases of generalized dystonia when the DBS leads have to be removed.

The re-emergence of psychiatric neurosurgery: insights from a cross-national study of newspaper and magazine coverage

BACKGROUND

Surgical approaches to treat psychiatric disorders have made a comeback. News media plays an essential role in exposing the public to trends in health care such as the re-emergence of therapeutic interventions in psychiatric neurosurgery that were set aside for decades, and in shaping attitudes and acceptance to them.

METHOD

We conducted an analysis of media articles covering all types of psychiatric neurosurgery published in Canada, USA, Germany, and Spain between the years 1960 and 2015. We applied both quantitative and qualitative methods to elucidate patterns of reporting for conditions, themes and tone, across geographic regions, time, and for type of intervention.

RESULTS

Coverage of psychiatric neurosurgery has surged since 2001 and is largely consistent across the countries examined. It focuses on depression and deep brain stimulation, and is explicit about historical context. The tone of coverage becomes more positive for Canada, USA and Spain over time; the tone of coverage from Germany remains cautious. Identity and privacy are among the few ethical and philosophical issues raised, notably in the German press.

CONCLUSIONS

The focused and optimistic attention to contemporary psychiatric neurosurgery in the media, but inattention to ethical issues, places an extra burden on functional neurosurgeons, psychiatrists, and other frontline health professionals to attend to queries from patients and policy makers about the full range of relevant emergent and emerging interventions and the mental health issues to which they may beneficially apply.

Current and Expected Advances in Deep Brain Stimulation for Movement Disorders

Deep brain stimulation (DBS) has become an established treatment for medically refractory movement disorders including Parkinson's disease, essential tremor, and dystonia. The field of DBS continues to evolve with advances in patient selection, target identification, electrode and pulse generator technology, and the development of more effective stimulation paradigms such as closed-loop stimulation. Furthermore, as the safety and efficacy of DBS improves through better hardware design and deeper understanding of its mechanisms of action, the indications for DBS will continue to expand to cover a wider range of disorders. Finally, the recent approval of MR-guided focused ultrasound for the treatment of essential tremor and potentially other movement disorders heralds a resurgence in lesion creation as a viable alternative to DBS for selected patients.

Deep brain stimulation for disorders of consciousness: Systematic review of cases and ethics

BACKGROUND

A treatment for patients suffering from prolonged severely altered consciousness is not available. The success of Deep Brain Stimulation (DBS) in diseases such as Parkinson's, dystonia and essential tremor provided a renewed impetus for its application in Disorders of Consciousness (DoC).

OBJECTIVE

To evaluate the rationale for DBS in patients with DoC, through systematic review of literature containing clinical data and ethical considerations.

METHODS

Articles from PubMed, Embase, Medline and Web of Science were systematically reviewed.

RESULTS

The outcomes of 78 individual patients reported in 19 articles from 1968 onwards were pooled and elements of ethical discussions were compared. There is no clear clinical evidence that DBS is a treatment for DoC that can restore both consciousness and the ability to communicate. In patients who benefitted, the outcome of DBS is often confounded by the time frame of spontaneous recovery from DoC. Difficult ethical considerations remain, such as the risk of increasing self-awareness of own limitations, without improving overall wellbeing, and the issues of proxy consent.

CONCLUSION

DBS is far from being evident as a possible future therapeutic avenue for patients with DoC. Double-blind studies are lacking, and many clinical and ethical issues have to be addressed. In the rare cases when DBS for patients with DoC is considered, this needs to be evaluated meticulously on a case by case basis, with comprehensive overall outcome measures including psychological and quality-of-life assessments, and with the guidance of an ethical and interdisciplinary panel, especially in relation to proxy consent.

Neuromodulation interventions for addictive disorders: challenges, promise, and roadmap for future research

Addictive disorders are a major public health concern, associated with high relapse rates, significant disability and substantial mortality. Unfortunately, current interventions are only modestly effective. Preclinical studies as well as human neuroimaging studies have provided strong evidence that the observable behaviours that characterize the addiction phenotype, such as compulsive drug consumption, impaired self-control, and behavioural inflexibility, reflect underlying dysregulation and malfunction in specific neural circuits. These developments have been accompanied by advances in neuromodulation interventions, both invasive as deep brain stimulation, and non-invasive such as repetitive transcranial magnetic stimulation and transcranial direct current stimulation. These interventions appear particularly promising as they may not only allow us to probe affected brain circuits in addictive disorders, but also seem to have unique therapeutic applications to directly target and remodel impaired circuits. However, the available literature is still relatively small and sparse, and the long-term safety and efficacy of these interventions need to be confirmed. Here we review the literature on the use of neuromodulation in addictive disorders to highlight progress limitations with the aim to suggest future directions for this field.

Interventional procedures and future drug therapy for hypertension

Hypertension management poses a major challenge to clinicians globally once non-drug (lifestyle) measures have failed to control blood pressure (BP). Although drug treatment strategies to lower BP are well described, poor control rates of hypertension, even in the first world, suggest that more needs to be done to surmount the problem. A major issue is non-adherence to antihypertensive drugs, which is caused in part by drug intolerance due to side effects. More effective antihypertensive drugs are therefore required which have excellent tolerability and safety profiles in addition to being efficacious. For those patients who either do not tolerate or wish to take medication for hypertension or in whom BP control is not attained despite multiple antihypertensives, a novel class of interventional procedures to manage hypertension has emerged. While most of these target various aspects of the sympathetic nervous system regulation of BP, an additional procedure is now available, which addresses mechanical aspects of the circulation. Most of these new devices are supported by early and encouraging evidence for both safety and efficacy, although it is clear that more rigorous randomized controlled trial data will be essential before any of the technologies can be adopted as a standard of care.

Neurosurgery of the future: Deep brain stimulations and manipulations

Important advances are afoot in the field of neurosurgery-particularly in the realms of deep brain stimulation (DBS), deep brain manipulation (DBM), and the newly introduced refinement "closed-loop" deep brain stimulation (CLDBS). Use of closed-loop technology will make both DBS and DBM more precise as procedures and will broaden their indications. CLDBS utilizes as feedback a variety of sources of electrophysiological and neurochemical afferent information about the function of the brain structures to be treated or studied. The efferent actions will be either electric, i.e. the classic excitatory or inhibitory ones, or micro-injection of such things as neural proteins and transmitters, neural grafts, implants of pluripotent stem cells or mesenchymal stem cells, and some variants of gene therapy. The pathologies to be treated, beside Parkinson's disease and movement disorders, include repair of neural tissues, neurodegenerative pathologies, psychiatric and behavioral dysfunctions, i.e. schizophrenia in its various guises, bipolar disorders, obesity, anorexia, drug addiction, and alcoholism. The possibility of using these new modalities to treat a number of cognitive dysfunctions is also under consideration. Because the DBS-CLDBS technology brings about a cross-fertilization between scientific investigation and surgical practice, it will also contribute to an enhanced understanding of brain function.

Closed-loop neuromodulation systems: next-generation treatments for psychiatric illness

Despite deep brain stimulation's positive early results in psychiatric disorders, well-designed clinical trials have yielded inconsistent clinical outcomes. One path to more reliable benefit is closed-loop therapy: stimulation that is automatically adjusted by a device or algorithm in response to changes in the patient's electrical brain activity. These interventions may provide more precise and patient-specific treatments. This article first introduces the available closed-loop neuromodulation platforms, which have shown clinical efficacy in epilepsy and strong early results in movement disorders. It discusses the strengths and limitations of these devices in the context of psychiatric illness. It then describes emerging technologies to address these limitations, including pre-clinical developments such as wireless deep neurostimulation and genetically targeted neuromodulation. Finally, ongoing challenges and limitations for closed-loop psychiatric brain stimulation development, most notably the difficulty of identifying meaningful biomarkers for titration, are discussed. This is considered in the recently-released Research Domain Criteria (RDoC) framework, and how neuromodulation and RDoC are jointly very well suited to address the problem of treatment-resistant illness is described.

The future of psychiatry: brain devices

Recent advances in deep brain stimulators and brain-machine interfaces have greatly expanded the possibilities of neuroprosthetics and neuromodulation. Together with advances in neuroengineering, nanotechnology, molecular biology and material sciences, it is now possible to address fundamental questions in neuroscience in new, more powerful ways. It is now possible to apply these new technologies in ways that range from augmenting and restoring function to neuromodulation modalities that treat neuropsychiatric disorders. Recent developments in neuromodulation methods offer significant advantages and potential clinical benefits for a variety of disorders. Here we describe the current state of the art in neuromodulation methods, and some advances in brain-machine interfaces, describing the advantages and limitations of the clinical applications of each method. The future applications of these new methods and how they will shape the future of psychiatry and medicine, along with safety and ethical implications, are also discussed.

My 25 Stimulating Years with DBS in Parkinson's Disease

The year 2017 marks the 30th anniversary of the birth of modern deep brain stimulation (DBS), which was introduced by Benabid, Pollak et al. in 1987, initially targeting the motor thalamus to treat tremor, and subsequently targeting the subthalamic nucleus (STN) for treatment of symptoms of advanced Parkinson's disease (PD). STN DBS is undoubtedly "the most important discovery since levodopa", as stated by David Marsden in 1994. In 2014, The Lasker- DeBakey Clinical Medical Research Award to "honor two scientists who developed deep brain stimulation of the subthalamic nucleus", was bestowed upon Benabid and DeLong. STN DBS remains today the main surgical procedure for PD, due to its effectiveness in ameliorating PD symptoms and because it is the only surgical procedure for PD that allows a radical decrease in medication. Future improvements of DBS include the possibility to deliver a "closed-loop", "on demand" stimulation, as highly preliminary studies suggest that it may improve both axial and appendicular symptoms and reduce side effects such as dysarthria. Even though DBS of the subthalamic nucleus is the main surgical procedure used today for patients with PD, all patients are not suitable for STN DBS; as a functional neurosurgeon performing since more than 25 years various surgical procedures the aim of which is not to save life but to improve the patient's quality of life, I consider that the surgery should be tailored to the patient's individual symptoms and needs, and that its safety is paramount.

Short-Term Adverse Outcomes After Deep Brain Stimulation Treatment in Patients with Parkinson Disease

BACKGROUND

Despite ongoing progress in our understanding of long-term outcomes after neuromodulation procedures, acute adverse outcomes shortly after deep brain stimulation (DBS) treatment have remained remarkably limited.

OBJECTIVE

To identify risk factors associated with acute 30-day outcomes after DBS treatment in patients with Parkinson disease (PD).

METHODS

We evaluated patients who underwent DBS treatment for PD from 2005 to 2014 through the American College of Surgeons National Surgical Quality Improvement Program database. We used bivariate analysis and multivariate logistic regression to identify short-term postoperative outcomes, including 30-day complication, discharge destination, and unplanned readmission.

RESULTS

Overall, 650 patients with PD underwent DBS procedures and complications were identified in 32 patients (4.9%). Of 481 patients who had complete discharge data, 18 patients (3.7%) were discharged to a facility and 16 patients (3.3%) experienced an unplanned readmission. Patients with PD who were obese (P = 0.045), who had preoperative anemia (P = 0.008), and who experienced longer operative durations (P = 0.01) had increased odds of postoperative complications. Inpatient status (P = 0.001), dependent functional status (P < 0.001), and anemia (P = 0.043) were all associated with discharge to a facility other than home. Longer operative duration (P = 0.013), anemia (P = 0.036), and dependent functional status (P = 0.03) were significantly associated with unplanned readmission. As expected, complications increased the likelihood of unplanned readmission (P < 0.001).

CONCLUSIONS

This study provides individualized estimates of the risks associated with short-term adverse outcomes based on patient demographics and comorbidities. These data can be used as an adjunct for short-term risk stratification of patients with PD being considered for DBS treatment.

Technological Advances in Deep Brain Stimulation

Functional and stereotactic neurosurgery has always been regarded as a subspecialty based on and driven by technological advances. However until recently, the fundamentals of deep brain stimulation (DBS) hardware and software design had largely remained stagnant since its inception almost three decades ago. Recent improved understanding of disease processes in movement disorders as well clinician and patient demands has resulted in new avenues of development for DBS technology. This review describes new advances both related to hardware and software for neuromodulation. New electrode designs with segmented contacts now enable sophisticated shaping and sculpting of the field of stimulation, potentially allowing multi-target stimulation and avoidance of side effects. To avoid lengthy programming sessions utilising multiple lead contacts, new user-friendly software allows for computational modelling and individualised directed programming. Therapy delivery is being improved with the next generation of smaller profile, longer-lasting, re-chargeable implantable pulse generators (IPGs). These include IPGs capable of delivering constant current stimulation or personalised closed-loop adaptive stimulation. Post-implantation Magnetic Resonance Imaging (MRI) has long been an issue which has been partially overcome with 'MRI conditional devices' and has enabled verification of DBS lead location. Surgical technique is considering a shift from frame-based to frameless stereotaxy or greater role for robot assisted implantation. The challenge for these contemporary techniques however, will be in demonstrating equivalent safety and accuracy to conventional methods. We also discuss potential future direction utilising wireless technology allowing for miniaturisation of hardware.

Deep brain stimulation: current applications and future prospects

Deep Brain Stimulation (DBS) has proven to be an effective and minimally invasive surgical treatment for a variety of neurological and psychiatric diseases such as Parkinson's Disease, essential tremor, dystonia, Tourette's Syndrome and depression. In contrast to early surgical lesioning procedures, DBS has a considerably lower side-effect rate and is usually reversible. Common targets include nuclei involved in the basal ganglia circuitry as well as its efferent and afferent pathways such as the subthalamic nucleus (STN), the globus pallidus internus (GPi) or the ventral striatal region. Despite the increasing application of DBS, the exact mechanism of action is still matter of debates. Current trials focus on establishing alternative targets, exploring new indications as well as on capturing cortical responses during DBS in order to improve individual stimulation parameters.

Responsive neurostimulation in epilepsy

Various neurostimulation modalities have emerged in the field of epilepsy. Despite the fact that delivery of an electrical current to the hyperexcitable epileptic brain might, at first, seem contradictory, neurostimulation has become an established therapeutic option with a promising efficacy and adverse effects profile. In "responsive" neurostimulation the strategy is to interfere as early as possible with the accumulation of seizure activity to prematurely abort or even prevent an upcoming seizure. The design of technology required for responsive stimulation is more challenging compared with devices for open-loop neurostimulation. The achievement of therapeutic success is dependent on adequate sensing and stimulation algorithms and a fast coupling between both. The benefits of delivering current only at the time of an approaching seizure merit further investigation. Current experience with responsive neurostimulation in epilepsy is still limited, but seems promising.

[Deep brain stimulation: past, present time and future]

Recently awarded by the prestigious Lasker Foundation, high-frequency deep brain stimulation (DBS) has been used for the first time in 1987 in tremor and in 1993 in Parkinson's disease (PD) by the Grenoble group. So far, over 100 000 patients have been operated on worldwide. In PD, DBS induces an almost complete abatement of tremor, motor fluctuations and dyskinesias along with a reduction in levodopa dose. Although its mechanism of action is not fully understood, DBS would inhibit or modulate the expression of abnormal neuronal networks associated with given symptoms. It is therefore expected that DBS will extend to other severe neurological and psychiatric disorders. Furthermore, technological advances of the procedure are ongoing to optimize final outcomes.

Short- and long-term outcome of chronic pallidal neurostimulation in monogenic isolated dystonia

OBJECTIVES

Deep brain stimulation of the internal pallidum (GPi-DBS) is an established therapeutic option in treatment-refractory dystonia, and the identification of factors predicting surgical outcome is needed to optimize patient selection.

METHODS

In this retrospective multicenter study, GPi-DBS outcome of 8 patients with DYT6, 9 with DYT1, and 38 with isolated dystonia without known monogenic cause (non-DYT) was assessed at early (1-16 months) and late (22-92 months) follow-up using Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) scores.

RESULTS

At early follow-up, mean reduction of dystonia severity was greater in patients with DYT1 (BFMDRS score: -60%) and non-DYT dystonia (-52%) than in patients with DYT6 dystonia (-32%; p = 0.046). Accordingly, the rate of responders was considerably lower in the latter group (57% vs >90%; p = 0.017). At late follow-up, however, GPi-DBS resulted in comparable improvement in all 3 groups (DYT6, -42%; DYT1, -44; non-DYT, -61%). Additional DBS of the same or another brain target was performed in 3 of 8 patients with DYT6 dystonia with varying results. Regardless of the genotype, patients with a shorter duration from onset of dystonia to surgery had better control of dystonia postoperatively.

CONCLUSIONS

Long-term GPi-DBS is effective in patients with DYT6, DYT1, and non-DYT dystonia. However, the effect of DBS appears to be less predictable in patients with DYT6, suggesting that pre-DBS genetic testing and counseling for known dystonia gene mutations may be indicated. GPi-DBS should probably be considered earlier in the disease course.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence that long-term GPi-DBS improves dystonia in patients with DYT1, DYT6, and non-DYT dystonia.

Deep brain stimulation: new directions

The role of deep brain stimulation (DBS) in the treatment of movement disorders is well established, but there has recently been a proliferation of additional indications that have been shown to be amenable to this technology. The combination of innovative approaches to neural interface technology with novel target identification based on previously discovered clinical effects of lesioning procedures has led to a fundamental paradigm for new directions in the application of DBS. The historical use of neurosurgical lesioning procedures in the treatment of psychiatric diseases such as obsessive compulsive disorder provided an initial opportunity to expand the use of DBS. The list is rapidly expanding and now includes major depressive disorder, Tourette's syndrome, addiction disorders, and eating disorders. Keen observations by neurosurgeons using these devices have lead to the incidental discovery of treatments for diseases without previous neurosurgical treatments. These discoveries are breaking new ground in the treatment of disorders of cognition, headache syndromes, disorders of consciousness, and epilepsy. Two features of DBS make it well-suited for treatment of disorders of nervous system function. First, the reversible, non-lesional nature of DBS allows for investigation of new targets without the morbidity of permanent side effects. Second, the programmable nature of DBS allows practitioners to alter stimulation patterns to minimize side effects and potentially improve efficacy through reprogramming. More importantly, proper scientific evaluation of new targets is aided by the ability to turn stimulation on and off with evaluators blinded to the stimulation status. Knowledge of these emerging therapies is important for practitioners, as there are many situations where a single target can effectively treat the symptoms of more than one disease. The intersection of advances in neuromodulation, neurophysiology, neuroimaging, and functional neuroanatomy has created an environment rife with new therapeutic possibilities.

Psychosurgery: past, present, and future, including prefrontal lobotomy and Connecticut's contribution

Psychosurgery, a subspecialty of functional neurosurgery, has been used in the treatment of psychiatric illness, intractable pain, and, controversially, as ameans to control and modify violent human behavior. Prefrontal lobotomy, a procedure developed in the 20th century, arose as a result of pioneering research, includingwork done atYaleUniversity in New Haven. Prominent clinicians throughout Connecticut contributed to the development of modern psychosurgery. Neuroethics or ethics of neuroscience is essential to the study and practice ofpsychosurgery. New technology has provided improved accuracy with less morbidity. The progressive replacement of ablative procedures with deep-brain stimulation and restorative neurosurgery offers new perspectives in the treatment of some psychiatric conditions.

Brain stimulation in the treatment of late-life severe mental illness other than unipolar nonpsychotic depression

Late-life mental illness is a growing concern. Current medications have limited efficacy and are associated with safety concerns. A variety of brain stimulation approaches offers alternative treatments. We performed a systematic literature search on the efficacy and safety of brain stimulation in late-life mental illnesses, excluding unipolar nonpsychotic depression. Studies on deep brain stimulation, electroconvulsive therapy (ECT), repetitive transcranial magnetic stimulation (rTMS), and vagal nerve stimulation that enrolled exclusively older adults (≥65 years) or analyzed older adults as a separate group were included. The search identified 1,181 publications, of which 43 met the above inclusion criteria: 24 were related to the treatment of non-unipolar depression (ECT: 21; rTMS: 2; ECT and rTMS: 1), 14 related to dementia (ECT: 7[2 of these studies were also related to depression]; vagal nerve stimulation: 2; rTMS: 4; deep brain stimulation: 1), and 7 to schizophrenia (ECT: 7). These studies reported a high degree of variability in efficacy and safety with promising results in general, particularly in the treatment of dementia and schizophrenia. Most publications were limited by small sample sizes, lack of control conditions, and lack of randomization. Large studies with a randomized controlled design or other designs such as crossover or off-on-off-on are needed. In contrast to the empiric and nonspecific use of ECT, future studies using modalities other than ECT could focus on novel biologically based interventions that target specific circuitry. These interventions could also be combined with other non-brain stimulation treatments for possible synergistic effects.

Deep brain stimulation in the treatment of neurological and psychiatric disease

Deep brain stimulation has become a topic of intense interest both from a clinical and basic science perspective. Its indications, currently including Parkinson's disease, tremor and dystonia, may expand in the future to include not only other movement disorders but also epilepsy, obsessive-compulsive disorder and other neuropsychiatric conditions. The mechanism(s) of action of deep brain stimulation have only recently begun to be characterized and have already yielded surprises that may open the door to a greater expansion of the indications for this novel and powerful therapeutic intervention.

Brain stimulation in the treatment of epilepsy

Stimulation of the brain for the treatment of epilepsy, indirectly via the vagus nerve and directly through intracranial targets, is feasible and has increased in use and complexity over the past 10 years. Vagus nerve stimulation is widely applied and the present indications and outcomes together with possible ways in which the treatment could be refined are reviewed. The application of stimulation to deep-brain targets is also reviewed along with present practice and results. Possible developments in the use of direct intracranial stimulation are also considered.

Criteria for deep-brain stimulation in Parkinson’s disease: review and analysis

Deep-brain stimulation is currently the most effective surgical treatment for advanced Parkinson's disease. The relevant targets to date are the subthalamic nucleus and the globus pallidus internus, although the thalamus (ventralis intermedius nucleus) is preferred in tremor-dominant, aged Parkinson's disease patients. Long-term benefit in cardinal parkinsonian signs, motor fluctuations and dyskinesia has been reported in 5-year follow-up studies of subthalamic nucleus deep-brain stimulation. However, some psychiatric consequences have raised important issues and emphasized the need for an experienced deep-brain stimulation surgical team. This team should be multidisciplinary and involve movement disorder neurologists, neurosurgeons, neuropsychologists and psychiatrists. The recent observation that deep-brain stimulation of the pedunculopontine nucleus improves axial signs, possibly even in those less responsive to levodopa, brings new hope to the management of advanced Parkinson's disease.

Overlapping molecular signatures in Parkinson's patients' leukocytes before and after treatment and in mouse model brain regions

Parkinson's disease (PD) is a chronic and progressive neurodegenerative disease with worldwide increasing incidence. PD is the second most prevalent neurodegenerative disease and the first that involves motor symptoms. The great majority of cases, defined as sporadic with non-familial disease, show a highly variable risk of disease due to environmental and genetic factors that remain largely unknown. Furthermore, the neurodegenerative process typically initiates decades prior to the appearance of hallmark motor symptoms; therefore, clinical diagnosis is enabled only when most of the relevant neurons have died and current treatment is palliative at best. Here, we review the application of genomic scale microarray based research aimed to enable early diagnosis and identify novel targets for therapeutic intervention. We demonstrate that blood leukocytes can serve as a feasible and reliable tissue source to test for disease-induced and treatment-related transcript changes. We cover our reports of transcription and alternative splicing modifications in PD patient's leukocytes based on 3' and exon microarray analyses and the identified inflammatory modulations. We further describe the effects of deep brain stimulation (DBS) neurosurgery on the leukocyte transcripts as reflecting the patient's neurological status. A focus is gained on common genes identified both in the molecular signature of human PD leukocytes and in brain RNA from engineered PD mouse models subjected to risk and protection manipulations. Finally, we discuss potential future directions of high-throughput RNA research as facilitators of the PD knowledge base through next generation sequencing technologies of both long and short RNA transcripts including microRNAs.

Deep brain stimulation (DBS) at the interface of neurology and psychiatry

Deep brain stimulation (DBS) is an emerging interventional therapy for well-screened patients with specific treatment-resistant neuropsychiatric diseases. Some neuropsychiatric conditions, such as Parkinson disease, have available and reasonable guideline and efficacy data, while other conditions, such as major depressive disorder and Tourette syndrome, have more limited, but promising results. This review summarizes both the efficacy and the neuroanatomical targets for DBS in four common neuropsychiatric conditions: Parkinson disease, Tourette syndrome, major depressive disorder, and obsessive-compulsive disorder. Based on emerging new research, we summarize novel approaches to optimization of stimulation for each neuropsychiatric disease and we review the potential positive and negative effects that may be observed following DBS. Finally, we summarize the likely future innovations in the field of electrical neural-network modulation.

Technological advances in the surgical treatment of movement disorders

Technological innovations have driven the advancement of the surgical treatment of movement disorders, from the invention of the stereotactic frame to the adaptation of deep brain stimulation (DBS). Along these lines, this review will describe recent advances in inserting neuromodulation modalities, including DBS, to the target, and in the delivery of therapy at the target. Recent radiological advances are altering the way that DBS leads are targeted and inserted, by refining the ability to visualize the subcortical targets using high-field strength magnetic resonance imaging and other innovations, such as diffusion tensor imaging, and the development of novel targeting devices enabling purely anatomical implantations without the need for neurophysiological monitoring. New portable computed tomography scanners also are facilitating lead implantation without monitoring, as well as improving radiological verification of DBS lead location. Advances in neurophysiological mapping include efforts to develop automatic target verification algorithms, and probabilistic maps to guide target selection. The delivery of therapy at the target is being improved by the development of the next generation of internal pulse generators (IPGs). These include constant current devices that mitigate the variability introduced by impedance changes of the stimulated tissue and, in the near future, devices that deliver novel stimulation patterns with improved efficiency. Closed-loop adaptive IPGs are being tested, which may tailor stimulation to ongoing changes in the nervous system, reflected in biomarkers continuously recorded by the devices. Finer-grained DBS leads, in conjunction with new IPGs and advanced programming tools, may offer improved outcomes via current steering algorithms. Finally, even thermocoagulation-essentially replaced by DBS-is being advanced by new minimally-invasive approaches that may improve this therapy for selected patients in whom it may be preferred. Functional neurosurgery has a history of being driven by technological innovation, a tradition that continues into its future.

Pallidal deep brain stimulation in patients with primary generalised or segmental dystonia: 5-year follow-up of a randomised trial

BACKGROUND

Severe forms of primary dystonia are difficult to manage medically. We assessed the safety and efficacy of pallidal neurostimulation in patients with primary generalised or segmental dystonia prospectively followed up for 5 years in a controlled multicentre trial.

METHODS

In the parent trial, 40 patients were randomly assigned to either sham neurostimulation or neurostimulation of the internal globus pallidus for a period of 3 months and thereafter all patients completed 6 months of active neurostimulation. 38 patients agreed to be followed up annually after the activation of neurostimulation, including assessments of dystonia severity, pain, disability, and quality of life. The primary endpoint of the 5-year follow-up study extension was the change in dystonia severity at 3 years and 5 years as assessed by open-label ratings of the Burke-Fahn-Marsden dystonia rating scale (BFMDRS) motor score compared with the preoperative baseline and the 6-month visit. The primary endpoint was analysed on an intention-to-treat basis. The original trial is registered with ClinicalTrials.gov (NCT00142259).

FINDINGS

An intention-to-treat analysis including all patients from the parent trial showed significant improvements in dystonia severity at 3 years and 5 years compared with baseline, which corresponded to -20·8 points (SD 17·1; -47·9%; n=40) at 6 months; -26·5 points (19·7; -61·1%; n=31) at 3 years; and -25·1 points (21·3; -57·8%; n=32). The improvement from 6 months to 3 years (-5·7 points [SD 8·4]; -34%) was significant and sustained at the 5-year follow-up (-4·3 [10·4]). 49 new adverse events occurred between 6 months and 5 years. Dysarthria and transient worsening of dystonia were the most common non-serious adverse events. 21 adverse events were rated serious and were almost exclusively device related. One patient attempted suicide shortly after the 6-month visit during a depressive episode. All serious adverse events resolved without permanent sequelae.

INTERPRETATION

3 years and 5 years after surgery, pallidal neurostimulation continues to be an effective and relatively safe treatment option for patients with severe idiopathic dystonia. This long-term observation provides further evidence in favour of pallidal neurostimulation as a first-line treatment for patients with medically intractable, segmental, or generalised dystonia.

FUNDING

Medtronic.

Somatic treatments for mood disorders

Somatic treatments for mood disorders represent a class of interventions available either as a stand-alone option, or in combination with psychopharmacology and/or psychotherapy. Here, we review the currently available techniques, including those already in clinical use and those still under research. Techniques are grouped into the following categories: (1) seizure therapies, including electroconvulsive therapy and magnetic seizure therapy, (2) noninvasive techniques, including repetitive transcranial magnetic stimulation, transcranial direct current stimulation, and cranial electric stimulation, (3) surgical approaches, including vagus nerve stimulation, epidural electrical stimulation, and deep brain stimulation, and (4) technologies on the horizon. Additionally, we discuss novel approaches to the optimization of each treatment, and new techniques that are under active investigation.

Deep brain stimulation: current and future clinical applications

Deep brain stimulation (DBS) has developed during the past 20 years as a remarkable treatment option for several different disorders. Advances in technology and surgical techniques have essentially replaced ablative procedures for most of these conditions. Stimulation of the ventralis intermedius nucleus of the thalamus has clearly been shown to markedly improve tremor control in patients with essential tremor and tremor related to Parkinson disease. Symptoms of bradykinesia, tremor, gait disturbance, and rigidity can be significantly improved in patients with Parkinson disease. Because of these improvements, a decrease in medication can be instrumental in reducing the disabling features of dyskinesias in such patients. Primary dystonia has been shown to respond well to DBS of the globus pallidus internus. The success of these procedures has led to application of these techniques to multiple other debilitating conditions such as neuropsychiatric disorders, intractable pain, epilepsy, camptocormia, headache, restless legs syndrome, and Alzheimer disease. The literature analysis was performed using a MEDLINE search from 1980 through 2010 with the term deep brain stimulation, and several double-blind and larger case series were chosen for inclusion in this review. The exact mechanism of DBS is not fully understood. This review summarizes many of the current and potential future clinical applications of this technology.

[Deep brain stimulation for epilepsy]

Despite the advances in pharmacologic treatments for epilepsy, approximately one-third of patients with epilepsy continue to have seizures, and alternative treatment approaches are necessary in such cases. For many patients, resective surgery can be an alternative for achieving seizure freedom; however, its success depend on identifying seizure foci before surgery. Many patients with medically intractable epilepsy are not suitable candidates for surgery. The therapeutic effect of electrical stimulation on the brain has been studied for decades. Currently, the thalamus, subthalamic nucleus, hippocampus, cerebellar nuclei, and cortical seizure foci are stimulated for treating epilepsy. In 2010, the results of the first, multicenter randomized double-blinded controlled study were published. This report documents a clinical trial involving stimulation of the anterior nucleus of the thalamus for epilepsy (SANTE). These results showed bilateral stimulation of the anterior nucleus of the thalamus reduces seizures. The responsive neurostimulator, which can be called a brain pacemaker, is another stimulation device for the treatment of epilepsy. A clinical trial involving the Neuropace system is in progress in the USA. Preliminary results indicating the efficacy of the Neuropace study were presented at the annual American Epilepsy Society meeting in 2010; the final results of this study are awaited.

Occipital nerve stimulation for intractable chronic cluster headache: new hope for a dreadful disease?

Chronic cluster headache (CCH) is one of the most painful primary headaches. A small percentage of CCH become intractable (iCCH) and is refractory to the majority of preventing drugs. Various invasive and sometimes destructive procedures have been tempted to help these patients, but none gave satisfactory results for the long term. Hypothalamic deep-brain stimulation (hDBS) has recently raised expectations with an average improvement of 50 to 70%, but is not a riskless procedure. Harmless methods were therefore warranted, and in this perspective occipital nerve stimulation (ONS) trials were undertaken. Up to now, nearly 38 iCCH patients benefited from ONS in the available literature and the technique appears to give results similar to hDBS, having the advantage to have much milder side effects. The mechanism by which ONS is efficient in iCCH remains unknown but preliminary results of neurophysiological and imaging studies suggest ONS is just a symptomatic treatment which does not act on the disease generator. We would however advocate ONS as first choice alternative therapy in iCCH.

Rationale for hypothalamus-deep brain stimulation in food intake disorders and obesity

Appetite modulation in conjunction with enhancing metabolic rate with hypothalamic lesions has been widely documented in animal and even in humans. It appears these effects can be reproduced by DBS, and the titratability and reversibility of this procedure, in addition to well established safety profile, make DBS an appealing option for obesity treatment. Targeting the hypothalamus with DBS has already been shown to be feasible and potentially effective in managing patients with intractable chronic cluster headache [26]. The surgical risk however must be cautiously taken into account when targeting the hypothalamus, where some mortality cases have been reported when targeting the posterior part [34]. The development of new surgical approach will probably reduce this surgical risk. Moreover, the role of functional neurosurgery in obesity is not a new idea. In fact, LH was targeted in obese humans with electrocoagulation more than 30 years ago, resulting in significant yet transient appetite suppression and slight weight reduction [36]. All those elements have made possible the recent regain of interest in DBS for morbid obesity and open an exciting new area of research in neurosurgery and endocrinology.

The translational value of the MPTP non-human primate model of Parkinsonism for deep brain stimulation research

Deep brain stimulation (DBS) has been applied in more than 70000 patients worldwide during the last two decades. The main target is the subthalamic nucleus (STN) for the treatment of motor complications in late stage Parkinson's disease (PD). Positive results in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated non-human primates have set the grounds for its successful translation to PD patients. Since then, this model has allowed gaining significant insights in the underlying mechanisms of action of DBS and is currently being used for the development of new stimulation techniques. Altogether, this underpins the high potential of this preclinical model for future translation of DBS research in PD.

Commentary: the pedunculopontine nucleus: clinical experience, basic questions and future directions

This issue is dedicated to a potential new target for the treatment of movement disorders, the pedunculopontine tegmental nucleus (PPTg), or, more simply, the pedunculopontine nucleus, that some authors abbreviate as PPN. We provide an overview of the field as an introduction to the general reader, beginning with the clinical experience to date of Mazzone and co-workers in Rome, some basic questions that need to be addressed, and potential future directions required in order to ensure that the potential benefits of this work are realized.