The Therapeutic Potential of Non-Invasive and Invasive Cerebellar Stimulation Techniques in Hereditary Ataxias.

The degenerative ataxias comprise a heterogeneous group of inherited and acquired disorders that are characterized by a progressive cerebellar syndrome, frequently in combination with one or more extracerebellar signs. Specific disease-modifying interventions are currently not available for many of these rare conditions, which underscores the necessity of finding effective symptomatic therapies. During the past five to ten years, an increasing number of randomized controlled trials have been conducted examining the potential of different non-invasive brain stimulation techniques to induce symptomatic improvement. In addition, a few smaller studies have explored deep brain stimulation (DBS) of the dentate nucleus as an invasive means to directly modulate cerebellar output, thereby aiming to alleviate ataxia severity. In this paper, we comprehensively review the clinical and neurophysiological effects of transcranial direct current stimulation (tDCS), repetitive transcranial magnetic stimulation (rTMS), and dentate nucleus DBS in patients with hereditary ataxias, as well as the presumed underlying mechanisms at the cellular and network level and perspectives for future research.

Deep brain stimulation in Parkinson's disease: state of the art and future perspectives.

For more than 30 years, Deep Brain Stimulation (DBS) has been a therapeutic option for Parkinson's disease (PD) treatment. However, this therapy is still underutilized mainly due to misinformation regarding risks and clinical outcomes. DBS can ameliorate several motor and non-motor symptoms, improving patients' quality of life. Furthermore, most of the improvement after DBS is long-lasting and present even in advanced PD. Adequate patient selection, precise electric leads placement, and correct DBS programming are paramount for good surgical outcomes. Nonetheless, DBS still has many limitations: axial symptoms and signs, such as speech, balance and gait, do not improve to the same extent as appendicular symptoms and can even be worsened as a direct or indirect consequence of surgery and stimulation. In addition, there are still unanswered questions regarding patient's selection, surgical planning and programming techniques, such as the role of surgicogenomics, more precise imaging-based lead placement, new brain targets, advanced programming strategies and hardware features. The net effect of these innovations should not only be to refine the beneficial effect we currently observe on selected symptoms and signs but also to improve treatment resistant facets of PD, such as axial and non-motor features. In this review, we discuss the current state of the art regarding DBS selection, implant, and programming, and explore new advances in the DBS field.

Deep brain stimulation in Parkinson's disease: state of the art and future perspectives / Estimulação cerebral profunda na doença de Parkinson: estado da arte e perspectivas futuras

ABSTRACT For more than 30 years, Deep Brain Stimulation (DBS) has been a therapeutic option for Parkinson's disease (PD) treatment. However, this therapy is still underutilized mainly due to misinformation regarding risks and clinical outcomes. DBS can ameliorate several motor and non-motor symptoms, improving patients' quality of life. Furthermore, most of the improvement after DBS is long-lasting and present even in advanced PD. Adequate patient selection, precise electric leads placement, and correct DBS programming are paramount for good surgical outcomes. Nonetheless, DBS still has many limitations: axial symptoms and signs, such as speech, balance and gait, do not improve to the same extent as appendicular symptoms and can even be worsened as a direct or indirect consequence of surgery and stimulation. In addition, there are still unanswered questions regarding patient's selection, surgical planning and programming techniques, such as the role of surgicogenomics, more precise imaging-based lead placement, new brain targets, advanced programming strategies and hardware features. The net effect of these innovations should not only be to refine the beneficial effect we currently observe on selected symptoms and signs but also to improve treatment resistant facets of PD, such as axial and non-motor features. In this review, we discuss the current state of the art regarding DBS selection, implant, and programming, and explore new advances in the DBS field.

RESUMO Há mais de 30 anos, a Estimulação Cerebral Profunda (ECP) é uma opção de tratamento para pessoas com doença de Parkinson (DP). Apesar disso, a ECP ainda é subutilizada, em grande parte por desinformação acerca dos riscos e dos benefícios desse tratamento. A ECP melhora os sintomas motores e não motores da DP, melhorando, assim, a qualidade de vida dos pacientes. Grande parte dos benefícios gerados pela ECP têm longa duração, estando presentes até mesmo em fases avançadas da doença. A seleção adequada dos pacientes, o preciso posicionamento dos eletrodos cerebrais, e a programação correta da ECP são fundamentais para que haja benefício após a cirurgia. Todavia, existem ainda muitas limitações em relação ao tratamento com ECP. Sintomas axiais, como fala e marcha, não melhoram tanto quanto os sintomas apendiculares, e podem até mesmo piorar após a cirurgia. Existem muitas dúvidas relacionadas à seleção de pacientes, especialmente nos aspectos de imagem e genética. Em relação à questão cirúrgica, novas técnicas de imagem podem auxiliar o posicionamento correto dos eletrodos cerebrais. Novas estratégias de programação e avanços de hardware podem melhorar desfechos que ainda são limitados. A fim de melhorar sintomas resistentes à ECP, como cognição e marcha, novos alvos cerebrais estão sendo explorados. Na presente revisão, discutimos o atual estado da arte relacionado à ECP, abordando seleção de pacientes, implante cirúrgico de eletrodos, e programação do dispositivo, além de explorarmos novos avanços em desenvolvimento.

Safety and Outcomes of Dentate Nucleus Deep Brain Stimulation for Cerebellar Ataxia.

Cerebellar symptoms remain orphan of treatment options despite being prevalent and incapacitating. Investigate whether dentate nucleus deep brain stimulation (DN DBS) is safe and leads to improvements in cerebellar symptoms when compared to sham stimulation. This randomized double-blind crossover pilot trial enrolled five patients with spinocerebellar ataxia type 3 or post-lesion ataxia. Active or sham phases were randomly performed three months apart. The primary outcome was ataxia improvement as measured by the Scale for the Assessment and Rating of Ataxia (SARA) after the active compared to the sham period. Secondary outcome measures included safety and tolerability, the Fahn-Tolosa-Marin Tremor Rating Scale (FTMRS), quality of life measurements, and patients' global impression of change. The effects on ataxia were numerically better in four out of five patients after active versus sham stimulation. The composite SARA score did not change after comparing active to sham stimulation (8.6 ± 3.6 versus 10.1 ± 4.1; p = 0.223). The FTMRS showed significant improvement after active stimulation versus sham (18.0 ± 17.2 versus 22.2 ± 19.5; p = 0.039) as did patients' global impression of change (p = 0.038). The quality of life was not modified by stimulation (p = 0.337). DN DBS was well tolerated without serious adverse events. One patient had the electrode repositioned. DN DBS is a safe and well tolerated procedure that is effective in alleviating cerebellar tremor. In this small cohort of ataxic patients, DN DBS did not achieve statistical significance for ataxia improvement.

Dentate nucleus deep brain stimulation: Technical note of a novel methodology assisted by tractography.

BACKGROUND: The cerebellum has emerged as an attractive and promising target for neuromodulation in movement disorders due to its vast connection with important cortical and subcortical areas. Here, we describe a novel technique of deep brain stimulation (DBS) of the dentate nucleus (DN) aided by tractography. METHODS: Since 2015, patients with movement disorders including dystonia, ataxia, and tremor have been treated with DN DBS. The cerebellar target was initially localized using coordinates measured from the fastigial point. The target was adjusted with direct visualization of the DN in the susceptibility-weighted imaging and T2 sequences of the MRI and finally refined based on the reconstruction of the dentatorubrothalamic tract (DRTT). RESULTS: Three patients were treated with this technique. The final target was located in the anterior portion of DN in close proximity to the DRTT, with the tip of the lead on the white matter and the remaining contacts on the DN. Clinical outcomes were variable and overall positive, with no major side effect. CONCLUSION: Targeting the DN based on tractography of the DRTT seems to be feasible and safe. Larger studies will be necessary to support our preliminary findings.

Use of non-invasive stimulation in movement disorders: a critical review.

BACKGROUND: Noninvasive stimulation has been widely used in the past 30 years to study and treat a large number of neurological diseases, including movement disorders. OBJECTIVE: In this critical review, we illustrate the rationale for use of these techniques in movement disorders and summarize the best medical evidence based on the main clinical trials performed to date. METHODS: A nationally representative group of experts performed a comprehensive review of the literature in order to analyze the key clinical decision-making factors driving transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) in movement disorders. Classes of evidence and recommendations were described for each disease. RESULTS: Despite unavoidable heterogeneities and low effect size, TMS is likely to be effective for treating motor symptoms and depression in Parkinson's disease (PD). The efficacy in other movement disorders is unclear. TMS is possibly effective for focal hand dystonia, essential tremor and cerebellar ataxia. Additionally, it is likely to be ineffective in reducing tics in Tourette syndrome. Lastly, tDCS is likely to be effective in improving gait in PD. CONCLUSIONS: There is encouraging evidence for the use of noninvasive stimulation on a subset of symptoms in selected movement disorders, although the means to optimize protocols for improving positive outcomes in routine clinical practice remain undetermined. Similarly, the best stimulation paradigms and responder profile need to be investigated in large clinical trials with established therapeutic and assessment paradigms that could also allow genuine long-term benefits to be determined.

Little Brain, Big Expectations.

The cerebellum has been implicated in the mechanisms of several movement disorders. With the recent reports of successful modulation of its functioning, this highly connected structure has emerged as a promising way to provide symptomatic relief not yet obtained by usual treatments. Here we review the most relevant papers published to date, the limitations and gaps in literature, discuss why several papers have failed in showing efficacy, and present a new way of stimulating the cerebellum. References for this critique review were identified by searches on PubMed for the terms "Parkinson's disease", "ataxia", "dystonia", "tremor", and "dyskinesias" in combination with the type of stimulation and the stimulation site. Studies conducted thus far have shed light on the potential of cerebellar neuromodulation for attenuating symptoms in patients with some forms of isolated and combined dystonia, dyskinesia in Parkinson's disease, and neurodegenerative ataxia. However, there is still a high heterogeneity of results and uncertainty about the possibility of maintaining long-term benefits. Because of the complicated architecture of the cerebellum, the modulation techniques employed may have to focus on targeting the activity of the cerebellar nuclei rather than the cerebellar cortex. Measures of cerebellar activity may reduce the variability in outcomes.

Effects of cerebellar transcranial magnetic stimulation on ataxias: A randomized trial.

INTRODUCTION: Cerebellar ataxia remains a neurological symptom orphan of treatment interventions, despite being prevalent and incapacitating. We aimed to study, in a double-blind design, whether cerebellar modulation could improve ataxia. METHODS: We included patients with diagnosis of spinocerebellar ataxia type 3, multiple systems atrophy cerebellar type, or post-lesion ataxia. Patients received five sessions each of sham and active cerebellar 1 Hz deep repetitive transcranial magnetic stimulation in randomized order. Our primary outcome was the decrease in the Scale for the Assessment and Rating of Ataxia when comparing phases (active x sham). Secondary outcomes measures included the International Cooperative Ataxia Rating Scale, and other motor, cognitive, and quality of life scales. This study was registered at clinicaltrials.gov (protocol NCT03213106). RESULTS: Twenty-four patients aged 29-74 years were included in our trial. After active stimulation, the Scale for the Assessment and Rating of Ataxia score was significantly lower than the score after sham stimulation [median (interquartile range) of 10.2 (6.2, 16.2) versus 12.8 (9.6, 17.8); p = 0.002]. The International Cooperative Ataxia Rating Scale score also improved after active stimulation versus sham [median (interquartile range) of 29.0 (21.0, 43.5) versus 32.8 (22.0, 47.0); p = 0.005]. Other secondary outcomes were not significantly modified by stimulation. No patient presented severe side effects, and nine presented mild and self-limited symptoms. CONCLUSIONS: Our protocol was safe and well-tolerated. These findings suggest that cerebellar modulation may improve ataxic symptom and provide reassurance about safety for clinical practice.

Medical management after subthalamic stimulation in Parkinson's disease: a phenotype perspective.

Subthalamic nucleus deep brain stimulation (STN DBS) is an established treatment that improves motor fluctuations, dyskinesia, and tremor in Parkinson's disease (PD). After the surgery, a careful electrode programming strategy and medical management are crucial, because an imbalance between them can compromise the quality of life over time. Clinical management is not straightforward and depends on several perioperative motor and non-motor symptoms. In this study, we review the literature data on acute medical management after STN DBS in PD and propose a clinical algorithm on medical management focused on the patient's phenotypic profile at the perioperative period. Overall, across the trials, the levodopa equivalent daily dose is reduced by 30 to 50% one year after surgery. In patients taking high doses of dopaminergic drugs or with high risk of impulse control disorders, an initial reduction in dopamine agonists after STN DBS is recommended to avoid the hyperdopaminergic syndrome, particularly hypomania. On the other hand, a rapid reduction of dopaminergic agonists of more than 70% during the first months can lead to dopaminergic agonist withdrawal syndrome, characterized by apathy, pain, and autonomic features. In a subset of patients with severe dyskinesia before surgery, an initial reduction in levodopa seems to be a more reasonable approach. Finally, when the patient's phenotype before the surgery is the severe parkinsonism (wearing-off) with or without tremor, reduction of the medication after surgery can be more conservative. Individualized medical management following DBS contributes to the ultimate therapy success.

Medical management after subthalamic stimulation in Parkinson's disease: a phenotype perspective / Manejo medicamentoso após estimulação subtalâmica na doença de Parkinson: uma perspectiva fenotípica

Abstract Subthalamic nucleus deep brain stimulation (STN DBS) is an established treatment that improves motor fluctuations, dyskinesia, and tremor in Parkinson's disease (PD). After the surgery, a careful electrode programming strategy and medical management are crucial, because an imbalance between them can compromise the quality of life over time. Clinical management is not straightforward and depends on several perioperative motor and non-motor symptoms. In this study, we review the literature data on acute medical management after STN DBS in PD and propose a clinical algorithm on medical management focused on the patient's phenotypic profile at the perioperative period. Overall, across the trials, the levodopa equivalent daily dose is reduced by 30 to 50% one year after surgery. In patients taking high doses of dopaminergic drugs or with high risk of impulse control disorders, an initial reduction in dopamine agonists after STN DBS is recommended to avoid the hyperdopaminergic syndrome, particularly hypomania. On the other hand, a rapid reduction of dopaminergic agonists of more than 70% during the first months can lead to dopaminergic agonist withdrawal syndrome, characterized by apathy, pain, and autonomic features. In a subset of patients with severe dyskinesia before surgery, an initial reduction in levodopa seems to be a more reasonable approach. Finally, when the patient's phenotype before the surgery is the severe parkinsonism (wearing-off) with or without tremor, reduction of the medication after surgery can be more conservative. Individualized medical management following DBS contributes to the ultimate therapy success.

Resumo A estimulação cerebral profunda do núcleo subtalâmico (ECP NST) é um tratamento estabelecido para doença de Parkinson (DP), que leva à melhora das flutuações motoras, da discinesia e do tremor. Após a cirurgia, deve haver uma estratégia cuidadosa de programação da estimulação e do manejo medicamentoso, pois um desequilíbrio entre eles pode comprometer a qualidade de vida. O gerenciamento clínico não é simples e depende de vários sintomas motores e não motores perioperatórios. Nesta revisão, discutimos os dados da literatura sobre o tratamento clínico agudo após a ECP NST na DP e propomos um algoritmo clínico baseado no perfil fenotípico do paciente no período perioperatório. Em geral, nos estudos clínicos, a dose diária equivalente de levodopa é reduzida em 30 a 50% um ano após a cirurgia. Em pacientes que recebem altas doses de medicações dopaminérgicas ou com alto risco de impulsividade, recomenda-se redução inicial do agonista dopaminérgico após a ECP NST, para evitar síndrome hiperdopaminérgica, particularmente a hipomania. Por outro lado, uma rápida redução de agonistas dopaminérgicos em mais de 70% durante os primeiros meses pode levar à síndrome de abstinência do agonista dopaminérgico, com apatia, dor e disautonomia. Em pacientes com discinesia grave antes da cirurgia, é recomendada redução inicial na dose de levodopa. Finalmente, quando o fenótipo do paciente antes da cirurgia é o parkinsonismo grave (flutuação motora) com ou sem tremor, a redução da medicação após a cirurgia deve ser mais conservadora. O tratamento médico individualizado após a ECP contribui para o sucesso final da terapia.

Connectivity Patterns of Subthalamic Stimulation Influence Pain Outcomes in Parkinson's Disease.

Background: Pain is highly prevalent in Parkinson's disease and is associated with significant reduction in health-related quality of life. Subthalamic deep brain stimulation can produce significant pain relief in a subset of patients after surgery. However, the mechanism by which deep brain stimulation modulates sensory function in Parkinson's disease remains uncertain. Objective: To describe the motor and pain outcomes of deep brain stimulation applied to a series of patients with Parkinson's disease and to determine whether the structural connectivity between the volume of tissue activated and different regions of the brain was associated with the changes of these outcomes after surgery. Methods: Data from a long-term prospective cohort of 32 Parkinson's disease patients with subthalamic stimulation were combined with available human connectome to identify connections consistently associated with clinical improvement (Unified Parkinson Disease Rating Scale), pain intensity, and experimental cold pain threshold after surgery. Results: The connectivity between the volume of tissue activated and a distributed network of sensory brain regions (prefrontal, insular and cingulate cortex, and postcentral gyrus) was inversely correlated with pain intensity improvement and reduced sensitivity to cold pain after surgery (p < 0.01). The connectivity strength with the supplementary motor area positively correlated with motor and pain threshold improvement (p < 0.05). Conclusions: These data suggest that the pattern of the connectivity between the region stimulated and specific brain cortical area might be responsible, in part, for the successful control of motor and pain symptoms by subthalamic deep brain stimulation in Parkinson's disease.

Interleaving Stimulation in Parkinson Disease: Interesting to Whom?

BACKGROUND: Interleaving stimulation (ILS) is a stimulation strategy that can help the physician manage more challenging cases of patients with deep brain stimulation (DBS) for Parkinson disease (PD). It consists of altering 2 different programs on the electrode with the same frequency. OBJECTIVES: Our objective was to overview our patients' experience with ILS and explore clinical scenarios in which ILS should be considered when programming DBS in patients with PD. METHODS: We retrospectively reviewed medical charts from 120 patients with PD treated with DBS between 2011 and 2018. RESULTS: Eighteen patients received ILS. One was excluded because of the medical chart was incomplete. The remaining 17 patients had subthalamic nucleus DBS (n = 14) and globus pallidus internus DBS (n = 3). Eight patients (47%) received ILS to improve rigidity and bradykinesia, 4 to improve dyskinesias, 4 because of refractory tremor, and 1 for gait management. Until the end of data collection, 13 of 17 patients (70%) were still on ILS, with a mean duration time of 28.8 months (range, 2-44 months). Four patients reported no benefit from ILS and had their program changed. CONCLUSIONS: Overall, ILS is useful 1) to use 2 contacts that optimally improve 2 specific symptoms but have different therapeutic windows; 2) to avoid side effects related to current spreading to nearby areas; 3) to increase frequency in a small region; or 4) to stimulate a larger target area.

Exploring the clinical outcomes after deep brain stimulation in Tourette syndrome.

INTRODUCTION: Deep brain stimulation (DBS) of the thalamic centromedian-parafascicular (CM-Pf) region is the most common target to treat refractory Tourette syndrome (TS), but the improvement among the patients is quite variable. This study describes the outcomes of stimulation in TS patients and attempts to determine whether the volume of tissue activated (VTA) inside the thalamus or the structural connectivity between the area stimulated and different regions of the brain is associated with tic improvement. METHODS: The DBS patient response was measured as the percentage change in the Yale Global Tic Severity Scale (YGTSS) before and 12 months after surgery. The sum of the two overlapping VTA/CM-Pf volumes from both hemispheres was correlated with the percent change in YGTSS scores to assess whether the area stimulated inside the CM-Pf affects the clinical outcome. Structural connectivity estimates between the VTA (of each patient) and different regions of the brain were computed using a normative connectome that was taken from healthy subjects. RESULTS: Five male patients aged 26.8 ±â€¯9.3 years were included. No relationships were found between the areas stimulated and the changes in patient tics (p = .374). However, the right frontal middle gyrus (R = 0.564, p = .03), the left frontal superior sulci region (R = 0.900, p = .030) and the left cingulate sulci region (R = 0.821, p = .045) structurally correlated with tic improvement. CONCLUSION: These data suggests that the volume of thalamic area that is stimulated does not explain the variance in outcomes in TS, however, the pattern of connectivity between the region stimulated and specific brain cortical areas is linked to patient outcome.

Essential oils of Varronia curassavica accessions have different activity against white spot disease in freshwater fish.

The aim of this study was to evaluate the antiprotozoal activity of essential oils from Varronia curassavica accessions against different stages of Ichthyophthirius multifiliis. Essential oils from each accession were tested in vitro at the concentrations 0, 10, 25, 50, 75, 100, and 200 mg/L. The VCUR-001, VCUR-202, VCUR-509, and VCUR-601 accessions presented the major compounds α-pinene, germacrene D-4-ol, (E)-caryophyllene and epiglobulol, and sabinene, respectively. These isolated compounds were tested in vitro at a concentration proportional to that found in the essential oil which caused 100% mortality of the parasite. The concentrations of 10 and 50 mg/L of the essential oil of accession VCUR-202 provided 100% mortality of trophonts and tomonts, respectively. For the accession VCUR-509, 100% mortality of trophonts and tomonts was observed at concentrations 75 and 200 mg/L of essential oil, respectively. The same mortality was observed at concentration 200 mg/L in both stages of the parasite for the other accessions. The major compounds α-pinene, sabinene, and the (E)-caryophyllene + epiglobulol mixture caused 100% mortality of trophonts and tomonts. The in vivo assay for white spot disease control was performed in a therapeutic bath of 1 h with the essential oil of accession VCUR-202 at concentrations of 0.5 and 2.0 mg/L. A significant reduction of about 30% of trophonts on infected fish was observed, independent of the oil concentration. The V. curassavica essential oil, especially the VCUR-202 accession, is a potential source of raw material for the formulation and commercialization of bioproducts to control freshwater white spot disease in fish.