Siobhan Ewert

Siobhan Ewert

MD

About

30
Publications
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1,150
Citations

Publications

Publications (30)
Article
Three-dimensional atlases of subcortical brain structures are valuable tools to reference anatomy in neuroscience and neurology. For instance, they can be used to study the position and shape of the three most common deep brain stimulation (DBS) targets, the sub-thalamic nucleus (STN), internal part of the pallidum (GPi) and ventral intermediate nu...
Article
Full-text available
Dystonia is a debilitating disease with few treatment options. One effective option is deep brain stimulation (DBS) to the internal pallidum. While cervical and generalized forms of isolated dystonia have been targeted with a common approach to the posterior third of the nucleus, large-scale investigations regarding optimal stimulation sites and po...
Preprint
Full-text available
Dystonia is a debilitating disease with few conservative treatment options but many types of isolated dystonia can be effectively treated using deep brain stimulation (DBS) to the internal pallidum. While cervical and generalized forms of isolated dystonia have been targeted with a common approach to the posterior third of the nucleus, large-scale...
Article
Introduction: Deep brain stimulation (DBS) is a highly efficacious treatment for essential tremor (ET). Still, the optimal anatomical target in the (sub)thalamic area is a matter of debate. The aim of this study was to determine the optimal target of DBS for ET regarding beneficial clinical outcome and impact on activities of daily living as well...
Article
Full-text available
Objective Observational study to evaluate the long-term motor and non-motor effects of deep brain stimulation (DBS) of the globus pallidus internus (GPi) on medically refractory dystonia. Background Dystonia is a chronic disease affecting mainly young patients with a regular life expectancy and lifelong need for therapy. Pallidal DBS is an establi...
Cover Page
Full-text available
Cover image: Structural and functional connectivity profiles seeded from volume of tissue activated predict deep brain stimulation-induced improvement in patients with essential tremor. From Al-Fatly et al. Connectivity profile of thalamic deep brain stimulation to effectively treat essential tremor. Pp. 3086–3098.
Article
Full-text available
Essential tremor is the most prevalent movement disorder and is often refractory to medical treatment. Deep brain stimulation offers a therapeutic approach that can efficiently control tremor symptoms. Several deep brain stimulation targets (ventral intermediate nucleus, zona incerta, posterior subthalamic area) have been discussed for tremor treat...
Article
Full-text available
Deep brain stimulation of the internal globus pallidus is a highly effective and established therapy for primary generalized and cervical dystonia, but therapeutic success is compromised by a non-responder rate of up to 25%, even in carefully-selected groups. Variability in electrode placement and inappropriate stimulation settings may account for...
Cover Page
Full-text available
Wilson's pencils in the vervet monkey shown on PLI (image courtesy Dr. Markus Axer and Prof. Dr. Karl Zilles).
Article
Full-text available
The “direct” and “indirect” pathways play crucial roles in movement disorder pathophysiology. Both traverse from the striatum to the internal pallidum and substantia nigra, the latter detouring to external pallidum and subthalamic nucleus. Anatomically, the pathways manifest within the striatofugal bundle that passes radially through the pallidum i...
Preprint
Full-text available
Essential tremor is the most prevalent movement disorder and is often refractory to medical treatment. Deep brain stimulation offers a therapeutic approach that can efficiently control tremor symptoms. Several deep brain stimulation targets (ventral intermediate nucleus, zona incerta, posterior subthalamic area) have been discussed for tremor treat...
Article
Full-text available
Objective Gait disturbances are frequent side effects occurring during chronic thalamic deep brain stimulation (DBS) in patients with essential tremor (ET). Adapting stimulation settings to shorter pulse widths has been shown to reduce side effects of subthalamic DBS. Here, we assess how a reduction of pulse width changes gait performance of affect...
Article
Full-text available
Deep brain stimulation (DBS) is a highly efficacious treatment option for movement disorders and a growing number of other indications are investigated in clinical trials. To ensure optimal treatment outcome, exact electrode placement is required. Moreover, to analyze the relationship between electrode location and clinical results, a precise recon...
Article
Full-text available
Nonlinear registration of individual brain MRI scans to standard brain templates is common practice in neu- roimaging and multiple registration algorithms have been developed and refined over the last 20 years. How- ever, little has been done to quantitatively compare the available algorithms and much of that work has ex- clusively focused on corti...
Article
Full-text available
Dopamine exerts modulatory signals on cortex-basal ganglia circuits to enable flexible motor control. Parkinson's disease is characterized by a loss of dopaminergic innervation in the basal ganglia leading to complex motor and non-motor symptoms. Clinical symptom alleviation through dopaminergic medication and deep brain stimulation in the subthala...
Article
Objective 1. To evaluate and optimize commonly used nonlinear deformation algorithms when applied to human brain MRI. 2. To evaluate and optimize accuracy of automated atlas-based segmentation of the two most commonly used target regions for deep brain stimulation (DBS), the nucleus subthalamicus (STN) and the internal part of the globus pallidus (...
Preprint
Full-text available
Deep brain stimulation (DBS) is a highly efficacious treatment option for movement disorders and a growing number of other indications are investigated in clinical trials. To ensure optimal treatment outcome, exact electrode placement is required. Moreover, to analyze the relationship between electrode location and clinical results, a precise recon...
Poster
Full-text available
1. First, we identified two nonlinear deformation algorithms (SPM Segment and ANTs SyN) that perform superiorly to other commonly used algorithms in the field. We then further optimized their performance resulting in a more precise alignment of subcortical structures. 2. The results of atlas-based segmentations are similar to inter-rater results ma...
Article
Full-text available
Objective: Deep brain stimulation (DBS) allows for direct recordings of neuronal activity from the human basal ganglia. In Parkinson's disease, a disease-specific physiomarker was identified that is now used to investigate adaptive closed-loop stimulation in first studies. In dystonia such a physiomarker is missing. Methods: Pallidal oscillation...
Article
Parkinsonian bradykinesia and rigidity are typically associated with excessive beta band oscillations in the subthalamic nucleus. Recently another spectral peak has been identified that might be implicated in the pathophysiology of the disease: high-frequency oscillations (HFO) within the 150–400 Hz range. Beta-HFO phase-amplitude coupling (PAC) ha...
Preprint
Full-text available
Three-dimensional atlases of subcortical brain structures are valuable tools to reference anatomy in neuroscience and neurology. In the special case of deep brain stimulation (DBS), the three most common targets are the subthalamic nucleus (STN), the internal part of the pallidum (GPi) and the ventral intermediate nucleus of the thalamus (VIM). Wit...
Poster
Full-text available
Three-dimensional atlases of subcortical brain structures are valuable tools to reference anatomy in neuroscience. In the special case of deep brain stimulation (DBS), the three most common targets are the subthalamic nucleus (STN), the internal part of the pallidum (GPi) and the ventral intermediate nucleus of the thalamus (VIM). With the help of...
Poster
Full-text available
Poster presented at Movement Disorders 2016 about a novel certified version of Lead-DBS.
Thesis
Ziel der Studie war es, mittels fMRT Aufschluss über die Lokalisation derjenigen neuronalen Areale zu gewinnen, welche in der Sprachproduktion den Schritt der phonetischen Enkodierung ausführen. Die Studie gründete zum einen auf der Hypothese, dass vermehrte artikulatorische Schwierigkeit von Stimuli selektiv eine "erhöhte Rechenlast" des Gehirns f...

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Projects

Projects (2)
Project
Continuous development of a toolbox aimed at precisely localizing deep brain stimulation electrodes based on postoperative data. Toolbox website here: www.lead-dbs.org / www.leadsuite.io / www.lead-connectome.org