Biology subjects

Dembek, T. A.

Publications and source records attributed to Dembek, T. A..

4 recordsLinked to original sources

bioRxiv2021

A functional network target for tic reduction during thalamic stimulation for Tourette Syndrome

BackgroundDeep brain stimulation (DBS) of the medial thalamus is an evolving therapy for severe, treatment-refractory Tourette syndrome (TS). It remains unanswered which functionally connected networks need to be modulated to obtain optimal treatment results. MethodsWe assessed treatment response of 15 patients with TS untergoing thalamic DBS six and twelve months postoperatively using the Yale Global Tic Severity Scale (YGTSS) tic score. For each time point, functional connectivity maps seeding from stimulation sites were calculated based on a normative functional connectome derived from 1000 healthy subjects. Resulting maps were analyzed in a voxel-wise mixed model for repeated measurements to identify patterns of connectivity associated with tic reduction. ResultsConnectivity of stimulation to the medial frontal cortex, bilateral insulae and sensorimotor cortex was associated with tic reduction. Connectivity with the temporal lobe, cerebellum, ventral striatum and orbitofrontal cortex was negatively associated. The overall connectivity pattern was robust to leave-one-out cross-validation, explaining 25 % of outcome variance (R = 0.500; p = 0.005). ConclusionsWe delineated a functional connectivity profile seeding from stimulation sites associated with TS-DBS outcome. This pattern comprised areas linked to the processing of premonitory urges and tic execution, thereby extending our current understanding of effective neuromodulation for TS.

neuroscience↗

bioRxiv2020

Cortical network fingerprint and prediction of stimulation induced speech impairment in essential tremor

ObjectiveTo gain insights into structural networks associated with stimulation-induced dysarthria (SID) and to predict stimulation-induced worsening of intelligibility in essential tremor patients with bilateral thalamic deep brain stimulation (DBS). MethodsMonopolar reviews were conducted in 14 essential tremor patients. Testing included determination of SID thresholds, intelligibility ratings and a fast syllable repetition task. Volumes of tissue activated (VTAs) were calculated to identify discriminative fibers for stimulation-induced worsening of intelligibility in a structural connectome. The resulting fiber-based atlas structure was than validated in a leave-one-out design. ResultsFibers determined as discriminative for stimulation-induced worsening of intelligibility were mainly connected to the ipsilateral precentral gyrus as well as to both cerebellar hemispheres and the ipsilateral brainstem. In the thalamic area, they ran laterally to the thalamus and postero-medially to the subthalamic nucleus, in close proximity, mainly antero-laterally, to fibers beneficial for tremor control as published by Al-Fatly et al. (2019). The overlap of the respective clinical stimulation settings VTAs with these fibers explained 62.4% (p<0.001) of the variance of stimulation-induced change in intelligibility in a leave-one out analysis. InterpretationThis study demonstrates that SID in essential tremor patients is associated with both, motor cortex and cerebellar connectivity. Furthermore, the identified fiber-based atlas structure might contribute to future postoperative programming strategies to achieve optimal tremor control without speech impairment in ET patients with thalamic DBS.

neuroscience↗

bioRxiv2019

Directional DBS Leads Show Large Deviations from their Intended Implantation Orientation

ObjectiveLead orientation is a new degree of freedom with directional deep brain stimulation (DBS) leads. We investigated how prevalent deviations from the intended implantation direction are in a large patient cohort.\n\nMethodsThe Directional Orientation Detection (DiODe) algorithm to determine lead orientation from postoperative CT scans was implemented into the open-source Lead-DBS toolbox. Lead orientation was analysed in 100 consecutive patients (198 leads). Different anatomical targets and intraoperative setups were compared.\n\nResultsDeviations of up to 90{degrees} from the intended implantation direction were observed. Deviations of more than 30{degrees} were seen in 42 % of the leads and deviations of more than 60{degrees} in about 11 % of the leads. Deviations were independent from the neuroanatomical target and the stereotactic frame but increased depending on which microdrive was used.\n\nDiscussionOur results indicate that large deviations from the intended implantation direction are a common phenomenon in directional leads. Postoperative determination of lead orientation is thus mandatory for investigating directional DBS.\n\nFull DisclosuresTill A. Dembek reports speaker honoraria from Medtronic and Boston Scientific.\n\nMauritius Hoevels has nothing to disclose.\n\nAlexandra Hellerbach has nothing to disclose.\n\nAndreas Horn reports speaker honoraria from Medtronic.\n\nJan Niklas Petry-Schmelzer reports travel grants from Boston Scientific.\n\nJan Borggrefe has nothing to disclose.\n\nJochen Wirths reports travel grants from Boston Scientific.\n\nHaidar Salimi-Dafsari reports honoraria from Medtronic and Boston Scientific.\n\nMichael T. Barbe reports grants from Medtronic and Boston Scientific.\n\nVeerle Visser-Vandewalle is a member of the advisory boards and reports consultancies for Medtronic, Boston Scientific and St Jude Medical. She received a grant from SAPIENS Steering Brain Stimulation. Harald Treuer has nothing to disclose.

neuroscience↗

bioRxiv2018

Lead-DBS v2: Toward a comprehensive pipeline for deep brain stimulation imaging

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 reconstruction of electrode placement is required, posing specific challenges to the field of neuroimaging. Since 2014 the open source toolbox Lead-DBS is available, which aims at facilitating this process. The tool has since become a popular platform for DBS imaging. With support of a broad community of researchers worldwide, methods have been continuously updated and complemented by new tools for tasks such as multispectral nonlinear registration, structural / functional connectivity analyses, brain shift correction, reconstruction of microelectrode recordings and orientation detection of segmented DBS leads. The rapid development and emergence of these methods in DBS data analysis require us to revisit and revise the pipelines introduced in the original methods publication. Here we demonstrate the updated DBS and connectome pipelines of Lead-DBS using a single patient example with state-of-the-art high-field imaging as well as a retrospective cohort of patients scanned in a typical clinical setting at 1.5T. Imaging data of the 3T example patient is co-registered using five algorithms and nonlinearly warped into template space using ten approaches for comparative purposes. After reconstruction of DBS electrodes (which is possible using three methods and a specific refinement tool), the volume of tissue activated is calculated for two DBS settings using four distinct models and various parameters. Finally, four whole-brain tractography algorithms are applied to the patients preoperative diffusion MRI data and structural as well as functional connectivity between the stimulation volume and other brain areas are estimated using a total of eight approaches and datasets. In addition, we demonstrate impact of selected preprocessing strategies on the retrospective sample of 51 PD patients. We compare the amount of variance in clinical improvement that can be explained by the computer model depending on the method of choice.\n\nThis work represents a multi-institutional collaborative effort to develop a comprehensive, open source pipeline for DBS imaging and connectomics, which has already empowered several studies, and may facilitate a variety of future studies in the field.

neuroscience↗