White Matter Stimulation with SEEG Electrodes Highlights Specific Tract Contribution to Cognition
Abstract number :
2.163
Submission category :
3. Neurophysiology / 3E. Brain Stimulation
Year :
2024
Submission ID :
980
Source :
www.aesnet.org
Presentation date :
12/8/2024 12:00:00 AM
Published date :
Authors :
Presenting Author: Davide Giampiccolo, MD – Department of Clinical and Experimental Epilepsy, Institute of Neurology, Faculty of Brain Sciences, University College London
Lawrence Binding, PhD – Department of Clinical and Experimental Epilepsy, Institute of Neurology, Faculty of Brain Sciences, University College London
Alejandro Granados Martinez, PhD – King's College London
Joana Oliveira, MD – UCL/National Hospital for Neurology and Neurosurgery
Emma Torzillo, MD – UCL/NHNN
Umesh Vivekananda, MD, PhD – UCL/NHNN
Roman Rodionov, PhD – UCL
Jane de Tisi, BSc – University College London
Fenglai Xiao, MD PhD – Department of Clinical and Experimental Epilepsy, Institute of Neurology, Faculty of Brain Sciences, University College London
Marine Fleury, PhD – Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology,University College London
Andrew McEvoy, MD – University College London
Beate Diehl, MD – University College London
Neil Burgess, PhD – UCL
Fahmida A. Chowdhury, MD – University College London
Anna Miserocchi, MD – University College London
Rationale:
With the advent of white matter stimulation during awake surgery, contemporary perspectives of brain function and dysfunction have moved from cortical localizationism to networks. Mapping of seizure onset zones in patients implanted with SEEG for invasive recording in drug-resistant focal epilepsy relies on direct stimulation of the cortex, however implantation of depth electrodes also allows testing of white matter contacts to identify functional networks as well. We used direct white matter stimulation in patients implanted with SEEG for drug-resistant epilepsy to test the role of white matter in language.
Methods:
13 patients underwent SEEG implantation for drug resistant focal epilepsy (2 bilateral, 6 left, 5 right). They all underwent 1mm T1-weighted imaging and diffusion MRI (1.6 mm isovolumetric, multi shell 500-2500 b-values, 18 b0). The arcuate fasciculus (AF) and inferior fronto-occipital fasciculus (IFOF) were reconstructed using probabilistic constrained spherical deconvolution in MRTrix3. Patients were tested with validated batteries from awake surgery, adding hand movements when tolerated (double-task). Stimulation was bipolar with adjacent white matter contacts, biphasic, with a 50 Hz frequency lasting up to 4 seconds and was based on individual white matter tracts dissected in the native space.
Results: The IFOF was stimulated in 12/13 patients (32 couples of electrodes, 20R-12L), the AF in 6/13 (7 couples of electrodes, all left). Average intensity of stimulation was 3 mA. The pattern of deficits differed among language tracts: stimulation of IFOF predominantly resulted in impairment of visual tasks involving pictures, regardless of verbal modality (picture naming, but also semantic associations, praxis, face recognition) and stimulation was often associated with hallucinations (8/12 patients) or perseverations (3/12 patients). Conversely, stimulation of AF resulted in impairments in language (anomia, phonological distortions) across sensory (visual and acoustic) modality.
Conclusions: We introduced a novel paradigm using SEEG for tract-specific white matter stimulation. Our preliminary results are in line with novel proposals for language, providing subcortical grounding for a distinction between domain-general executive processes impacting – but not exclusive to - verbal semantics supported by the IFOF in the left hemisphere, and language-specific pathways involved in phonological processing supported by the AF.
Funding: DG is supported by the Epilepsy Research Institute UK with an Emerging Leaders fellowship
Neurophysiology