title: Motor Cortex Neurostimulation Technologies for Chronic Post-stroke Pain: Implications of Tissue Damage on Stimulation Currents.
abstract: Background:Central post stroke pain (CPSP) is a highly refractory syndrome that can occur after stroke. Primary motor cortex (M1) brain stimulation using epidural brain stimulation (EBS), transcranial magnetic stimulation (TMS), and transcranial direct current stimulation (tDCS) have been explored as potential therapies for CPSP. These techniques have demonstrated variable clinical efficacy. It is hypothesized that changes in the stimulating currents that are caused by stroke-induced changes in brain tissue conductivity limit the efficacy of these techniques.Methods:We generated MRI-guided finite element models of the current density distributions in the human head and brain with and without chronic focal cortical infarctions during EBS, TMS, and tDCS. We studied the change in the stimulating current density distributions' magnitude, orientation, and maxima locations between the different models.Results:Changes in electrical properties at stroke boundaries altered the distribution of stimulation currents in magnitude, location, and orientation. Current density magnitude alterations were larger for the non-invasive techniques (i.e., tDCS and TMS) than for EBS. Nonetheless, the lesion also altered currents during EBS. The spatial shift of peak current density, relative to the size of the stimulation source, was largest for EBS.Conclusion:In order to maximize therapeutic efficiency, neurostimulation trials need to account for the impact of anatomically disrupted neural tissues on the location, orientation, and magnitude of exogenously applied currents. The relative current-neuronal structure should be considered when planning stimulation treatment, especially across techniques (e.g., using TMS to predict EBS response). We postulate that the effects of altered tissue properties in stroke regions may impact stimulation induced analgesic effects and/or lead to highly variable outcomes during brain stimulation treatments in CPSP.
authors.affiliation: Neuromodulation Lab and Center for Clinical Research and Learning - Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Harvard Medical School, Boston MA, USA.
authors.forename: Anthony T
authors.initials: AT
authors.lastname: O'Brien
authors.affiliation: Neuromodulation Lab and Center for Clinical Research and Learning - Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Harvard Medical School, Boston MA, USA.
authors.forename: Rivadavio
authors.initials: R
authors.lastname: Amorim
authors.affiliation: Laboratory of Cerebral Dynamics, Plasticity and Rehabilitation, Boston University School of Medicine, BostonMA, USA; Department of Anatomy and Neurobiology, Boston University School of Medicine, BostonMA, USA.
authors.forename: R Jarrett
authors.initials: RJ
authors.lastname: Rushmore
authors.affiliation: Department of Mathematics and Statistics, Boston University, Boston MA, USA.
authors.forename: Uri
authors.initials: U
authors.lastname: Eden
authors.affiliation: Laboratory of Cerebral Dynamics, Plasticity and Rehabilitation, Boston University School of Medicine, BostonMA, USA; Department of Anatomy and Neurobiology, Boston University School of Medicine, BostonMA, USA.
authors.forename: Linda
authors.initials: L
authors.lastname: Afifi
authors.affiliation: Highland Instruments, Cambridge MA, USA.
authors.forename: Laura
authors.initials: L
authors.lastname: Dipietro
authors.affiliation: Highland Instruments, CambridgeMA, USA; Division of Health Sciences and Technology, Harvard Medical School/Massachusetts Institute of Technology, BostonMA, USA.
authors.forename: Timothy
authors.initials: T
authors.lastname: Wagner
authors.affiliation: Laboratory of Cerebral Dynamics, Plasticity and Rehabilitation, Boston University School of Medicine, BostonMA, USA; Department of Anatomy and Neurobiology, Boston University School of Medicine, BostonMA, USA; Université Pierre et Marie Curie, CNRS UMR 7225-INSERM U1127, Institut du Cerveau et la Moelle EpinièreParis, France; Cognitive Neuroscience and Information Technology Research Program, Open University of CataloniaBarcelona, Spain.
authors.forename: Antoni
authors.initials: A
authors.lastname: Valero-Cabré
keywords: analgesia; epidural brain stimulation; motor cortex; neurological model; pain; stroke; transcranial direct current stimulation; transcranial magnetic stimulation