DTI-TMS assessment of corticospinal tracts integrity and unaffected hemisphere state in chronic ischemic stroke patients
Adequate assessment of individual functional motor potentials is important for developing appropriate rehabilitation strategies in ischemic stroke . Microstructural changes in corticospinal tract (CST) and corpus callosum (CC) were repeatedly correlated to post-stroke outcome [2, 3]. However, relationship between them and functional recovery remains unclear. Here we investigated relationship between integrity of CST and CC assessed with diffusion tensor imaging (DTI) and brain functional state assessed with navigated transcranial magnetic stimulation (nTMS) in chronic ischemic supratentorial stroke.
Hand motor recovery prognosis in stroke patients is crucial to develop a realistic individual rehabilitation plan. The aim of this study was to perform a multimodal assessment in chronic ischemic stroke patients and to compare predictive role of corticospinal tract (CST) integrity measured by diffusion tensor imaging (DTI) and navigated TMS (nTMS), and functional condition of the motor cortex measured by functional MRI (fMRI) and multi-muscle nTMS cortical mapping for hand motor recovery.Total of 30 patients with the only chronic supratentorial ischemic stroke and various severity of hand paresis were enrolled (12 females, medium age 50,0±8,0). The assessment included fractional anisotropy FA (index, %) measurement in internal capsule (ic), cerebral peduncle (pc) and pons. Functional assessment included analysis of BOLD response induced by passive motor task, assessment of intracortical inhibition (SICI) and intracortical facilitation (ICF) phenomena in Abductor Pollicis Brevis (APB) and nTMS mapping of APB and Extensor Digitorum Communis (EDC) cortical representations in both hemispheres. A group of 14 healthy volunteers (7 females, mean age 36,6±15,2) completed fMRI and nTMS investigation. A strong correlation between clinical outcome and FA let to consider FA as an available clinical measurement for hand motor prognosis. Significantly higher disinhibition in the unaffected hemisphere (UH) in well recovered and normal SICI in the UH in poorly recovered patients allow to suppose that interhemispheric interaction might change extensively by chronic phase. A software for multi-muscle nTMS mapping was developed, though this approach need deeper exploration.
In the internal medicine wide spectrum the gastroenterology is one of the chapters, less enlightened by the scientific evidence. It does not mean that the practice of the grasntroenterology may ot be improved by the systematic use of the approaches of the evidence based medicine
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Transcranial magnetic stimulation (TMS) is a modern non-invasive approach to study brain organization in humans. In TMS a time-varying magnetic fields generate induced electrical currents in the targeted brain regions with focal location of its maximum. Using of MRI navigation systems allows to fully realizing the advantages of TMS focality for brain mapping purposes. Due to this development, nowadays motor and speech nTMS mapping is becoming a routinely used procedure in neurosurgery. However, nTMS mapping for dynamic cortical assessment, for example, to study neuroplastic changes is still limited. An important reason for that is a lack of a standardized methodology for nTMS mapping results assessment. Here we propose TMSmap – a standalone graphical interface software for quantative analysis of the results of motor nTMS mapping (http://tmsmap.ru/), which allows considering both standard parameters like the size of the cortical muscle representation, the hotspot and the center of gravity location, as well as the additional ones such as the volume of the representation, the profile of the muscle cortical area and the overlap between the cortical representations and other user-defined parameters. The input data includes coordinates of the coil position and the response in each point of stimulation and individual structural MRI data.
Modern neuroimaging studies begin to explore neurobiological mechanisms of social norms enforcement. Several regions of frontal lobes and temporo-parieto-occipital cortex play a key role in decision making of social punishment of fairness’ norm violation. The cutting–edge methods of brain stimulation allow to change a frequency and intensity of social punishment in different economic tasks (games). The analysis of modern studies show that brain mechanisms of decision making to punish non–cooperative individual requires further investigation with brain stimulation methods to differentiate a role of frontal and temporo-parieto-occipital regions and clarify its interaction.
Despite being a routine technique for presurgical motor assessment, transcranial magnetic stimulation (TMS) mapping is underused for probing of neuroplastic brain changes. We investigated the test-retest reproducibility of the TMS cortical maps of several hand muscles using both standard and alternative parameters of the cortical representation.Pilot study results for four healthy right-handed male volunteers (19-33y.o.) are presented. Two TMS mapping sessions with the stimulation of the left motor cortex were performed within 5-10 days (Day1 and Day2). Day2 points repeated an exact order of the Day1. For quantative comparison of 3D profiles similarities earth mover's distance metrics was used. Analysis of nTMS maps was performed using custom-made software TMSmap (http://tmsmap.ru).The between-days difference in the area of cortical representation for four analyzed subjects was 14.5-30.4% for one and 3.9-11.2% for five repetitions of each cortical point. Considering 3D profiles of cortical representation, higher similarity was shown for the same muscles’ representations and their overlaps compared to the representations of the different muscles. The study is ongoing, further analyzed results will be present.
TMSmap software was developed for quantative analysis of the results of motor nTMS mapping, which allows to consider not only standard parameters like the size of the cortical muscle representation and hotspot and center of gravity location, but as well the volume of the representation considering the amplitude of MEPs in each stimulation spot, the shape of the area, the profile/landscape of the muscle cortical representation and the overlap between representations.
This prototype development explains the challenges encountered during the ISO/IEEE 11073 standard implementation process. The complexity of the standard and the consequent heavy requirements, which have not encouraged software engineers to adopt the standard. The developing complexity evaluation drives us to propose two possible implementation strategies that cover almost all possible use cases and eases handling the standard by non-expert users. The first one is focused on medical devices (MD) and proposes a low-memory and low-processor usage technique. It is based on message patterns that allow simple functions to generate ISO/IEEE 11073 messages and to process them easily. MD act as X73 agent. Second one is focused on more powerful device X73 manager, which do not have the MDs' memory and processor usage constraints. The protocol between Agent and Manager is point-to-point and we can distribute the functionality between devices.
Developed both implementation X73 Agent and Manager will cut developing time for applications based on ISO/EEE 11073.