Harston, George

Introduction: Selection criteria for endovascular thrombectomy (EVT) for emergent large-vessel occlusion (ELVO) stroke increasingly rely on CT perfusion (CTP) findings at presentation. While perfusion imaging is used to estimate the likelihood of deriving long-term functional benefit from EVT, there is comparatively little data on how perfusion deficits relate to domains of neurological function. Here, we investigated region-specific hypoperfusion as a driver of neurological dysfunction through correspondence between NIHSS items and CTP. Methods: We included 169 patients with ELVO presenting to Mayo Clinic Rochester or Jacksonville, who had baseline CTP and itemised NIHSS data. Perfusion was quantified as mean transit time using e-CTP (Brainomix Ltd., Oxford, UK) and thresholded to ≥5 s for lesion masking. Voxel-wise lesion-symptom mapping (VLSM) was performed using sparse canonical correlations analysis (Lesymap package, R). Results: Total NIHSS was most strongly predicted by left MCA territory hypoperfusion, corresponding to language-eloquent cortical areas and dominant hemisphere motor tracts (figure 1). Contralateral limb motor deficits (NIHSS 5 and 6) were mainly associated with subcortical and white matter hypoperfusion; there was an additional strong signal for left frontal cortex in language function (NIHSS 9). The remaining NIHSS items were less well localised. Conclusions: Expanding on previous pilot data, our results provide further evidence for the feasibility of hypoperfusion-to-symptom mapping in ELVO. This could allow for more nuanced clinical-imaging mismatch determination, and selection of patients based on specific neurological deficits that may be reversible.

Introduction: Patient selection for acute stroke revascularisation therapies is commonly based on clinical-imaging mismatch paradigms. Anatomical scores or total volumes of brain affected are assumed to correlate with clinical deficit without reference to the functional eloquence of the regions involved. In this study we used the relationship between presenting hypoperfusion abnormality and the corresponding NIHSS to generate functionally weighted atlases from patients with acute ischaemic stroke. Methods: Patients with acute large vessel occlusion (LVO) of the anterior circulation and with CTP at the time of presentation were included in this study. CTP was analysed with e-CTP (Brainomix Ltd., Oxford, UK) and hypoperfusion maps defined (Tmax >6s). Voxelwise lesion to symptom mapping was used to generate probability maps associating regions of hypoperfusion with clinical deficit at presentation. Results: 58 patients with itemised NIHSS and CTP were included. Discrete patterns of deficit were associated with each NIHSS domain. Total NIHSS correlated most strongly with left MCA involvement, consistent with the weighting towards language in this clinical scale. Regions associated with upper and lower limb deficits identified the respective motor cortex regions and descending motor tracts. Example mapping is presented in the Figure (A: total NIHSS, B: left arm paresis, C: left leg paresis). Data from a larger cohort will be presented at the meeting. Conclusions: Functional mapping using associations between presenting NIHSS and hypoperfusion lesion can be used to create eloquence-weighted atlases. Such atlases from stroke patients may be helpful to develop tools to predict clinical deficit associated with a presenting ischemic core lesion defined on non-contrast CT or CTP. This approach could refine clinical-imaging mismatch concepts, expanding endovascular treatment to a wider group of patients who would not currently be treated.