Abstract WP90: Voxel-Based Lesion Symptom Mapping (VLSM) of NIH Stroke Scale Subscore Deficits

Abstract

Background: Studies identifying brain regions required to preserve specific neurologic functions after stroke typically analyze infarct volume or location. Lesion topography studies have found that, independent of volume, involvement of specific regions have greater impact on clinical outcome than others, suggesting location-determined differences in eloquence. However, most anatomy-based studies define location broadly. VLSM is an imaging analysis technique that establishes a relationship between precise lesion location and clinical deficit. A group of patients with a symptom (e.g. aphasia) is analyzed; every voxel on each patient’s MRI is evaluated for lesion presence or absence. Each voxel is assigned a t-statistic, and a statistical map of all lesioned voxels is generated to pinpoint regions most strongly associated with the deficit; a high t-score indicates a lesion in that voxel has a significant effect on the specified symptom. We generated VLSM maps for 6 NIHSS subscores (aphasia, right- and left-limb weakness, and sensory loss) in a novel characterization to be used in future research. Methods: 172 acute ischemic stroke (AIS) patients with large vessel occlusions (LVOs) were analyzed. Binary masks of infarcts on D5 FLAIR sequences were created. Lesions were coregistered to standard MNI atlas space. VLSM V2.55 was used to generate statistical maps of lesion contribution to clinical deficit. Maps were thresholded to p<0.001 on basis of cluster size and permutation method. A symptom reference area was defined as a region on which voxels had a t-score >3.14. Results: VLSM maps with voxelwise thresholds of p<0.001 were generated for 6 NIHSS categories (examples in figure). Conclusions: VLSM successfully generated unique maps of 6 NIHSS subscore deficits. These maps will be used to study patients presenting with perfusion/diffusion mismatch to predict the potential for resolution of specific deficits with reperfusion therapy and aid in prognostication.