Abstract
Background: The Network Modification (NeMo) Tool uses a library of brain connectivity maps from normal subjects to quantify the amount of structural connectivity loss caused by focal brain lesions. We hypothesized that the NeMo Tool could predict remote brain tissue loss caused by Wallerian degeneration after stroke. Methods: Baseline and follow-up MRIs from 27 patients with acute ischemic stroke were collected (74±14 years, initial NIHSS 2±3, 5.7±2.8 months b/w scans). Diffusion-weighted image derived lesion masks were superimposed on the NeMo Tool’s connectivity maps in order to predict changes to the structural connectivity network and to investigate correlations with future atrophy. Regional connectivity losses were estimated via the Change in Connectivity (ChaCo) score, i.e. the percent of “injured” tracks going through lesions that connect to a given region. ChaCo scores and longitudinal tissue changes were calculated using a standard 116 region atlas. Results: Lesion location and size varied greatly, but they occurred more frequently in the left hemisphere. The ChaCo scores, which were generally higher in regions near stroke lesions, reflected this heterogeneity. In general, ChaCo was higher in the left hemisphere than the right and was high in the postcentral and precentral gyri, insula, middle cingulate, thalami, putamen, caudate nuclei, and pallidum. Moderate correlations were found between ChaCo scores at baseline and measures of subsequent tissue loss (change in volume and average mean diffusivity [MD] from baseline to follow-up, see Figure 1). Conclusions: ChaCo scores varied greatly, but the most affected regions included those with sensorimotor, perception, learning and memory functions. Moderate correlations were found between ChaCo scores at baseline and subsequent tissue loss. These results suggest that the NeMo Tool could enable more accurate prognosis, as it may identify regions most susceptible to degeneration from remote infarcts.
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