Stroke assessment: morphometric infarct size versus neurologic deficit

We presently examine the relation between histologic infarct size and neurologic deficit as endpoints and seek to clarify their sensitivity in defining stroke outcome. Neurologic deficits of 76 cats subjected to middle cerebral artery occlusion were assessed daily and correlated with the corresponding infarct sizes determined morphometrically after 2 weeks' survival. A five-item neurologic deficit score included the time elapsed until hemiparesis, and forced circling resolved (if ever), presence of impaired placing reactions and time elapsed until able to stand and being alert. We then evaluated the two endpoints' statistical powers to detect group differences using two sets of comparison groups. The neurologic deficit score correlated well with infarct size (r = 0.76, p < 0.001) and each of the individual deficit score components named above, in turn, correlated with decreasing power with infarct size. Even so, the number of study subjects required to achieve the same level of statistical significance in assessing group differences was two-fold greater when using the neurologic deficit than the infarct size data: Group sizes of eight and five animals were sufficient for significant infarct size differences while the groups needed be expanded to 15 and 10 animals to similarly achieve significant neurologic score differences. Thus, infarct size emerges as a more sensitive measure of stroke outcome than does the assessment of neurologic deficits.