The paradoxical relationship of sensorimotor deficit and lesion volume in acute ischemic stroke

Understanding the relationship between the degree of neurological deficit and lesion volume is key to predicting outcomes in patients with acute ischemic stroke (AIS). Over the past 40 years, AIS research has relied on a perceived linear relationship between lesion volumes and neurological deficit. Here, we found that these variables do not show a relationship in a mouse model of AIS. Acute ischemic stroke was induced by transient (60 minutes) intraluminal microfilament occlusion of the middle cerebral artery in 15 male isoflurane (0.8%-1%)-anesthetized mice. Acute ischemic stroke-induced sensorimotor deficits were assessed daily for 72 hours using the Garcia Neuroscore Scale (GNS). Lesion size was estimated 72 hours after AIS using a rodent MRI system. Lesion sizes ranged from 17 to 130 mm3. In 3/15 mice (atypical cases: lesion <30 mm3 and GNS <11), small infarcts (14.6 ± 6.2 vs 51.7 ± 19.9 mm3, atypical vs typical) were associated with low GNS values at 72 hours (9 ± 2 vs 11 ± 2 pts; atypical vs typical). Consequently, we found no relationship between lesion size and GNS in this AIS model (R = 0.058). These results suggest that lesion size is not a reliable predictor of neurological outcome in AIS models.