Magnetic resonance imaging detection of multiple ischemic injury produced in an adult rat model of minor stroke followed by mild transient cerebral ischemia

OBJECTIVES: To determine whether cumulative brain damage produced adjacent to a minor stroke that is followed by a mild transient ischemia is detectable with MRI and histology, and whether acute or chronic recovery between insults influences this damage. MATERIALS AND METHODS: A minor photothrombotic (PT) stroke was followed acutely (1–2 days) or chronically (7 days) by a mild transient middle cerebral artery occlusion (tMCAO). MRI was performed after each insult, followed by final histology. RESULTS: The initial PT produced small hyperintense T(2) and DW infarct lesions and peri-lesion regions of scattered necrosis and modestly increased T(2). Following tMCAO, in a slice and a region adjacent to the PT, a region of T(2) augmentation was observed when recovery between insults was acute but not chronic. Within the PT slice, a modest region of exacerbated T(2) change proximate to the PT was also observed in the chronic group. Corresponding histological changes within regions of augmented T(2) included increased vacuolation and cell death. CONCLUSION: Within regions adjacent to an experimental minor stroke, a recurrence of a mild transient cerebral ischemia augmented T(2) above increases produced by tMCAO alone, reflecting increased damage in this region. Exacerbation appeared broader with acute versus chronic recovery between insults. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s10334-016-0597-5) contains supplementary material, which is available to authorized users.