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

Abstract

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 Tand DW infarct lesions and peri-lesion regions of scattered necrosis and modestly increased T. Following tMCAO, in a slice and a region adjacent to the PT, a region of Taugmentation was observed when recovery between insults was acute but not chronic. Within the PT slice, a modest region of exacerbated Tchange proximate to the PT was also observed in the chronic group. Corresponding histological changes within regions of augmented Tincluded increased vacuolation and cell death. CONCLUSION: Within regions adjacent to an experimental minor stroke, a recurrence of a mild transient cerebral ischemia augmented Tabove increases produced by tMCAO alone, reflecting increased damage in this region. Exacerbation appeared broader with acute versus chronic recovery between insults.