Secondary Deterioration of Apparent Diffusion Coefficient After 1-Hour Transient Focal Cerebral Ischemia in Rats

Abstract

Recent investigations on transient focal cerebral ischemia suggested recovery of energy metabolism during early reperfusion, but followed by secondary energy failure. As disturbances of energy metabolism are reflected by changes of the apparent diffusion coefficient (ADC) of water, the aim of the current study was to follow the dynamics of the ADC during 1 hour of middle cerebral artery occlusion (MCAO) and 10 hours of reperfusion. The right MCA was occluded in male Wistar rats inside the magnet using a remotely controlled thread occlusion model. Diffusion-, perfusion-, and T2-weighted images were performed repetitively, and ADC, perfusion, and T2 maps were calculated and normalized to the respective preischemic value. The lesion volume at each time point was defined by ADC < 80% of control. At the end of 1-hour MCAO the hemispheric lesion volume was 22.3 +/- 9.0%; it decreased to 6.4 +/- 5.7% in the first 2 hours of reperfusion (P < 0.01), but then increased again, and by the end of 10 hours of reperfusion reached 17.3 +/- 9.3%. The mean relative ADC in the end ischemic lesion volume significantly improved within 2 hours of reperfusion (from 65.7 +/- 1.2% to 90.1 +/- 6.7% of control), but later declined and decreased to 75.4 +/- 7.3% of control by the end of the experiment. Pixels with secondary deterioration of ADC showed a continuous increase of T2 value during the first 2 hours of reperfusion in spite of ADC improvement, indicating improving cytotoxic, but generation of vasogenic edema during early reperfusion. A significant decrease of the perfusion level was not observed during 10 hours of recirculation. The authors conclude that the improvement of ADC in the early phase of reperfusion may be followed by secondary deterioration that was not caused by delayed hypoperfusion.

Mild Hypoxic-Ischemic Injury in the Neonatal Rat Brain: Longitudinal Evaluation of White Matter Using Diffusion Tensor MR Imaging

“…Dynamic change in trace reflects the water distribution between extra-and intracellular space. Initial increase in trace post-HI injury as found in our study is commonly explained as water influx from vessels to brain tissue, 27 namely vasogenic edema. In the subsequent time points, similar trace was found between both sides of the EC.…”

Dynamic changes of ADC, perfusion, and NMR relaxation parameters in transient focal ischemia of rat brain

“…Ischemic T 1 alterations have been described (33) and can be attributed, at least in part, to a decline in blood flow and/or the above-described magnetization transfer effects (34). The increase in T 2 is ascribed to edema formation, which is most pronounced in irreversibly damaged tissue (35)(36)(37)(38). During the 90-min vascular occlusion, this is mainly cytotoxic edema, because blood-brain barrier breakdown (a criterium of vasogenic edema) is observed only after much longer intervals (35,36).…”

“…Transient focal ischemia is frequently followed by hyperemia, which is explained by vasoparalysis due to the acidification of the tissue (38). The more pronounced hyperemia after 90 min of ischemia thus reflects a more severe acidosis developing over the longer ischemic period.…”

Infarct Volume Prediction by Early Magnetic Resonance Imaging in a Murine Stroke Model Depends on Ischemia Duration and Time of Imaging

“…[17][18][19][20][21] Full recovery of ADC at 3 hours after MCAO onset has been reported for MCAO duration of 8 to 30 minutes in rats and mice. [22][23][24] Of note, this does not reflect complete tissue recovery, as MR spectroscopy may still detect significant changes in neurochemical profiles.…”