Role of vasogenic edema and tissue cavitation in ischemic evolution on diffusion-weighted imaging: comparison with multiparameter MR and immunohistochemistry.
OBJECTIVE
To examine the mechanisms of further evolution that occurs from the early to late phase after initial changes in diffusion-weighted imaging after cerebral ischemia.


METHODS
Sprague-Dawley rats were subjected to middle cerebral artery occlusion. Diffusion-, proton density-, T1- and T2-weighted imaging were performed on days 0, 2, and 6. Histologic examination (IgG, glial fibrillary acidic protein, and cresyl violet staining) was done after scanning.


RESULTS
Apparent diffusion coefficients (ADCs) in the ischemic hemisphere were significantly decreased on day 0. Thereafter, ADCs increased over time and became significantly higher than the contralateral side by day 6. Changes in basal ganglia occurred more rapidly than in cortex. Proton density-, T1-, and T2-weighted scans showed maximal changes on day 2. From day 0 to day 2, there are significant correlations between changes in ADC and changes in T1-weighted signals and T2-weighted signals. Histologic exam showed early neuronal injury on day 0, intense gliotic activity and protein leakage associated with infarction and edema on day 2, and cavitation in severely infarcted areas on day 6.


CONCLUSIONS
After initial reduction of ADC, the subsequent increase in ADC values on day 2 may be associated with vasogenic edema and cell lysis. Later elevations in ADC may be related to cavitation of infarcted tissue.
Matsumoto
K
K
Center for Imaging and Pharmaceutical Research, Harvard Medical School, Massachusetts General Hospital, Charlestown 02129, USA.
Lo
E H
EH
Pierce
A R
AR
Wei
H
H
Garrido
L
L
Kowall
N W
NW
D000818:Animals; D001479:Basal Ganglia / Q000098:blood supply / Q000473:pathology; D001812:Blood-Brain Barrier / Q000502:physiology; D001921:Brain / Q000098:blood supply* / Q000473:pathology; D001929:Brain Edema / Q000175:diagnosis* / Q000473:pathology; D002545:Brain Ischemia / Q000175:diagnosis* / Q000473:pathology; D002540:Cerebral Cortex / Q000098:blood supply / Q000473:pathology; D002544:Cerebral Infarction / Q000175:diagnosis / Q000473:pathology; D004058:Diffusion; D004292:Dominance, Cerebral / Q000502:physiology*; D005904:Glial Fibrillary Acidic Protein / Q000032:analysis; D007124:Immunoenzyme Techniques; D008279:Magnetic Resonance Imaging; D008297:Male; D009336:Necrosis; D009457:Neuroglia / Q000473:pathology; D009474:Neurons / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley
D005904:Glial Fibrillary Acidic Protein