Correlation of cerebral hypoxic-ischemic T2 changes with tissue alterations in water content and protein extravasation

• Published in: Stroke (1970) Vol. 32; no. 4; pp. 958 - 963
• Main Authors: MIN QIAO, MALISZA, Krisztina L, DEL BIGIO, Marc R, TUOR, Ursula I
• Format: Journal Article
• Language: English
• Published: Hagerstown, MD Lippincott Williams & Wilkins 01.04.2001; American Heart Association, Inc
• Subjects: Age Factors; Aging - metabolism; Animals; Biological and medical sciences; Blood-Brain Barrier; Brain - metabolism; Brain - pathology; Brain Chemistry; Brain Edema - metabolism; Disease Models, Animal; Humans; Hypoxia-Ischemia, Brain - metabolism; Hypoxia-Ischemia, Brain - pathology; Hypoxia-Ischemia, Brain - physiopathology; Immunoglobulin G - analysis; Immunoglobulin G - metabolism; Magnetic Resonance Imaging; Medical sciences; Neurology; Organ Size; Rats; Rats, Wistar; Reproducibility of Results; Specific Gravity; Vascular diseases and vascular malformations of the nervous system; Water - analysis; Water - metabolism; Nervous system diseases; Oxygen; Pathophysiology; Rat; Rodentia; IgG; Cardiovascular disease; Blood brain barrier; Nuclear magnetic resonance imaging; Young animal; Cerebral disorder; Vascular disease; Vertebrata; Mammalia; Ischemia; Newborn animal; Extravasation; Central nervous system disease; Water content; Medical imagery; Evolution; Hypoxia; Cerebrovascular disease; Brain (vertebrata)
• ISSN: 0039-2499; 1524-4628
• DOI: 10.1161/01.STR.32.4.958

Age-dependent changes in T2-weighted MR images have been reported in cerebral hypoxia-ischemia. However, the biophysical mechanisms responsible for the image changes remain poorly defined. We investigated whether cerebral hypoxia-ischemia-induced T2 changes correlate with alterations in either water content or protein extravasation. One- and 4-week-old rats were subjected to unilateral carotid artery occlusion plus hypoxia in 8% oxygen. T2 images were acquired before, during, and 1 or 24 hours after hypoxia-ischemia. Blood-brain barrier disruption and brain edema were evaluated by immunohistological detection of IgG extravasation and measurement of water content by dry-wet weight and specific gravity methods. In 1-week-old rats, T2 values, areas of hyperintensity on T2-weighted images, and water content in the ipsilateral hemisphere increased during hypoxia-ischemia, recovered at 1 hour after hypoxia-ischemia, and increased again at 24 hours after hypoxia-ischemia. Extravasation of IgG occurred during hypoxia-ischemia and remained detectable 24 hours after hypoxia-ischemia. In 4-week-old rats, an increase in T2 or extravasation of IgG did not occur until 24 hours after hypoxia-ischemia despite a comparable elevation in water content during and soon after hypoxia-ischemia. T2 imaging appears reliable for detecting edema associated with disruption of the blood-brain barrier but not necessarily an increase in cerebral water or plasma proteins alone. The different hypoxic-ischemic changes in T2 in immature and older brain are associated with differences in alterations in water content plus extravasation of protein, consistent with age-dependent differences in hypoxic-ischemic alterations in vascular permeability.