TIME-COURSE OF THE APPARENT DIFFUSION-COEFFICIENT (ADC) ABNORMALITY IN HUMAN STROKE

Diffusion-weighted MRI can rapidly detect acute cerebral ischemic inju ry as hyperintense signal changes, reflecting a decline in the apparen t diffusion coefficient (ADC) of water through brain parenchyma, where as ADC is elevated in the chronic stage because of increased extracell ular water content. To determine the time course of these ADC changes, we analyzed 157 diffusion-weighted MRI studies performed at varying t ime points from the initial ischemic event from 101 patients. Data wer e expressed as the relative ADC (rADC), the ratio of lesion to control regions of interest. We observed two phases in the time course of rAD C changes in acute human stroke: a significant (p < 0.005) reduction i n rADC lasting for at least 96 hours from stroke onset (mean, 58.3% of control; SEM, 1.47) and an increasing trend from reduction to pseudon ormalization to elevation of rADC values at later subacute to chronic time points (greater than or equal to 7 days). We suggest that the per sistent reduction of rADC within the first four days may reflect ongoi ng or progressive cytotoxic edema to a greater degree than extracellul ar edema and cell lysis.