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Time course of the apparent diffusion coefficient (ADC) abnormality in human stroke
G Schlaug1, B Siewert, A Benfield
1Department of Neurology and Radiology, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA.
Abstract:
Diffusion-weighted MRI can rapidly detect acute cerebral ischemic injury as hyperintense signal changes, reflecting a decline in the apparent diffusion coefficient (ADC) of water through brain parenchyma, whereas ADC is elevated in the chronic stage because of increased extracellular water content. To determine the time course of these ADC changes, we analyzed 157 diffusion-weighted MRI studies performed at varying time points from the initial ischemic event from 101 patients. Data were expressed as the relative ADC (rADC), the ratio of lesion to control regions of interest. We observed two phases in the time course of rADC changes in acute human stroke: a significant (p < 0.005) reduction in 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 pseudonormalization to elevation of rADC values at later subacute to chronic time points (> or = 7 days). We suggest that the persistent reduction of rADC within the first four days may reflect ongoing or progressive cytotoxic edema to a greater degree than extracellular edema and cell lysis.
Insights
Diffusion-weighted MRI reveals acute stroke injury through reduced apparent diffusion coefficient (ADC) values. This reduction persists for at least 96 hours, indicating cytotoxic edema in early stroke stages.
Area of Science:
- Neuroimaging
- Radiology
- Neurology
Background:
- Diffusion-weighted MRI (DW-MRI) detects acute cerebral ischemic injury via hyperintense signals.
- Apparent diffusion coefficient (ADC) declines in acute injury and elevates in chronic stages due to altered water content.
Purpose of the Study:
- To characterize the temporal evolution of ADC changes in acute human stroke.
- To differentiate between cytotoxic and vasogenic edema based on ADC kinetics.
Main Methods:
- Analysis of 157 DW-MRI studies from 101 patients with ischemic stroke.
- Measurement of relative ADC (rADC) by comparing lesion to control regions.
- Correlation of rADC values with time elapsed since stroke onset.
Main Results:
- A significant reduction in rADC (mean 58.3% of control) was observed, persisting for at least 96 hours post-stroke (p < 0.005).
- A trend towards pseudonormalization and elevation of rADC was noted at subacute to chronic time points (≥7 days).
Conclusions:
- The sustained rADC reduction in the initial four days suggests a dominant role of cytotoxic edema.
- ADC changes provide a dynamic marker for edema evolution and tissue injury in acute stroke.