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Severe ADC decreases do not predict irreversible tissue damage in humans
Jens Fiehler1, Mascha Foth, Thomas Kucinski
1Department of Neurology, University Hospital Hamburg-Eppendorf, University of Hamburg, Hamburg, Germany. fiehler@uke.uni-hamburg.de
Background And Purpose:
A mismatch between diffusion- and perfusion-weighted MRI is thought to define tissue at risk of infarction. This concept is based on the assumption that diffusion slowing of and decreases in the apparent diffusion coefficient (ADC) serve as indicator of tissue proceeding to infarction. We tested this hypothesis.
Methods:
MRI (diffusion weighted, perfusion weighted, MRA, T2 weighted) was performed in 15 patients with acute stroke within 2.9+/-0.8 hours (mean+/-SD) of onset and on days 1 and 7. After intraindividual realignment of the ADC maps, the development of ADC range volumes and ADC values was determined.
Results:
An increase (354%, group A1) in the total ADC-based lesion volume below a threshold of < 80% occurred in 4 patients on day 1, persisting on day 7 with a pronounced increase of ADC range volumes with low ADC values. An increase in total ADC-based lesion volume (201%, group A2) followed by a secondary drop to day 7 was found in 7 patients. A significant reduction in total ADC-based lesion volume (14%, group B) was found in 4 patients. ADC-based lesion volume increase was associated with persistent vessel occlusion in group A, whereas recanalization in group B resulted in ADC volume decrease. ADC normalization was observed independently from the degree of the initial ADC decrease on days 1 and 7 in group B.
Conclusions:
In line with results from animal experiments, ADC decreases do not reliably indicate tissue infarction Even severely decreased ADC values may normalize in human stroke, and it seems likely that ADC normalization depends on the duration and severity of ischemia rather than the absolute value.
Insights
Diffusion-weighted MRI apparent diffusion coefficient (ADC) decreases do not reliably predict infarction in acute stroke. Severely decreased ADC values can normalize, suggesting recovery is dependent on ischemia duration and severity, not just initial ADC values.
Area of Science:
- Neuroimaging
- Stroke research
- Diffusion-weighted MRI
Background:
- Diffusion-weighted MRI (DWI) and perfusion-weighted MRI (PWI) mismatch is assumed to identify tissue at risk of infarction.
- Apparent diffusion coefficient (ADC) decreases are hypothesized to indicate progressing infarction.
Observation:
- 15 acute stroke patients underwent serial MRI (DWI, PWI, MRA, T2-weighted) within 2.9 hours of onset and on days 1 and 7.
- ADC maps were analyzed intraindividually to track lesion volume and ADC values over time.
Findings:
- In 4 patients (group A1), ADC lesion volume increased >350% by day 1, persisting by day 7.
- In 7 patients (group A2), ADC lesion volume increased >200% then dropped by day 7.
- In 4 patients (group B), ADC lesion volume significantly decreased by 14%.
- Persistent vessel occlusion correlated with ADC volume increase (group A), while recanalization correlated with ADC volume decrease (group B).
- ADC normalization occurred in group B irrespective of initial ADC decrease severity.
Implications:
- Apparent diffusion coefficient (ADC) decreases are not definitive indicators of infarction in human stroke.
- ADC normalization in stroke patients suggests tissue viability can be preserved even with initially severe diffusion restriction.
- Recovery potential in stroke may depend more on the duration and severity of ischemia than on the initial ADC values.