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Updated: Jul 11, 2026
A Magnetic Resonance Imaging Protocol for Stroke Onset Time Estimation in Permanent Cerebral Ischemia
Published on: September 16, 2017
Time course of diffusion imaging in acute brainstem infarcts
Hubertus Axer1, David Grässel, Dirk Brämer
1Department of Neurology, Friedrich-Schiller-University Jena, Jena, Germany. Hubertus.Axer@med.uni-jena.de
Purpose:
To study the time course of diffusion imaging at the lesion site in brainstem infarcts.
Materials And Methods:
Sequential MR scans were acquired from 24 patients with brainstem infarcts. Diffusion-weighted images (DWI), T(2)-weighted images (T(2)w), maps of apparent diffusion coefficient, and maps of fractional anisotropy were generated from each MR scan. A trend function was fitted to these measurements to model an objective, general time course of the studied parameters.
Results:
Apparent diffusion coefficient (ADC) continuously decreased over time until a transition time around 45 hours; afterwards a continuous increase took place. After the 14th day ADC reached values similar to the ADC of the intact contralateral side (pseudonormalization) and then further increased. Fractional anisotropy (FA) decreased continuously over 3 to 6 months.
Conclusion:
Times of transition and pseudonormalization of ADC were longer than described for territorial hemispheric infarcts and describe the acute to subacute phase of brainstem ischemia. In contrast, the continuous decline of FA over 3 to 6 months indicates a chronic process of change of histological structures in brainstem ischemia, and may be regarded as an indicator of the chronic phase.
Insights
Diffusion imaging in brainstem infarcts shows apparent diffusion coefficient (ADC) pseudonormalization takes longer than in hemispheric strokes. Fractional anisotropy (FA) decline indicates chronic changes in brainstem ischemia.
Area of Science:
- Neuroimaging
- Neurology
- Radiology
Background:
- Brainstem infarcts present unique challenges in understanding lesion evolution.
- Diffusion imaging parameters like ADC and FA are crucial for characterizing ischemic tissue changes.
Purpose of the Study:
- To investigate the temporal dynamics of diffusion imaging parameters at the lesion site in brainstem infarcts.
- To establish the time course of apparent diffusion coefficient (ADC) and fractional anisotropy (FA) changes following brainstem ischemia.
Main Methods:
- Sequential magnetic resonance (MR) scans were performed on 24 patients with brainstem infarcts.
- Diffusion-weighted imaging (DWI), T(2)-weighted imaging (T(2)w), ADC maps, and FA maps were generated.
- Trend functions modeled the time course of these imaging parameters.
Main Results:
- Apparent diffusion coefficient (ADC) decreased initially, transitioning around 45 hours, followed by pseudonormalization after 14 days.
- Fractional anisotropy (FA) showed a continuous decline over 3 to 6 months.
- These temporal patterns differ from those observed in hemispheric infarcts.
Conclusions:
- The prolonged pseudonormalization of ADC in brainstem infarcts reflects the acute to subacute phase of ischemia.
- The sustained decrease in FA over months suggests chronic alterations in histological structures.
- ADC and FA dynamics provide insights into the distinct phases of brainstem ischemia.
