Related Experiment Video
Updated: Jun 17, 2026
A Versatile Murine Model of Subcortical White Matter Stroke for the Study of Axonal Degeneration and White Matter Neurobiology
Published on: March 17, 2016
Multimodal microglia imaging of fiber tracts in acute subcortical stroke
Basia A Radlinska1, Sasan A Ghinani, Paul Lyon
1Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, Canada.
Objective:
Case series with (11)C-PK11195 and positron emission tomography (PET) in stroke patients suggest that activated microglia may be detected in remote brain regions with fiber tract connections to the lesion site as an indicator of poststroke neuroinflammation. However, the specificity of these imaging findings remains to be demonstrated.
Methods:
In a prospective controlled study, we measured microglia activity using (11)C-PK11195-PET along the pyramidal tract, as defined by diffusion tensor imaging, in 21 patients with first-time acute subcortical ischemia within 2 weeks of stroke. Uptake ratios (affected vs unaffected side) were determined for a set of standardized volumes of interest along the pyramidal tracts (PT). Uptake ratios from patients in whom the PT was affected were compared with those in whom the PT was not affected. Uptake ratios were related to motor deficit and lesion size according to correlation analyses.
Results:
Increased uptake ratios were only found in patients in whom the PT was affected by stroke. In the affected hemisphere, uptake was increased at the level of pons, midbrain, and internal capsule, but not in the oval center. The extent of remote microglia activation was independent of infarct size or clinical measures of stroke severity.
Interpretation:
A specific activation of microglia was only found in patients in whom the PT was affected by the stroke and only caudal (anterograde) to the lesion; no activation was found in the retrograde direction or in those patients in whom the PT was not affected. These findings were independent of infarct size and may represent changes secondary to early Wallerian degeneration.
Insights
Positron emission tomography (PET) with (11)C-PK11195 detected specific microglia activation only caudal to the stroke lesion along the pyramidal tract. This neuroinflammation marker was independent of infarct size, suggesting early Wallerian degeneration.
Area of Science:
- Neuroscience
- Radiology
- Neurology
Background:
- Microglia activation in remote brain regions after stroke is suggested by (11)C-PK11195 positron emission tomography (PET).
- The specificity of this neuroinflammation indicator, particularly its relationship with white matter tracts, requires further investigation.
Purpose of the Study:
- To investigate the specificity of (11)C-PK11195 PET for detecting microglia activation along the pyramidal tract in acute subcortical ischemic stroke.
- To correlate microglia activation with lesion characteristics and motor deficits.
Main Methods:
- A prospective controlled study involving 21 acute ischemic stroke patients within 2 weeks of symptom onset.
- Diffusion tensor imaging defined the pyramidal tract (PT) for (11)C-PK11195 PET analysis.
- Uptake ratios of (11)C-PK11195 were measured along the PT and compared between affected and unaffected hemispheres and patients.
Main Results:
- Increased (11)C-PK11195 uptake, indicating microglia activation, was observed only in patients with PT involvement.
- Activation was detected caudal to the lesion in the pons, midbrain, and internal capsule, but not in the oval center.
- The extent of remote microglia activation did not correlate with infarct size or stroke severity.
Conclusions:
- Specific microglia activation, detected by (11)C-PK11195 PET, occurs selectively along the pyramidal tract caudal to the stroke lesion.
- This activation pattern is independent of infarct size and may reflect early Wallerian degeneration.
- Findings support the use of (11)C-PK11195 PET for assessing specific neuroinflammatory responses in stroke.
