85 year old lady presented with acute right hemiplegia and inattention. CT brain was ‘normal’. She also had a background of normocytic anaemia with raised ESR and a cranial vasculitis was considered.
MRI revealed abnormal high signal intensity (T2 and FLAIR sequences) in the left posterior parietal lobe consistent with acute infarction in the distribution of the Left Middle Cerebral Artery (MCA). There was no haemorrhage.
T2 axial
FLAIR axial
A diffusion-weighted sequence (DW) was performed and revealed the infarction to be more extensive, involving the left temporal and parietal lobes (in the Left MCA territory).
Diffusion-weighted axial image
Magnetic resonance angiography (MRA) of the Circle of Willis was performed (NO contrast injection is required) and revealed occlusion of the left internal carotid artery (ICA) with no flow in the left MCA.
MRI will detect hyperacute (<24 hours) and acute (24-72 hours) brain infarction whereas CT will be normal for at least 6-12 hours post-infarction. DW imaging detects brain infarction after 10 minutes (and is sensitive up to 10 days post-infarction). This sequence detects Brownian motion, which is altered in infarction as a result of cell death and swelling.
In summary, diffusion-weighted MRI is the imaging of choice for hyperacute/acute stroke and is sensitive 10 minutes after infarction.
Dr Craig Dyer
media@nrdgp.org.au
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