Presentation
Acute onset left sided weakness, ataxia, dysarthria.
Patient Data
On the plain CT, hypodensities are seen in the pons and it is not clear if they are artefacts, infarcts or small vessel ischemic change. There is raised MTT and TTP in the right hemi-pons, with low CBF consistent with ischemia. The symmetrical CBV would suggest penumbra rather than core. Note that these perfusion changes are not demonstrated by the fused image provided by the software, showing the importance of not relying on these images.
Evolution to established acute infarct in the right hemi-pons as predicted by CT perfusion. Old infarct in left hemi-pons noted.
Case Discussion
One of the traditional pitfalls of CT perfusion is limited coverage of the brain. However with improving multi-detector CT, larger coverage can be obtained (at the cost of increased radiation dose). The posterior fossa can be difficult to analyze due to streak artefacts and the small volume of brain. However, as demonstrated in this case, acute infarcts can also be picked up in the posterior fossa. In the setting of an apparently 'normal' CT perfusion, the brainstem and cerebellar hemispheres should be review areas.
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