Monday 2 April 2012

Gyriform enhancement

Gyral enhancement is an abnormal superficial enhancement of the brain parenchyma confined to cortical grey matter, on both Contrast enhanced CT as well as MRI studies, seen in vascular and inflammatory processes. May be seen in neoplastic lesion but very rare.
Enhancement occur in serpentine pattern, altered blood-brain barrier in the involved areas appears to be the basic mechanism behind enhancement let it be ischemia or inflammation.
Gyral enhancement is often seen in reperfused subacute stage infarcts, other common causes include posterior reversible encephalopathy, focal cerebritis and encephalitis.
In an imaging wise typical vascular territory infarct contrast enhanced study is not required, not done in many institutions. Practically speaking contrast enhanced study has no role in an obvious infarct on MRI, even on CT.
If at all it is done in cases of confusion, to distinguish between vascular and inflammatory causes of the serpentine pattern of enhancement, may need correlation with clinical history like abrupt onset of symptoms which may support an infarct. Area of involvement corresponding to particular vascular territory, an associated restricted diffusion on Dw images with an CT or MR Angiography depicting corresponding vessel occlusion can be of great help.
In infarct, the gyral enhancement results from various mechanisms depending up on time course of event. In acute stages it appears to be the blood brain barrier where as in sub acute stages it appears to be due to reperfusion or luxurious hyper perfusion.
Contrast enhancement may take 4 weeks to 4 months to fade off.

1) A typical case of right cortical PCA territory infarct with restricted diffusion on Dw images with Right PCA occlusion on MR Angio, showing abnormalgyriform enhancement in right medial occipital lobe on post contrast T1w images. 

Case 2) A known case of Tubercular meningitis under treatment. Follow up imaging, right medial occipital lobe shows focal vasogenic odema on FLAIR with an abnormal Gyriform enhancement on post contrast T1.

Patterns of Contrast Enhancement in the Brain and Meninges, James G. Smirniotopoulos, MD, Frances M. Murphy, MD, MPH, Radiographics.

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