Gravid seizures-MRI

19 year gravid patient with seizures and systolic hypertension shows asymmetrical vasogenic edema in the perisylvian regions with extension to frontoparietal locations with reduced caliber of right cavernous and  supracavernous ICA and MCA as compared to the left, suggesting possible perusion abnormality on account of loss of autoregulation (Akin to PRES).

Teaching points by Dr MGK Murthy, Dr Sumer Sethi, Mr Narasimhulu, Mr Venkat:

-      Brain perfusion is maintained by autoregulatory system of the small arteries and arterioroles that has myogenic and neurogenic components. Endothelial damage may attenuate / abolish myogenic response.

-      Perivascular sympathetic nerves which protect the brain if the myogenic response is blunted, travel in the adventitious layer of the vessels and hence protected from endothelial damage.

-      Vertebrobasilar and posterior cerebral arteries are sparsely innervated by sympathetic nerves, making PRES, primarily posterior event.

-      Elevated cerebral perfusion pressure and reduced cerebral vascular resistance is present in eclampsia due to elevated systolic BP. The fluid in the subcortical and the cortical tissues in brain edema produces seizures.

-      Disrupted blood brain barrier in the regions produces contrast enhancement on MR (contrast is preferably avoided in pregnancy in view of uncertain teratogenecity).