Sub arachnoid haemorrhage

Sub arachnoid haemorrhage (SAH) presents as an acute neurological dysfunction.
Non contrast CT is the imaging modality of choice.
CT is positive in 95% in the first 24 hours and pick up rate drops to 50% after a week.
The first 2 pictures are of an acute SAH in the first 24 hours and third picture is after 2 weeks.
SAH appears as high attenuating substance in the normally dark coloured CSF filled sub arachnoid space.
Blood in the anterior interhemispheric fissure suggests ACA aneurysm, in the sylvian fissure suggests MCA aneurysm and post interhemispheric fissure suggest posterior circulation aneurysm.
In children AV malformations are a more common cuse of SAH than aneurysms unlike adults.