EDH
Typically lentiform (lens-shaped, biconvex shaped) and do not cross sutures.
Almost always arterial explaining the progressive growth of the haematoma.
Classicallydue to injury of the middle meningeal artery.
SDH
Typicallycrescentic (crescent moon-shaped) and more extensive than EDH, with the internal margin paralleling the cortical margin of the adjacent brain.
As these occur in the subdural space, they cross sutures.
Almost always venous due to tearing of subdural cortical bridging veins