Hematomas

hematoma that results from damage to the middle meningeal artery (blow to pterion region of the skull) 

blood collects in between the periosteal layer of dura matter and skull

infection that spreads to THIS region from infection in any of the following valveless veins:

ophthalmic vein
facial vein
pterygoid venous plexus 
basilar plexus
internal vertebral plexus

hematoma that results from tearing of the superior cerebral veins at their point of entrance to superior sagittal sinus 

usually occurs due to a blow to the front or back of the head causing excessive AP displacement of brain

hematoma results from leakage of blood (usually arterial) into the subarachnoid space. Results from a leakage or rupture of  a congenital aneurysm on the circle of Willis