HEMATOMAS
Epidural hematomas
occur with trauma or skull fractures that tear meningeal arteries (especially
middle meningeal artery branches). Blood from the tear dissects the outer layer
of the dura from the skull, forming a space-occupying mass in what was normally
only a potential space.
The hematoma may compress adjacent brain tissue,
producing localized signs, and may also cause herniation of distant brain
regions across the free edge of the tentorium cerebelli (a transtentorial
herniation) or across the falx cerebri (a subfalcial herniation). Such herniation
may produce changes in consciousness, breathing, and blood pressure, and
altered motor, pupillary, and other neurological signs. It may be fatal.
Severe head trauma in an adult may tear bridging veins that lead
from the brain through the subarachnoid space and into the dural sinuses,
especially the superior sagittal sinus. The subsequent venous bleeding dissects
the arachnoid membrane from the inner layer of the dura, and the blood
accumulates as a subdural hematoma. The subdural space is normally only a
potential space. Some of the proteins and other solutes in the hematoma attract
edema, adding fluid accumulation to the hematoma and further exacerbating the
space-occupying nature of the bleed. A subdural hematoma also may be associated
with bleeding directly into the brain, an intracerebral hematoma.
