In the brain, there are two layers of cranial dura mater, the bone-adhering endosteal layer , and the more conventional meningeal layer . These two separate out into the dural sinuses , where blood pools before drainage into the internal jugular veins . To complicate matters, the cavernous sinus contains many trabeculae that make thrombosis more likely. Until then head injuries can be associated with intracranial bleeding.
Pressure can build up and herniate the brain through the foramen magnum.
Classically, the patient loses consciousness after the head injury, reawakens, but several hours later slips into coma. These tend to be more chronic than the epidural hematoma, and typically present with drowsiness that may be fluctuating. It is produced by specialized ependymal cells forming choroid plexuses . Major sites for CSF are the ventricles and subarachnoid space . CSF exits the fourth ventricle into subarachnoid space via median and lateral aperatures.