Symptoms appearing in less than 48 hours are due to an acute subdural hematoma. This type of bleeding is often fatal, and results from tearing of the venous sinus.
Your skull is like a Box. You can only "fit" so much into it. When you introduce blood due to an injury (trauma), the blood has no where to go so this causes pressure on the brain and eventually you...
The pressure of the accumulated blood on the brain can cause a variety of symptoms including problems with speech, vision, or even a loss of consciousness.