A subdural hematoma occurs when there is a tear in the blood vessels that lie between the brain, and the lining around the brain. The collection of blood places pressure against the brain, which causes the brain to malfunction.

Head injuries are the most common cause of subdural hematoma.

Rare causes of subdural hematoma include:

• Shaken baby syndrome:
• Violent shaking of a baby's head
• Blood thinner medication:
• Coumadin (Warfarin)
• Heparin
• Aspirin
• Arachnoid cyst rupture
• Polycystic kidney disease
• Ruptured cerebral aneurysm