Final answer:
A subdural hematoma is a condition where blood collects between the arachnoid membrane and pia mater, often after head trauma. It can cause significant pressure on the brain and is a medical emergency requiring prompt treatment.
Step-by-step explanation:
A subdural hematoma is head trauma that results in blood accumulating below the arachnoid membrane and above the pia mater. Most often, this condition is supratentorial, meaning it affects the area that contains the cerebrum. The protective coverings of the brain and spinal cord, known as the meninges, consist of the dura mater, arachnoid mater, and pia mater. If a person suffers a blow to the head, especially in the pterion area, there could be a fracture that affects the major arterial branches beneath, leading to bleeding and the formation of a hematoma. With the accumulation of blood, pressure is exerted on the brain, which can lead to severe symptoms and even death if not treated promptly.