What causes a subdural hematoma?

A subdural hematoma is primarily caused by a tear in the bridging veins that run between the brain's surface and the dural sinuses, which are responsible for draining blood from the brain. These bridging veins can become stretched or torn as a result of acceleration-deceleration forces often seen in traumatic brain injuries, such as falls or motor vehicle accidents. When these veins rupture, blood leaks into the subdural space, leading to the accumulation of blood.

This accumulation can create pressure on the brain, and the symptoms can develop gradually over time, which is why subdural hematomas are often classified as "chronic" or "acute" depending on the timing of onset after the initial injury. Understanding this mechanism is crucial, as it distinguishes subdural hematomas from other types of intracranial hemorrhages, such as epidural hematomas, which are typically associated with the rupture of arteries.