What is the primary mechanism underlying a subdural hematoma?

A subdural hematoma primarily results from the rupture of bridging veins, which connect the surface of the cerebral cortex to the dural sinus. These veins are particularly vulnerable to tearing due to their location and the nature of their attachment. In cases of trauma, especially when there is a rapid acceleration-deceleration movement, as seen in falls or motor vehicle accidents, the brain may move within the skull. This movement can cause shear forces that lead to the rupture of these bridging veins, resulting in bleeding between the dura mater and the arachnoid mater, where a subdural hematoma forms.

The accumulation of blood in this space can create significant pressure and result in symptoms such as headache, confusion, or loss of consciousness, particularly in older adults or individuals with atrophy of the brain, whose bridging veins are more susceptible to tearing. The gradual nature of the symptom onset in subdural hematomas is often related to the slow accumulation of blood compared to other types of hematomas. This underscores the importance of recognizing the mechanism of injury and the anatomy involved in diagnosing and managing subdural hematomas.