A subdural hematoma (Subdural hematoma) (SDH) is a form of traumatic brain injury in which blood gathers between the dura (the outer protective covering of the brain) and the arachnoid (the middle layer of the meninges). Unlike in epidural hematomas, which are usually caused by tears in arteries, subdural bleeding usually results from tears in veins that cross the subdural space. This bleeding often separates the dura and the arachnoid layers. Subdural hemorrhages may cause an increase in intracranial pressure (ICP), which can cause compression of and damage to delicate brain tissue. Acute subdural hematoma (ASDH) has a high mortality rate and is a severe medical emergency.
Subdural hematomas are most often caused by head injury, when fast changing velocities within the skull may stretch and tear small bridging veins. Subdural hematomas due to head injury are described as traumatic. Much more common than epidural hemorrhages, subdural hemorrhages generally result from shearing injuries due to various rotational or linear forces. Subdural hemorrhage is a classic finding in shaken baby syndrome, in which similar shearing forces classically cause intra- and pre-retinal hemorrhages. Subdural hematoma is also commonly seen in the elderly and in alcoholics, who have evidence of brain atrophy. Cerebral atrophy increases the length the bridging veins have to traverse between the two meningeal layers, hence increasing the likelihood of shearing forces causing a tear. It is also more common in patients on anticoagulants, especially Aspirin and Warfarin. Patients on these medications can have a subdural hematoma with a minor injury.
Signs and symptoms
Symptoms of subdural hemorrhage have a slower onset than those of epidural hemorrhages because the lower pressure veins bleed more slowly than arteries. Thus, signs and symptoms may show up within 24 hours but can be delayed as much as 2 weeks. If the bleeds are large enough to put pressure on the brain, signs of increased ICP or damage to part of the brain will be present. Other signs and symptoms of subdural hematoma include the following:
- A history of recent head injury
- Loss of consciousness or fluctuating levels of consciousness
- Headache (either constant or fluctuating)
- Weakness or lethargy
- Nausea or vomiting
- Personality changes
- Inability to speak or slurred speech
- Ataxia, or difficulty walking
- Altered breathing patterns
- Blurred Vision
- Deviated gaze, or abnormal movement of the eyes.