Subdural hemorrhage

A subdural hematoma (SDH) is a type of hematoma—usually associated with traumatic brain injury—in which blood gathers between the inner layer of the dura mater and the arachnoid mater. It usually results from tears in bridging veins that cross the subdural space. A subdural hematoma (SDH) is a type of hematoma—usually associated with traumatic brain injury—in which blood gathers between the inner layer of the dura mater and the arachnoid mater. It usually results from tears in bridging veins that cross the subdural space. Subdural hematomas may cause an increase in intracranial pressure (ICP), which in turn can cause compression of and damage to delicate brain tissue. Acute subdural hematomas are often life-threatening. Chronic subdural hematomas have a better prognosis if properly managed. In contrast, epidural hematomas are usually caused by tears in arteries, resulting in a build-up of blood between the dura mater and the skull. The third type of brain hemorrhage, subarachnoid hemorrhage, causes bleeding into the subarachnoid space between the arachnoid mater and the pia mater. Symptoms of subdural hematomas have a slower onset than those of epidural hematomas because the lower-pressure veins involved bleed more slowly than arteries. Signs and symptoms of acute hematomas may appear in minutes, if not immediately, but can also be delayed as much as two weeks. Symptoms of chronic subdural hematomas are usually delayed four to seven weeks. If the bleeds are large enough to put pressure on the brain, signs of increased intracranial pressure or brain damage will be present. Other symptoms of subdural hematoma can include any combination of the following: Subdural hematomas are most often caused by head injury, in which rapidly changing velocities within the skull may stretch and tear small bridging veins. Much more common than epidural hemorrhages, subdural hemorrhages generally result from shearing injuries due to various rotational or linear forces. There are claims that they can occur in cases of shaken baby syndrome, although there is no scientific evidence for this (Lynoe et al. 2017). They are also commonly seen in the elderly and in alcoholics who have evidence of cerebral atrophy. Cerebral atrophy increases the length the bridging veins have to traverse between the two meningeal layers, thus increasing the likelihood of shearing forces causing a tear. It is also more common in patients on anticoagulants or antiplatelet drugs, such as warfarin and aspirin. Patients on these medications can have a subdural hematoma after a relatively minor traumatic event. Another cause can be a reduction in cerebrospinal fluid pressure, which can reduce pressure in the subarachnoid space, pulling the arachnoid away from the dura mater and leading to a rupture of the blood vessels. Factors increasing the risk of a subdural hematoma include very young or very old age. As the brain shrinks with age, the subdural space enlarges and the veins that traverse the space must cover a wider distance, making them more vulnerable to tears. The elderly also have more brittle veins, making chronic subdural bleeds more common. Infants, too, have larger subdural spaces and are more predisposed to subdural bleeds than are young adults. It is often claimed that subdural hematoma is a common finding in shaken baby syndrome, although there is no science to support this. In juveniles, an arachnoid cyst is a risk factor for subdural hematoma.