Subdural hematoma
A subdural hematoma (SDH) is a type of bleeding in which a collection of blood—usually but not always associated with a traumatic brain injury—gathers between the inner layer of the dura mater and the arachnoid mater of the meninges surrounding the brain. It usually results from tears in bridging veins that cross the subdural space.
Subdural hematoma
Subdural haematoma, subdural haemorrhage
Head injury, alcoholism, reduction in cerebrospinal fluid pressure[1][2]
Senescence, long-term excessive alcohol consumption, dementia, and cerebrospinal fluid leak[3][4]
Subdural hematomas may cause an increase in the pressure inside the skull, 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, known as a subarachnoid hemorrhage (SAH), causes bleeding into the subarachnoid space between the arachnoid mater and the pia mater. SAH are often seen in trauma settings, or after rupture of intracranial aneurysms.
Pathophysiology[edit]
Acute[edit]
Acute subdural hematoma is usually caused by external trauma that creates tension in the wall of a bridging vein as it passes between the arachnoid and dural layers of the brain's lining—i.e., the subdural space. The circumferential arrangement of collagen surrounding the vein makes it susceptible to such tearing.
Intracerebral hemorrhage and ruptured cortical vessels (blood vessels on the surface of the brain) can also cause subdural hematoma. In these cases, blood usually accumulates between the two layers of the dura mater. This can cause ischemic brain damage by two mechanisms: one, pressure on the cortical blood vessels,[13] and two, vasoconstriction due to the substances released from the hematoma, which causes further ischemia by restricting blood flow to the brain.[14] When the brain is denied adequate blood flow, a biochemical cascade known as the ischemic cascade is unleashed, and may ultimately lead to brain cell death.[15]
Subdural hematomas grow continually larger as a result of the pressure they place on the brain: As intracranial pressure rises, blood is squeezed into the dural venous sinuses, raising the dural venous pressure and resulting in more bleeding from the ruptured bridging veins. They stop growing only when the pressure of the hematoma equalizes with the intracranial pressure, as the space for expansion shrinks.[13]
Treatment[edit]
Treatment of a subdural hematoma depends on its size and rate of growth. Some small subdural hematomas can be managed by careful monitoring as the blood clot is eventually resorbed naturally. Others can be treated by inserting a small catheter through a hole drilled through the skull and sucking out the hematoma.
Large or symptomatic hematomas require a craniotomy. A surgeon opens the skull and then the dura mater; removes the clot with suction or irrigation; and identifies and controls sites of bleeding.[28][29] The injured vessels must be repaired. Postoperative complications can include increased intracranial pressure, brain edema, new or recurrent bleeding, infection, and seizures. In patients with a chronic subdural hematoma but no history of seizures, it is unclear whether anticonvulsants are harmful or beneficial.[30]
Those with chronic subudural haematoma (CSDH) with few or no symptoms or have high risk of complication during surgery may be treated conservatively with medications such as atorvastatin, dexamethasone,[31] and mannitol, although supporting conservative treatment is still weak.[32] HMG-CoA reductase inhibitor such as Atorvastatin can reduce the haematoma volume and improving neurological function in eight weeks.[33] HMG-CoA reductase inhibitor may also reduce risk of recurrences in CSDH.[34] Dexamethasone, when used together with surgical drainage, may reduce the recurrence rate of subdural haematoma.[35] Even with surgical evacuation of chronic subdural haematoma, the recurrence rate is high, ranging from 7 to 20%.[32]
Prognosis[edit]
Acute subdural hematomas have one of the highest mortality rates of all head injuries, with 50 to 90 percent of cases resulting in death, depending on the underlying brain injury. About 20 to 30 percent of patients recover brain function.[36] Higher Glasgow Coma Scale score, younger age and responsive pupils are associated with better outcomes in acute subdural hematomas, while the time between the injury and the surgical evacuation, or the type of surgery, do not have a statistically significant impact on the outcomes.[37] Additionally, chronic subdural hematomas (CSDHs) have a relatively high mortality rate (up to 16.7% in patients over the age of 65); however, they have an even higher rate of recurrence (as mentioned in the previous section).[38] For the aforementioned reasons, researchers have developed predictive grading scales to identify patients at high risk of CSDH recurrence, one of which is the Puerto Rico Recurrence Scale developed by Mignucci-Jiménez et al.[38]