Subdural hemorrhage is a bleed inside the head along the surface of the brain. The bleed is located between dura and arachnoid layers of the meninges or covering of the brain. The bleed usually occurs because of trauma. These can also occur spontaneously because of a bleeding disorder or because of underlying vascular abnormalities.
The clinical presentation is often of altered consciousness. In the elderly, there may be symptoms of dementia with more chronic subdural hemorrhages. It is thought that these occur because veins that cross the subdural space get torn from shearing forces.
On head CT, these bleeds look crescent shaped and can be very thin and barely noticeable to large causing shift of the brain. Usually CT is all that is needed for diagnosis and management. Mimickers include atrophy as patients get older with expansion of the subarachnoid space. Subdural empyema can look like a chronic subdural collection but the patients will have fever and be sick. Even artifacts can give an appearance of subdural hemorrhages.
When they first happen, classically they look like dense blood, sometimes intermixed with other densities. Patients who have anemia or sickle cell disease may have atypical or low density appearance. This type of bleed can coexist with bleeds in other parts of the brain.
Subdural bleeds can become difficult to see if they did not happen recently (subacute). They can blend with the brain and be difficult to diagnose in these cases. An infusion of contrast or MR is helpful in these cases. More chronic subdural hemorrhages can look dark, similar to the cerebrospinal fluid density. There can also be an intermixed appearance where new bleeding happens on top of chronic subdural hemorrhages.
Treatment depends on the condition of the patient, the degree of impairment, and how much it pushes on other structures. Smaller subdural hemorrhages may be observed with follow up CT scans. Larger acute symptomatic collections need to be evacuated within hours. More chronic collections can be evacuated via burr holes. The mortality rate in subdural hemorrhages that require surgery can be fairly high.