A subdural hematoma occurs when there is bleeding into the space between the outer two of the three membranes covering the brain. This produces a pocket of clotted blood (a hematoma) that presses on the brain.
The bleeding may be slow (chronic) or rapid (acute).
Chronic bleeding may result from an apparently trivial head injury, and it may take up to several months before symptoms develop. These typically include headaches, gradual confusion, weakness, and a decline in consciousness. Rapid bleeding usually follows a severe head injury and typically causes rapid loss of consciousness.
A person who develops any of these symptoms should seek urgent medical attention.
Treatment is usually with surgery. Many people make a good recovery, although some residual symptoms may persist. A large, severe hematoma may be fatal.