A subdural hematoma is a collection of blood over the surface of the brain. The brain is surrounded by cerebrospinal fluid and the fluid is in turn surrounded by 2 layers of membrane called the arachnoid(inner) and dura (outer). External to the dura is the skull bone. The reason the blood clot is called a subdural hematoma is because the blood is under the dura layer.

There are two types of subdural hematoma, acute and chronic. They are two vastly different conditions with different treatments and outcomes.

A chronic subdural hematoma is a collection of blood over the surface of the brain. It lies below the dura layer and it occurs after mild to moderate head trauma. This occurs especially in the elderly. There is gradual accumulation of blood which results from small veins lining the surface of the brain that are torn as a result of the injury. After some time, the blood clot gradually liquefies. However, in some individuals, the blood clot can expand over time and cause symptoms due to compression of the adjacent brain structures. This can usually develop over a period of several months.

The commonest symptom that occurs is the complaint of headache. Other symptoms include drowsiness, behavioral change, fits or weakness or numbness in one or more limbs. When such symptoms occur, one needs to be admitted to hospital for surgery.

The surgery is usually performed under general anaesthesia. The head is partially shaved and one or two skin incisions need to be made. Subsequently, one or two holes are drilled on the skull of about five cent coin size diameter. The membrane covering the brain is opened and the liquefied blood clots washed out. After surgery, one usually needs to remain in hospital for about 4 to 5 days before discharge.

An acute subdural hematoma is a rapid accumulation of blood below the dura membrane layer covering the brain. This usually occurs after a severe blow to the head such as after a hard fall or after a motor vehicle accident. The accumulation of blood occurs from damaged arteries on the surface of the brain and usually causes significant compression of the surrounding brain structures. The result is that one may become immediately unconscious or fall into a semiconscious state after the injury. There is usually associated injury to the surrounding brain tissues as well from the impact of the head injury. This may include skull fractures, extradual hematoma or intracerebral hematoma.

An emergency craniotomy will need to be performed as a life saving procedure to remove the blood clot and to prevent further brain injury.

An extra dural hematoma is an accumulation of blood on the surface of the brain outside of the dural layer. This occurs after a head injury where there is a severe blow causing a tear in arteries on the dura membrane layer. There is rapid collection of blood which causes compression of the adjacent brain. There is often associated skull fractures with such injury.

An emergency craniotomy also needs to be performed as a life saving procedure to remove the blood clot and to prevent further brain injury.

An intracerebral hematoma is a collection of blood clot within the brain substance. This occurs in the context of trauma after the head has sustained high impact injuries. When such events occur, the brain is shifted about within the skull and the forces that the brain encounters results in twisting and tearing of blood vessels within the brain substance and on the surface of the brain. Such injuries occur concomitantly with extradural hematomas, subdural hematomas or skull fractures depending on the severity of the injury.

The collection of blood clot within the substance of the brain can gradually expand and will push against the surrounding brain tissues. This can compress on vital blood vessels as well as important nerves in the surrounding region. If the clot is very large, it can also compress on vital areas of the brain stem that control our heartbeat and breathing. The brain tissue that is injured is often also associated with surrounding brain swelling which can worsen the problem.

If the blood clot is small, the patient needs to be monitored closely for progressive deterioration from an enlarging clot. If the blood clot is large and the patient is already unconscious, then surgery needs to be performed urgently for evacuation of the blood clot and to relieve pressure from the surrounding brain structures.

Patients with such injuries are often critically ill and require admission to the intensive care unit (ICU) for management. The main issue is that of diffuse swelling of the brain which can compromise blood flow to the brain resulting in further damage from stroke. The patient is usually kept sedated with medications and put on a ventilator to control the breathing. Various other medications may also be given to help reduce brain swelling as well as to control the patients blood pressure.