Subdural haematoma

A subdural haematoma (SDH) is a blood clot that forms in the space between the brain and the skull. It is also sometimes called a subdural haemorrhage.

The brain and skull

Inside the skull, the brain is covered by three protective membranes (layers) that are known collectively as the meninges. The meninges cushion and protect the brain from any kind of impact to the head, which could cause the brain to collide with the inside of the skull.

The three separate membranes that make up the meninges are:

• Dura mater: the outer layer that lies next to the skull.
• Arachnoid: the middle layer.
• Pia mater: the inner layer, closest to the brain.

The space between the two outer membranes (the dura mater and the arachnoid) is called the subdural space.

Subdural haematoma

A subdural haematoma occurs when a blood vessel in the subdural space is ruptured (torn), and blood escapes to form a blood clot (haematoma). As it gets bigger, the blood clot presses on the brain, and causes symptoms such as headaches, drowsiness and confusion.

A blood vessel can be ruptured in several ways, although most subdural haematomas occur as the direct result of a severe head injury.

Types of subdural haematoma

There are two main types of subdural haematoma:

• Acute: usually develops within 48 hours of an injury to the head.
• Chronic: usually develop more than two weeks after an injury to the head.

Glossary

Haemorrhage

To haemorrhage means to bleed or lose blood.

Blood

Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.

Blood vessels

Blood vessels are the tubes in which blood travels to and from parts of the body. The three main types of blood vessels are veins, arteries and capillaries.

Brain

The brain controls thought, memory and emotion. It sends messages to the body controlling movement, speech and senses.

Haematoma

Haematoma is a collection of blood in the tissues from a leaking blood vessel, which causes bruising.

Drowsiness

Drowsiness is when someone feels extremely tired and uncontrollably near to sleep.