Causes of a subdural haematoma

Subdural haematomas are usually caused by a head injury.

Head injuries that cause subdural haematomas are often severe, such as from a car crash, Falls or violent assault. Minorbumps to the head can also lead to a subdural haematoma ina fewcases.

A subdural haematoma develops if there's bleedinginto the space between the skull and the brain (the subdural space) caused by damage to the blood vessels of the brain or the brain itself.

As this blood starts to build up in the subdural space, it canplace pressure on the brain (intracranial hypertension) and can cause brain damage.

Who's most at risk?

Anyone can develop a subdural haematoma after a severe head injury.

Chronic subdural haematomas form graduallya few weeks after a minor head injury. These are more commonly seen in older people and those who take blood-thinning medication, drink excessively, or have another medical condition. This is explained below.

Increasing age

Mostchronic subdural haematomas affect people over 60, and the chances of developing one increase with age.

This is thought to be because most people's brains shrink to some degree as they get older. Thisplaces the brain's blood vessels under increased tension, like a stretchedrubber band, and means they're more vulnerable to damage from minor injuries.

Alcohol misuse

Drinking too much alcohol over a long period of time can also gradually cause the brain to shrink and make thebrain's blood vesselsmore vulnerable to damage.

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Blood-thinningmedication

Taking medication to reduce your risk of blood clots can increase your risk ofdeveloping a chronic subdural haematoma because it means your blood clots less easily and any bleeding caused by a head injury is likely to be more severe.

Both anticoagulantmedicines , such as warfarin , and antiplatelet medicines, such as aspirin , may increase your risk.

Other conditions

An increased risk of chronic subdural haematoma has also been linked with:

• epilepsy a condition that causes repeated seizures (fits)
• haemophilia a conditionthat stops your blood clotting properly
• having aventriculoperitoneal (VP) shunta thin tube implanted in the brain to drain away any excess fluid(to treat hydrocephalus )
• brain aneurysms a bulge inone of the brain'sblood vessels that can burst and cause bleeding on the brain
• cancerous (malignant) brain tumours