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Several blood vessels supply the lining of the brain, and this includes the three meningeal arteries on each side of the skull. The middle meningeal artery is particularly important as it runs through the skull near the temple at a weak point called the pterion. This makes it particularly prone to damage following a serious head injury. A torn meningeal artery will bleed into the potential space between the skull and the outer lining of the brain1. The pooling blood (haematoma) creates and enlarges a gap between the skull and the dura, putting pressure on the brain and forcing it to shift towards the opposite side of the skull.
Extradural haematomas are just one type of bleed within the skull. Subdural haematomas occur, often in the elderly, following a bump to the head, but develop slowly and do no present as emergencies. Subarachnoid haemorrhages also occur, whereby a blood vessel more closely related to the brain bursts due to an aneurysm. These produce a severe sudden onset 'thunderclap' headache and do present as emergencies; however, they are often treated from the inside via the blood vessels, and are covered in the entry on aneurysms.
Symptoms and Signs
The individual unfortunate enough to suffer an extradural haematoma will initially recover from the head injury, but may then become drowsy or vomit. The pupil on the injured side will become dilated ('blown') as the third cranial nerve on that side is compressed by the shifting brain. A low heart rate, fixed dilated pupils on both sides, reduced consciousness and abnormal movements will follow. If the bleeding continues it will eventually push the brain down against the base of the skull and into the spinal column – this is known as 'coning' and is fatal.
Diagnosis and Treatment
The diagnosis can be suspected based upon the above, and is confirmed with a CT scan of the head. This shows the collection of blood clearly pooling between the skull and the brain. Drugs and careful intensive care management can be used to improve blood supply to the brain and reduce swelling. However, definitive treatment must be surgical, namely the drilling of a burr hole in the skull to allow the haematoma to be evacuated. If this is done quickly enough, most patients can make a full recovery, though this is dependent on them being fit for surgery.
An extradural haematoma forms following trauma to one of the blood vessels running through the skull. Though it is potentially life-threatening, in many cases emergency surgery will completely restore the patient.
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