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An extradural (or ‘epidural’) haematoma is a collection of blood that is between the skull and the dura. It is almost always caused by trauma and most typically by ‘low-impact’ trauma (e.g. a blow to the head or a fall).
Incidence: 1.00 cases per 100,000 person-years
Peak incidence: 20-30 years
Sex ratio: more common in males 3:1
The collection is often in the temporal region since the thin skull at the pterion overlies the middle meningeal artery and is therefore vulnerable to injury.
The classical presentation is of a patient who initially loses, briefly regains and then loses again consciousness after a low-impact head injury. The brief regain in consciousness is termed the ‘lucid interval’ and is lost eventually due to the expanding haematoma and brain herniation. As the haematoma expands the uncus of the temporal lobe herniates around the tentorium cerebelli and the patient develops a fixed and dilated pupil due to the compression of the parasympathetic fibers of the third cranial nerve.
On imaging, an extradural haematoma appears as a biconvex (or lentiform), hyperdense collection around the surface of the brain. They are limited by the suture lines of the skull.
In patients who have no neurological deficit, cautious clinical and radiological observation is appropriate. The definitive treatment is craniotomy and evacuation of the haematoma.