Traumatic Brain Injury and Intracranial Haematomas
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Direct answer
Traumatic brain injury can cause three main intracranial lesions: extradural, subdural and contusion haematomas, which differ in source, shape and urgency. An extradural haematoma usually arises from a torn middle meningeal artery, forms a lens-shaped collection that stops at sutures, and classically causes a lucid interval. Subdural haematomas from torn bridging veins cross sutures and look crescent-shaped on CT, while contusions are cortical bruises.
What you must remember
- GCS grading: eye opening scores 1 to 4, verbal 1 to 5 and motor 1 to 6, giving a total from 3 to 15, with 13 to 15 mild, 9 to 12 moderate and 8 or below severe.
- Airway: a GCS of 8 or below usually warrants intubation for airway protection.
- Extradural shape: biconvex or lens-shaped on CT, bounded by sutures, and often linked to a temporal bone fracture.
- Lucid interval: the classic history for extradural haematoma, with brief unconsciousness, recovery and then rapid decline.
- Subdural pattern: acute collections are hyperdense and crescent-shaped, while chronic ones are hypodense and common in older patients and those on anticoagulants.
- Surgical thresholds: extradural collections above about 30 mL, or with midline shift above about 5 mm, are usually evacuated, with thresholds varying between texts.
- Contusion and axonal injury: contusions can expand over hours, while diffuse axonal injury has no surgical lesion to evacuate.
Reading the CT pattern against the history
A 24-year-old man falls from a motorcycle and is briefly unconscious at the scene. He wakes, becomes drowsy over two hours, and now has a dilated right pupil and left hemiparesis. The combination of ipsilateral pupil and contralateral weakness points to a lesion that compresses the brain on one side.
| Feature | Extradural | Subdural | Contusion |
|---|---|---|---|
| Usual source | Middle meningeal artery | Bridging veins | Cortical vessels and brain tissue |
| CT shape | Biconvex, lens-shaped | Crescent-shaped | Patchy and irregular |
| Crosses sutures | No | Yes | Not limited by sutures |
| Lucid interval | Classic | Usually absent | Uncommon |
The shape on CT is the most useful discriminator, because extradural bleeding is bounded by suture lines where dura is firmly attached.
Clinical course matters as well, since an extradural bleed can be rapidly fatal even when the first examination looks reassuring. A large extradural collection needs prompt evacuation, whereas a small, stable collection may be watched with serial scans and neurological observation. Scans and observation therefore guide the decision rather than the first picture alone.
Where the exam tries to catch you
Most errors come from misreading the CT shape or waiting for a lucid interval that may never appear.
- Trap: waiting for a lucid interval before imaging Correct: CT is urgent for any patient whose consciousness is falling, and the absence of a lucid interval does not exclude a haematoma.
- Trap: calling an extradural haematoma crescent-shaped Correct: extradural collections are lens-shaped and stop at sutures, whereas crescent-shaped collections crossing sutures are subdural.
- Trap: deciding surgery by GCS alone Correct: volume, midline shift and pupil signs guide evacuation, so a low GCS is not the only criterion.
Frequently asked questions
Why does an extradural haematoma cause a lucid interval?
An extradural haematoma causes a lucid interval because arterial bleeding from the middle meningeal artery builds up over time and compresses the brain gradually. The patient may lose consciousness briefly, regain it and then deteriorate as the collection expands. Not every extradural haematoma follows this course, so its absence does not exclude one.
How does a subdural haematoma differ on CT from an extradural haematoma?
A subdural haematoma is crescent-shaped on CT and can cross cranial sutures, because it lies in the subdural space after torn bridging veins. An extradural haematoma is lens-shaped and stops at sutures, because the dura is firmly attached there. This shape is the key discriminating feature on imaging.
Which GCS score indicates severe head injury and need for intubation?
A GCS of 8 or less denotes severe head injury, and airway protection with intubation is usually indicated. The score ranges from 3 to 15, combining eye opening, verbal and motor responses. Scores of 13 to 15 are mild, and scores of 9 to 12 are moderate.
What size of extradural haematoma usually needs surgical evacuation?
An extradural haematoma with a volume above about 30 mL, or with midline shift above about 5 mm, is usually evacuated surgically. Thresholds vary between texts and centres, so clinical state matters alongside imaging. Small collections in a neurologically intact patient may be observed with serial scans.
What does Cushing's reflex signify in head injury?
Cushing's reflex, with hypertension, bradycardia and irregular breathing, signals raised intracranial pressure and impending brainstem compromise. It is a late and urgent sign that needs immediate neurosurgical review and treatment of the raised pressure.