Extradural vs subdural haematoma — the CT distinction

The extradural (epidural) haematoma. The collection lies between the skull and the dura. On the non-contrast CT it is lentiform (biconvex, lens-shaped) and does NOT cross the cranial suture lines, because the dura is tethered to the skull at the sutures. It may cross the midline falx. It most often sits at the pterion and is associated with a temporal or parietal skull fracture. The source is the middle meningeal artery (torn by a fracture across its groove at the pterion) — an arterial, high-pressure bleed that expands over hours. The patient may show the lucid interval (brief LOC, recovery, then the deterioration). The surgical indication is a volume over 30 cm³ — evacuate regardless of the GCS (under 30 cm³ with under 15 mm thickness and under 5 mm shift and GCS above 8 without deficit may be observed); coma with anisocoria — evacuate as soon as possible. The prognosis is excellent if evacuated before the herniation (mortality under 10 per cent), because the underlying brain is often uninjured.

The subdural haematoma. The collection lies between the dura and the arachnoid. On the CT it is crescent-shaped (concavo-convex) and DOES cross the suture lines, but it does NOT cross the midline falx — it tracks along the convexity. The acute form is hyperdense; the subacute form is isodense (and easily missed — look for the effaced sulci and the midline shift); the chronic form is hypodense. The source is the bridging veins (the venous, slower bleed) or a cortical laceration/contusion (the acute traumatic form). The surgical indication for the acute subdural is a thickness over 10 mm OR a midline shift over 5 mm — evacuate regardless of the GCS; a comatose small subdural is evacuated if the GCS falls by 2 or more, the pupils are asymmetric or fixed and dilated, or the ICP exceeds 20 mmHg — surgical evacuation as soon as possible once indicated. The chronic subdural is evacuated by the burr-hole craniostomy. The prognosis is worse than the extradural — the acute subdural mortality is 40 to 60 per cent because the underlying brain is contused and oedematous.^[2][5]

^[1][2]Both share the management: the ABCDE, the intubation if GCS 8 or below, the normocapnia, the SBP above 110, the head up 30 degrees, the mannitol 0.5 g per kg or the hypertonic saline 3 per cent 250 mL for the herniation, and the urgent neurosurgical referral. The anticoagulation is reversed early. The lumbar puncture is NEVER performed.