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Don't mix these up for NEET PG: extradural vs subdural haematoma

SurgeryPublished 28 October 2026 · Recallab

A high-yield NEET PG pair. One layer separates them. Extradural blood sits outside the dura; subdural blood sits beneath it. Where the dura is fixed decides the shape, and the shape decides the answer.

Recallab Ace Shot for NEET PG: extradural vs subdural haematoma, 1 minute 53 seconds.

Extradural vs subdural haematoma: side by side

	Extradural haematoma	Subdural haematoma
Location	Outside the dura	Beneath the dura
Bleeding vessel	Usually the middle meningeal artery	Bridging veins
Shape	Biconvex lens	Crescent
Sutures	Stops at sutures	Crosses sutures
Midline	Can cross	Limited by the falx

This pair is one of the Don't mix these up questions in Recallab's NEET PG High yield screener.

The dura is firmly attached to the skull at the sutures. Blood outside the dura is held between those attachments, so it pushes inward as a lens. Blood beneath the dura is not held by them, so it spreads along the brain as a crescent.

The one trap

The trap is confusing sutures with the midline. An extradural haematoma stops at sutures but can cross the midline. A subdural haematoma crosses sutures but cannot cross the midline, because the falx, a fold of dura, stops it there.

A lucid interval is classic for extradural haematoma, but it occurs in only a minority of cases. Its absence does not rule an extradural out.

Try it: say it once before the questions: lens stops at sutures; crescent stops at the falx.

Shape and vessel

Recallab example 1 · lucid, then deteriorating

Two intracranial collections are drawn in the figure, with the skull sutures marked. A young man struck on the temple was briefly unconscious, then lucid, and is now deteriorating. Which shape fits, and what is bleeding?

Look first: find where each collection meets the coronal suture, then match the vessel to the space.

Two axial sections of the head with the coronal suture marked on each. In the first, the collection is lens-shaped, thickest in the middle and tapering at both ends, and it stops abruptly at the suture. In the second, the collection is a thin crescent following the whole curve of the inner skull and continuing past the suture without interruption. — Recallab question 54775. Two collections, Shape 1 and Shape 2, with the coronal suture marked.

AShape 1, a bridging vein
BShape 1, middle meningeal artery
CShape 2, middle meningeal artery
DShape 2, middle cerebral artery

Show the answer and explanation

Answer: B. Shape 1, middle meningeal artery

B. Shape 1, middle meningeal artery. The dura is firmly attached to the inner skull at the suture lines. Blood collecting outside it is held between those attachments, so it pushes inward as a lens that stops at the suture. That is an extradural haematoma, and the vessel is the middle meningeal artery, which runs in a groove under the thin pterion. The blow causes a brief concussion, and the clot needs time to strip the dura from the bone and enlarge, which is why the patient is lucid before deteriorating.

Why the other options lose: Shape 1 with a bridging vein (A) has the right shape and the wrong vessel; bridging veins bleed into the subdural space. Shape 2 with the middle meningeal artery (C) pairs the subdural shape with the artery of the extradural space. Shape 2 with the middle cerebral artery (D) is wrong because that artery runs in the subarachnoid space; its bleeding goes into the subarachnoid space or the brain, not into either of these spaces.

Recallab question 54775 · Surgery › Cardiothoracic & Neurosurgery · reference: Bailey & Love's Short Practice of Surgery

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Sutures and the midline

Recallab example 2 · a lens that crosses the midline

A head scan after a fall shows a dense biconvex collection that does not cross the coronal suture but does cross the midline. Which haematoma is this?

Look first: use the two boundaries: which layer is fixed at the sutures, and which one forms the falx?

AExtradural haematoma
BSubdural haematoma
CIntracerebral haemorrhage
DSubarachnoid haemorrhage

Show the answer and explanation

Answer: A. Extradural haematoma

Two axial head scans drawn side by side, the first with a dense biconvex lens-shaped collection against the inner table that stops abruptly at the coronal suture and extends across the midline, and the second with a thin crescentic collection following the whole convexity across several sutures but stopping at the falx, those two boundaries shaded as the key finding, with a coronal diagram beneath showing the dura attached to the skull at the sutures and continuous with the falx at the midline. — Recallab question 51664. The lens stops at the sutures; the crescent stops at the falx. From the question's explanation.

A. Extradural haematoma. It usually follows a temporal fracture that tears the middle meningeal artery. Arterial pressure strips the dura from the bone, giving a biconvex shape, and the dura's attachment at the sutures stops it there. The falx limits a subdural collection at the midline, but an extradural collection lies outside the dura and can cross it.

Why the other options lose: Subdural haematoma (B) is crescentic, crosses sutures and is limited by the falx, the reverse of both features. Intracerebral haemorrhage (C) lies within the brain rather than against the skull. Subarachnoid haemorrhage (D) fills the sulci and basal cisterns rather than forming a lens.

Recallab question 51664 · Radiology › Neuroimaging & Head/Neck · reference: Bailey & Love's Short Practice of Surgery

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The slow one

Recallab example 3 · three weeks of confusion on warfarin

A man of 76 on warfarin has been increasingly confused and unsteady for three weeks, with a headache that varies through the day. He recalls no injury. CT shows a crescent-shaped hypodense collection over the left convexity that extends across the coronal suture. What is it?

Look first: read the shape and the suture first, then let the three weeks tell you how old the blood is.

AAcute subarachnoid haemorrhage
BChronic subdural haematoma
CMiddle cerebral artery infarct
DExtradural haematoma

Show the answer and explanation

Answer: B. Chronic subdural haematoma

Two axial CT-style head diagrams. On the left a subdural collection drawn as a thin crescent following the curve of the skull and continuing across a marked coronal suture, labelled bridging veins and weeks. On the right an extradural collection drawn as a biconvex lens that stops abruptly at the same suture line, labelled middle meningeal artery and hours. — Recallab question 50647. Two shapes, two spaces, two speeds, from the question's explanation.

B. Chronic subdural haematoma, from torn bridging veins. Brain atrophy in old age stretches those veins, so trivial force tears them, often too trivial to remember. Venous bleeding is slow, so symptoms take weeks to appear. The subdural space is not limited by the sutures, so the collection spreads as a crescent across them, and old blood has become hypodense, matching the three-week history. Anticoagulation, alcohol and previous falls are the usual risk factors.

Why the other options lose: Acute subarachnoid haemorrhage (A) gives hyperdense blood in the cisterns and sulci with a thunderclap onset, not a convexity crescent. A middle cerebral artery infarct (C) follows an arterial territory, with a focal deficit rather than fluctuating confusion. Extradural haematoma (D) is biconvex and stops at sutures; it is arterial and evolves over hours, not weeks.

Recallab question 50647 · Medicine › Neurology · reference: Harrison's Principles of Internal Medicine

Practise more Don’t mix these up stacks →

Practise more Don’t mix these up stacks, where each pair of look-alikes is taught side by side. For more lesions placed by their anatomy, see neurology localisation.

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Drawn from questions #54775, #51664, #50647 in the Recallab bank, each with its own verified answer and current-edition reference. Last reviewed 28 October 2026.