Step 1 topics → Neurology and Special Senses → Intracranial Hemorrhage (SAH, SDH, EDH, IPH)

Intracranial Hemorrhage (SAH, SDH, EDH, IPH)

USMLE Step 1 trap: Confuses the arterial source of EDH with the venous source of SDH. Epidural hematomas classically result from rupture of the middle meningeal artery (arterial bleeding), producing a biconvex lens-shaped hyperdensity on CT.

Intracranial hemorrhage is one of the highest-yield neurology topics on USMLE Step 1, and it's tested in a very specific way: the exam will give you a clinical vignette and expect you to identify which compartment is bleeding, what vessel is responsible, and what happens next. The four types — SAH, SDH, EDH, and IPH — each have a distinct presentation, imaging finding, patient profile, and vascular source. The exam loves mixing these up in stem descriptions, especially swapping EDH and SDH features, so pattern recognition is critical.

The trickiest part of this topic isn't memorizing the individual facts — it's keeping the associations straight under pressure. Students routinely assign the lucid interval to the wrong hemorrhage type, assume a negative CT head rules out SAH, and misplace hypertensive hemorrhage to the cortex instead of the deep structures. These aren't random mistakes; they reflect predictable gaps in the underlying mental model. USMLE Step 1 is specifically designed to exploit these gaps through application-style questions that require you to reason through a clinical scenario rather than just recall a list.

You'll also see passage-based questions where a patient's history and imaging description are layered together — for example, a temporal bone fracture with a biconvex hyperdensity and a brief period of consciousness — and you need to integrate those details into the correct diagnosis. The key is building a clean, comparative framework: know what distinguishes each hemorrhage type from the others, not just what each one is in isolation.

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Common misconceptions

Common mistake
Wrong: Epidural hematomas arise from venous bleeding.
Right: Epidural hematomas classically result from rupture of the middle meningeal artery (arterial bleeding), producing a biconvex lens-shaped hyperdensity on CT.
EDH comes from arterial bleeding — specifically rupture of the middle meningeal artery, which runs in grooves along the inner surface of the temporal bone. Because it's arterial, the blood accumulates rapidly under high pressure and cannot cross suture lines, producing the characteristic biconvex (lens-shaped) hyperdensity on CT. SDH, by contrast, comes from torn bridging veins (venous), which is why it spreads across the brain surface in a crescent shape and evolves more slowly.
Common mistake
Wrong: The lucid interval followed by deterioration is characteristic of subdural hematoma.
Right: The lucid interval (brief recovery then rapid deterioration) is the classic presentation of epidural hematoma; chronic SDH presents with gradual cognitive decline, often in elderly or alcoholic patients.
The lucid interval belongs to EDH, not SDH. In EDH, arterial bleeding temporarily tamponades and the patient briefly regains consciousness before rapid expansion causes herniation — that's the lucid interval. Chronic SDH follows a completely different course: slow venous oozing over days to weeks leads to gradual cognitive decline, personality changes, or headache, classically in elderly patients or alcoholics who may not even remember a head injury.
Common mistake
Wrong: A normal CT head rules out subarachnoid hemorrhage.
Right: CT is highly sensitive early but sensitivity decreases over hours, so a negative CT in a patient with thunderclap headache requires lumbar puncture to look for xanthochromia.
CT is highly sensitive for SAH within the first 6-12 hours, but sensitivity drops significantly after that as blood breaks down and becomes isodense. A patient who presents with a thunderclap 'worst headache of my life' and a negative CT must still undergo lumbar puncture — you're looking for xanthochromia (yellowish discoloration from RBC breakdown products) or elevated RBCs that don't clear between tubes. Skipping the LP when CT is negative is a dangerous and testable error.
Common mistake
Wrong: Hypertensive intraparenchymal hemorrhage most commonly occurs in the cortex.
Right: Hypertensive IPH most commonly occurs in the basal ganglia (putamen), followed by thalamus, pons, and cerebellum — all sites of Charcot-Bouchard microaneurysms on lenticulostriate arteries.
Hypertensive IPH targets deep structures, not the cortex. Chronic hypertension causes Charcot-Bouchard microaneurysms specifically on the small penetrating lenticulostriate arteries, which supply the basal ganglia, thalamus, pons, and cerebellum. The putamen is the single most common site. Cortical hemorrhage, by contrast, suggests a different etiology — think amyloid angiopathy in an elderly patient, or hemorrhagic transformation of an ischemic stroke.
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What the exam tests

  1. Given a thunderclap headache presentation, you must recognize SAH, identify berry aneurysm rupture as the classic cause, and know that a negative CT requires lumbar puncture to detect xanthochromia — a negative CT alone is not enough to exclude SAH.
  2. Given an elderly or alcoholic patient with gradual cognitive decline or chronic headache, you must identify SDH, recognize bridging veins as the vessel source, and understand why CT shows a crescent-shaped hypodensity (chronic) or hyperdensity (acute) that follows the brain contour.
  3. Given a patient with head trauma and temporal bone fracture who has a brief lucid interval followed by rapid neurological deterioration, you must identify EDH, link it to middle meningeal artery rupture, and recognize the classic biconvex (lens-shaped) hyperdensity on CT.
  4. Given a hypertensive patient with sudden focal neurological deficits, you must identify intraparenchymal hemorrhage, localize it correctly to the basal ganglia or deep structures (not the cortex), and connect it to Charcot-Bouchard microaneurysm rupture on lenticulostriate arteries.

Can you avoid these mistakes?

A 45-year-old man describes the sudden onset of 'the worst headache of my life' while exercising. CT head in the ER is read as normal. What is the next step, and what finding would confirm the diagnosis?
A 78-year-old woman on warfarin presents with two weeks of progressive confusion and mild left-sided weakness. Her family reports she fell three weeks ago but seemed fine afterward. CT shows a crescent-shaped hypodensity over the right hemisphere. What vessel bled, and why does it look hypodense rather than hyperdense?
A 22-year-old man is brought in after a motorcycle accident. He was briefly unconscious, then woke up and spoke to paramedics, but is now unresponsive with a blown right pupil. CT shows a biconvex hyperdensity in the right temporal region. What is the bleeding source, and what structural landmark is involved?
A 60-year-old man with poorly controlled hypertension presents with sudden left arm and leg weakness plus dysarthria. MRI shows a hemorrhage in the right putamen. What is the underlying vascular pathology, and what other deep brain sites are at risk from the same mechanism?

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