Subdural Hematoma (SDH) — CT Brain (Non-contrast) Key Features

 

Subdural Hematoma (SDH) — CT Brain (Non-contrast) Key Features

Typical Appearance






1. Shape & Location

  • Crescent-shaped (concavo-convex) extra-axial collection
  • Lies between dura and arachnoid
  • Crosses sutures, but does NOT cross midline (limited by falx/tentorium)

2. Density (depends on age)

  • Acute (0–3 days): Hyperdense (bright)
  • Subacute (3–21 days): Isodense → may be subtle (“CT occult”)
  • Chronic (>3 weeks): Hypodense (dark)
  • Mixed density: Rebleed → fluid-fluid levels / layering

3. Mass Effect

  • Sulcal effacement
  • Midline shift
  • Compression of ventricles
  • Possible subfalcine / transtentorial herniation

4. Internal Characteristics

  • Homogeneous (acute) or heterogeneous (chronic/rebleed)
  • May show septations/membranes (chronic SDH)

5. Associated Findings

  • Underlying cerebral edema
  • Cortical contusions
  • Skull fracture less common than in EDH

High-yield Differentiation (SDH vs EDH)

  • SDH: Crescentic, crosses sutures
  • EDH: Biconvex (lens-shaped), does NOT cross sutures

Rapid Mnemonic

“SDH = Sickle, Spreads, Slowly changes density”

  • Sickle (crescent)
  • Spreads across sutures
  • Slow evolution → density changes
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