Intracranial Hematomas: Epidural, Subdural, and Subarachnoid

Blood Collections Within the Meningeal Layers

The meninges (dura, arachnoid, pia) create potential spaces where blood can accumulate after trauma or vascular rupture:

1. Epidural Hematoma (EDH)

• Location: Between skull and dura mater (dura stripped from inner table).
• Source: Usually arterial (middle meningeal artery tear from temporal bone fracture).
• Imaging: Biconvex (lentiform) hyperdense collection; does not cross suture lines.
• Classic presentation: Lucid interval → rapid neurological decline.

2. Subdural Hematoma (SDH)

• Location: Between dura and arachnoid (tearing of bridging veins).
• Source: Venous (bridging veins) or arterial (cortical vessels).
• Imaging: Crescentic hyperdense collection; crosses suture lines, limited by dural reflections (falx, tentorium).
• Types: Acute (<3 days), subacute (3–21 days), chronic (>21 days—often in elderly/atrophic brains).

3. Subarachnoid Hemorrhage (SAH)

• Location: Subarachnoid space (between arachnoid and pia), filled with CSF.
• Source: Ruptured aneurysm (80%), trauma, AVM, perimesencephalic, unknown.
• Imaging: Hyperdense blood in basal cisterns, Sylvian fissures, interhemispheric fissure; "star" pattern.
• Presentation: Thunderclap headache, meningismus, photophobia, possible coma.

All are neurosurgical emergencies requiring urgent imaging (non-contrast head CT) and often intervention.