A 25-year-old man is brought to the emergency department after assault. CT brain shows a biconvex hyperdense (white) lenticular collection with a midline shift of 8 mm. GCS is 14. The lucid interval preceding deterioration in extradural hematoma (EDH) is most accurately attributed to:

• A Temporary reduction in ICP from cerebrospinal fluid redistribution
• B Vasospasm causing transient ischemia followed by reperfusion
• C Delayed activation of inflammatory mediators
• D Initial concussive loss of consciousness followed by a period of clinical compensation as brain accommodates the expanding hematoma before herniation ✓

Explanation

The lucid interval in EDH (present in ~30% of cases) represents initial concussive LOC followed by a period of neurological recovery, during which the expanding extradural hematoma is accommodated by intracranial compliance mechanisms (CSF displacement, venous compression). As the hematoma volume exceeds compensatory capacity (typically 150-200 mL total intracranial buffer), ICP rises precipitously, causing rapid neurological deterioration and uncal herniation. EDH is typically arterial (middle meningeal artery, 80% temporal location) and expands rapidly. Urgent surgical evacuation (craniotomy within 4 hours of deterioration) is required. A biconvex lenticular shape is characteristic — unlike subdural hematoma which is concavoconvex.

Reference: Bailey & Love's Short Practice of Surgery, 27th ed.

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Written and medically reviewed by the StethoPrep medical team.