THE LUCID interval following head trauma and unconsciousness is described classically in epidural hematomas. The historic emphasis placed on the lucid interval in cases of extradural hematoma has made this one of the best-remembered signs of the syndrome. Initial unconsciousness is thought to be due to the concussive effect of the blow to the head. The lucid period is the time required for the clot to grow to proportions great enough to produce compression of the brain.
The percentage of patients with epidural hematoma who have lucid intervals varies in different reports from 10%1 to 72%.2 Although the occurrence of a lucid period in patients with acute subdural hematoma has been mentioned in previous literature, it has not been stressed in any of the recent series published.2-3 My patient had an acute subdural hematoma in which head trauma and initial unconsciousness were followed by a lucid interval, then