Lucid Interval

LUCID INTERVAL
A lucid interval is a temporary improvement in a patient's condition after a traumatic brain injury, after which the condition deteriorates.
SIGNIFICANCE
It is significant that during this period (lucid interval), the person can :
  • (i) Make a valid will, (ii) Can give valid evidence, and (iii) Is legally responsible for act done (civil/criminal).
MECHANISM
  • The lucid interval occurs after the patient is knocked out by the initial concussive force of the trauma, then lapses into unconsciousness again after recovery when bleeding causes the hematoma to expand past the extent for which the body can compensate.
  • Because a patient may have a lucid interval, any significant head trauma is regarded as a medical emergency and receives emergency medical treatment even if the patient is conscious.
  • Delayed cerebral edema, a very serious and potentially fatal condition in which the brain swells dramatically, may follow a lucid interval that occurs after a minor head trauma 
CONTITIONS WHEN LUCID INTERVAL IS SEEN
  • Lucid interval is seen in
  1. Extradural Hemorrhage/Hematoma
  2. An estimated 20 to 50% of patients with epidural hematoma experience such a lucid interval.
  • Intradural Hemorrhage/Hematoma
  • Insanity
  • Heat stroke. 
  • Postictal phase after a seizure in epileptic patients
Exam Question
  • Lucid Interval is seen in Extradural Hemorrhage/Hematoma,Intradural Hemorrhage/Hematoma and Insanity.

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