It usually develops during preschool years and is characterised by several seizure types and developmental delay.
Seizures are generally difficult to control due to their resistance to anti-epileptic drugs.
In many instances, LGS is a sequel to infantile spasms which are sudden spasms or bending of the body, either at the trunk or neck. These usually commence between three and eight months, and may develop into the mixed seizure pattern which characterises LGS, at two to three years. It is estimated that LGS occurs in between three to eleven per cent of childhood epilepsies with slightly more males than females affected. The average age of onset is three years. An EEG is a graphic chart which displays electrical activity generated from the brain, recorded at the skin surface of the head.