LENNOX-GASTAUT SYNDROME (LGS)

OVERVIEW

This syndrome is characterized by 1) multiple seizure types that are drug resistant (in particular tonic seizures in sleep), 2) cognitive and behavioral impairments (that may not be present at seizure onset) and 3) diffuse slow spike-wave and generalized paroxysmal fast activity on EEG. It is an epilepsy syndrome that arises due to high frequency synchronized activity developing in bilaterally distributed brain networks during a susceptible age period in childhood. This syndrome develops from a prior epilepsy syndrome or etiology, thus is rarely present at initial seizure onset. Structural brain abnormalities are present in the majority of cases.

NOTE Lennox-Gastaut syndrome is a syndrome with developmental and epileptic encephalopathy.

CAUTION As Lennox-Gastaut syndrome evolves from a prior epilepsy syndrome/etiology in many cases, repeat screening for this syndrome during the susceptible age period is important. Around 10-30% of cases of Lennox-Gastaut syndrome evolve from a prior epilepsy syndrome e.g. infantile epileptic spasms syndrome or early-infantile developmental and epileptic encephalopathy.

Clinical context

This syndrome develops between 18 months and 8 years of age (peak 3-5 years). Onset in the second decade is rare. There is a slight male predominance. Antecedent and developmental history, head circumference and neurological examination may be normal or may reflect the underlying etiology (e.g. structural brain abnormality). Most children have prior developmental impairment, further stagnation or regression can occur when this syndrome emerges such that ultimately >90% of patients will have moderate to severe intellectual impairment. Behaviour and sleep disorders are common. This syndrome persists into adulthood in nearly all cases. Atonic seizures are less frequent in adults.