Lennox-Gastaut Syndrome (LGS) is one of the Developmental Epileptic Encephalopathy syndromes characterized by a triad of multiple seizure types including tonic seizures, generalized slow spike-wave discharges and generalized paroxysmal fast activity on electroencephalogram (EEG); intellectual/developmental disability, with its typical age of onset between 18 months and 8 years; and peak age of onset between 3 years and 5 years.

Since the early 1960’s when LGS was conceptualized, there have been reports of a population of cases where the onset was relatively late, and a few articles published over the subsequent couple of decades focused specifically on this late onset subgroup of patients with LGS.1, 2, 3, 4, 5, 6

Late-Onset Lennox-Gastaut Syndrome (LOLGS) is currently considered a subset of LGS with onset after age 8 years, although in various reports, different age criteria have been used, with some reports utilizing age cut off of more than 6 years,3,5, 6, 7 and others using age cutoff of after 10 years or more.4,8,9

In this article, the clinical features of LOLGS will be reviewed based on the available English language literature, in an attempt to highlight differing features between LOLGS and those seen in the typical early form of the condition – Early-Onset Lennox-Gastaut syndrome (EOLGS).