Infantile epileptic encephalopathy with late-onset spasms: report of 19 patients

Late-onset spasms (LOS) are epileptic spasms starting after the first year of life. Our aim was to assess the electroclinical features and the follow-up of the patients with this particular type of epileptic seizure.

We retrospectively included all patients with LOS confirmed by electroencephalography between 1989 and 2008. Clinical and electroencephalographic findings at diagnosis and during follow-up were collected. The Vineland scale was used to evaluate the neuropsychological outcome.

We report 19 patients with LOS of 240 patients with recorded epileptic spasms. Eighteen patients had an epileptic encephalopathy with late-onset spasms. The ictal electroencephalography (EEG) showed a focal or generalized discharge of triphasic slow-waves, slow-spikes, or slow spikes-waves with fast activities. The interictal EEG usually showed focal or generalized slow-waves or slow spikes-waves without hypsarhythmia. LOS were controlled in only six patients. Three developed typical Lennox-Gastaut syndrome and 10 had a severe epileptic encephalopathy. Neuropsychological outcome was evaluated in 15 patients with the Vineland scale. Cognitive functions were normal in only one patient, whereas severe cognitive delay was observed in 12 of 15.

Epileptic spasms may appear after the age of one. They are more frequently observed in patients with epileptic encephalopathy. In few patients this type of seizure was observed before the patients fulfill Lennox-Gastaut syndrome criteria. In one patient, we diagnosed a focal epilepsy with seizures occurring in cluster. When LOS are related to an epileptic encephalopathy, this epileptic syndrome seems to be linked to refractory epilepsy and severe cognitive outcome unrelated to the etiology.