Ictal electroencephalography and electromyography features in symptomatic infantile epileptic encephalopathy with late-onset spasms.

AIM: Recently, epilepsy with late-onset epileptic spasms (ES) has been reported to be distinct from West syndrome and Lennox-Gastaut syndrome. We identified the characteristics of this clinical entity by analyzing clinical data, including ictal electroencephalography (EEG) and electromyography (EMG) in symptomatic patients.

METHODS: We evaluated retrospectively eight symptomatic patients with epilepsy with late-onset ES. All patients underwent video-EEG analysis for more than 24 hours and have been followed up for at least 1 year. Interictal EEG, ictal EEG, ictal EMG, coexistence seizures, response to treatment, and intellectual or daily activity level were assessed. Ictal EMG was evaluated by spectral analysis.

RESULTS: All patients exhibited neurological deterioration and had multiple seizure types; seven of them had intractable seizures. Interictal EEG showed no typical hypsarrhythmia in any case. Ictal EMG analysis revealed that the predominant seizure types presenting with the tonic component were distributed among ES, spasms followed by tonic seizures (SFT), and tonic seizures.

CONCLUSIONS: The clinical characteristics of our patients were identical to infantile epileptic encephalopathy with late-onset spasms. Our patients had ES, SFT, and tonic seizures as the core seizure types, developed ES beyond the age of 1 year, and showed neurological deterioration. These may be essential symptoms of this clinical entity.