Clinical and electrographic features of epileptic spasms persisting beyond the second year of life.

PURPOSE: Few reports detailing the electroclinical features of epileptic spasms persisting beyond infancy have been published. We sought to characterize this unique population further.
METHODS: We retrospectively reviewed the clinical and video-EEG data on 26 patients (4-17 years; mean, 93 months) with a confirmed diagnosis of epileptic spasms and who were evaluated at our tertiary referral center between 1993 and 2000.
RESULTS: In half of our cases, epileptic spasms were associated with disorders of neuronal migration, severe perinatal asphyxia, and genetic anomalies. Interictal EEGs showed generalized slowing in the majority of patients, and a slow-wave transient followed by an attenuation of the background amplitude was the most common ictal EEG pattern associated with an epileptic spasm (19 cases). Other seizure types (number of cases in parentheses) included tonic seizures with or without a preceding spasm (13), partial seizures (11), myoclonic seizures (11), generalized tonic-clonic seizures (six), atypical absence seizures (two), and atonic seizures (one). Cases with a more organized EEG background (especially with frequencies > or =7 Hz) were more likely to have better cognition. Continued disorganization of the EEG background and persistence of hypsarrhythmia were associated with poor developmental outcome.
CONCLUSIONS: Patients with epileptic spasms persisting beyond age 2 years constitute a truly refractory population, one that should be better recognized by clinicians. Interestingly, although many therapies resulted in a >50% reduction in seizures, neither neurocognitive function nor quality of life was substantially improved with intervention. The interictal EEG background is the most helpful in predicting neurologic outcome.