Predictive value of EEG findings at control of epileptic spasms for seizure relapse in patients with West syndrome

PURPOSE To evaluate the prognostic importance of electroencephalography (EEG) findings at cessation of epileptic spasms for seizure outcome. METHODS We reviewed 71 children with West syndrome (cryptogenic 14) who had obtained control of epileptic spasms with initial treatment (adrenocorticotropic hormone (ACTH) 37, high-dose vitamin B6 2, and antiepileptic drugs 32). According to the EEG findings at control of epileptic spasms, the subjects were divided into three groups: normal group (no epileptic activity, n=12), abnormal group (residual epileptic activity without hypsarrhythmia, n=53), and hypsarrhythmic group (persisting hypsarrhythmia, n=6). RESULTS Overall, 47 (66%) of the 71 patients (cryptogenic 4) had experienced relapses of seizures (epileptic spasms 23 and focal seizure 24) after initial control of epileptic spasms. Within symptomatic cases, seizure relapse rate varied widely from 0% (Down syndrome) to 100% (tuberous sclerosis), depending on underlying causes. Seizure relapse depended on the EEG findings at control of epileptic spasms. The normal group had a significantly lower seizure relapse rate (17%) in comparison with the abnormal group (75%), the hypsarrhythmic group (83%), and the epileptiform (abnormal plus hypsarrhythmic, 76%) group. No significant difference in seizure relapse rate was observed between non-hypsarrhythmic (normal plus abnormal, 65%) and hypsarrhythmic groups. At the last follow-up, normal group children also showed a favorable seizure prognosis (seizure control 100%). CONCLUSIONS A favorable seizure prognosis is associated with the disappearance of epileptic activity, but not the resolution of hypsarrhythmic pattern on EEG at control of epileptic spasms. We suggest that effective treatment for West syndrome should produce both cessation of epileptic spasms and disappearance of epileptic activity on EEG.