Characteristics of electroencephalogram and preoperative location of epileptogenic foci of infantile spasms in tuberous sclerosis

Objective To investigate the characteristics of electroencephalogram (EEG) and location of epileptogenic foci of infantile spasms in tuberous sclerosis (TS). Methods Characteristics of EEG and its relation to age,and location of epileptogenic foci in 31 TS patients who underwent the surgical treatment were reviewed retrospectively. Results Typical hypsarrhythmia was shown in EEG of patients within one-year-old. Typical hypsarrhythmia,variant hypsarrhythmia and normal background were shown in patients of 1 year to 3 years old. In patients over 3 years,86% EEG presented as variant hypsarrhythmia and normal background,10% transformed into slow-spike wave and only 4% presented typical hypsarrhythmia. One epileptogenic focus was indicated in 6 patients,two epileptogenic foci (unilateral) in 7 patients,multifoci (unilateral) in 7 patients,and bilateral changes with unilateral predominance in 11 patients. All patients were followed-up from 3 months to 6 years (average 3.5 years) after surgery. Among 31 patients,20 were seizure free,7 patients had rare seizure,3 patients had a decrease in seizure frequency and 1 patient had no remarkable change. Intelligence quotient (IQ) score of all patients was improved from 52.6 to 61.8. Conclusion EEG of TS patients with infantile spasms can transform from typical hypsarrhythmia to variant hypsarrhythmia or normal background with age advancing. General discharge is shown in EEG with two foci or multifoci changes. However,the unilateral predominance of epileptiform waves can be located by analysis of background,interictal and ictal EEG. which contributes to the favorable surgical outcome after operation,in combination with clinical manifestations and imaging data.