Researchers at Chung Shan Medical University, Taichung, and other centers in Taiwan analyzed 969 EEGs from 463 children with epilepsy to determine outcome differences over 3 years between those with fixed epileptic foci and those with migrated foci. Seventy-nine met inclusion criteria: 24 (30%) had fixed and 55 (70%) migrated foci. In 16 (29%) of the migrated foci cases, migration was from posterior to anterior, in 29 (53%) it was anterior to posterior, in 3 (5%) it was lateral, and in 7 (13%) unclassified. More patients with fixed than with migrated foci required multiple AEDs (P=0.004), and had abnormal image findings (P=0.014), mental retardation (P=0.035), and worse seizure control (P=0.047). Seizure frequency and number of prescribed drugs were greater in the fixed group than in the migrated foci group. Migrated foci correlate with better outcomes in both symptomatic and cryptogenic cases. A comparison of cases of BECTs and Panayiotopoulos syndrome found more fixed foci among BECTs (38% vs 0%, P=0.03). Migrating EEG foci in a child with epilepsy may be associated with a better outcome than fixed foci for seizure control, less abnormal imaging, and less mental retardation. [1]

COMMENT. Hughes JR, U Illinois, reported EEG epileptiform abnormalities at different ages. (Epilepsia 1967;8:93-106). Hughes JR also studied changes during a 15- to 40-year period in EEG paroxysms on 1645 EEG tracings [2]. Frontal and then temporal foci were most common. Patterns changed in 6 to 8 years, and EEG changes accurately predicted the type of later clinical attacks. Most manifested a temporal spike. Bilateral foci, as opposed to unilateral temporal foci, increased with age 1% per year. Right-sided foci were slower than left-sided foci to manifest bilaterality. Lateral migration was the most common intrahemispheric change; anterior migration was not statistically more common than posterior migration. Gibbs EL and colleagues also reported the migration of epileptic foci in childhood [3]. The current study from Taiwan demonstrates that children with epilepsy and age-related migrating foci have a better prognosis than those with EEG fixed foci.