[Clinicoencephalographic study of periodic lateralized epileptiform discharges in infants].

The mechanism of periodic lateralized epileptiform discharges (PLEDs) still remains unclear, although it has been the subject of a number of theories. We investigated the relationship between the level consciousness and PLEDs in order to clarify both the clinical significance and the mechanism of PLEDs. We studied two neonates and two infants with acute organic lesions of the brain (cerebral infarction, meningoencephalitis, cerebral hemorrhage, acute infantile hemiplegia), of whom all showing PLEDs in EEG. In each case, we analyzed sequential EEG records and the level of consciousness, and measured the periodicity, voltage and duration of PLEDs by a computer controlled digitizer. In each case, the periodicity and voltage of the discharges were related to the level of consciousness. The appearance rate of PLEDs was relatively high at the level of consciousness from III-100 to III-200. The inverse correlation between the frequency (1/periodicity) and the voltage of PLEDs was significant in 53% of the total records of PLEDs; it was also frequently observed at the level of consciousness between III-100 and III-200. From above findings we concluded that an appropriate degree of damage to produce PLEDs is required in both the cerebral cortex and subcortical white matter corresponding to the level of consciousness from III-100 to III-200.