EEG, cognitive and psychopathological abnormalities in children irradiated in utero.

Computerised EEG, a clinical neuropsychiatric examination, and IQ tests were examined in 50 randomly selected prenatally irradiated 9-10-year-old children and compared with 50 randomly selected non-exposed control children of the same age. In the prenatally irradiated children a disorganised EEG-pattern with slow and paroxysmal activity (acute and high-voltage delta-waves, sometimes: spike-waves) in the left fronto-temporal region was disclosed. There was also a significant predominance of delta- and beta (dominant frequency: 20 Hz)-power in the frontal lobe, particularly, in the left fronto-temporal region, together with depressed spectral theta-power. The more disorganised EEG-patterns were observed in those children exposed at 8-15 weeks of prenatal development, while left-hemisphere abnormalities were more typical for those exposed later at 16-25 weeks of gestation. There was also a significant increase of borderline and low range (70-90) IQ scores and a significant decrease of high verbal (> 110) IQ scores. Disorders of psychological development, particularly specific developmental disorders of speech, language, and scholastic skills were more common and correlated with left-sided slow- and fast-wave activity. Behavioural and emotional disorders (social estrangement, exhaustion, emotional lability, tearfulness, apathy) were also more common and associated with a L > R imbalance in arousal. We hypothesise that the cerebral basis of mental disorders in the prenatally irradiated children is the malfunction of the left hemisphere limbic-reticular structures, particularly in those exposed at the most critical period of cerebrogenesis (16-25 weeks of gestation). We propose that the left hemisphere is more vulnerable to prenatal irradiation than the right.