A twin population of 1631 pairs of the same sex included 64 monozygotic (MZ) and dizygotic (DZ) pairs one or both of whom had a history of febrile convulsions (FC). 59 of these pairs were investigated by EEG about 11 years after the first FC seizure. All the EEG's were done by a uniform technique and blind-evaluated by both authors. None of the twins had had any kind of seizure during the past 5 years before the examination. Out of the 59 pairs 13 were concordant and 46 discordant for FC. Analysis of the 46 discordant pairs, comparing the twins having had FC with their healthy co-twins without FC, revealed significant differences in EEG: Spontaneous paroxysmal activity was more common among the twins with a history of FC than among their healthy co-twins (p = 0.006). Moreover, amplitude asymmetry was more common among the twins with FC than among the healthy controls (p = 0.09). With respect to the frequency of dominant activity there was no definite difference between the two groups. By a concordance analysis, the aetiological role of genetic factors in the paroxysmal EEG activity was assessed: 6 out of 11 MZ pairs and 1 out of 8 DZ pairs were concordant as regards spontaneous paroxysmal activity. This corresponds to a pairwise concordance ratio of 6/11 for the MZ pairs and of 1/8 for the DZ pairs (p = 0.08), a result indicating a role of genetic factors in the occurrence of this EEG activity. The study also showed a correlation between paroxysmal EEG and clinical neurological abnormalities. There was no correlation between paroxysmal EEG and a number of birth data or between paroxysmal EEG and clinical features of the FC.
Electroencephalogram - twins - febrile convulsions - follow-up
