Published online by Cambridge University Press: 01 August 2014
A follow-up EEG study in 28 cases with closed head injuries, using MZ co-twins as controls, is described. A new concept in EEG analysis is introduced. A combined EEG code and point scale are more effective in discriminating subtle differences between two EEG records. A high concordance was found whether the EEG showed normal or abnormal patterns. Not only the head-injured twins but also the controls showed more abnormalities than in the normal population. Without this check by co-twins the EEG abnormalities could have been taken for persisting signs of the proband injury. It was found, however, in late follow-up that proband twins showed more EEG aberrations and abnormalities than co-twins, but the probands differed already in pre-traumatic mental make-up from their genetically identical controls. Neither differences in mental make-up nor in EEG characteristics showed any statistically significant correlation with the severity of the proband injury. These observations limit the significance of EEG abnormalities in late concussional states.
This study also indicates that there are individually specific EEG patterns, which in health retain their characteristics throughout life. The EEG pattern is therefore concordant in identical twins. Thus, when a twin is influenced by a brain disease or lesion, the co-twin may serve as a biological control in both acute and follow-up studies.