Corpus callosum volumes and line bisection performance in childhood recent-onset epilepsy

In recent years, several authors have hypothesized that line bisection performance in children may be a measure of corpus callosum maturation (Hausmann, Corballis et al., 2003; Hausmann, Waldie et al., 2003). Previous studies have shown that normal prepubescent children typically bisect lines to the right of true center with their right hand and to the left with their left hand (symmetrical bias). Children entering puberty typically bisect lines to the left with both the right and left hands (pseudoneglect ) (Bowers & Heilman, 1980; Hausmann, Waldie et al., 2003). This shift in performance is called the crossover effect. Because of substantial posterior corpus callosum growth during this period and its involvement in the transfer of attention-based visuospatial processes, it has been suggested that this leftward shift task may be a manifestation of callosal maturation (Hausmann, Waldie et al., 2003). Despite reports discussing this issue, no study has directly examined this relationship in children. Additionally, no previous study has examined corpus callosum volume in children with recent-onset epilepsy. Previous studies in adults indicate mixed findings regarding callosal volumes, although abnormalities have been demonstrated in posterior callosal volumes of adults with childhood-onset temporal lobe epilepsy (Atkinson et al., 1996; Hermann, Hansen, Seidenberg, Magnotta, & O'Leary, 2003). It was expected that epilepsy subjects would have smaller corpus callosum volumes than controls, and therefore show the crossover effect at an older age.; Forty-six healthy children and fifty children with recent-onset epilepsy completed the line bisection test and underwent quantitative MRI of the corpus callosum. Subjects ranged in age from 8-18 years, with a mean age of 13 years. The corpus callosum was manually traced and divided into seven Witelson regions using an automated process. Analyses were conducted by grouping the Witelson regions into anterior, posterior, and midbody.; Subjects did not show the typical age associated pattern of symmetrical bias and pseudoneglect, but rather showed varying patterns of line bisection performance. The same performance patterns were seen equally in both epilepsy and control groups. Line bisection performance also did not differ between groups. Corpus callosum volumes also did not differ between epilepsy and control groups (Wilks' Lamba F(4, 89) = .69, p = .60). Correlations between the sections of the corpus callosum and line bisection performance did not yield any significant relationships (p's > .05).; Corpus callosum volumes do not appear to differ between healthy controls and children with recent-onset epilepsy. Despite the presumed relationship between line bisection and CC, the line bisection task does not appear to be an adequate measure of gross callosal maturation. Microstructural changes in the corpus callosum may underlie the proposed association.