Spina bifida meningomyelocele with hydrocephalus (SBM) is commonly associated with anomalies of the corpus callosum (CC). We describe MRI patterns of regional CC agenesis and relate CC anomalies to functional laterality based on a dichotic listening test in 90 children with SBM and 27 typically developing controls. Many children with SBM (n = 40) showed regional CC anomalies in the form of agenesis of the rostrum and/or splenium, and a smaller number (n = 20) showed hypoplasia (thinning) of all CC regions (rostrum, genu, body, and splenium). The expected right ear advantage (REA) was exhibited by normal controls and children with SBM having a normal or hypoplastic splenium. It was not shown by children with SBM who were left handed, missing a splenium, or had a higher level spinal cord lesion. Perhaps the right hemisphere of these children is more involved in processing some aspects of linguistic stimuli. (JINS, 2008, 14, 771–781.)

Previous research had demonstrated diminished interhemispheric Stroop effects in individuals with agenesis of the corpus callosum (ACC), suggesting an important role for the callosum in interhemispheric color-word and color-patch interactions. However, this outcome rested on the results of only 1 ACC participant, who had normal intelligence and a minimum of other neuropathology. In the research reported herein, the role of the corpus callosum in interhemispheric Stroop interference and facilitation was investigated in 9 individuals with complete or partial ACC and normal intelligence, and in non-ACC controls. Congruent, incongruent, or neutral stimulus pairs were presented either unilaterally (color-patch and color-word in the same visual field) or bilaterally (color-patch and color-word in different visual fields). Both unilateral and bilateral (interhemispheric) Stroop interference were found for both ACC and non-ACC groups, with no significant difference in magnitude, indicating that extracallosal pathways are sufficient for mediating this phenomenon. It is suggested that the anterior commissure is a more likely candidate for the interhemispheric transmission of the semantic information resulting in Stroop interference. (JINS, 2001, 7, 302–311.)