Corpus Callosum

Anatomy

• The largest commissure, made of about 200 million axons.
• Parts: rostrum, genu (frontal — forceps minor), body (motor/somatosensory), isthmus, splenium (occipitotemporal — forceps major).
• Roof of the lateral ventricles; the cingulate gyrus lies above, the fornix and septum pellucidum below.
• Blood supply: pericallosal artery (ACA); splenium PCA.

Functions

• Interhemispheric transfer of information and coordination.
• Bimanual motor coordination.
• Giving right-hemisphere information access to the language system (naming).
• Interhemispheric inhibition and support of lateralization; processing speed.

Connections and chemistry

• Homotopic cortical areas (both hemispheres)
• Forceps minor (frontal), forceps major (occipital)
• Cingulum bundle (above)

Development

Developmental course through childhood and adolescence.

• Myelinates rapidly after birth; maturation continues into adolescence and young adulthood.
• The decrease in mirror movements is linked to callosal maturation.
• Cross-sectional area increases in childhood and adolescence.

Clinical

• Agenesis or hypoplasia of the corpus callosum: about 1.8 per 10,000 births in a California population registry (3.4 million live births); about 4 times more common in preterm infants (California population study, 2008). Isolated or syndromic; associated with social-cognitive difficulties and ASD. Developmental outcomes in isolated cases vary widely, and prenatal counseling should reflect this. A
• ASD: reduced CC volume and FA (meta-analyses).
• Early-life neglect: reduced CC area (Teicher et al., 2004).
• CC anomalies are common in fetal alcohol spectrum disorder and prematurity.

Treatment

This region from the perspective of medication, psychotherapy and neuromodulation. Letter badges are evidence levels.

• In agenesis: developmental follow-up and early intervention (speech, motor, social skills); assessment for epilepsy and associated anomalies, genetic testing. B
• After early neglect (Teicher et al., 2004), early placement in a safe caregiving environment and attachment-focused interventions are the strongest supports for development. B

Assessment

Neuropsychological tasks and measures that probe this region's function.

• Dichotic listening, cross-localization of fingers
• Bimanual coordination tasks
• Fractional anisotropy (FA) measures with DTI

Lesions and damage

Clinical findings expected with damage or dysfunction.

• Disconnection syndrome (split brain): tactile anomia and apraxia of the left hand.
• Alien hand syndrome; alexia without agraphia with a left occipital + splenium lesion.

In the model

How this structure is defined in the 3D model, and the data source.

A slab of the template’s white matter probability within ±6 mm of the midline. May include part of the fornix.

References

Full citations for the card; links go to the paper (DOI) or a PubMed search.

1. Agenesis of the corpus callosum in California 1983–2003: a population-based study. Am J Med Genet A 2008. Search PubMed