Commissural malformations: beyond the corpus callosum.

Corpus callosum agenesis is frequently only the tip of the iceberg in midline commissural anomalies. Agenesis or hypogenesis of the remaining commissures including the anterior and hippocampal commissures should be excluded. Magnetic resonance imaging is the most sensitive imaging modality to identify commissural anomalies. Diffusion tensor imaging can be helpful to identify hypogenetic or absent commissures even in the preterm neonate.