Agenesis of the corpus callosum and colloid cyst of the third ventricle: magnetic resonance imaging of an unusual association.

Agenesis of the corpus callosum is usually associated with brain malformations or with anomalies outside the central nervous system. A colloid cyst of the third ventricle may give rise to hydrocephalus and even sudden death. The authors report the case of a 23-year-old man in whom both these uncommon conditions coexisted. The findings on computed tomography and magnetic resonance imaging are described. The colloid cyst was completely excised through a frontal craniotomy and the patient made a smooth recovery.