Cavum septum pellucidum and cavum vergae
Embryologically the cavum vergae and cavum septum pellucidum are a single cavity called the cavum corpus callosum. It lies in the midline of the brain under the corpus callosum. It is present in 100% of fetuses at 6 months gestation but in only 30% at term. It is seen in approximately 0.4% of individuals at all ages. This cavity contains cerebrospinal fluid that does not usually communicate. Loosely associated with schizophrenia, post-traumatic stress disorder and chronic brain trauma.