[A case of interhemispheric glio-ependymal cyst in a newborn infant].

An interhemispheric glio-ependymal cyst in a male neonate is reported. Neuroradiologically, the cyst, which had a septum like component within it, was located in the right frontoparietal interhemispheric and displaced the third and lateral ventricles. It had no communication with the ventricular system. As for anomalies associated with it, the total callosal agenesis and congenital hydrocephalus were revealed in CT scan. Angiogram suggested that polymicroglia accompanied with the cyst. It was confirmed that the cyst was divided into two parts by the septum during surgery. Microscopic examination showed that the cyst wall was composed of ependyma, connective tissue and glial cells. Choroid plexus component was also found in the septum. On the basis of the fact above, it was diagnosed interhemispheric glio-ependymal cyst. We believe that this interhemispheric cyst described above is a true cyst and differs morphologically and embryologically from the midline cyst which is produced with callosal agenesis and due to increased intraventricular pressure. In fact, the latter is an encystic third ventricle but not a true cyst. Both of them are, however, usually called interhemispheric cyst in the literature. We conclude that this case is appeared to be a true cyst because we can differentiate it from third ventricle by neuroradiological findings. We discussed nature of different interhemispheric cysts with callosal agenesis and suggested that recognition of the morphological relationship between the interhemispheric cysts and third ventricle was utmost important to make a correct diagnosis.