Dandy-Walker Spectrum and Septo-optic Dysplasia

This is a case of Dandy-Walker Spectrum and Septo-optic Dysplasia. The images demonstrate absence of the vermis inferiorly with a large posterior cranial fossa cyst lying in communication with the fourth ventricle. The posterior cranial fossa is enlarged. These findings are compatible with Dandy-Walker Spectrum, with an estimated prevalence of 1:30,000. Patients are usually diagnosed within the first year after undergoing evaluation for hydrocephalus and other neurologic deficits. In addition, there is superior displacement and thinning of the corpus callosum, particularly of the body, as well as absence of the septum pellucidum and thinning of the optic nerves. These findings are compatible with at least mild septo-optic dysplasia, which is a condition characterized by absence of the septum pellucidum and optic nerve hypoplasia. There may be hypothalamic-pituitary dysfunction in up to 2/3 of cases. Septo-optic dysplasia falls into the spectrum of holoprosencephalic disorders, with an incidence of 1:50:000.