Chiari III Malformation on Prenatal and Postnatal Imaging Complicated by Syndrome of Inappropriate Secretion of Anti-diuretic Hormone (SIADH) and Serratia marcescens Meningitis.

Among various types of Chiari malformations (CMs), CM III is the most infrequently encountered. In this article, we present a case of CM III with occipital cephalocele appreciated on both prenatal imaging and postnatal follow-up MRI. This case illustrates not only the evolution of this malformation from the in-utero images of fetal MRI to the newborn MRI but also highlights the complications that may accompany this diagnosis such as hydrocephalus and infection. The patient also developed syndrome of inappropriate secretion of anti-diuretic hormone (SIADH). The most current thoughts on the pathophysiology of this entity are also reviewed along with an approach to the differential diagnosis and treatment.