Cavum Septum Pellucidum

The septum pellucidum (meaning translucent wall in Latin - SP), also known as the ventricle of Sylvius, is a thin, triangular double membrane separating the frontal horns of the right and left lateral ventricles of the brain. It extends between the anterior portion of the corpus callosum, and the body of the fornix and its width varies from 1.5 to 3.0 mm  The cavum septum pellucidum (CSP) is a potential cavity between the membranous leaves of the septum pellucidum, separated by at least 1 mm, and is considered a normal anatomical variation (see Cavum Septum Pellucidum). It contains a filtrate of cerebrospinal fluid transferred from the ventricles through the septal laminae, and it does not communicate with the subarachnoid space. Sometimes, it may connect to a more posterior cavity called cavum vergae (CV), but separates from each other by an arbitrary vertical plane formed by the columns of the fornix. CSP and CV were respectively and incorrectly called the fifth and sixth ventricles in the past. Both are not parts of the ventricular system as they have a different embryological origin and lack a lining with ependymal or choroid plexus cells. Superiorly - Inferior surface of the body of the corpus callosum Antero-inferiorly - Superior surface of the genu of the corpus callosum Posteroinferiorly - Corpus and columns of the fornix Laterally - Medial wall of frontal horns of lateral ventricles Medially - Virtual space with the contralateral septum Anteriorly - Genu of the corpus callosum Superiorly - Body of the corpus callosum Posteriorly - Anterior limb and pillars of the fornix Inferiorly - Anterior commissure and the rostrum of the corpus callosum and Laterally - Leaflets of the septum pellucidum. SP is an important part of the limbic system, with prominent connections to both the medial and the basolateral limbic circuit. Disease affecting the CSP can cause symptoms either by mass effect or by disturbance of the emotional and behavioral functions of the limbic system.