Absent septum pellucidum

What it means

Absence of the septum pellucidum (meaning translucent wall in Latin - SP), also known as the ventricle of Sylvius. The septum pellucidum 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.

In contrast to the septum pellucidum, 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.

Rare diseases that can present with this20

The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions. A sign on this page is a conversation to have with a clinician, not a conclusion.

Part of the broader category

Also called: Absence of septum pellucidum · Absence of the septum pellucidum · Agenesis of the septum pellucidum · Missing septum pellucidum