The septum pellucidum (SP) is a thin membrane located at the midline of the brain between the two cerebral hemispheres, or halves of the brain. It is connected to the corpus callosum — a collection of nerve fibers that connect the cerebral hemispheres. This rare abnormality accompanies various malformations of the brain that affect intelligence, behavior, and the neurodevelopmental process, and seizures may occur. Children who are born without this membrane and also have other abnormalities–pituitary deficiencies and abnormal development of the optic disk–have a disorder known as septo-optic dysplasia.
When the absence of the septum pellucidum is part of septo-optic dysplasia, the prognosis varies according to the presence and severity of associated symptoms. By itself, absence of the septum pellucidum is not life-threatening.
Absence of the SP alone is not a disorder but is instead a characteristic noted in children with septo-optic dysplasia or other developmental anomalies.