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Cave of septum pellucidum

The Cave of Septum Pellucidum (CSP) is a cerebrospinal fluid (CSF)-filled midline cavity situated between the two laminae of the septum pellucidum, located anterior to the columns of the fornix and posterior to the genu of the corpus callosum. CSP is a normal variant seen in fetal life and early infancy, but can persist into adulthood in a small percentage of individuals. It is often asymptomatic and detected incidentally on imaging studies.

Synonyms

  • CSP

  • Septum pellucidum cyst

  • Cavum septi pellucidi

  • Fifth ventricle (historical, now obsolete)

Arterial Supply

  • Supplied primarily by the anterior cerebral artery (ACA), especially the pericallosal branches.

  • Additional minor contribution may come from the anterior communicating artery.

Venous Drainage

  • Drained mainly via the internal cerebral veins.

  • Some drainage also occurs through the anterior septal veins.

Function

  • CSP does not serve a direct physiological function; it is a vestigial space and considered a normal anatomical variant.

  • Its presence may be of clinical interest as a neurodevelopmental marker, especially in fetal or neonatal brain imaging.

MRI Appearance

  • T1-weighted images: CSP appears as a well-defined, non-enhancing, CSF-intensity (hypointense) cavity.

  • T2-weighted images: CSP is hyperintense (bright), reflecting its fluid content, similar to CSF.

  • FLAIR: The cavity is hypointense or null, as CSF is suppressed on FLAIR sequences, making the CSP appear dark.

CT Appearance

  • CSP appears as a well-circumscribed, low-attenuation (hypodense), CSF-density space in the midline, anterior to the fornix.

  • No associated enhancement or mass effect in uncomplicated cases.

  • Easily distinguished from pathological cysts due to lack of wall thickening or contrast enhancement.

MRI images

Cave of septum pellucidum mri 3t coronal image