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Definition/Background
Cavum septi pellucidi (CSP) and cavum vergae (CV) represent
collections of cerebrospinal fluid (CSF) between the leaves of septum
pellucidum and have been mis-named as the fifth and sixth ventricles. CSP is a
constant feature in the human fetus and usually gets obliterated toward term.
However, persistence is relatively common, and has been reported in 20% of
brain autopsies. CV is a posterior extension of CSP and is never described alone.
Characteristic
Clinical Features
CSP and CV are usually asymptomatic.
Characteristic
Radiologic Findings
Both CT and MR demonstrate nonenhancing CSF-filled midline
cavities bounded superiorly by the corpus
callosum and laterally by the leaves of the septum pellucidum and the
fornices. There is no communication with the lateral ventricles.
Primary Differential
Diagnoses
1. Cavum
Velum Interpositum (CVI)
2.
Arachnoid Cyst
3.
Epidermoid Cyst
Discussion of
Differential Diagnoses
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Cavum Velum
Interpositum (CVI): Typically triangular, nonenhancing CSF-filled midline
cavity will be seen within the cistern of velum interpositum at the level of
the bodies of the lateral ventricles. CVI does not extend anteriorly into the
region of the frontal horns of the lateral ventricles.
Arachnoid Cyst:
Based on imaging alone, it can be difficult to distinguish an arachnoid cyst
from CSP or CV. Presence of hydrocephalus should favor arachnoid cyst; also, it
should be noted that midline CSF-containing cysts should favor CSP, CV, or CVI,
or, less likely, an arachnoid cyst.
Epidermoid Cyst:
Diffusion restriction will be seen.
The patient is a 42-year-old man with change in mental status.
Axial T2WI at the level of the frontal horns demonstrates cerebrospinal fluid (CSF)between the leaves of the septum pellucidum suggestive of cavum septi pellucidi.
Axial T2WI at the level of the body of the lateral ventricle demonstrates cerebrospinal fluid (CSF) between the leaves of the septum pellucidum suggestive of cavum septi vergae.
Sagittal T1WI in a different patient demonstrates upward bowing of the fornix (arrowhead) and downward displacement of the internal cerebral vein (arrow). Diagnosis: Cavum septi pellucidi and vergae.
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Labels: Brain, Congenital Anomalies
