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Definition & Terminology
- Cystic CSF cavity of septum pellucidum (SP)
- Occurs ± cavum vergae (CV)
Diagnostic checklist
- Elongated finger-shaped CSF collection between lateral ventricles
- Cavum septi pellucidi (CSP): Between frontal horns of lateral ventricles
- Cavum vergae: Posterior extension between fornices
- Size : varies from slit like to several mm, occasionally > 1 cm
- Septum Pellucidium : invariably cystic in fetus
- Width of fetal cavum Septum Pellucidium increases between 19-27 weeks
- Plateaus at 28 weeks
- Gradually closes in rostral direction between 28 weeks and term
- CSP present in 100% of premature, 85% of term infants
- CSP seen in up to 15-20% of adults
TOP DIFFERENTIAL DIAGNOSES
- Asymmetric lateral ventricles
- Cavum velum interpositum
- Ependymal cyst
- Absent SP
PATHOLOGY
• CSP forms if fetal SP fails to obliterate
• CSP is not "5th ventricle"
• CV is not "6th ventricle"
CLINICAL ISSUES
• Usually asymptomatic, incidental
• Headache (relationship to cyst unclear)
• CSP frequent among athletes with history of repeated traumatic brain injury, such as boxers
DIAGNOSTIC CHECKLIST
• CV almost never occurs without CSP
Imaging Gallery
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Coronal graphic with axial insert shows classic cavum septi pellucidi (CSP) with cavum vergae (CV) . Note the finger-like CSF collection between the lateral ventricles.
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Axial T2WI MR shows cavum septi pellucidi as a CSF collection between the leaves of the septum pellucidum (blue opened arrows). Although seen incidentally, some studies have report that CSP is frequent among athletes with a history of repeated traumatic brain injury (TBI), such as boxers, and American professional football players.
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Coronal T1WI MR shows a classic large CSP between the frontal horns (blue arrows) bowing the leaves of the septum pellucidum laterally (curves blue arrows).
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Axial FLAIR MR shows a large CSP with CV as a large CSF collection between the leaves of the septum pellucidum (blue arrows) continuing directly posteriorly with the CSF collection, splaying the fornices laterally (curved blue arrows). |