Cistern, Subarachnoid Space Normal Variant

Cistern, Subarachnoid Space Normal Variant
Karen L. Salzman, MD
DIFFERENTIAL DIAGNOSIS
Common
  • Cavum Septi Pellucidi (CSP)
  • Mega Cisterna Magna
  • Flow-Related MR Artifacts
  • Enlarged Subarachnoid Spaces
Less Common
  • Cavum Velum Interpositum (CVI)
  • Enlarged Optic Nerve Sheath
Rare but Important
  • Blake Pouch Cyst
  • Liliequist Membrane
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
  • Normal variants have CSF density/intensity
  • Important to recognize normal variants and not mistake for more ominous pathology
Helpful Clues for Common Diagnoses
  • Cavum Septi Pellucidi (CSP)
    • Elongated finger-shaped CSF collection between frontal horns of lateral ventricles
    • Posterior continuation between fornices often associated (cavum vergae)
  • Mega Cisterna Magna
    • Enlarged cisterna magna communicates freely with 4th ventricle and basal cisterns
    • Large posterior fossa
    • Normal vermis
    • Cistern crossed by falx cerebelli, tiny veins
    • Occipital bone may appear scalloped
  • Flow-Related MR Artifacts
    • CSF flow artifact is common in basal cisterns, ventricles
    • Commonly seen on FLAIR MR
    • Artifact often extends outside skull
  • Enlarged Subarachnoid Spaces
    • Idiopathic enlargement of subarachnoid spaces (SAS) during 1st year of life
    • Increased head circumference (> 95%)
    • Resolves without therapy by 12-24 months
Helpful Clues for Less Common Diagnoses
  • Cavum Velum Interpositum (CVI)
    • Triangular-shaped CSF space between bodies of lateral ventricles, below fornices, above 3rd ventricle
    • Often elevates, splays fornices and causes inferior displacement of internal cerebral veins and 3rd ventricle
  • Enlarged Optic Nerve Sheath
    • May occur as normal variant
    • Occurs in idiopathic intracranial hypertension (pseudotumor cerebri), NF1
Helpful Clues for Rare Diagnoses
Tags:
Aug 10, 2016 | Posted by in PEDIATRICS | Comments Off on Cistern, Subarachnoid Space Normal Variant

Full access? Get Clinical Tree
Get Clinical Tree app for offline access