Normal variation of the cerebral pool and subarachnoid space
Cistern，subarachnoid space normal variants
differential diagnosis
common
Transparent Compartment Cavity (CSP)
Big pillow big pool
MR artifacts, flow-dependent
The subarachnoid space is enlarged
Uncommon
Intermediate sail cavity (CVI)
The optic nerve sheath is enlarged
Rare (but important)
Blake cyst
Liliequist membrane
Differential diagnostic points
Normal variation in CSF density/signal intensity
Recognize the importance of normal variation and not mistake it for a lesion
Useful clues for common diagnoses
Transparent Compartment Cavity (CSP)
An elongated area of finger-like cerebrospinal fluid accumulation between the anterior corners of the lateral ventricles
Often communicates backwards with the vault (sixth ventricle)
The occipital pool is enlarged and freely communicates with the fourth ventricle or basal pool
The posterior fossa enlarges
Cerebellar worms are normal
The cerebral pool has cerebellar sickles and tiny veins passing through
The occipital bone may present with scallop-like depressions
Transparent compartment cavity + sixth ventricle. The occipital pool, cerebellar worm and the fourth ventricle are normal.
BSF flow artifacts in the basal pool and ventricle are common
Commonly found in FLAIR sequences
Artifacts often extend out of the skull
Occipital pool with scallop-like compression of the adjacent occipital skull plate may be associated with cerebrospinal fluid pulsation.
FLARI shows flow artifacts within the third ventricle and foramen.
Idiopathic subarachnoid space (SAS) enlargement at 1 year of age after birth
Increased head circumference (95% >)
Self-remission without treatment for 12 to 24 months is required
T2WI shows enlargement of the frontal cerebrospinal fluid space, and empty duct veins (arrows) are visible, proving that the subarachnoid space is enlarged, rather than an epidural or subdural effusion.
Useful clues for uncommon diagnoses
Intermediate sail cavity (CVI)
Located below the vault, above the third ventricle, between the ventricular bodies on both sides, the triangular CSF space
Often elevates, compresses, or causes the veins in the brain/third ventricle to move down
May present as normal variation
Occurs in idiopathic intracranial hypertension (pseudo-brain tumor), NF1
Useful clues for rare diagnoses
Blake cysts do not degenerate and compress the puncture
The fourth ventricle communicates with the distinct CSF space below it
Cerebellar worms are normal and present only as rotations
A thin arachnoid membrane separates the saddle pool, the foot pool, and the bridge front pool
Excerpt from the book: Differential Diagnosis by Imaging Experts: Cranial Brain and Spinal Cord, please purchase the relevant books for the full content.
Source: Panda Radiation
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