CSF-like Parenchymal Lesion(s)

CSF-like Parenchymal Lesion(s)

Anne G. Osborn, MD, FACR

James D. Eastwood, MD



  • Enlarged Perivascular Spaces

  • Encephalomalacia

  • Lacunar Infarction

  • Neurocysticercosis

Less Common

  • Porencephalic Cyst

  • Multiple Sclerosis

  • Normal Variant

    • Hippocampal Sulcus Remnants

    • Connatal Cysts

Rare but Important

  • Neuroglial Cyst

  • Cryptococcosis

  • Parasites, Miscellaneous

  • Mucopolysaccharidoses

  • Germinolytic Cysts

  • Miscellaneous Congenital Malformations


Key Differential Diagnosis Issues

  • Key imaging questions

    • Does lesion follow CSF on all modalities/sequences?

    • Is there any mass associated effect?

    • Does lesion enhance?

  • Included

    • CSF-like cystic mass(es), e.g., enlarged perivascular spaces, neuroglial cysts

  • Excluded

    • Cystic neoplasms, abscess, resolving hematoma (rarely exactly like CSF)

    • Developmental cysts that do not behave exactly like CSF (e.g., epidermoid, neurenteric cysts)

Helpful Clues for Common Diagnoses

  • Enlarged Perivascular Spaces

    • Perivascular spaces (PVSs)

    • Can be seen at all ages but ↑ with age

    • Filled with interstitial fluid but follow CSF on all sequences

    • Most have no abnormality in surrounding parenchyma on PD/FLAIR

      • ≈ 25% have thin hyperintense rim

    • Bilateral > unilateral

    • Multiple > solitary

      • “Clusters” of variably sized CSF-like cysts characteristic

      • Can occur anywhere but most common locations = basal ganglia, hemispheric white matter, midbrain, dentate nuclei

      • Variant (mostly in elderly) = “état criblé” (“cribriform state”) with multiple tiny cysts in basal ganglia (BG)

  • Encephalomalacia

    • Etiology varies (trauma, infarction, etc.)

    • Can be solitary, multifocal, multicystic

    • CSF-like ± adjacent FLAIR hyperintensity

  • Lacunar Infarction

    • Solitary or multiple

    • Typically along single long unpaired penetrating arteries &/or vascular watershed zones

      • BG, thalamus, white matter (WM) common

      • Multifocal BG infarcts + surrounding gliosis = “état lacunaire” or “lacunar state”

  • Neurocysticercosis

    • Most neurocysticercosis (NCC) cysts are actually in sulci

    • Cysts in vesicular stage smooth, thin-walled, with scolex generally visible as “dot” within cyst

    • Multiple lesions in mixed stages common

      • Some enhance, some do not

      • Ca++ (multiple = “starry sky” pattern)

Helpful Clues for Less Common Diagnoses

  • Porencephalic Cyst

    • Communicates with ventricle &/or pial surface

    • Does not enhance

  • Multiple Sclerosis

    • Chronic “burned-out” lesions

    • Appear as CSF foci with hyperintense rinds on FLAIR/PD

    • Look for faint hyperintensity surrounding lesions on T1WI (“lesion within a lesion”)

    • Do sagittal FLAIR or T2WI to look for other lesions along callososeptal interface

  • Hippocampal Sulcus Remnants

    • “String of beads” cysts medial to temporal horns of lateral ventricles

    • Developmental variant, incidental

      • Remnants of vestigial primary embryonic hippocampal sulcus

    • Imaging

      • Between hippocampus, dentate gyrus

      • Follow CSF on all sequences

      • No surrounding gliosis

  • Connatal Cysts

    • Single or multiple

    • Location

      • Intra- or periventricular (may actually be cysts of anterior choroid plexus)

      • Small cyst adjacent to tip of frontal horn may be normal anatomic variant

    • Lined with ependyma

    • Present at birth

    • Usually transient

    • Occasionally seen in older patients

    • No septations, no hemosiderin

    • Generally isolated without associated abnormalities

Helpful Clues for Rare Diagnoses

  • Neuroglial Cyst

    • Nonenhancing CSF-like cyst

    • No surrounding signal abnormality

    • Does not communicate with ventricle

    • Subcortical WM, choroidal fissure common sites

  • Cryptococcosis

    • Nonenhancing gelatinous pseudocysts in perivascular spaces (PVS)

    • Multifocal > > solitary lesions

    • Most patients have HIV/AIDS

  • Parasites, Miscellaneous

    • Other than NCC, parasitic brain cysts uncommon

    • Hydatid cyst = large nonenhancing unilocular cyst

  • Mucopolysaccharidoses

    • Multiple, bilateral

    • Dilated PVSs in deep periventricular WM

  • Germinolytic Cysts

    • Periventricular/subependymal cysts

      • Cyst(s) along caudothalamic groove probably result from germinolysis

      • Glial (not ependymal) lined cysts/pseudocysts resulting from germinolysis

      • Distinguish from “connatal” cysts (intraventricular anterior choroid plexus cysts)

      • Many etiologies, including inherited metabolic disorders (e.g., Zellweger, infantile Refsum), congenital infections (CMV)

      • CSF-like; ± septations, hemosiderin; do not enhance

    • Look for associated abnormalities

      • Leukoencephalopathy

      • Delayed myelination

      • Polymicrogyria, pachygyria, heterotopias

  • Miscellaneous Congenital Malformations

    • Several have parenchymal CSF-like cysts as part of syndrome

      • Van der Knaap leukoencephalopathies (megaloencephalic leukoencephalopathy with subcortical cysts, anterior temporal lobe cavitations)

      • Congenital muscular dystrophy (cerebellar cysts common, may represent dilated perivascular spaces)

Image Gallery

Coronal T2WI MR shows cluster of variable-sized CSF-like cysts in left parietal subcortical white matter image. Lesions did not enhance. Follow-up scan 5 years later showed no change.

Axial T1WI MR in a patient with old left internal artery occlusion shows multicystic encephalomalacia. FLAIR, T2-weighted scans showed extensive hyperintensity in residual parenchyma secondary to gliosis, spongiosis.

(Left) Coronal T1WI MR in an elderly patient with bilateral chronic subdural hematomas image shows multiple lacunar infarcts image in white matter, basal ganglia. (Right) Axial T1 C+ MR shows several nonenhancing CSF-like cysts image of variable sizes in a patient with NCC. Several may be cisternal, invaginating into brain. (Courtesy E. Bravo, MD).

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Aug 7, 2016 | Posted by in NEUROLOGY | Comments Off on CSF-like Parenchymal Lesion(s)
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