· Four predominant imaging patterns of pilocytic astrocytoma have been described:
1. Mass with a nonenhancing cyst and an intensely enhancing mural nodule
2. Mass with an enhancing cyst wall and an intensely enhancing mural nodule
3. Necrotic mass with a central nonenhancing zone
4. Predominantly solid mass with minimal to no cystlike component
· Hence, two-thirds of all cases demonstrate the classic imaging manifestation of a cystlike mass with an enhancing mural nodule.
· Although most cyst walls do not enhance, some may enhance intensely, even as much as the mural nodule.
· Differential diagnosis : hemangioblastoma
JUVENILE PILOCYTIC ASTROCYTOMA
|
HEMANGIOBLASTOMA
|
Hypoattenuating cystic componenet with hypo to isoattenuating mural nodule with avid contrast enhancement
|
Hypoattenuating cyst and isodense nodule with avid contrast enhancement
|
Well demarcated lesion
|
Well demarcated lesion
|
Solid component: iso to hypointense relative to normal brain
|
Nodule peripherally located near pial surface and isointense to gray matter on T1
|
Cystic component follows fluid signal intensity
|
Iso or slightly hyperintense on T1 compared with CSF
|
Nodule: hyperintense with minimal surrounding T2WI signal
|
Nodule : hyperintense
|
Cyst follows fluid signal
|
High signal intensity
|
Avid enhancement of mural nodule
|
Avid enhancement of solid component
|
No reported abnormal flow voids
|
Peripheral in location due to vascular supply from pia mater with nodule located near pial surface. May see abnormal vessels/ flow voids
|
Low signal on DWI and high on ADC
|
Low signal on DWI and high on ADC
|
Rarely calcifies
|
May bleed into cyst leading to fluid levels
|
Rarely hemorrhage into the nodule or into subarachnoid space
|
If hemorrhage into nodule, appearance depends on age of hemorrhage
|
References :
1. Pilocytic Astrocytoma: Radiologic-Pathologic Correlation, November 2004 RadioGraphics, 24
2. Practical differential diagnosis for CT and MRI.
No comments:
Post a Comment
Please leave your comments