CASE HISTORY/CLINIC:
5-year-old patient with gait disturbance.


FINDINGS:
A homogeneous, almost liquor-isotense mass lesion with an irregular periphery can be visualized in the posterior cranial fossa. The lesion displaces the fourth ventricle ventrolaterally to the right, leading to a subtotal compression. Resulting enlargement of the lateral ventricles (left > right) - see T1-w before and after contrast administration.
The postcontrast T1-w shows a typical contrast enhancement of the cyst wall and of the peripheral knotty portion.
The T2-w and Flair images show an inhomogeneous perifocal high signal.


DIAGNOSIS:
Pilozytic astrocytoma with perifocal edema and obstructive hydrocephalus.

DIFFERENTIAL DIAGNOSIS:
Haemangioblastoma
Medulloblastoma
Metastasis
Ependymoma

web resources:

1) Medicine worldwide
2) DGN
3) ACR Learning file
4) Amersham health