T1 pre-gad 1991 T1 pre-gad 1995

Diagnosis: Intraparenchymal cyst

Benign intraparenchymal cysts of the brain are rare. Fluid within the cyst may signal slightly differently compared to CSF. They are lined by neuroglial tissue and occasionally gliosis may be present within the brain parenchyma surrounding the cyst. This patient was biopsied twice with no evidence of malignancy and follow-up shows some enlargement.

A low grade cystic neoplasm may resemble this, although some enhancement might be expected. Hemangioblastomas above the tentorium are extremely rare and if cystic have an enhancing mural nodule. Cystic juvenile pilocytic astrocytomas should also have an enhancing nodule. They usually occur near the third and fourth ventricles or in the posterior fossa.

Neuroepithelial cysts include ependymal, choroid plexus and choroidal fissure cysts. In general, these cysts are found in association with the ependyma or the choroid; however, they may rarely be intraparenchymal. Cysts of the choroid plexus tend to be small and asymptomatic. Ependymal cysts typically occur in the atria of the lateral ventricles and may grow to a very large size. Neuroepithelial cysts do not enhance or calcify. Signal characteristics are similar to CSF. Hydatid disease may affect the CNS in 2% of cases. Hydatid cysts are more commonly seen in the liver and lung. The disease is caused by the canine tapeworm echinococcus granulosus in sheep and cattle grazing areas. Hydatid cysts of the brain are usually single, large, rounded lesions in the subcortical white matter which do not enhance and have no surrounding edema. Arachnoid cyst is not in the differential because they are, by definition, associated with the leptomeninges. Related Cases

Hemangioblastoma Arachnoid cyst Pilocytic astrocytoma