Subependymoma - 4th ventricle

Q: Where is the abnormality located? show answer

A: 4th ventricle.

Q: Is this lesion T2 hyperintense? show answer

A: That is a trick question, as it does not state to why it is being compared to. The term hyperintense is a relative term and as such unless it is completely obvious to what the mass is being compared to it is safest to include the comparison tissue. In other words, yes this mass is slightly hyperintense compared to the adjacent cerebellum, but quite hypointense compared to the adjacent CSF.

Q: What is the most likely diagnosis? show answer

A: Subependymoma. Imaging features are characteristic although age group is atypical (subependymomas are usually found in older patients).

Q: What other differentials are worth considering? show answer

A: Ependymoma is the second most likely diagnosis. Other less likely entities (especially given the lack of enhancement) are a choroid plexus tumour or a haemangioblastoma; neither of which should really be considered unless pushed.

Q: What WHO grade are subependymomas considered? show answer

A: They are WHO grade I lesions.

Q: Where are they most commonly located? show answer

A: They are most commonly seen in the fourth ventricle, but can arise anywhere where there is ependyma.

Q: What is the treatment approach for these lesions? show answer

A: If appearances are characteristic then followup is a viable option, especially in the asymptomatic elderly. Resection should be considered if the patient is symptomatic (hydrocephalus, or mass effect), the mass has atypical appearances or demonstrates growth. Local resection is curative.