This video is the fifth video in an overview about the emergent approach to brain tumor imaging. This video talks about some of the other brain masses that you might encounter that are not primary brain parenchymal tumors. This includes other masses such as meningiomas, metastatic disease, lymphoma, and calvarial tumors.
This case shows a CT in a patient that has a hyperdense mass along the sphenoid wing. It is quite hard to see on CT, but the edema and mass effect on the frontal lobe is a great clue. It looks like an extra-axial mass that probably has some hyperostosis of the adjacent sphenoid wing. The MRI confirms the finding that there is a mass there and that it is extra-axial. Its appearance is avidly enhancing and pretty homogeneous.
Meningiomas are the most common intracranial primary tumors and most common extra-axial masses. They are relatively homogeneous, avidly enhancing, and can have FDG uptake on a PET, so make sure you don’t confuse them with a metastasis on PET. Also remember that even low-grade meningiomas can have edema. It is very challenging to tell if there is brain invasion on imaging and that is often a pathologic distinction.
This patient has a very striking CT with a number of high density lesions scattered throughout the posterior fossa and supratentorial brain. These are sufficiently dense that they look like hemorrhage. A few of the larger lesions have edema around them. The differential leads of with metastatic disease, although trauma, infection, and amyloid would be some of your alternate considerations. The MRI confirms the presence of these masses. Some of them have intrinsic T1 hyperintensity from the blood products that are present, but others are enhancing. There are numerous lesions.
Metastases are common brain masses and can be seen in a variety of tumors such as lung, breast, melanoma, renal, and melanoma. About half of brain metastases are solitary, so don’t let that fool you. Hemorrhage is common, and the presence of multiple lesions should point you down a search for primary tumors.
On this case, we start with a CT that shows a hyperdense mass in the midline cerebellum with surrounding edema, possibly a hyperdense mass in the left caudate, and hydrocephalus. For this case, you want to think about multiple masses, such as lymphoma, infection, and metastatic disease. The MRI really highlights how involved the posterior fossa and periventricular white matter are. Masses with intermediate to low T2 make you think about lymphoma or granulomatous disease. The solid enhancement and periventricular involvement are very suspicious for lymphoma, as is the DWI hyperintensity.
Primary CNS lymphoma is a relatively rare disease associated with HIV and other immunosuppression. It commonly presents with periventricular and basal ganglia involvement. It is often solid but can be ring enhancing in an immune compromised patient.
This CT shows a calvarial lesion along the left frontal and parietal convexity. There is a lot of edema in the underlying brain and it has an intracranial and extracranial component, but it is primarily centered in the bone.
When you see a case centered in the bone, your differential should include:
You may not be able to differentiate these on CT or even MRI. The MRI in this case shows an expanded bone, relatively T2 hypointense appearance, and striations radiating out from the bone. This is a classic appearance for a meningioma. B-cell lymphoma and myeloma can have a very similar case.
When you approach brain tumors, think about whether they are in the parenchyma or extra-axial and also consider whether they are multiple, which can help guide you towards another diagnosis. For most tumors you’re going to need an MRI and potentially a biopsy to make the final diagnosis.
Be sure to tune in for upcoming videos which will cover tumor mimics and some red flags to be alert to in the ER setting.