Emergency Imaging of Brain Tumors: Oligodendrogliomas & Others
This video is the fourth video in an overview about the emergent approach to brain tumor imaging. This video talks about different presentations of oligodendrogliomas, ranging from grade 2 to grade 3, showing representative emergency presentations and CT examples with emphasis on how to report the CT and next steps. The video also shows some of the more common lower grade circumscribed gliomas like DNET, ganglioglioma, PXA, and pilocytic astrocytoma.
Types of oligodendrogliomas.
Oligodendrogliomas range from grade 2 to grade 3 and are characterized by IDH mutation and 1p19q codeletion. Theoretically, they do not transform into grade 4 tumors.
Case 1. Grade 2 Oligodendroglioma.
We start with a scout image from a CT. If you look closely, you can see calcification which is confirmed on the axial CT images. There is a a pretty ill-defined hypodense mass in the right posterior frontal and inferior parietal lobe. There is extremely dense calcification centrally. Your initial differential should include calcified tumors (such as oligodendroglioma, calcifying metastasis, or vascular malformation). The MRI confirms what was seen on CT, an expansile mass with central calcification. There is very little if any enhancement.
Grade 2 oligodendrogliomas tend to be middle age patients and are characterized by IDH mutation a. Common locations are the frontal and temporal lobe. Calcification and cystic changes are pretty common, but grade 2 tumors rarely enhance.
Case 2. Grade 3 Oligodendroglioma.
In this case, we go straight to MRI. There is a really heterogeneous mass in the left frontal lobe with cyst, hematocrit/fluid levels, and probably some calcification and blood products. Compared to the grade 2 tumor, there is definitely more mass effect. There is lots of heterogeneous enhancement. In your differential, you would think about an high grade tumor, including a glioblastoma.
Grade 3 oligodendrogliomas, or anaplastic oligodendrogliomas, look a lot like high grade tumors, and you will almost never make the diagnosis on imaging as you should suggest high grade tumors like glioblastoma as well. Like GBMs, they have, cysts, enhancement, and hemorrhage.
Other low grade tumors
There are a number of other low grade gliomas that are well circumscribed and are usually low grade (grade 1 or 2). This includes pilocytic astrocytomas, dysembroplastic neuroepithelial tumors (DNET), gangliogliomas, and pleomorphic xanthoastroctyomas (PXA).
Tumors with an enhancing nodule have a short differential, including pilocytic astrocytoma, PXA, and ganglioglioma.
If you see a small lesion with a cystic appearance, if there is no enhancement, favor DNET and if there is some enhancement favor ganglioglioma.
In this video, we’ve seen a couple of oligodendrogliomas and how they can appear on imaging, and covered some of the more common lower grade tumors.
Be sure to tune in for upcoming videos which will cover other common tumors, and some red flags to be alert to in the ER setting.