Neuroradiology Board Review – Brain Tumors – Case 8
Neuroradiology brain tumor board review. This lecture is geared towards the ABR core exam for residents, but it would be useful for review for the ABR certifying exam or certificate of added qualification (CAQ) exam for neuroradiology.
More description and the answer (spoiler!) are seen below the video.
In this case, there is an MRI of the brain in a patient with headache. There is a lesion along the left carotid terminus adjacent to the sella. Its most distinguishing characteristic is that it has intrinsic T1 hyperintensity, is bright on T2/FLAIR, and has relatively no enhancement. There is no associated diffusion abnormality.
One key thing that you need to know to get this case correct is what kinds of things can be intrinsically hyperintense. Blood can be hyperintense at appropriate times (because of methemoglobin). Fat is intrinsically hyperintense. Paramagnetic materials such as gadolinium and manganese are T1 hyperintense. Melanin can also be hyperintense. Because of this relatively short number of things that is intrinsically bright on T1, when you see something that is T1 hyperintense it often has a relatively short differential.
On the CT images, you can confirm that the reason that it is T1 hyperintense is because the lesion contains fat. Additionally, you can see additional unexpected areas of fat in the sylvian fissure and quadrigeminal plate cistern.
The diagnosis is: ruptured dermoid
Dermoids are part of the spectrum of masses from retained embryonal tissues, with the other possibilities including epidermoid and teratoma. The major characteristic of dermoids is they have internal fat contents and are not bright on DWI. These can rupture and cause a chemical meningitis from irritation of fat in the subarachnoid space. This can lead to a number of symptoms such as headache or seizure. Dermoids are often resected but they are indolent lesions which are non-aggressive.