Neuroradiology Board Review – Brain Tumors – Case 16

Posted on May 13, 2022May 1, 2022 by Brent Weinberg, MD

Neuroradiology Board Review – Brain Tumors – Case 16

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.

This case shows a 20 year-old with seizures. MRI shows a lesion in the medial temporal lobe along the tentorium. It is relatively well circumscribed with a cystic portion as well as an enhancing nodule. There is not much mass effect.

The diagnosis is: ganglioglioma

Gangliogliomas are low grade tumors often found in the temporal lobes of patients with seizures. They are mixed in their cell origin, containing both components of glial and neuronal cells. Along with pilocytic astroctyoma, PXA, and hemangioblastoma, they are one of the tumors in the differential for a tumor with a cyst and a nodule. They can be impossible to differentiate from DNET, but if you see enhancement it is more likely to be a ganglioglioma. Gangliogliomas are the most common neoplastic cause of epilepsy.

When you see a minimally enhancing cortical tumor, you should have a relatively short differential which includes:

First consider whether they are ill-defined or well-marginated. If ill-defined, the differential includes astrocytoma or oligodendroglioma. If well-marginated, then consider whether there is enhancement. If no enhancement, DNET is most likely. If there is a small amount of nodular enhancement, favor ganglioglioma, as in this case.

In a testing situation, if a small and minimally enhancing cortical tumor enhances a little bit, choose ganglioglioma. If you don’t seen enhancement, choose DNET. PXAs tend to be much more heterogeneous and irregular.

If you use a structured approach to these tumors, you can fall back on it if you aren’t really sure what you are looking at. With these relatively simple rules, you can be sure to get the most points on your exams AND give the most meaningful differential diagnosis.

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Neuroradiology Board Review – Brain Tumors – Case 15

Posted on May 11, 2022May 1, 2022 by Brent Weinberg, MD

Neuroradiology Board Review – Brain Tumors – Case 15

More description and the answer (spoiler!) are seen below the video.

As we start this case, we see a brain and a bone window from a CT through the posterior fossa. It is a little bit hard to see because it is a midline abnormality. The sagittal and coronal reformats are helpful in identifying where the lesion is located.

MRI is a little bit easier to see the lesion, but only a little. There is a well-demarcated lesion along the inferior aspect of the 4th ventricle. There is calfication, which you could see both on CT and GRE sequences from MRI. On post-contrast imaging, there is little, if any enhancement.

The diagnosis is: subependymoma

Subependymomas are relatively benign tumors arising from the walls of the ventricles. In contrast to most other intraventricular tumors, they often do not have much enhancement. The most common locations are in the 4th ventricle and lateral ventricles. Many times they are incidental but they can cause symptoms related to hydrocephalus.

Your differential diagnosis for intraventricular lesions includes meningioma, ependymoma (more enhancing), choroid plexus tumors (also more enhancing), and other tumors such as subependymal giant cell tumors (SEGT, often seen in patients with tuberous sclerosi).

Some tumor types have characteristic histologies that you should be familiar with for the test. Ependymomas are associated with perivascular pseudorosettes, while other tumors such as glioblastoma have their own histologic keywords (pseudopallisading necrosis, microvascular proliferation). These are pretty low yield to study but if you see them it’s good to be familiar with them.

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Neuroradiology Board Review – Brain Tumors – Case 14

Posted on May 9, 2022May 1, 2022 by Brent Weinberg, MD

Neuroradiology Board Review – Brain Tumors – Case 14

More description and the answer (spoiler!) are seen below the video.

This case shows an MRI with a mass in the left parietal region near the midline. It is pretty well circumscribed and is probably extra-axial. It is homogeneously enhancing on postcontrast, and both T2 and T1 images demonstrate significant vascular flow voids suggesting that this is a very vascular lesion.

The diagnosis is: solitary fibrous tumor

Solitary fibrous tumors of the CNS (previously known as hemangiopericytomas) are similar in histology to fibrous tumors elsewhere in the body, such as the pleura. These were originally thought to be related to meningiomas, but their genetics has proven this to be false. However, the imaging features are similar to aggressive meningiomas. They are most often extra-axial, have avid enhancement, and broad dural attachments. It is common to have flow voids showing a high degree of vascularity.

Like meningiomas, these can be highly vascular lesions with much of their blood supply coming from external carotid branches. This angiogram shows the high degree of vascularity. It can be favorable to embolize as many of these vessels as possible prior to surgical resection to minimize bleeding.

Remember that the nomenclature has changed but you still may run into the term hemangiopericytoma. It’s something that should be on your differential if you see something that looks like an aggressive meningioma.

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Neuroradiology Board Review – Brain Tumors – Case 13

Posted on May 6, 2022May 1, 2022 by Brent Weinberg, MD

Neuroradiology Board Review – Brain Tumors – Case 13

More description and the answer (spoiler!) are seen below the video.

This case presents an MRI in a patient with symptoms that sound like partial seizures. There is a pretty subtle abnormality in the medial right temporal lobe. The abnormality is a little bit hard to see, but there is some FLAIR and T2 hyperintensity in the right medial temporal lobe and amygdala. You see it best on the coronal images.

The diagnosis is: dysembryoplastic neuroepithelial tumor, or DNET

DNETs are benign and relatively slow growing tumors often in the gray matter of the medial temporal lobe. They rarely have much enhancement or hemorrhage. They are often described as “bubbly” or “soap bubble” lesions. They are often associated with seizures. Resection or ablation can be curative.

When you see a minimally enhancing cortical tumor, you should have a relatively short differential which includes:

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Neuroradiology Board Review – Brain Tumors – Case 12

Posted on May 4, 2022April 29, 2022 by Brent Weinberg, MD

Neuroradiology Board Review – Brain Tumors – Case 12

More description and the answer (spoiler!) are seen below the video.

In this case, you first see a CT with a hyperdense mass anterior to the frontal horn of the left lateral ventricle. On MRI, you see a somewhat nodular appearing mass with a rim of hypointensity on T2. Centrally, there are areas of T1 and T2 hyperintensity. On postcontrast, there is minimal if any enhancement, best seen on the 3D postcontrast images.

The diagnosis is: cavernous malformation

Cavernous malformations are benign collections of disorganized blood vessels. They have previous names, including cavernoma and cavernous hemangioma, but these have fallen out of favor because these lesions do not have a proliferative component.

On imaging, these are characterized as “popcorn” like masses with a rim of hemosiderin. They usually have areas of T1 and T2 hyperintensity centrally. Classically they are described as non-enhancing, but in my experience it is relatively common (maybe 25-30% of the time), probably because of the increase in thin-slice 3D imaging. Cavernous malformations can be isolated (about 2/3 of cases) or familial (the remaining 1/3). Familial cavernous malformation are associated with mutations in the KRIT or CCM genes. There is a relatively low annual risk of hemorrhage from these lesions (about 0.25-0.75% per year for single lesions or 1% per year per lesion for familial cavernous malformations).

Cavernous malformations can mimic hemorrhage, particularly if the history is trauma. CT sometimes has calcification, which can be a nice clue. Otherwise, the lack of symptoms and lack of edema can help you. Sometimes, you may need an MRI or a delayed CT follow-up (24-48 hours later) to show that it is stable and prove it is not a hemorrhage.

Often cavernous malformations have an associated developmental venous anomaly adjacent to them. This is a venous structure which has a tree-like branching pattern and otherwise resembles a normal vein. These can sometimes be large and confuse people into thinking it is an arteriovenous malformation, but there is no shunting.

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Neuroradiology Board Review – Brain Tumors – Case 11

Posted on May 2, 2022April 29, 2022 by Brent Weinberg, MD

Neuroradiology Board Review – Brain Tumors – Case 11

More description and the answer (spoiler!) are seen below the video.

This case shows an MRI with mass along the left cerebral convexity. The mass is pretty homogeneous on all sequences. On pre- and post-contrast T1, there is pretty avid enhancement.

Anytime you are looking at a brain mass, you should try to decide if it is arising within the brain parenchyma (intraaxial) or outside the brain parenchyma (extraaxial). The main clue that a mass is extra-axial is if it displaces the adjacent brain and you can see a cleft of CSF between the tumor and the adjacent brain. The differential diagnosis for an extra-axial mass (meningioma, lymphoma, metastatic disease) is very different from the differential diagnosis for an intra-axial mass (glioma, metastasis, demyelinating disease, infection).

The diagnosis is: meningioma

Meningiomas are the most common brain tumors overall and the most common extra-axial tumors. They are usually homogeneous and can have avid enhancement. Nice clues are if you see a cleft of CSF between the mass and the brain and if you have dural tails (small enhancing components extending along the dura adjacent to the mass). Sometimes meningiomas have a radiating spoke pattern extending out from the calvarium.

Meningiomas can be WHO grade 1, 2, or 3. All grades are treated with resection. Since Grade 2 and 3 have a higher risk of recurrence, they are often treated with radiation after resection.

The ABR loves to add anatomy questions as a follow-up. In this video, I’ve shown you the hand knob, which is an “inverted omega” shaped gyrus in the precentral gyrus. This is a good clue that you are in front of the central sulcus and is a reliable way to identify the central sulcus.

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Neuroradiology Board Review – Brain Tumors – Case 10

Posted on April 29, 2022April 25, 2022 by Brent Weinberg, MD

Neuroradiology Board Review – Brain Tumors – Case 10

More description and the answer (spoiler!) are seen below the video.

This case shows you a posterior fossa mass in a child. It his relatively homogeneously T2 hyperintense with relatively avid central enhancement on post-contrast imaging. On ADC, it is relatively dark centrally. A sagittal FLAIR image looks like it confirms that the mass is arising from the cerebellar wall of the ventricle and is displacing the ventricle anteriorly.

Anytime you have a posterior fossa mass in a child, you should be able to list a differential diagnosis, which includes:

pilocytic astroctyoma
ependymoma
medulloblastoma
atypical teratoid/rhabdoid tumor (ATRT)

These are listed in order of decreasing ADC values, because the tumors at the bottom are more cellular and have more tightly packed cells that will be bright on DWI and dark on ADC.

The diagnosis is: medulloblastoma

Medulloblastomas are aggressive tumors in children most commonly found in the posterior fossa. They can be differentiated from other tumors in these age groups by their aggressive appearance and lower ADC values. They arise from the walls of the 4th ventricle or cerebellar hemispheres. There are 4 types (WNT, SHH, group 3, and group 4), but for most radiologists this is beyond the expected knowledge. Genetic features will ultimately guide the prognosis and treatment.

The main differential diagnosis in a child with a lesion such as this is ATRT. I recommend an age based approach to making your differential diagnosis. Because ATRT patients usually are around 6 months old, if a patient is less than 2 years old, choose ATRT. If older, choose medulloblastoma. This will not always be true but is probably true > 95% of the time.

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Neuroradiology Board Review – Brain Tumors – Case 9

Posted on April 27, 2022April 25, 2022 by Brent Weinberg, MD

Neuroradiology Board Review – Brain Tumors – Case 9

More description and the answer (spoiler!) are seen below the video.

This case shows you some images from an axial head CT demonstrating a mass in the lateral ventricles near the septum pellucidum. On CT, it is somewhat heterogeneous. The MRI also shows a heterogeneous mass along the septum pellucidum which has some areas of avid enhancement and some areas of non-enhancement.

Anytime you have an intraventricular mass, you should be able to list a differential diagnosis, which includes:

Meningioma
Central neurocytoma (classic location along septum pellucidum)
Subependymal giant cell tumor (associated with tuberous sclerosis)
Ependymoma
Subependymoma (usually doesn’t enhance)
Choroid plexus tumors (both benign and malignant)

Then, the imaging features can help you favor one diagnosis over the other.

The diagnosis is: central neurocytoma

Central neurocytomas are classically masses along the anterior septum pellucidum near the foramen of Monro. They often look rather heterogenous both on T1, T2, and post-contrast T1. If you see a heterogeneous mass in the lateral ventricle in a testing scenario, it’s probably a central neurocytoma. The other lesions are possible and if you see any of the classical features of other lesions (such as a homogeneous and avidly enhancing mass that looks like a meningioma), you can consider other things.

This patient had a history of melanoma, but you can be pretty confident that this is not a melanoma metastasis because it lacks edema, has heterogeneous non-enhancing components, and has a classic appearance for central neurocytoma. They decided to manage this conservatively with imaging follow-up and it did not change with time, further corroborating the diagnosis.

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Neuroradiology Board Review – Brain Tumors – Case 8

Posted on April 25, 2022April 25, 2022 by Brent Weinberg, MD

Neuroradiology Board Review – Brain Tumors – Case 8

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.

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Neuroradiology Board Review – Brain Tumors – Case 7

Posted on April 22, 2022April 16, 2022 by Brent Weinberg, MD

Neuroradiology Board Review – Brain Tumors – Case 7

More description and the answer (spoiler!) are seen below the video.

The CT of the head shows a lesion in the right temporal lobe with masslike expansion and calcification.

0:55 The differential diagnosis for calcified lesions in the brain is pretty selective. A few tumors, including oligodendroglioma, meningioma, and pleomorphic xanthoastrocytoma (PXA) are well known for calcification. Only a few metastases calcify, and those are mostly bone tumors like osteosarcoma and chondrosarcoma. Vascular lesions including arteriovenous malformations (AVM) and cavernous malformations can also calcify, but the calcifications may look vascular.

The MRI shows a heterogeneous mass in the right temporal lobe. There are T2 hyperintense areas of non-enhancement that appear almost cystic. There is some surrounding edema, although the extent of mass effect is less than expected given the size of the mass. GRE or susceptibility imaging show areas of hypointensity likely corresponding to the calcification on CT. On post-contrast imaging, there is heterogeneous, irregular enhancement with a broad dural margin.

2:12 The diagnosis is: pleomorphic xanthoastrocytoma (PXA)

PXAs are relatively rare tumors occurring in teenagers and younger adults. They are WHO grade 2 tumors. They are most commonly supratentorial. A classic trademark is a dural tail, which is relatively uncommon for intraparenchymal tumors. In many cases they can look like a much more aggressive tumor, but it is a nice clue if it has less mass effect than expected. Think about PXA if you see a tumor that looks more aggressive than it should for size and mass effect.

Framework for evaluating cortical temporal tumors. There are a few common tumors you may encounter in the temporal lobes in seizure patients. First consider whether they are ill-defined or well-marginated. If ill-defined, the differential includes astrocytoma or oligodendroglioma. If well-marginated, then consider whether there is enhancement. If no enhancement, DNET is most likely. If there is a small amount of nodular enhancement, favor ganglioglioma. As in this case, PXAs tend to have more enhancement in a more irregular pattern.

In summary, it is helpful to have an approach to cortical tumors that can help you differentiate these lesions. Remember, it can be challenging to differentiate them without a biopsy in real life, but it is nice to be able to hone your differential diagnosis.

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