Emergency Imaging of Brain Tumors: Tumor mimics

This video is the sixth video in an overview about the emergent approach to brain tumor imaging. This video talks about some of the common mimics for things that look like tumors. The most common diagnoses you need to be aware of are infection, abscess, and demyelination.

Herpes encephalitis

This case shows a CT in a patient that has hypodensity in the left medial temporal lobe. It is ill-defined and not well marginated. On CT, the differential is an acute encephalitis and tumor. Stroke is less likely given that it isn’t in a vascular distribution and doesn’t have the right clinical onset. The MRI shows really apparent swelling and edema/hyperintensity on T2 and FLAIR. Diffusion is also hyperintense. On post-contrast imaging, there is avid and solid nodular and ill-defined enhancement.

Herpes encephalitis is a dreaded intracranial infection that requires urgent recognition and treatment. It can be unilateral or bilateral, and is often asymmetric. Red flags include temporal involvement, acute clinical signs of illness, and not following a vascular distribution. These patients may have rapid progression. If no cause is found via clinical workup or lumbar puncture, these patients should get a follow-up in 6-12 weeks to ensure that it is improve and is not a tumor.

Abscess

This case has a CT which shows marked edema in the left frontal lobe with a mass in the left frontal lobe adjacent to the frontal horn. It looks like the mass is peripherally hyperdense but hypodense centrally. It is not following a vascular distribution. Your differential diagnosis includes tumors, both primary tumors and metastatic disease. An MRI and systemic work-up for malignancy are justified. The MRI shows a mass with peripheral T2 hyperintensity and small areas of susceptibility which are probably blood products. On post-contrast imaging, the periphery is avidly enhancing with blurry margins. The DWI images are key and show pretty marked central diffusion hyperintensity which is dark on ADC.

This is a case of intracranial abscess. Brain abscesses are areas of pus and infection within the brain which have central diffusion restriction. Sometimes there are thinner along the ventricular margin. In many ways they can mimic tumors, but the central DWI hyperintensity which is “light-bulb” bright is a huge clue that you should suspect abscess. Red flags that should make you suspect infection are immune compromised patient, systemic signs of infection, rapid onset, and severe symptoms.

Tumefactive demyelination

This patient has a CT which looks somewhat similar to the previous patient. There is a marked area of edema with sparing of the cortex in the left parietal lobe. There is no clear central mass that you see there, but given that it is vasogenic edema and there is mass effect you should be pretty suspicious. Your initial differential includes primary tumor and metastatic disease, but you want to see the MRI. The MRI shows a marked area of FLAIR and T2 hyperintensity. The area is markedly T1 hypointense but has heterogeneous and incomplete enhancement around the rim.

Tumefactive demyelination is associated with patients who have other demyelinating disease. In many cases, it’s going to be indistinguishable from tumor, but clues are sudden onset of symptoms and young age of the patient. Imaging features to look for are that incomplete rim of enhancement around the margin and the leading edge of abnormal diffusion.

Summary

When approaching a case that seems like a tumor, you have to remember that there are lesions that can mimic tumors. Systemic signs or clinical features can help you, but it can be particularly hard on CT alone. The next step is to get an MRI and work the patients up for their systemic features.

Thanks for tuning in. Be sure to check out the other videos on the brain tumor topic page if you want to learn more about brain tumors. Also check out the Emergency Imaging of Brain Tumors Playlist to see all the videos from this lecture.

Emergency Imaging of Brain Tumors: Non-gliomas

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.

Meningioma

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.

Metastases

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.

Lymphoma

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.

Calvarial meningioma

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:

• Metastatic disease
• Lymphoma
• Meningioma
• Myeloma

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.

Summary

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.

Thanks for tuning in. Be sure to check out the other videos on the brain tumor topic page if you want to learn more about brain tumors. Also check out the Emergency Imaging of Brain Tumors Playlist to see all the videos from this lecture.

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.

Summary

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.

Thanks for tuning in. Be sure to check out the other videos on the brain tumor topic page if you want to learn more about brain tumors. Also check out the Emergency Imaging of Brain Tumors Playlist to see all the videos from this lecture.

Emergency Imaging of Brain Tumors: Astrocytomas

This video is the third video in an overview about the emergent approach to brain tumor imaging. This video talks about different presentations of the most common primary brain tumor type, astrocytomas, ranging from grade 2 to grade 4, showing representative emergency presentations and CT examples with emphasis on how to report the CT and next steps.

Types of astrocytomas.

Astrocytomas range from grade 2 to grade 4, with the highest grade IDH wild type tumors being glioblastomas. Some lower grade gliomas behave like higher grade tumors if they have specific molecular features.

Case 1. Grade 2 Astrocytoma.

There is a low density mass in the insula and temporal lobe with moderately well-defined margins. The differential primarily includes tumor and infection with stroke and metastatic disease less likely. The MRI shows primarily a non-enhancing mass in the medial temporal lobe and insula with a lot of expansion.

Grade 2 astrocytomas tend to be younger patients and have IDH mutation. Common locations are the frontal and temporal lobe. Enhancement, hemorrhage, and cyst formation are relatively rare.

Case 2. Grade 3 Astroctyoma.

In this case, there is a more heterogenous mass in the right basal ganglia and corona radiata. Internal areas of high density may represent some areas of calcification or hemorrhage. There is definitely more mass effect. In your differential, you would think about an intermediate grade tumor or metastatic disease. The MRI confirms that there is a more heterogeneous mass with some faint/subtle areas of enhancement centrally. This makes you think of an intermediate to higher grade tumor.

Grade 3 astrocytomas, or anaplastic astrocytomas, make but about 25% of astrocytomas. They tend to be a little less defined and are more likely to have cysts, enhancement, and hemorrhage

Case 3. Grade 4 Astrocytoma

The CT in this case shows a much more heterogeneous mass spanning both frontal lobes and involving the corpus callosum. The high density material internally likely represents hemorrhage. There is a lot of mass effect on the frontal horns bilaterally. In this case, you are definitely thinking about a high grade mass or metastatic disease. Lymphoma would be less likely. The MRI confirms what you saw on the CT, with lots of internal hemorrhage, mass effect, and extension across the corpus callosum. There is a lot of heterogeneous and ill-defined enhancement.

Grade 4 astrocytomas are either glioblastomas (if they are IDH wild type) or IDH-mutated grade 4 astrocytomas. This was a case of glioblastoma. These tumors frequently have a hemorrhage, mass effect, and heterogeneous enhancement.

Summary

In this video, we’ve seen a range of astrocytomas and how they can appear on imaging, particularly on CT. Hopefully you learned a little bit about how to form a differential on CT and give an appropriate differential.

Be sure to tune in for upcoming videos which will cover oligodendrogliomas, other common tumors, and some red flags to be alert to in the ER setting.

Thanks for tuning in. Be sure to check out the other videos on the brain tumor topic page if you want to learn more about brain tumors. Also check out the Emergency Imaging of Brain Tumors Playlist to see all the videos from this lecture.

Emergency Imaging of Brain Tumors: Tumor Classification

This video is the second video in an overview about the emergent approach to brain tumor imaging.  The first video talked about the role of imaging in an emergent setting and how to approach cases. This tells you a little bit more about the common types of tumors you might encounter and how they are classified.

Common types of brain tumors. The most common brain tumors you may encounter are primary gliomas, meningioma, metastatic disease, and lymphoma. Calvarial tumors, or those centered in the skull, have a somewhat special differential.

Primary gliomas. The primary gliomas encompass all the grade 2, 3, and 4 oligodendrogliomas and astrocytomas. In 2016, the WHO started using genetic testing more to classify these tumors, and further refined these classifications in 2021. In general, tumors are first classified by whether they have isocitrate dehydrogenase (IDH) mutation. Mutated tumors tend to be lower grade astrocytomas and oligodendrogliomas. If they have 1p19q co-deletion, they are oligodendrogliomas, and otherwise astrocytomas. IDH wild type tumors are the most aggressive and include glioblastomas. Now, there are some tumors that have genetic features that make them a lot like glioblastomas.

Pearls about primary gliomas.

• Higher grade tumors will be characterized by mor mass effect, hemorrhage, and enhancement, although you aren’t always going to be able to tell.
• The term “multiforme” has fallen out of use, so you can just call them glioblastomas or GBM.
• Gliosarcomas are a special subset of tumors that have features of both gliomas and sarcomas. They are often characterized by broad dural involvement or bone involvement, but sometimes you can’t tell.
• Oligoastrocytoma is a deprecated term no longer used. If it has 1p19q codeletion and IDH mutation, it’s an oligodendroglioma.
• Gliomatosis cerebri is no longer it’s own diagnosis but simply a pattern of brain involvement

Pearls about other common tumors

• Meningiomas are the most common primary intracranial tumors. If you see an extra-axial tumor, it is likely a meningioma.
• Metastatic disease is the overall most common intracranial tumor and should be suspected in older patients and those with other malignancies
• Lymphoma can cause solid enhancing multifocal disease
• Calvarial tumors have a special differential including meningioma, lymphoma, myeloma, and metastatic disease

Thanks for tuning in. Be sure to check out the other videos on the brain tumor topic page if you want to learn more about brain tumors. Also check out the Emergency Imaging of Brain Tumors Playlist to see all the videos from this lecture.

Emergency Imaging of Brain Tumors: Introduction/Role of Imaging

Hi everyone! In this video, we’re going to talk about the emergent imaging of brain tumors, particularly as it applies to a general approach when you might see patients like this coming through the emergency department. We’ll have a special emphasis on computed tomography throughout this lecture. This is the ideal lecture for someone who practices neuroradiology and sees some patients with brain tumors, but isn’t exactly a brain tumor expert.

Role of imaging brain tumors in emergencies. There are 2 main tools for imaging brain tumors, CT and MRI. CT is the screening tool for initial identification of a potential mass and then evaluating complications such as hemorrhage, edema, mass effect, hydrocephalus, and herniation. However, MRI is the mainstay of tumor evaluation used for evaluation of tumor type, tumor worsening, and tumor details.

MRI. MRI is used to make a more specific initial diagnosis, for pre-treatment planning, and for follow-up after surgery and treatment. It will almost always have FLAIR, diffusion weighted imaging (DWI), and pre- and post-contrast T1 imaging. A few other tools are used for troubleshooting, such as perfusion and functional MRI (fMRI).

FLAIR. This is a key sequence for evaluating a mix of edema and infiltrative tumor. It is the best comparison for CT

Pre- and post-contrast T1. Areas of post-contrast enhancement show areas of breakdown of the blood brain barrier. This can happen when the tumor itself has disrupted it or when there has been tissue damage from radiation therapy. More aggressive tumors have more enhancement

Role of emergent imaging. When a patient comes to the ER, if a patient doesn’t have a known tumor, you might use it to identify a potential tumor, give a practical differential, and recommend next steps. In patients with tumors, you might use it to identify urgent complications. The role of emergent imaging is not to give an exact diagnosis or assess tumor progression.

Summary. In this video, we have covered some of the basics of imaging patients with brain tumors in emergent situations, including when CT and MRI are most appropriate.

This is the first lecture in this series about imaging brain tumors in the emergent setting. Hopefully you learned a little bit about the role of different imaging types. The next lectures are going to discuss some additional topics in detail, including how to classify these tumors, how to interpret common imaging studies, and how to avoid red flags.

Thanks for tuning in. Be sure to check out the other videos on the brain tumor topic page if you want to learn more about brain tumors.