Emergency Imaging of Brain Tumors: Tumor mimics
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- čas přidán 20. 05. 2024
- 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.
0:00 Introduction
0:50 Case 1. 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.
3:47 Case 2. 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.
6:55 Case 3. 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.
9:36 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.
Be sure to tune in for the final lecture in the emergency imaging of brain tumor series which is going to wrap things up with some complications you may see with brain tumors.
Check out this video and additional content on www.learnneuroradiology.com
Always great case to revisit.
See a lot of very textbook typical abscess in other channels, it is great to see not very textbook typical abscess. Keep on learning from your excellent lectures.
I'm third year neurology resident.
Hard core follower of your channel.
Thank you very much for the videos.
Keep it up!
Awesome! Thank you!
Great videoes... keep em coming!
Thanks! Will do!
great series thank you!
Glad you enjoy it!
Your lectures are very useful. I really love the impression part. I advise my residents. Thank you🙏
Thank you! 😃
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Your lectures are usefull for us. Many thanks teacher!
Glad you like them!
6:00 you say centrally increased restriction but at the very center of "8" form abscess you can see sub solid necrotic masses/fluid with bright ADC. On these images one could think that restriction is also peripheral with some internal masses that also appear restricting.
Could this be confused as a glial tumour signs as well? Because for a typical abscess youd expect the whole center to be restricting and not, like in this case, rim like restriction with only partial central masses restriction with fluid signal interposition?
You can see the other comment, but not every case is going to have uniform central diffusion abnormality. When they are perfectly smooth with a thin wall of enhancement and homogeneous central diffusion abnormality, they are not likely to be a tumor mimic. However, sometimes, as in this case, the central portion may have additional debris or blood products that affects the appearance of diffusion. You will see similar effects with an infected subdural hematoma after surgery.
Thank you
You're welcome
I meant case 2
there is no restriction centrally
I assume you are talking about the abscess. Yeah, its probably just due to some complex fluid and even blood products that have low T2.
So I had a CAT scan without contrast due to new headaches at the ER. It came back UNREMARKABLE that means NO TUMOR or MASS right?
Yes, that means that there is nothing seriously bad there that is large enough to be detected by a CT. No acute hemorrhage, stroke, or edema. Depending on the level of concern, your doctor might think it's necessary to get an MRI, but the most severe things have been ruled out.
Is this "classic" brain abscess? Looks unusual 🤔
Yeah ideally the centre should restrict in a typical bacterial abscess but the periphery is restricting here in case 2
I think you will find a lot of variation in how they restrict which can vary if there are septations or hemorrhage. The most classic abscesses will play by the rules and have a relatively thin enhancing wall and a uniform center which restricts diffusion. These are rarely mistaken for tumors. If they have a little bit of blood, maybe a few septations, then they can definitely be more complex.
Maybe in the future I can show some varying appearance of different abscesses.
Thanks for watching!
See the other reply, but yes, they can vary considerably. The more "atypical" they are, the harder it is to differentiate them from tumors, which is why I included one that was a little less typical here.