Neuroradiology Board Review – Brain Tumors – Case 6
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 images from an MRI of the posterior fossa. There is a mass in the right cerebellar hemisphere that has a predominantly cystic component and an enhancing nodule along the margin. There is some mass effect with effacement of the fourth ventricle.
The differential diagnosis for a posterior fossa cyst with a nodule has two main entities: pilocytic astrocytoma and hemangioblastoma. Pilocytic astrocytomas are the most common in children and young adults while hemangioblastomas are more common in adults. If you see flow voids on T2, that is also a nice clue that you are looking at a hemangioblastoma.
The diagnosis is: hemangioblastoma
Hemangioblastomas are cystic and solid masses that are commonly seen in the posterior fossa and spine. While they are often associated with von Hippel Lindau syndrome, the vast majority are sporadic (75-80%). They are usually cystic lesions with a solid nodule and minimal wall enhancement. Surgery can be curative, particularly if the entire enhancing nodule is resected, but it is not sufficient to drain the cystic component.
von Hippel Lindau is a syndrome of multiple lesions, with the most common in the kidneys (RCC, renal cysts, and angiomyolipomas). They are also associated with pancreatic cysts, adrenal pheochromocytomas, and other lesions. Think about this any time you see a CNS lesion with a corresponding abnormality elsewhere in the body.
Neuroradiology Board Review – Brain Tumors – Case 5
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 images from an MRI through the sella, including both coronal and sagittal images. There is expansion of the sella with a T1 isointense, T2 hyperintense mass replacing the sella and extending beyond the margins of the sella, including the cavernous sinuses bilaterally. The sella itself is also expanded. On postcontrast imaging, you see a pretty avidly enhancing sellar and suprasellar mass with no real risidual pituitary seen.
The diagnosis is: pituitary adenoma
Pituitary adenomas are extremely common brain masses and are very common incidental masses. They arise in the sella but can extend into the cavernous sinuses and suprasellar region. About half of these masses are non-secreting, while the most common secreting tumor is a prolactinoma. On imaging, they often enhance but typically enhance a little bit less than the surrounding normal pituitary. They can hemorrhage and have cystic degeneration. Because adenomas are slow-growing lesion, the sella is often expanded and remodeled but may not be completely destroyed.
When patients have pituitary hemorrhage, this is called apoplexy. This most often occurs in patients with an underlying adenoma. This is associated with a variety of conditions, including pregnancy/postpartum state, treatment of a prolactinoma with bromocriptine, and cerebral angiography (although admittedly I’ve never seen this).
Neuroradiology Board Review – Brain Tumors – Case 4
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 images from an MRI through the level of the pons. There is a mass in the left cerebellopontine angle (CP angle). It is causing mass effect on the pons. On postcontrast imaging, you can see that it is avidly enhancing with a few central areas of non-enhancement. A key to this case is identifying where the mass is centered. Does it look like it’s outside the IAC or centered in and expanding the IAC?
The diagnosis is: vestibular schwannoma
Vestibular schwannomas are extraaxial masses arising from the vestibular nerve (8th cranial nerve) either as they pass through the cerebellopontine cistern or in the internal auditory canal. They were previously called acoustic neuromas, but it is preferable to call them vestibular schwannomas given our current understanding of them. A key imaging feature is that they expand the internal auditory canal (IAC).
When approaching a cerebellopontine angle mass, it is useful to take a two step approach. First, determine if you think it is mostly solid and has enhancing components. If so, then think about schwannoma or meningioma as your top two differential considerations. If it is centered in the IAC and causes IAC enhancement, it’s probably a schwannoma. Meningiomas in this location occur but are more likely to have only minimal extension into the IAC without expansion.
This patient also had hydrocephalus from compression of the 4th ventricular outflow. Remember that masses in the posterior fossa can cause hydrocephalus due to mass effect.
Neuroradiology Board Review – Brain Tumors – Case 3
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 single image from a head CT as well as some MRI images at the same level. There is a dominant mass in the left parietal lobe which has some internal blood products. There is surrounding edema, but not much enhancement as most of the T1 hyperintensity is intrinsic (present on the pre-contrast exam) from blood products/methemoglobin. Upon closer inspection, there is also a smaller enhancing nodule in the adjacent cerebral hemisphere.
The diagnosis is: metastatic disease
Metastases to the brain are common manifestations of malignancies elsewhere in the body. The most common diseases to cause brain metastases are the same as the most common systemic cancers, including lung cancer, breast cancer, and melanoma. When brain metastases have hemorrhage, you might think about melanoma, renal cancer, and thyroid cancer (among others).
The most common locations for brain metastases are in the cerebral hemispheres and cerebellum. About 50% of brain metastases are solitary, so don’t be fooled if you see only a single lesion. It can still be a metastasis.
The differential diagnosis for most metastatic lesions includes infection and high grade glioma. Demyelinating disease can also sometimes have a similar appearance.
Neuroradiology Board Review – Brain Tumors – Case 2
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 an MRI of the brain with a pretty well-defined, expansile mass in the inferior aspects of the right parietal lobe with some extension into the adjacent frontal and temporal lobes. It is markedly T2 hyperintense, but somewhat less intense centrally on FLAIR. On pre- and post-contrast imaging, this shows that the tumor is predominantly non-enhancing, although there is a thin rim of enhancement around the anterior margin.
The diagnosis is: anaplastic astrocytoma (grade 3)
Anaplastic astrocytomas are grade 3 astrocytomas that are most commonly IDH mutated. They tend to have slightly more mass effect and enhancement than grade 2 tumors but do not have the necrosis and avid enhancement of grade 4 tumors most of the time. 1p19q codeletion is absent in these tumors because if present these would be oligodendrogliomas.
The T2 mismatch sign is a relatively recently described imaging finding of IDH mutated astrocytomas. When a portion of the tumor is very bright on T2 but suppresses on FLAIR, this is a pretty specific sign for IDH-mutation. This fact could appear on an ABR exam, especially the CAQ exam.
Neuroradiology Board Review – Brain Tumors – Case 1
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 an MRI of the brain with a highly heterogeneous, expansile mass in the right frontal lobe extending into the corpus callosum. There is a large degree of mass effect. On postcontrast imaging, there is a rim of avid enhancement with central necrosis.
The diagnosis is: glioblastoma
Glioblastomas, or GBMs, are high grade primary glial tumors and the most common primary brain tumor. The definition has recently been changed to only include IDH-wild type tumors, with IDH-mutated tumors now called grade 4 astrocytomas. These tumors have a very poor prognosis despite maximal therapy. They are characterized by avidly enhancing, necrotic masses with surrounding T2 hyperintensity that is a mix of tumor and edema.
Molecular markers are increasingly important in determining the prognosis of brain tumors. IDH-mutated tumors have a better prognosis, as do tumors with MGMT methylation. 1p19q codeletion is the characteristic mutation associated with oligodendrogliomas. These facts are fair game on ABR exams.
Welcome to this new board review series for 2022. In this series, we are going to focus on all things brain tumors that you might need to know as you prepare for the American Board of Radiology exams. While these videos are geared towards those taking the ABR core exam, they would also be useful for people taking the certifying or certificate of added qualification (CAQ) in neuroradiology exam.
There are going to be a total of 20 cases covering the most common brain tumors you might encounter in neuroradiology practice. Each one will have a series of images followed by 1 or 2 questions you can answer on your own as you follow along. Then there will be an explanation of the answers before you can move on.
By doing this series, hopefully you can quickly cover everything you need to know about brain tumors.
If you have not yet seen the other board review videos, I recommend you check out the categorized board review page.
A few lesions within the spinal canal are predominantly cystic or nonenhancing. They are almost always intradural extramedullary. The three most common entities are arachnoid cysts, dermoid cysts, and neuroenteric cysts. A contrast enhanced myelogram can often give you a little bit more information about what the entity is by determining if it fills with contrast.
Case 1. Arachnoid cyst. Arachnoid cysts in the spine are somewhat uncommon but will have the same characteristics as CSF on all images. They may often be identified only by their deflection of the spinal cord and mass effect. Their main differential is arachnoid webs or adhesions which cause similar mass effect on the spinal cord. On myelography, they often fill with contrast but more slowly than the surrounding CSF.
Case 2. Dermoid. Dermal inclusion cysts, or dermoids, are complex lesions made out of tissue from more than one embryonal layer. Their characteristic feature is internal fat contents. Like intracranial dermoids, they can rupture and cause a chemical meningitis. Their appearance overlap with lipomas but they are more likely to have complex features
Case 3. Neuroenteric cysts. Neuroenteric cysts are relatively simple cystic lesions which often occur ventral to the brainstem or spinal cord. They often are similar to but not exactly like CSF, and can be T1 hyperintense. They are indolent lesions but can cause mass effect. They do not fill on myelography.
Cyst summary. These are three of the most common cystic lesions. They are best differentiated by whether they communicate with the thecal sac (arachoid cysts), have complex or fatty features (dermoids), or are ventral to the cord and slightly differ from CSF (neuroenteric cysts).
Summary of spine tumors by location. Overall, when thinking about spine tumor, you should take a location-based approach. If you haven’t seen the introduction video yet, then definitely check it out. When divided by intramedullary, intradural extramedullary, and extradural, this can help you decide what type of lesion you are dealing with. Overall, always remember that the spine is an extension of the central nervous system, and consider imaging the brain because that may help you hone your differential diagnosis.
The level of this lecture is appropriate for radiology residents, radiology fellows, and trainees in other specialties who have an interest in neuroradiology or may see patients with spine tumors.
Lesions outside the thecal sac are categorized as extradural lesions. Remember that everything that isn’t in the thecal sac is extradural, including discs, bones, meninges, nerves, and blood vessels. Anything that can occur in the surrounding areas can have extradural components. Look for lesions that have mass effect on the dura and deflect both the dura and the thecal sac to the side. Many of these lesions will require a biopsy as they have a differential diagnosis on imaging. CT and diffusion weighted imaging are useful adjunct tools that can help you refine your diagnosis.
The rest of this lecture consists of a mix of case presentations of different extradural lesions with tips on how to refine your differential diagnosis.
Case 1 – Disc extrusion. These are one of the most common extradural pathologies, particularly in patients with a history of degenerative disc disease. They tend to be contiguous with the disc and follow the disc in signal. Don’t be alarmed if they have enhancement, particularly if the enhancement pattern is peripheral. These can be confused with schwannomas and meningiomas.
Case 2 – Lymphoma. Lymphoma can involve the bones at any spinal level and can result in pathologic fracture. Anytime you see involvement of the pedicles and posterior elements you should worry about pathologic fracture, particularly if there is soft tissue or epidural involvement and enhancement. When the bone is involved, think about performing a CT to see the pattern and extent of bone destruction. This lesion has a mixed lytic and sclerotic appearance with bone destruction and was ultimately proven to be lymphoma.
CT pattern of different bone lesions. When you have a bone lesion, the trabecular pattern and pattern of bone destruction can be helpful. Lesions such as benign vascular malformations (hemangiomas) have a classic trabecular or corduroy pattern, while Paget’s disease is characterized by cortical thickening.
Case 3 – Osteosarcoma. Bone sarcomas are aggressive lesions that have bone destruction and can have soft tissue components. Their characteristic finding is matrix deposition which is best seen on CT. Osteosarcomas tend to have fluffy cloudlike matrix (osteoid) while chondrosarcomas have arcs and rings with interrupted calcification (chondroid). This was a case of osteosarcoma.
Benign versus pathologic fractures. It can be challenging to differentiate fractures from bone insufficiency or trauma from those with an underlying lesion (pathologic fracture). Pathologic fractures are more likely to have bowing of the posterior cortex, a surrounding soft tissue mass, and abnormality on DWI. Looking for lesions elsewhere in the body can be a clue that it is metastatic disease, lymphoma, or myeloma. Sometimes these diseases can also have diffuse involvement of all of the marrow which can manifest as low T1 intensity throughout all the vertebral bodies.
Epidural tumor. Ventral epidural tumor can form a curtain or drape appearance because the dorsal dura is tacked down to the vertebral body at the midline. When it becomes more circumferential, it can extent completely around the thecal sac and extent both cranially and caudally.
Case 4 – Chordoma. Chordoma’s are aggressive tumors arising from notochordal remnant cells that can occur anywhere along the spinal axis. They are most common in the sacrum > clivus > remaining spine. Their characteristic appearance is a lytic lesion with bone destruction and marked T2 hyperintensity.
Enhancement pattern of extradural lesions. The enhancement pattern can help differentiate extradural lesions which may look similar. Tumors tend to have solid enhancement, abscess has peripheral enhancement, and a hematoma may have little or no enhancement.
Case 5 – Spinal dural arteriovenous fistula (dural AVF). These lesions have a classic presentation in older gentlemen with progressive myelopathy and are often missed. On MRI, they usually have edema and possibly enhancement in the cord, but the key finding is squiggly vascular enhancement along the margins of the cord. The pathology is from an abnormal connection between a vein and artery in the nerve root sleeve and can be treated endovascularly or with surgery.
Case 6 – Angiolipoma. These are fat containing lesions most common in the thoracic spine along the dorsal epidural space. They will have fat density on CT and can slowly increase in size, causing myelopathy.
Summary. There are a lot of things that can cause extradural masses, but they most commonly arise from the surrounding structures like discs and bones. Hopefully this video will help you refine your differential in the future.
The level of this lecture is appropriate for radiology residents, radiology fellows, and trainees in other specialties who have an interest in neuroradiology or may see patients with spine tumors.
In this lecture, Dr. Katie Bailey walks us through a rapid lecture about how to approach the basics of the spine. In about 5 minutes, you can learn most of what you need to know about spine interpretation when you first sit down to look at spine imaging.
This approach is based on the ABCDEs of spine. Each letter tells you something about what you should be looking for on the imaging.
Alignment. The way the vertebral bodies are oriented with respect to one another is alignment. This means lateral curvature (scoliosis), AP curvature (lordosis or kyphosis), and translation. Listhesis is conventionally described based on the level above with respect to the level below.
Bones. When thinking about the bones, you should look at the characteristics of the bones themselves. On CT, that could mean loss of normal bone density (lytic) or increased bone density (sclerotic). On MRI, you describe the appearance of a lesion with respect to the adjacent marrow. It is either hyperintense (more intense) or hypointense (less intense) compared to the normal marrow.
Cord/cauda equina. The cord itself is a key part of the image and you should look for any lesions within the cord or cauda equina. The cauda equina should be around the L1 level.
Disc. The discs have a wide range of degenerative pathology, which is discussed elsewhere. You should describe degenerative disease as well as any other abnormal conditions of the disc, such as infection.
Everything else. Finally, you should look at soft tissues and surrounding structures outside the spine. This is slightly different at each level of the spine where the structures vary slightly.
Summary. With this quick approach, you can rapidly move from a spine novice to a spine apprentice and you’re ready to learn more about different pathology within the spine. Check out some of the other spine videos to learn more about topics such as spine tumors, demyelinating disease, and degenerative disease.
