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.