Board Review 2 – Case 18

Neuroradiology 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 patient with cerebellar tonsils which extend below the foramen magnum. They have a “peglike” or triangular configuration, and extend well below the foramen magnum. The differential for this finding includes Chiari malformation, cerebellar tonsillar ectopia, idiopathic intracranial hypertension (IIH), and spontaneous intracranial hypotension (SIH).

The diagnosis is: Chiari malformation

Chiari malformation is a congenital abnormality in which the cerebellar tonsils extend below the foramen magnum and the posterior fossa is small. Patients can have chronic headaches. CSF flow studies of the foramen magnum can be useful to determine if patients are likely to benefit from surgical decompression with suboccipital craniectomy.

When combined with other abnormalities, there are specific diagnoses, which are:

  • Chiari II – cerebellar tonsillar abnormality + lumbar meningocele/myelomeningocele
  • Chiari III – cerebellar tonsillar abnormality + occipital meningocele

Board Review 2 – Case 17

Neuroradiology 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 CT with hyperdensity ventral to the pons and midbrain consistent with hemorrhage. Further imaging, including MRI and CT angiogram, were normal

The diagnosis is: benign perimesencephalic hemorrhage

This is a relatively benign form of subarachnoid hemorrhage of unknown etiology. The blood products are seen ventral to the pons, and are more common in younger patients. No vascular abnormality or tumor is found, and it is thought to be a result of disrupted veins, although the real cause is unknown. Outcomes are better compared to aneurysmal or traumatic subarachnoid hemorrhage.

Advanced MRI imaging of the brain

There are several advanced MRI techniques for more sophisticated imaging of brain structure and function. The most common advanced imaging techniques include spectroscopy, perfusion, diffusion tensor imaging (DTI), and functional MRI (fMRI). This playlist shows some of the details of using advanced imaging techniques for brain imaging and surgical planning.

This playlist includes some of the details about using advanced MRI for surgical planning and determining additional details about brain MRI.

Functional MRI (fMRI) language localization – conjunction display

Blood oxygen level dependent functional MRI, or BOLD fMRI, is an advanced MRI technique in which level of oxygen present in an area of the brain is used to map out what parts of the brain are activated in specific tasks. In this method, repeated imaging of the brain can be performed while the patient performs a task, and the level of oxygenation changes, showing which parts of the brain are most activated.

A key application of fMRI is mapping of language areas, or language localization, for surgical planning. The patient will perform more than 1 language task while in the scanner, and the activation data is overlaid on anatomic imaging (like conventional T1 or T1 postcontrast imaging). This is used to determine which side of the brain is language dominant as well as where exactly important language areas, including Broca’s and Wernicke’s areas, are located. This way they can be avoided in complex surgical procedures. However, sometimes results can be difficult to interpret because of the high number of images and high amounts of noise.

In this video, Dr. Michael Hoch demonstrates how use a conjunction technique to increase sensitivity for mapping language areas. In this method, all the language paradigms are overlaid on a single set of images using different colors. This increases the visibility of otherwise hard to see areas, increasing reader confidence.

The level of this lecture is appropriate for radiology residents, radiology fellows, and trainees in other specialties who have an interest in advanced MRI techniques such as diffusion tensor imaging (DTI) tractography, functional MRI (fMRI), and surgical planning.

For more information, see the whole video playlist on Advanced MRI.

 

Functional MRI (fMRI) Brainlab Processing Guide

Blood oxygen level dependent functional MRI, or BOLD fMRI, is an advanced MRI technique in which level of oxygen present in an area of the brain is used to map out what parts of the brain are activated in specific tasks. In this method, repeated imaging of the brain can be performed while the patient performs a task, and the level of oxygenation changes, showing which parts of the brain are most activated.

A key application of fMRI is mapping of language areas, or language localization, for surgical planning. The patient will perform more than 1 language task while in the scanner, and the activation data is overlaid on anatomic imaging (like conventional T1 or T1 postcontrast imaging). This is used to determine which side of the brain is language dominant as well as where exactly important language areas, including Broca’s and Wernicke’s areas, are located. This way they can be avoided in complex surgical procedures. However, sometimes results can be difficult to interpret because of the high number of images and high amounts of noise.

There are a number of processing suites that you can use to process fMRI data, including Brainlab and Dynasuite. The processing can be slightly different depending on which software package you are using, but the general principles are the same. To begin, you take each functional paradigm and overlay it on anatomical imaging, selecting statistical parameters and colormapping as you go.

In this video, Dr. Michael Hoch demonstrates the use of Brainlab to process fMRI data for language processing. He goes through the step-by-step process of generating each set of overlay imaging and how to interpret the results. In the second part of the video, he demonstrates conjunction overlay technique to increase sensitivity for mapping language areas by showing only the areas which have overlapping results on multiple paradigms, increasing reader confidence.

The level of this lecture is appropriate for radiology residents, radiology fellows, and trainees in other specialties who have an interest in advanced MRI techniques such as diffusion tensor imaging (DTI) tractography, functional MRI (fMRI), and surgical planning.

For more information, see the whole video playlist on Advanced MRI.

MRI Diffusion Tensor Imaging (DTI) interpretation:
Locating the corticospinal tract (CST)

Diffusion tensor imaging, or DTI, is an advanced MRI technique in which the asymmetric motion of water is used to map out specific properties in the brain. One application of DTI is called tractography, or identifying the specific tracts of neurons which pass through the brain.

One of the most important fiber tracts in the brain is the corticospinal tract, or CST. This tract connects the motor cortex with the spinal cord, passing through the cerebral peduncles. This fiber tract is important because it is the tract most responsible for voluntary movement. It can be affected by a number of pathologies, such as tumors, cortical malformation, and stroke. For some conditions, such as tumors, it can be critically important to locate the CST before performing surgery, so that the surgeons can properly plan their surgery. That’s where DTI comes in.

In this video, Dr. Michael Hoch demonstrates how to use a two region of interest method to identify the corticospinal tract, first placing a region of interest in the cerebral peduncle and a second in the motor cortex. He also talks about some of the pitfalls of diffusion tensor imaging and what kind of problems to look out for.

The level of this lecture is appropriate for radiology residents, radiology fellows, and trainees in other specialties who have an interest in advanced MRI techniques such as diffusion tensor imaging (DTI) tractography, functional MRI (fMRI), and surgical planning.

For more information, see the whole video playlist on Advanced MRI.

 

Board Review 2 – Case 16

Neuroradiology 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 mass within the spinal canal of the upper thoracic spine. For any spinal canal mass, your first step is to determine if it is:

  • intramedullary (in the spinal cord)
  • intradural extramedullary (inside the dura, but outside the spinal cord)
  • extradural

This mass appears to be extramedullary but intradural. The main differential considerations are meningioma, nerve sheath tumor/schwannoma, or metastasis. This mass has a relatively benign appearance and enhances avidly and homogenously.

The diagnosis is: meningioma

Spinal meningiomas are extramedullary masses that share an imaging appearance with intracranial meningiomas. They are often homogenous and enhance avidly. They can have calcification. The treatment, if symptomatic, is surgical resection.

Board Review 2 – Case 15

Neuroradiology 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 trauma patient who had a significant fall and now has lower extremity symptoms. On the MRI, there are a few compression fractures that you can see, but in addition there is T1 hyperintense fluid in the dorsal epidural space. In the setting of trauma, this is likely to be an epidural hematoma.

The diagnosis is: fracture with spinal epidural hematoma

Epidural hematoma is a dreaded complication of spine trauma that can cause worsening cord injury. It requires close monitoring and possibly surgical drainage if this may improve the symptoms. Look for intraspinal fluid collections after trauma, as they can be hard to identify.

Board Review 2 – Case 14

Neuroradiology 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 patient with a new neurologic deficit and a relatively normal noncontrast head CT. Perfusion, on the other hand, shows an area of decreased CBV, increased MTT, and increased Tmax in the posterior aspect of the left middle cerebral artery (MCA) distribution. There is an associated vessel occlusion on CT angiogram.

The diagnosis is: cerebral ischemia (stroke)

This patient has an area of ischemia in the left MCA territory. Because the CBV is relatively maintained, this tissue is mostly considered penumbra. When there is a significant decrease in volume and flow, it is considered core infarct that is not likely to recover.

Board Review 2 – Case 13

Neuroradiology 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 aggressive lesion of the upper thoracic spine in a relatively young patient. It appears to be centered in the posterior elements of the upper thoracic spine. There is central osseous matrix formation as well as a surrounding soft tissue mass with adjacent bone destruction. This is causing significant narrowing of the spinal canal.

The diagnosis is: osteosarcoma

In this case, you know you are dealing with an aggressive mass because of the soft tissue component and bone destruction. The differential includes primary bone lesions, metastatic disease, and lymphoma, but because of the new bone formation (osteoid matrix), it suggests osteosarcoma.