Brain MRI – Seizure search pattern

Many times when patients have a history of seizures, they undergo a workup including a physical exam, detailed EEG analysis, and finally brain MRI to try to identify any potential structural causes of seizures. In this video, Dr. Michael Hoch walks us through his approach to a brain MRI to maximize your sensitivity for finding abnormalities.

 

Dr. Hoch suggests a 4-step approach using the mnemonic “3-2-1 go to the hippocampus”. In this way, he divides his search into more digestible parts.

“3” indicates the 3 planes that you have in a non-contrast T1 weighted MP-RAGE MRI. On this you should focus on the cortex, particularly at the 3 poles, the frontal, temporal, and occipital poles.

“2” indicates the 2 planes of FLAIR and 2 window settings you should use. You should review FLAIR images in both the coronal and axial planes. You should also use a window that is normal and a window that is narrow, or aggressive, to highlight lesions, particularly in the cortex, which are hard to see.

“1” indicates the single plane of blood sensitive imaging, either GRE or SWI, which can often see areas of prior hemorrhage or cavernou

“Go” to the hippocampus last to look for signs of mesial temporal sclerosis, which is manifested as a small hippocampus with loss of internal architecture and abnormal T2/FLAIR hyperintensity. This can be either from primary epilepsy or secondary to another lesion.

See this and other videos on our Youtube channel .

Board Review 3 – 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.

https://youtu.be/nJLmYJalT8s

This case shows a CT with a soft tissue density mass extending from the frontal sinus through the outer table to the prefrontal scalp soft tissues.

The diagnosis is: frontal sinus osteomyelitis/Pott’s puffy tumor

Sometimes acute sinusitis can be complicated by adjacent osteomyelitis and bone destruction, such as in this case. The most likely location for this to happen is in the frontal sinus, when the diagnosis has the moniker “Pott’s puffy tumor”.

It is important when this happens to do an MRI of the brain to check for intracranial complications, such as meningitis, dural sinus invasion, and epidural abscess. The differential diagnosis includes malignancy (metastatic disease, lymphoma, and primary sinus malignancy), mucocele, and inflammatory diseases such as granolumatosis with polyangiitis.

Board Review 3 – 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 CT of the head with scattered areas of hemorrhage centered at the gray-white matter junctions and along the corpus callosum. MRI confirms these findings, with areas of edema and susceptibility from blood products in those locations.

The diagnosis is: traumatic shear injury

In high energy traumas, areas of brain at interfaces, such as the gray-white junction, corpus callosum, and brain stem. These can be seen on CT and MRI, although MRI is more sensitive for small areas of injury. This can sometimes be referred to as diffuse axonal injury, or DAI.

Susceptibility weighted imaging (SWI) is a specialized MRI sequence tailored to detecting small areas of distortion of the magnetic field, which can be related to calcium or hemosiderin. It is a nice tool to see subtle areas of brain injury.

Board Review 3 – 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
bilateral hippocampal and medial temporal T2/FLAIR hyperintensity with relatively little enhancement. The abnormal signal extends superiorly into the insula and subinsular white matter bilaterally.

The diagnosis is: limbic encephalitis

There is a differential diagnosis for this case which includes:

  • herpes encephalitis
  • other viral encephalitis
  • limbic encephalitis
  • infiltrative astroctyoma

Limbic encephalitis is an autoimmune condition often as part of a paraneoplastic syndrome. Patients have bilateral temporal lobe abnormalities that can be symmetric or asymmetric, and presence of enhancement is possible. Patients often have circulating antibodies, such as anti-GAD.

Herpes encephalitis usually has more enhancement and diffusion abnormality, but this is not reliable. Any patient suspected of having herpes encephalitis should be treated with antivirals (acyclovir) until herpes is ruled out to minimize the high morbidity and mortality. Other viral encephalitis can have this appearance as well, but the bilateral symmetry is highly suggestive of autoimmune limbic encephalitis.

Board Review 3 – 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 a left frontal hyperdense collection on a CT. The patient is on anticoagulation.

The diagnosis is: subdural hematoma

Subdural hematomas are extra-axial hemorrhages that are common in the elderly, particularly those who are on anticoagulation. They have the highest mortality of intracranial hemorrhages. Key features are an extra-axial hemorrhage that has a crescent shape that crosses sutures and tracks along dural reflections such as the falx and tentorium.

Epidural hematomas do not cross sutures because the outer layers of the dura are adherent to the bone and continuous with the periosteum. Most epidural hematomas are associated with skull fractures.

Board Review 3 – Case 12

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 is a patient who has a remote history of “meningitis”. Her imaging shows marked edema in the frontal lobes on CT, with a follow up MRI confirming significant leptomeningeal and parenchymal nodular enhancement worst in the frontal lobes. There is involvement of the right optic nerve.

With severe leptomeningeal enhancement such as this, there is a differential diagnosis which includes:

  • leptomeningeal carcinomatosis
  • unusual infections (fungi, tuberculosis, or other unusual pathogens)
  • sarcoidosis

The diagnosis is: neurosarcoidosis

The most common findings of sarcoidosis are leptomeningeal enhancement centered in the basal cisterns, sometimes with parenchymal nodular or perivascular enhancement. The diagnosis of neurosarcoid consists of checking a serum ACE level, performing an LP (particularly to rule out other causes), and chest imaging (including x-ray or CT). Often the easiest tissue diagnosis is through biopsy of hilar nodes.

Board Review 3 – Case 11

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 nodular lesion with calcification in the right frontal lobe. There is surrounding vasogenic edema with sparing of the cortex. CT images from higher in the brain show other areas of calcification at the gray-white junction thoughout the brain.

MR confirms these findings. There is an area of right frontal edema with a rounded enhancing structure at the gray-white junction. There is a differential diagnosis for this finding which includes infection and metastatic disease.

The diagnosis is: neurocysticercosis

Neurocysticercosis is a parasitic infection with a dual life cycle that goes through pigs and humans. When eggs excreted in human feces are ingested, it can affect the CNS. It is the most common cause of acquired seizure in endemic areas.

The treatment is anti-parasitic agents, specifically albendazole.

Board Review 3 – Case 10

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 right posterior frontal tumor. There is mild mass effect with infiltrative T2 hyperintensity. On gradient imaging, there is some evidence of internal blood products or hemorrhage. Post-contrast imaging shows a multilobular and enhancing mass with irregular margins and central necrosis.

The diagnosis is: glioblastoma (GBM)

Glioblastoma, formerly known as glioblastoma multiforme, is a grade 4 primary astrocytoma and the most common primary glioma. They have extremely poor prognosis and are characterized by irregular and necrotic enhancing masses. The surrounding T2 abnormality is a result of vasogenic edema and infiltrative tumor.

With any solitary enhancing parenchymal mass, there is a differential diagnosis that should be considered, including:

  • glioblastoma
  • metastasis
  • lymphoma
  • abscess (should have bright internal DWI)
  • other infections

Board Review 3 – Case 9

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 in the left cerebellopontine angle (CP angle). It is predominantly outside of the internal auditory canal (IAC), although there is extension into the canal. It is relatively homogeneous with avid post-contrast enhancement.

The diagnosis is: meningioma

Meningiomas are the most common brain tumors (although they are extra-axial). They often have a cerebrospinal fluid (CSF) cleft around them which allow you to determine that they are extra-axial. They can calcify and cause adjacent hyperostosis of the bone.

A useful approach to CP angle masses is to first consider whether it is cystic or solid. Solid masses enhance on post-contrast imaging. If they are centered in the IAC and cause expansion, it is most likely a schwannoma. If it does not cause expansion or looks centered outside the IAC, think about meningioma.

Board Review 3 – Case 8

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 teenager with T2 hyperintense mass in the left posterior fossa resulting in mass effect on the 4th ventricle. On post-contrast imaging there is scattered hazy enhancement throughout portions of the mass.

The diagnosis is: pilocytic astrocytoma

Pilocytic astrocytomas are the most common brain tumors in children. They most commonly occur in the posterior fossa and are often characterized by a cystic mass with a nodular enhancing area. They are relatively benign tumors with a good 10 year survival.

When you encounter a cyst with a nodule, there is a relatively short differential diagnosis which includes:

  • Pilocytic astrocytoma
  • Ganglioglioma
  • Hemangioblastoma (has blood vessels/flow voids)
  • Plemomorphic xanthoastrocytoma – PXA