Stroke vascular distributions – Imaging Case Review

Dr. Bailey is back for a case-based review of stroke and the vascular distributions commonly seen in stroke.

Introduction

In this video, we’ll review vascular territories in the brain as well as typical appearance of acute infarcts. This covers the distribution of the anterior cerebral artery (ACA), middle cerebral artery (MCA), posterior cerebral artery (PCA), cerebellar arteries, and basilar artery.

Case 1 – ACA infarct

This case shows an infarct in the right anterior cerebral artery distribution. There is loss of gray white differentiation on the CT. On MRI, it is even more apparent, with DWI abnormality which is dark on ADC. There is a corresponding abrupt occlusion of the ACA.

Case 2 – MCA infarct

In this case, there is hypoattenuation in the left posterior temporal lobe and inferior parietal lobe and posterior insular cortex. The MRI confirms that there is a stroke in this region. This is the posterior MCA distribution, with a posterior M2 branch occlusion

Case 3 – PCA infarct

There is subtle hypodensity in the left occipital lobe seen both on axial and sagittal CT. This is again confirmed on MRI, where there is T2 hyperintensity and diffusion abnormality. The MRA shows an abrupt cutoff of the left PCA.

Case 4 – Cerebellar infarct

This case shows a small, wedge shaped hypodensity in the left inferior cerebellum. MRI confirms abnormal diffusion in the left inferior cerebellum. In this case, the neck MRA shows

Case 5 – Multiple infarcts

This case shows multiple infarcts, including a right occipital and a left frontal infarct. When you have infarcts in multiple vascular territories, you should consider the possibility of a central source of thrombi, such as atrial fibrillation or cardiac disease, or vasculitis.

Case 6 – PCA plus

This case has an infarct in the left occipital lobe, but there is also hypoattenuation in the left midbrain and cerebral peduncle. MRI reveals even more areas of ischemia, including a small area in the right occipital lobe and multiple areas in the left thalamus. This indicates that the occlusion is more proximal and likely includes the basilar artery.

Case 7 – Medulla

This is a specific location which is frequently involved in infarcts, the lateral medulla. There is associated severe stenosis of the right vertebral artery.

Case 8 – Border zone

These are often seen as linear low attenuation along the border between vascular territories. In this case, it is the border between the ACA and MCA territories.

Special bonus case – artery of Percheron

This bonus case shows bilateral thalamic infarcts from an artery of percheron, a variant where the arterial supply for both thalami comes from a perforating branch on one PCA. This can also come from central venous thrombosis, so that is the other consideration

Special bonus case – venous infarct

If you have an infarction in an unusual location, particularly if associated with hemorrhage, then think about the possibility of sinus thrombosis. In this case, the straight sinus is dense and occluded on an MRV.

Summary

Hopefully these cases taught you something about the common locations of infarcts and their typical appearance on CT. Please check out the rest of the vascular and stroke content on the site.

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MRI of the Orbits

In this video, Dr. Bailey reviews the orbit on MRI, with a focus on anatomy and a few of the most common pathologies.

Introduction

In this video, we’ll review the normal anatomy of the orbit and its appearance on MRI.

Orbital contents and normal anatomy

The postseptal orbit includes the intraconal (within the extraocular muscles) contents and extraconal contents. The muscles themselves are a muscular compartment, but it is useful to think of them in the extraconal compartment. There are many things you’ll find in the orbit, including the muscles, the optic nerve, arteries and veins, and fat.

On pre- and post-contrast imaging, you can identify which structures enhance. The optic nerves, for example, should not normally enhance. Lacrimal glands, the extraocular muscles, and sinus mucosa enhance normally.

Optic nerve

The optic nerve can be affected by masses, infection and inflammation, demyelination, and other pathologies. Optic neuritis is inflammation of the nerve, which is usually seen by enhancement in the optic nerve itself. Radiation can cause optic neuropathy, which may even be bilateral. Optic gliomas are tumors that affect the optic nerve and are associated with neurofibromatosis. Optic nerve ischemia can also cause optic neuropathy, often in the acute setting. Optic nerve atrophy is chronic volume loss that can occur from prior insult. It can be hard to determine which of the nerves is abnormal when they are asymmetric.

Optic nerve sheath and retroorbital fat

The optic nerve sheath and periorbital fat are subject to different pathologies, including perineuritis, idiopathic orbital inflammation, sarcoid, certain tumors such as meningioma, lymphoma, and metastatic disease, and idiopathic intracranial hypertension.

Globes

The globes can be affected by inflammation, tumors, and degenerative changes. Inflammation can affect the entire globe or only portions, such as the posterior sclera. Phthisis bulbi is a chronic atrophy of a non-functional globe. Melanoma is a relatively common malignancy of the uvea, but can be hard to see. It is sometimes manifested as an intrinsic T1 hyperintense mass. Retinal detachment can often be seen on MRI as well.

Orbital apex

Cranial nerves and vessels are the main things passing through the orbital apex, and pathologies that you see probably arise from one of them. Slow flow venous malformations (previously called hemangiomas) are well circumscribed vascular lesions often occurring in the orbital apex and orbit. Masses such as meningioma also occur at the orbital apex.

Extraconal compartment

The extraconal structures include the muscles, lacrimal ducts, fat, and the periosteum. A common cause of extraocular muscle abnormality is thyroid ophthalmopathy, which causes bilateral symmetric enlargement that spares the myotendinous junction. Lymphoma can cause masses of the extraocular muscles or lacrimal ducts and often restricts diffusion. Infection can extend from the sinuses into the extraconal compartment and even extend intracranially. The lacrimal glands are subject to their own specific pathology. They can get inflammatory changes related to idiopathic orbital inflammation or sarcoidosis. Dermoids are well-defined masses in the orbit, likely near suture lines. Osseous lesions can also extend from the orbits into the orbital walls.

Conclusion

Hopefully you learned a little bit about the anatomy and common pathology of the orbit. Be sure to check out the other videos on search patterns as well as all the other head and neck topics.

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Vascular Imaging – Playlist

This playlist covers a range of topics in vascular imaging including general concepts about how to approach brain and neck vascular imaging, what intracranial aneurysms, are, and how to improve your aneurysm search pattern.

You can learn more about other concepts in vessel imaging and other abnormalities on the vascular imaging page. If you haven’t already, you might consider taking a look at the vascular imaging capstone course. Also, please check out our full channel on Youtube.

Fast 10: Neuroradiology high speed case review part 6 – Cases 51-60

In this 6th video, we present 10 more neuroradiology high speed review cases so you can review them quickly before your exams. If you want to see more information about these cases, you can find longer versions on the channel under the Board review playlist

Cases included in this set:
Neurocysticercosis
Sarcoidosis
Subdural hematoma
Limbic encephalitis
Arteriovenous malformation (AVM)
Traumatic shear injury/Diffuse axonal injury (DAI)
Frontal sinus osteomyelitis (Pott’s puffy tumor)
Carotid artery dissection
Tuberculosis lymphadenopathy (Scrofula)
Cauda equina syndrome imaging

Be sure to check back in for the remainder of the high speed cases.

Fast 10: Neuroradiology high speed case review part 5 – Cases 41-50

In this 5th video, we present 10 more neuroradiology high speed review cases so you can review them quickly before your exams. If you want to see more information about these cases, you can find longer versions on the channel under the Board review playlist

Cases included in this set:
Subependymoma
CNS lymphoma
Metastatic disease to calvarium
Meningioma
Metastatic melanoma
Hypothalamic hamartoma
Pituitary adenoma (with hemorrhage/apoplexy)
Pilocytic astrocytoma
Cerebellopontine angle meningioma
Glioblastoma

Be sure to check back in for the remainder of the high speed cases.

Fast 10: Neuroradiology high speed case review part 4 – Cases 31-40

In this fourth video, we present 10 more neuroradiology high speed review cases so you can review them quickly before your exams. If you want to see more information about these cases, you can find longer versions on the channel under the Board review playlist

Cases included in this set:
Renal cell carcinoma
Tuberculosis discitis osteomyelitis
Osteosarcoma of the spine
Ischemia with penumbra (tissue at risk)
Traumatic spine epidural hematoma
Thoracic spine meningioma
Benign perimesencephalic subarachnoid hemorrhage
Chiari malformation
Traumatic vertebral artery injury
Temporal lobe anatomy – fusiform gyrus

Be sure to check back in for the remainder of the high speed cases.

Fast 10: Neuroradiology high speed case review part 3 – Cases 21-30

In this third video, we present some 10 more neuroradiology high speed review cases so you can review them quickly before your exams. If you want to see more information about these cases, you can find longer versions on the channel under the Board review playlist

Cases included in this set:
Vestibular schwannoma
Surfer’s ear (external auditory canal exostosis)
Dural sinus thrombosis
Idiopathic basal ganglia calcification (Fahr disease)
Subclavian steal
Hypertensive hemorrhage
Craniopharyngioma
Ganglioglioma
Synovial cyst
Spinal lymphoma

Be sure to check back in for the remainder of the high speed cases.

Fast 10: Neuroradiology high speed case review part 2 – Cases 11-20

In this second video, we present some 10 more neuroradiology high speed review cases so you can review them quickly before your exams. If you want to see more information about these cases, you can find longer versions on the channel under the Board review playlist

Cases included in this set:
Colloid cyst
Sturge-Weber syndrome
Juvenile nasal angiofibroma (JNA)
Esthesioneuroblastoma
Traumatic ossicular dissociation/dislocation
Cavernous malformation (cavernoma)
Cerebellopontine angle ependymoma
Spine schwannoma
Osmotic demyelination/central pontine myelinolysis
Thyroid ophthalmopathy

Be sure to check back in for the remainder of the high speed cases.

Fast 10: Neuroradiology high speed case review – Cases 1-10

In this video, we present some high speed review cases so you can review them quickly before your exams. This video has the first 10 review cases. We’ll spend about 1 minute on each case so you can learn as quickly as possible. If you want to see more information about these cases, you can find longer versions on the channel under the Board review playlist

Cases included in this set:
Huntington’s disease
Progressive supranuclear palsy
Multisystem atrophy
Creutzfeld-Jakob disease
Parkinson’s disease
Posterior reversible encephalopathy
Leptomeningeal metastases
Subdural hematoma
Pyogenic abscess
Artery of Percheron infarct

Be sure to check back in for the remainder of the high speed cases.

Fast 10 – High speed case review

These videos focus on going quickly through neuroradiology cases, spending about 1 minute per case to get you through 10 cases in 10 minutes. Ideal for a quick review before an exam or neuroradiology rotation. An ideal way to go through a lot of cases quickly.

Each case shows a couple of images with a multiple choice question, followed by a quick review of the answer and the diagnosis.

If you prefer longer versions of these cases, check out the full “Neuroradiology board review cases – All” playlist on YouTube