Brain imaging course – 5 – Common imaging pathology

This video is the fifth in a series of a brain imaging course. In this video, we review some of the most common imaging pathologies that you’ll encounter, particularly in hospitalized patients.

Check out the entire course if you haven’t already.


This video is going to focus on some of the most common pathologies that you’ll encounter in brain imaging. We’ll review common CT and MRI findings that you’ll see on those cases. The most common pathologies a beginner should be familiar with are stroke, hemorrhage, hydrocephalus, tumor, and infection.


Stroke is death of tissue due to occlusion of blood flow, and more specifically, oxygen delivery, to the brain. This is most commonly caused by arterial obstruction or less commonly venous obstruction. Most of the time we start imaging with CT, where you may see loss of gray-white differentiation in a vascular territory. Vascular imaging and MRI are excellent supplements for evaluation stroke. Be sure to look out for complications such as stroke and hemorrhagic conversion. The example shows you an example of a left MCA infarct in a patient with endocarditis. Over time, stroke gets more hypodense and more well-defined. Cortical necrosis is a specific deposition of blood in the cortex which is a benign finding and should not be called hemorrhagic conversion. Stroke almost always corresponds to a vascular territory, so it is valuable to know the territory distributions of the ACA, MCA, and PCA.


Hemorrhage is the development of acute blood products, particularly in the brain. It is characterized by where it located, and the location is an excellent clue to what is the most common cause. Acute blood starts hyperdense to the surrounding brain parenchyma and will gradually decrease over time.

Subarachnoid hemorrhage is one of the most common types of hemorrhage that you may encounter. It is commonly caused by trauma or aneurysm rupture. If you see subarachnoid hemorrhage, you should get a CT angiogram to look for the cause of hemorrhage.

Extra-axial hemorrhages include subdural hematoma and epidural hematoma. Subdural hematomas can be spontaneous, associated with anticoagulation, or associated with trauma. They cross sutures and spread along dural reflections. Epidural hematomas are almost always associated with skull fractures.

Parenchymal hemorrhages occur in the brain itself. The most common cause is hypertensive hemorrhage, which occurs most commonly in central locations like the basal ganglia, thalamus, pons, and cerebellum. Peripheral hemorrhages may be caused by other things like venous infarct, cerebral amyloid angiopathy, or tumors.


Hydrocephalus is enlargement of the ventricles that can be due either to decreased resorption of CSF or blockage of CSF flow. There are two main types, communicating, which is an issue with CSF resorption, or non-communcating/obstructing. The example shows you a case of hydrocephalus from an obstructive mass at the foramen of Monro. Increase in size and ventricle contour are your clues. Edema around the ventricles is a clue that hydrocephalus may be acute.


Tumors are space occupying lesions or masses within the brain. They can be located within the brain parenchyma (intra-axial) or outside the brain (extra-axial). The most common intra-axial tumors are metastases and primary tumors, while the most common extra-axial tumor is a meningioma. If lesions are single, it’s more likely to be a primary tumor or solitary metastasis. Multiple lesions may be lymphoma or metastatic disease. The example shows you a peripherally enhancing and centrally necrotic high grade glioma in the left temporal lobe.


Infection is characterized by location. Meningitis is infection of the CSF space or meninges. Encephalitis is infection of the brain parenchyma. Walled off masslike infection is called abscess. Patients who are immunocompromised, such as patients with HIV or patients on immune suppression for organ transplants or autoimmune conditions are more at risk.

The example shows a patient with a single focal lesion with diffusion hyperintensity in the parietal lobe. Many times you can’t tell the cause of infection just from imaging, but will need correlation with CSF labs, systemic labs, and other history to know the organism. Sometimes you’ll even need a biopsy.


Thanks for tuning in to the video. Hopefully you are now familiar with some of the most common brain pathology and are ready to check out some cases on your own. The next 7 videos will walk you through independent review of cases you can review on the website.

See all of the brain course videos on the brain course playlist, or go back to the brain capstone course page.

Brain imaging course – 4 – Reviewing a normal case

This video is the fourth in a series from brain imaging course. In this video, we go through a normal brain imaging case in a patient who is normal. We first go through a head CT and then the patient’s brain MRI.

Check out the entire course if you haven’t already.


In this video, we are going to go through a normal case together. I’ll show you how to apply what you’ve learned in the other videos on your own. Be aware of the strength of having a structured pattern when looking at the images so you can use them effectively.

Normal Head CT

A normal head CT search pattern begins on the brain images. I go from top to bottom, looking for symmetry, gray-white differentiation, and normal underlying structures. I also first review the brain window, then the bone window, then any reformats.

Click here to get the Head CT

On the brain window, I start at the bottom, reviewing normal structures for symmetry, including normal CSF structures. White matter should be a little less dense than gray matter because it has higher fat/myelin content. You should see some gray-white differentiation in the basal ganglia structures. As you reach the vertex, you should see symmetric sulcation, and the brain should be coated with gray matter in all locations. If you lose gray-white differentiation, that can be a sign of stroke.

CT bone window

On the bone window, I also start at the bottom, looking for any fractures in the skull base, any destructive lesions, and that the cortex is maintained everywhere. I will often come back and look at soft tissues using a soft tissue window, including the orbits, sinuses, and facial soft tissues.

CT reformats

There are two reformats provided with this case. The coronal reformat is great to look at the convexity, the floor of the anterior and middle cranial fossa, and the posterior fossa (cerebellum). The sagittal reformat is similar with the additional advantage of being able to see some midline structures like the corpus callosum really well.

Normal Brain MRI

Reviewing a normal MRI is similar, but you need to make multiple passes because of the different information that is found on different sequences. Each sequence has its own advantages, so use them to your benefit.

Click here to get the Brain MRI

Diffusion weighted imaging

DWI is great for seeing restricted water movement. Strokes and abscesses are usually hyperintense. You can use the ADC (not shown) just to make sure it is not bright from T2 effects only (“T2 shine through”).


FLAIR is a real workhorse of clinical imaging. You can recognize FLAIR because the white matter is darker than gray matter. Pathology will be bright because it has excess water. CSF is suppressed on FLAIR imaging, which makes pathology easier to see.


Gradient recalled echo (GRE) T2 imaging is a blood sensitive sequence which is good to see iron, hemosiderin, blood, and air. These things will be dark on GRE. Some normal structures like blood vessels and iron containing nuclei can be darker normally.


T2 is like FLAIR in that pathology tends to be bright (hyperintense). However, the fluid is not suppressed. This gives you a little bit better view of fluid filled structures like the ventricles but you see pathology in the brain parenchyma worse.

Pre-contrast T1

T1 has the opposite contrast of T2, in that white matter is hyperintense to gray matter. This is a key trick for identifying what kind of imaging you are looking at. T1 precontrast images are great for seeing normal anatomical structures as well as the normal marrow. They are also important to compare pre-contrast

Post-contrast T1

The post-contrast T1 is a key sequence because it will identify areas of breakdown of the blood brain barrier. Pathology like tumors, infection, and demyelination, will often enhance. Some normal structures like vessels, the pituitary, and choroid plexus enhance normally.

Conclusion and recap

Thanks for tuning in to the video. Hopefully now you have developed your own basic approach to brain imaging that you can use on the test cases. On the next video, we’ll review some of the most common brain pathology. The final videos will provide some individual cases you can go through on your own.

See all of the brain course videos on the brain course playlist, or go back to the brain capstone course page.

Brain imaging course – 3 – How to review brain cases


This video is the third in a series of a brain imaging course. In this video, we talk about basics of how to review brain cases on your own, including some tips for how to get effective at finding abnormalities and learning your on your own.

Check out the entire course if you haven’t already.

Basics, slice thickness and reformats

When you are reviewing brain cases, you need a structured way of looking at each case to make yourself a sensitive and effective radiologist. This is called a search pattern. You also need to know the ways in which the different images you are provided are different. For example, images can be provided at different thicknesses. In general, thinner images have sharper edges but more noise. Thicker images are better for looking at the bones.

We also have different reformats. On CT, that is usually from one set of data that is displayed in a different plane. The most conventional is perpendicular to the long axis of the body, or axial. Coronal is parallel to the face. Sagittal is parallel to the long axis of the nose. Each of these views has relative strengths and weaknesses.

CT density, window, and level

CT images are standardized for the degree of x-ray absorption, which is closely tied to the density of the material. Each type of tissue has a typical expected density that will be roughly the same on different scanners.

The window and level of a set of images control what is shown on the screen at one given time. The window is the size of the range, or width of the range, of data shown. The level is the center of the range being shown, sometimes referred to as the center. These values are akin to brightness and contrast, although somewhat more exact.

Brain window is structured to see the difference between gray matter and white matter, which is very small, but is poor at seeing very dense structures like bone. For that, a much wider window, the bone window is used.

Basic search pattern

When you are looking at a CT, you need a pattern for looking at each feature in the images. I usually start from the bottom, looking at the brain and focusing on symmetry. Then I move to the bone windows, checking the calvarium, temporal bone, orbits, and sinuses. I may spend an extra minute or two looking at the orbits and soft tissues. To learn more in detail about a head CT search pattern, check out the video.

When reviewing an MRI, you have a similar strategy, but given the different strengths and weaknesses of each sequence, you use each one with a slightly different emphasis. To learn more in detail about how to review a brain MRI, check out the video overviewing MRI sequences and how to review them.


Thanks for tuning into the video about general approaches to brain imaging. On the next video, we’ll have a structured review of a normal case that you can follow along with on your own.

See all of the brain course videos on the brain course playlist, or go back to the brain capstone course page.

Salivary Glands

In this video, Dr. Bailey gives us an overview of salivary gland lesions, including briefly reviewing the normal anatomy and appearance of the salivary glands, common benign and malignant neoplasms, and other infectious, inflammatory, and systemic processes that may affect the salivary glands.

Salivary gland overview

There are three major sets of salivary glands, the parotid, submandibular, and sublingual glands. There are also minor salivary rests elsewhere. The parotid gland is the largest salivary gland, and drains through Stinson’s duct which empties near the 2nd molar. The submandibular and sublingual glands are in the floor of the mouth in the sublingual space.

Benign salivary gland neoplasms

There are a lot of salivary gland neoplasms, most of which are benign. A good tip is that the larger glands are more likely to have benign lesions. Most parotid lesions are benign, while minor glands have a higher percentage of malignant gland. The parotid is the most common location for both benign and malignant lesions.

The most common benign lesions are pleomorphic adenoma (benign mixed tumor) and Warthin tumors. Pleomorphic adenomas are the most common and tend to be homogeneously dense on CT. On MRI, they are relatively homogeneous, hypointense on T1, and VERY hyperintense on T2. They may have a fibrous rim. Warthin tumors are also benign, and are more common in older men. They are often bilateral, and tend to be more heterogeneous and less T2 hyperintense than pleomorphic adenomas. Bilateral tumors are more likely to be Warthin tumors.

Malignant salivary gland neoplasms

Mucoepidermoid carcinomas are the most common parotid malignancy. There is a lot of overlap with the appearance of benign lesions, but the margins tend to be more irregular. They may also have lower signal on T2. When you have malignant salivary gland lesions, you should check specifically for perineural spread, which can occur along the facial nerve up to the geniculate ganglion or along the trigeminal nerve to the foramen ovale.

Adenoid cystic carcinomas are more common in minor salivary glands and are the most common sinonasal salivary tumor. As the grade increases, they tend to be more T2 hypointense. There are also well known for perineural spread.

Parotid metastases are quite common because of intraparotid lymph nodes. Skin cancers and melanoma as well as lymphoma are common causes of metastatic disease. Like the other malignancies, they tend to have very irregular margins.

Inflammatory and other

Sjogren disease is an autoimmune disease of exocrine glands which results in a multinodular appearance of the parotid glands. Patients may have atrophy of the lacrimal glands. These patients have an increased risk of lymphoma.

Lymphoepithelial cysts are multifocal cystic lesions which are most often seen in patients with HIV due to lymphatic obstruction. They appear as bilateral parotid gland cysts.

Sialolithiasis is formation of stones (calculi) in the duct or parenchyma of glands. They are most common in middle age me and in the submandibular gland. This appears as very dense, calcified and well defined lesions either in gland or along the duct.

Sialadenitis is inflammation of the gland which can be caused by infection or inflammatory conditions. Ascending bacteria from the pharynx is the most common, but viruses and immune mediated causes are also possible.

Practice case

This is a relatively well-defined lesion in the superficial aspect of the left parotid gland. It is hyperdense and somewhat homogeneous, but superficial to the gland. If you review further, there is an additional superficial nodule, and this is spread of an adjacent malignancy. So, this case is malignant. An important lesson in evaluating salivary gland lesions is that you often cannot tell the difference between benign and malignant lesions, so biopsy is required.


Hopefully these cases taught you something about the normal appearance and anatomy of the salivary glands, some common tumors (both benign and malignant), and other conditions affecting the salivary glands. Be sure to check out the other videos on other head and neck topics.

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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.


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.


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.


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.


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.


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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Brain imaging course – 2 – Choosing brain imaging


This video is the second in a series of a brain imaging course. In this video, we talk about when to order different types of imaging and the relative advantages of each type of imaging. This includes head CT, brain MRI, and the different types of vascular imaging like CT angiography and MR angiography.

Check out the entire course if you haven’t already.

Head CT

Head CT is one of the most commonly performed neuroradiology exams. It’s a common screening exam that is performed for indications like trauma, new neurologic symptoms (such as weakness or sensory symptoms), or the worst headache of someone’s life. Head CT is also very commonly performed on patients with known brain abnormalities to investigate whether they are changing.

CT vessel imaging

CT can be performed with timing to evaluate arteries (angiography) or veins (venography). CT angiography (CTA) is frequently performed for acute stroke, trauma, or if the patient has a hemorrhage.

CT venography (CTV) is done to evaluate the veins. This is most commonly done if a patient has elevated intracranial pressure (or papilledema), an atypical hemorrhage that could be due to venous thrombosis, or if there is trauma near a dural sinus.

MRI brain

MRI of the brain is the workhorse of neuroradiology. You would want to order an MRI of the brain if a patient had a known abnormality that was found on a head CT. An MRI can give you much more information about the underlying abnormality.

If the patient has continued symptoms but a normal head CT, that is another reason to get an MRI. It is much better at seeing small or subtle abnormalities in the brain. In general MRI is a better exam for indications with it is not time-sensitive.

When do MRIs need contrast?

It’s a constant question of when patients should get contrast on MRI of the brain. For low probability screening exams for conditions like headache, stroke, or dizziness, an MRI without contrast is usually adequate. For higher probability of a significant abnormality, you may need contrast. For example, if a patient has concern for meningitis or intracranial abscess, contrast is helpful. Contrast is also usually used when patients have tumors or possible metastatic disease.

In general contrast is needed when there is a higher suspicion of an acute abnormality.

MR vessel imaging

MR angiography (MRA) and venography (MRV) is most commonly used when vascular abnormalities need to be evaluated, but time is not a major concern. This is often done in cases of strokes when the patient has had symptoms for a while (often more than 24 hours). MRA is great for evaluating aneurysm and vascular malformations. MRV can see venous thrombosis and other abnormalities.


Thanks for tuning in to the video. Hopefully you learned a lot about how to choose the best brain imaging for your patients. The next video will cover basic concepts about reviewing brain imaging on your own.

See all of the search pattern videos on the brain course playlist.

Brain imaging course – 1 – Imaging Modalities


This video is the first in a series of a brain imaging capstone course to learn some of the basics about brain imaging. The overall series will cover the range of imaging used to investigate the brain, information about how to choose what type of study will help your patient, teach you how to review images on your own, review some common pathology, and then provide some interactive courses that you can review on your own.

Check out the entire course if you haven’t already.

Modalities used

The main types of imaging, or modalities, used in brain imaging, are computed tomography (CT) and magnetic resonance imaging (MRI). Each of these can be tailored in specific ways to look at vessels, including arteries or veins.

CT head without contrast

CT head is the main screening exam used in neuroradiology. This is commonly done any time a patient has new neurologic symptoms and can see common pathologies such as stroke, hemorrhage, fracture, edema, and hydrocephalus. Once patients are in the hospital, it may be used to follow up their pathology.

CT head with contrast

While possible, we almost never perform CT of the head with contrast because MRI is a much better examination and will almost always be done anyway.

CT angiogram

CT angiogram, or CTA, is an arterial timed exam to look at the arteries of the brain. This is very commonly done in evaluation of stroke, intracranial hemorrhage, and trauma. Aneurysm and vascular malformations are very well evaluated by CTA.

CT venogram

A CT venogram, or CTV, is very similar to a CTA, but the timing is a little later. This is optimal for evaluating the veins of the brain for thrombosis or trauma.


We don’t use many x-rays in neuroradiology, but you may see a few to evaluate for shunts and hardware. CT is almost always better, particularly in trauma.

MRI brain

MRI of the brain is a workhorse of neuroradiology. It has great tissue contrast and is excellent for finding diseases of the brain. Some limitations include availability/expense, limitations in patients who have devices, and the time that it takes. There are a variety of sequences that we use in MRI of the brain, and each tells us a little bit of something different about the brain.

T1 precontrast

The T1 precontrast images are useful for evaluating the overall brain structure and alignment. It is also useful for comparing to postcontrast imaging to see how much enhancement there may be.


T2 images are water-sensitive images on which most pathology will show up as bright. It is great for looking at edema, swelling, and fluid-filled structures. FLAIR images are very similar to T2, but the fluid has been suppressed. This helps pathology be more obvious and easier to detect.

Diffusion (DWI)

This is a measure of how well water moves through tissue. In stroke, water moves into cells and can’t move as freely, resulting in areas of stroke being bright on DWI.

Blood sensitive imaging

Gradient imaging (GRE) or susceptibility weighted imaging (SWI) provide a chance to better detect calcium and blood, which will appear dark.

T1 postcontrast

These T1 images are obtained after an intravenous contrast agent has been administered. Things that enhance, or are bright on these images but not the precontrast images, accumulate contrast. This often occurs in pathologies like tumors because the blood-brain barrier has become leaky.

MRA head

MRA of the head is (most frequently) a noncontrast technique to evaluate the vessels of the brain. This is a great technique to see the vessels of the brain if you are not in a rush, particularly to see aneurysms and vascular malformations.

MRA neck

Similar to MRA of the head, this is vessel imaging of the neck. You can do it without contrast or with contrast, but contrast often helps see the vessels at the thoracic outlet better.

MR venogram

Like a CT venogram, an MR venogram is a dedicated exam to look at veins to look for venous thrombosis or venous injury.


Thanks for tuning in to the video. Hopefully you learned a lot about the types of imaging used to evaluate the brain.

See all of the search pattern videos on the brain course playlist.

Brain Vascular Malformations

In this video, Dr. Bailey discusses the most common vascular malformations and reviews the most common grading system for arteriovenous malformations (AVMs), the Spetzler-Martin grading scale.

Introduction to arteriovenous malformations

Arteriovenous malformations are vascular anomalies consisting of feeding arteries, a nidus where the shunt is located, and one or more draining veins. AVMs can be compact or have a diffuse nidus. There can be surrounding gliosis and potentially calcification on CT or calcium sensitive imaging. Imaging will demonstrate flow voids,

Spetzler-Martin grading scale

The Spetzler-Martin scale gives a score between 1-5, with points assigned based on size (< 3 cm, 1 point; 3-6 cm, 2 points, and > 6 cm, 3 points), involvement of eloquent cortex (1 point), and involvement of deep veins (1 point). This score can help predict the potential surgical morbidity and mortality.

Arteriovenous fistulas

Arteriovenous fistulas (AVFs) are abnormal shunts most commonly from dural vessels. These are abnormal connections between these arteries and the dural venous drainage. Often external carotid artery branches will be dilated as they are the abnormal supply. There is arterialization of the dural venous sinuses. These are most common at the transverse-sigmoid sinus junction.

Cavernous malformations

Cavernous malformations are slow flow venous malformations that have well contained abnormal veins and vessels. They have areas of hemosiderin with T1 hyperintensity, T2 hyperintensity centrally and a peripheral hemosiderin rim. They may have an abnormal adjacent vessel or developmental venous anomaly (DVA). On CT, they may be hyperdense and can be confused with hemorrhage, but central calcification is a good clue. Multiple cavernous malformations can occur in familial syndromes.

Developmental venous anomaly (DVA)

DVAs are congenital venous malformations draining normal veins. These are the most common vascular malformation and are benign. They appear as a branching tree of abnormal venous drainage going to normal veins.

Capillary telangiectasia

These are slow flow capillary malformations that are incidentally found. They have stippled enhancement and you may see something on the blood sensitive imaging (GRE or SWI). There is usually no abnormal edema or FLAIR.

Thanks for tuning in to this video about intracranial vascular malformations. Please check out the additional vascular videos on the site.

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Circle of Willis

In this video, Dr. Bailey reviews the anatomy of the Circle of Willis, or the confluence of the internal cerebral and basilar arteries within the brain. She reviews the normal anatomy, talks about some common variants you may encounter, and introduces a few less common variants.

Introduction to the Circle of Willis

The Circle of Willis is the circular anatomical construct of vessels made up by the internal carotid arteries, the basilar artery, and their intracranial proximal branches. This includes the anterior and posterior communicating arteries and the anterior, middle, and posterior cerebral arteries.

Posterior circulation

The posterior circulation includes the posterior cerebral arteries, the basilar artery, the superior cerebellar artery, the anterior inferior cerebellar artery (AICA), and the posterior inferior cerebellar artery (PICA). The AICA is particularly variable and may be hard to see, particularly on 3D imaging. The PICA arises from the vertebral artery and may also vary in size from one side to the other.

Common variants

One particularly common variant is a vertebral artery that terminates in PICA. That is, there is either no or a very vertebral artery is seen distal to the PICA origin. Dolichoectasia is a tortuous and prominent basilar artery larger than 4.5 mm in transverse diameter. It is also a common variant to have no posterior communicating arteries (P-comms). A fetal PCA, is vessel that arises from the posterior communicating artery with an absent or very small P1 segment of the PCA. A hypoplastic A1 is a small A1 on one side, with both A2 segments arising from one side. The A1 segments may arise at various levels and be tortuous. An azygous ACA is a single, or unpaired, ACA in the A2 segment where both sides fuse and there is a common ACA. Sometimes you can have the opposite and have 3 A2 segments. Any of the arteries can also be duplicated, or you can have a fenestration, a small wall within the center of the vessel. Fenestrations can mimic thrombus but they are often very linear along the course of the vessel.

Less common variants

The persistent trigeminal artery is a persistent fetal connection between the anterior and posterior circulation at the level of trigeminal artery. It is the most common persistent fetal connection and passes through Meckel’s cave (the trigeminal cistern).  

It’s also possible to see a missing vessel, such as an absent ICA. In these cases, they may be congenitally absent or chronically occluded.

Thanks for tuning in to this video about the normal and variant anatomy of the circle of willis. Please check out the vascular imaging page on the site.

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