Tag: Medical students

Pages geared towards the education level of a medical student.

Temporal bone CT search pattern

Posted on by Katie Bailey, MD

Temporal bone CT search pattern

Today we have a special guest, Dr. Katie Bailey from the University of South Florida who is presenting her approach to the temporal bone. Special thanks to her for this great video, and hopefully we will be having a lot of great new content from her in the future. This video will be part 1 of 2 in overviewing a starting approach to reviewing the temporal bone.

In this video, she goes through her structure approach to CT of the temporal bone. This approach is based upon an outside-in strategy, where you first look at the external ear, the middle ear, and then the inner ear. The coronal view is a nice place to start.

The key feature of the external ear is the external auditory canal, which should be patent but have a thin lining of mucosa. The external auditory canal ends at the scutum a thin sliver of bone along the top of the EAC.

The middle ear begins at the tympanic membrane, which should be so thin you can barely see it. The tympanic membrane articulates with the long arm of the malleus. A key space above the scutum is called Prussak’s space, which is a common location for cholesteatomas. The middle ear should only contain soft tissue and air. The middle ear is divided into upper (epitympanum), middle (mesotympanum), and lower (hypotempanum) segments. You should also be able to see the footplate of the stapes articulating with the oval window.

The mastoids connect with the middle ear and should be filled with air (no fluid or soft tissue). The roof of the mastoids is the tegmen mastoideum.

The inner ear contains the cochlea and semicircular canals. The cochlea should have 2 ½ turns and be surrounded by bright cortical bone. You have 3 semicircular canals (superior, lateral, and inferior) and should be about the same width. The internal auditory canal is hard to evaluate by CT but should be roughly a similar diameter with no expansion or loss of bone.

The facial nerve canal can be confusing. It is easiest to find at the stylomastoid foramen. You can follow it superiorly before turning and going under the lateral semicircular canal. The bone should be intact until it reaches the geniculate ganglion.

You can then turn to the axial views and review the ossicles. The malleus and incus should look like an ice cream cone. Another key feature is the fissula ante fenestrum, or the cortical bone next to the cochlea. This is a common place where otosclerosis can begin.

Finally, you want to review the axial images for everything out of the temporal bone. This includes the brain, sinuses, orbits, nasal cavity, salivary glands, and visible portions of the pharynx.

Summary. A coronal, outside-in approach to the temporal bone is a nice way to systematically review the temporal bone.

Thanks for tuning in and be sure to come back to check out part 2, temporal bone pathology. Or you can see all of the temporal bone videos or all the search pattern videos.

 

See this and other videos on our Youtube channel

Temporal bone playlist

Posted on by Katie Bailey, MD

Temporal bone

This is a collection of videos about the temporal bone. The temporal bone can be intimidating, especially to those just beginning their review of temporal bone imaging, particularly computed tomography (CT). These videos show you a systematic approach to the temporal bone which can help you master the basics and give you a foundation as you move on to learning more specifics about the pathology.

Vascular Imaging of the Head and Neck – Case D

Posted on by Brent Weinberg, MD

Vascular Imaging of the Head and Neck – Case D

his case is the fourth and final case that goes with the vascular capstone course. On that page, there is a scrollable case that you can go through to teach you how to approach a CTA of the head in a real patient.

This case is a 41 year-old man after a trauma in a motor vehicle collision (MVC). Take a look and see what you think before continuing on (https://bit.ly/CTAcaseD).

Starting with the CTA of the neck, this is not a normal case. If you follow your normal search pattern, you will see that there are a number of abnormalities, starting from the right internal carotid artery (ICA), which is lumpy and irregular looking. The left ICA is worse, with areas of narrowing, outpouchings, and linear filling defects that represent little areas of the intima that are lifted up by trauma. The little outpouchings along the margins of the vessel are little pseudoaneurysms, or areas where the vessel is injured and contrast is able to leak out into the surrounding area of damaged vessel. Both vertebral arteries are also abnormal with multifocal irregularity and a small pseudoaneurysm on the right.

This is a dramatic example of traumatic vascular injury in the neck. After high energy or penetrating (think gunshot or stab wound), the great vessels can be injured and jeopardize the blood supply to the brain. These injuries are graded on the Denver, or Biffl, scale which ranges from 1-5. You can read more about it on Radiopaedia. Injuries to the vessels in the neck are most commonly pseudoaneurysms, meaning that one layer or more of the vessel is injured and the wall of the aneurysm does not contain all the layers (intima-media-adventitia). Contrast this to intracranial aneurysms, which are true aneurysms and the wall contains all the layers.

This is the last of the case examples for the vascular capstone course. If you haven’t already, I recommend going back to the vascular capstone course, where you can review the other browseable cases with explanations.

The capstone overview is here, if you’d like to see all the cases and videos.

Or, see all of the vascular capstone videos in the vascular imaging capstone playlist.

Vascular Imaging of the Head and Neck – Case C

Posted on by Brent Weinberg, MD

Vascular Imaging of the Head and Neck – Case C

This case is the third of four cases that go with the vascular capstone course. On that page, there is a scrollable case that you can go through to teach you how to approach a CTA of the head in a real patient.

This case is a 43 year-old woman with seizure. Take a look and see what you think before continuing on ( https://bit.ly/CTAcaseC).

On the noncontrast CT, you see some high density material in the right frontal lobe. It is more dense than contrast, which is consistent with calcium. If you look more closely at the morphology, it is almost curvilinear or tubular, giving the impression that it might be calcification along vascular structures. The sulci of the frontal lobe are effaced with masslike effect on the brain.

While the diagnosis is uncertain, there are enough features to make us think that there is an underlying vascular malformation. To check, we need to do some sort of vascular imaging. The most readily available and fastest is to do a CT angiogram.

On the CT angiogram, the proximal vessels are normal, but the abnormalities start at the proximal middle cerebral artery (MCA) and anterior cerebral artery (ACA) on the right. There are too many vessels in this region and they are too tortuous. If you follow them up, they go to a large and tortuous vascular abnormality in the right frontal lobe.There are enlarged draining veins that empty into the superior sagittal sinus.

This is the classic imaging appearance of arteriovenous malformation (AVM) within the brain. AVMs are congenital vascular abnormalities that consist of an abnormal connection of arteries and veins with a tangle of abnormal vessels, the nidus. Go on and look at the volume rendered (VR) reconstruction and the coronal maximum intensity projection (MIP) images to better understand what this abnormality looks like.

Once you’ve finished this video, I recommend going back to the vascular capstone course, where you can review the other browseable cases with explanations. The capstone overview is here , if you’d like to see all the cases and videos.

Or, see all of the vascular capstone videos in the vascular imaging capstone playlist.

Vascular Imaging of the Head and Neck – Case B

Posted on by Brent Weinberg, MD

Vascular Imaging of the Head and Neck – Case B

This case is the second of four cases that go with the vascular capstone course. On that page, there is a scrollable case that you can go through to teach you how to approach a CTA of the head in a real patient.

This case is a 47 year-old woman with new neurologic symptoms. Take a look and see what you think before continuing on (https://bit.ly/CTAcaseB).

The patient in this case has scattered small infarcts in the left MCA distribution on diffusion weighted imaging from an MRI (top left window). This raises suspicion for an underlying vascular abnormality. Remember, for stroke and vascular supply issues, you want to include CTA of the neck because these vessels supply the vessels of the circle of Willis.

On the CTA, you see multiple abnormalities. The right internal carotid artery (ICA) is tortuous and irregular in the superior neck, which is highly atypical for a patient of this age. The left internal carotid artery (ICA) is even more abnormal, with smooth tapering of the vessel to severe narrowing just above the bifurcation. The low density filling defect is thrombus, some of which is probably under a dissection flap and some of which is free-floating in the vessel. The more distal ICA also has tortuosity and narrowing similar to the right, confirming the abnormality is bilateral.

Don’t forget to complete your search pattern, but the vertebral arteries and intracranial vessels are pretty normal.

Given the multiple areas of vascular narrowing of the cervical carotid in a middle age woman with an ICA dissection on the left, this patient most likely has fibromuscular dysplasia (FMD). Fibromuscular dysplasia is the most common vasculopathy in middle-aged women and frequently affects the renal arteries, ICAs, and vertebral arteries. Characteristic findings are the beads on a string appearance of the vessel with multifocal areas of narrowing interspersed with dilation.

Once you’ve finished this video, I recommend going back to the vascular capstone course, where you can review the other browseable cases with explanations. The capstone overview is here, if you’d like to see all the cases and videos.

Or, see all of the vascular capstone videos in the vascular imaging capstone playlist.

Vascular Imaging of the Head and Neck – Case A

Posted on by Brent Weinberg, MD

Vascular Imaging of the Head and Neck – Case A

This case is the first of four cases that go with the vascular capstone course. On that page, there is a scrollable case that you can go through to teach you how to approach a CTA of the head in a real patient.

This case is an 80 year-old woman who presented with altered mental status. Take a look and see what you think before continuing on.

The patient in this case has subarachnoid and parenchymal hemorrhage on a noncontrast CT. Because aneurysms and vascular malformations are possible causes of subarachnoid hemorrhage, we proceeded with vascular imaging, or a CT angiogram of the head, to look for aneurysms or other possible vascular causes. Remember, for an intracranial hemorrhage you don’t need the CTA of the neck because these don’t commonly have any pathology that can explain intracranial hemorrhage.

On the CTA, you see multiple abnormal outpouchings of the intracranial vessels, otherwise known as an aneurysm. Intracranial aneurysms are abnormal outpouchings of the vessels thatt contain all the layers of the vessel wall (true aneurysms). They have a risk of rupture of several percent per year, and can be treated with surgical clipping or endovascular methods such as coils. Remember, it is common for patients to have more than one aneurysm, as is seen in this case.

Once you’ve finished this video, I recommend going back to the vascular capstone course, where you can review the other browseable cases with explanations. The capstone overview is here, if you’d like to see all the cases and videos.

Or, see all of the vascular capstone videos in the vascular imaging capstone playlist.

Vascular Imaging of the Head and Neck – Pathology

Posted on by Brent Weinberg, MD

Vascular Imaging of the Head and Neck – Pathology

This lecture is the third part of a capstone course we have for our 4th year medical students. In the first lecture, we discussed general concepts about how to approach vascular imaging of the head and neck, including angiography, CT angiography, MR angiography, and ultrasound. The second part of the lecture covers a general search pattern for vascular imaging of the head and neck on a CT angiogram. To see more about this course, check out the full vascular capstone page. It contains interactive cases that you can scroll on your own as well as some additional videos explaining them.

In this lecture, we welcome back our special guest, Dr. Cynthia Wu, who is going to go over some of the common pathologies you might encounter on vascular imaging of the head and neck.

Common pathologies

There are a few common pathologies you might be looking for on vascular imaging of the head and neck, including aneurysm, thrombosis, dissection, and vascular malformations. Read on to learn more about each one.

Aneurysms

Aneurysms are abnormal outpouchings of the vessels. Sometimes they contain all the layers of the vessel wall (true aneurysms) or may be contained ruptures of one or more of the walls (false aneurysms, or pseudoaneurysms). Most intracranial aneurysms are true aneurysms while aneurysms in the neck are pseudoaneurysms.

Thrombosis

Thrombosis is occlusion of a vessel secondary to a blood clot. This is most commonly seen or suspected in the setting of a stroke, and can arise from rupture of an atherosclerotic plaque or from transmission of a thrombus more proximal in the circulation, such as from a cardiac valve or in the internal carotid artery. Most of the time, a thrombus will appear as abrupt severe narrowing or truncation of a vessel.

Thrombosis can also occur in veins, such as the dural venous sinuses. Venous thrombus will more commonly appear as a central filling defect.

Dissection

Dissection is a tear or injury to the lining of the artery, or intima. In this case, then blood goes into the space between the layers of the vessel wall, an area known as the false lumen. When the vessel is large enough, this vessel may fill with contrast on the injection, but in smaller vessels this may thrombose and be seen as a smooth tapering or narrowing of the vessel that can even result in occlusion. You can also sometimes get irregular enlargement of the vessel past it, or pseudoaneurysm.

Vascular malformations

Arteriovenous malformations, or AVMs, are abnormal clusters of vessels which have abnormal connections between the terminal arteries and veins. This results in a shunt, or passage of blood from an artery to a vein without a terminal capillary bed. Arteries and veins then are enlarged and at higher risk of rupture. The Spetzler Martin grading system is a grading system used to rate the risk of surgical mortality on resection which can help guide management.

What’s next?

Once you’ve finished this video, I recommend moving on to the next section of the vascular capstone, where you can review individual browseable cases with explanations. The capstone overview is here, if you’d like to see all the cases and videos.

Or, see all of the vascular capstone videos in the vascular imaging capstone playlist.

Introduction to Vascular Imaging of the Head and Neck

Posted on by Brent Weinberg, MD

Introduction to Vascular Imaging of the Head and Neck

This lecture is the first part of a capstone course we have for our 4th year medical students about how to approach vascular imaging of the head and neck, including angiography, CT angiography, MR angiography, and ultrasound. To see more about this course, check out the full vascular capstone page. It contains interactive cases that you can scroll on your own as well as some additional videos explaining them.

In this lecture, we have a special guest, Dr. Cynthia Wu, who is going to explain to us some of the general concepts behind vascular imaging of the head and neck, different techniques you can do to perform vascular imaging, and when you might order each type of study.

Basic concepts

In general, to see vessels better on imaging, we need to use some sort of contrast to differentiate the vessels from the surrounding tissues. For techniques like CT, we can use an injected contrast agent to see the vessels. For other techniques such as MR angiography and ultrasound, we can use intrinsic properties of flowing blood to emphasize the vessels.

This section covers the key concepts behind how we see the vessels for these major techniques.

When do I order these tests?

Once you know about the different possible techniques, then you have to figure out when you would possibly order them. Each technique (CTA, MRA, and US) have different advantages and disadvantages that make them more or less suited to different scenarios.

What’s next?

Once you’ve finished this video, I recommend moving on to the next section of the vascular capstone, where you can learn a general strategy for interpreting a CT angiogram of the head and neck.

The capstone overview is here, if you’d like to see all the browseable cases and videos.

Or, see all of the vascular capstone videos in the vascular imaging capstone playlist.

Multiple sclerosis – white spots and red flags – part 2

Posted on by Michael Hoch, MD

Multiple sclerosis – white spots and red flags – part 2

Mimics and Variants

Demyelinating disease is a common situation we encounter in neuroradiology, and properly diagnosing and tracking it using MRI is a key skill for neuroradiologists. In this second part of the lecture, Dr. Michael Hoch gives us some tips about other causes of white matter lesion, and information we can use to make our imaging diagnosis of multiple sclerosis more specific.

Clinical history has an important role in determining how specific imaging findings are for multiple sclerosis. Some features may suggest that a patient does not have multiple sclerosis, such as if they are the wrong age (< 20 or > 50 years old), if they have abrupt swift progression, if they have systemic symptoms such as fever or weight loss, and if they have uncommon CNS symptoms such as a movement disorder or meningitis signs. MS lesions also usually occur in some specific locations, such as in the corpus callosum, temporal lobe, periventricular white matter, and juxtacortical white matter.

Mimics of Multiple sclerosis

So, what are some of the common mimics of MS?

Migraine – migraine is the most common cause of non-specific white matter abnormalities in young patients, occurring in more than 50% of patients with migraine

Chronic small vessel ischemia – more common with increasing age, and worsening with risk factors such as diabetes, hypertension, and smoking

CNS vasculitis – an inflammatory syndrome of the intracranial vessels. Be on the lookout if someone has a history of TIAs or thunderclap headache, or systemic symptoms.

Behcet’s disease – a vasculitis most common in young males, characterized by brainstem involvement and oral ulcers

Susac syndrome – an autoimmune microangiopathy overlapping MS in age distribution. However, patients more often have a triad of encephalopathy, hearing loss, and visual changes. Corpus callosum involvement is more likely to be central. 

CADASIL – an autosomal dominant syndrome characterized by frequent infarcts. Look out for the characteristic locations in the temporal poles, external capsules, and paramedian superior frontla lobes. It is also usually quite symmetric.

Other rarer mimics are Neuro-Sweets disease and Lyme disease, which can cause white matter abnormalities.

Key take home points of this lecture include:

  • Multiple sclerosis is a clinical diagnosis, not an MRI diagnosis
  • White spot lesion location matters
  • Juxtacortical lesions must touch the cortex
  • Aggressively window the spine to look for cord lesions
  • Leptomeningeal enhancement is possible in multiple sclerosis

Variants of demyelinating disease

There are several common variants that you should know about across the demyelinating spectrum:

ADEM – acute disseminated encephalomyelitis – an autoimmune mediated and often self limited fulminant demyelinating process. May be related to a viral illness or vaccination.

Marburg disease – a clinically fulminant demyelinating disease usually affecting younger patients with a febrile prodrome.

Balo concentric sclerosis – a rare and monophasic demyelinating disease characterized by large lesions with alternating zones of demyelination/myelination

Tumefactive demyelinating lesions (TDL) – large and often fulminant demyelinating lesions that have mass effect and can mimic tumors. Perfusion imaging with low blood volumes can help differentiate from masses.

Neuromyelitis optica (NMO) – a demyelinating syndrome characterized by post-chiasmatic optic neuritis and long segment spine lesions. This is mediated by an aquaporin-4 antibody.

Progressive multifocal leukoencepalopathy (PML) – a JC virus mediated demyelinating lesion that occurs in immune suppressed patients. Usually has little or no enhancement and favors a subcortical location.

Summary

In summary, there are a couple of key things to keep in mind when evaluating potential demyelinating lesions:

  • Read the chart for clinical red flags
  • Look at the MRI for imaging red flags, like strokes, hemorrhages, cysts, findings that are too symmetric, subcortical, or normal
  • Remember that white matter lesions from migraine and microvascular disease are far more common that multiple sclerosis
  • NMO has differentiating features
  • PML is a rare complication of immune suppressing medications in MS patients

 

The level of this lecture is appropriate for radiology residents, radiology fellows, and trainees in other specialties who have an interest in imaging or treating patients with potential demyelinating diseases.

This video is part of a two part series on multiple sclerosis presented by Dr. Hoch.

If you haven’t seen it already, go back and check out part 1, in which Dr. Hoch discusses the key findings of demyelinating lesions.

Multiple Sclerosis: White Spots & Red Flags

Posted on by Michael Hoch, MD

Multiple sclerosis – white spots and red flags

Demyelinating disease is a common situation we encounter in neuroradiology, and properly diagnosing and tracking it using MRI is a key skill for neuroradiologists. In this two part lecture, Dr. Michael Hoch instructs us on how to approach white matter abnormalities in the brain and use them towards making a diagnosis of multiple sclerosis. The first part is focused on key tips on making a diagnosis of demyelinating disease while the second is focused on potential pitfalls.

Be sure to watch them both to get the complete overview of imaging findings of common autoimmune and inflammatory conditions.