How to read a CT angiogram (CTA) of the Head and Neck

With increasing ability to image vascular phenomena, such as stroke and vascular malformations, through the use of very efficient and high speed computed tomography scanner (CT), we now have the ability to perform angiographic imaging of large segments of the body at one time. This has led to an explosion of vascular imaging of the head and neck to look for a variety of pathologies, including stroke, vascular malformations, and other vascular abnormalities. Every starting radiology resident needs a firm foundation in how to interpret these images.

Overview

Because there are a ton of images and a ton of structures that you need to look at, you really need a regimented approach, or search pattern, to use as you look through the images. In this video, I teach you how to look at a CT angiogram of the head and neck from start to finish so you can learn how to do it yourself. There are interactive examples that you can follow along on the vascular capstone page.

In this video, we go through a normal example.

I divide the study into the CTA of the neck, which I review first, and the CTA of the head, which I review second. My pattern goes as follows:

Nonvascular structures

I first like to look at all the nonvascular structures to make sure I’m not missing anything. I look at the lungs, the thyroid, the soft tissues of the neck (particularly to look for lymph nodes or mucosal masses), and the brain. I use a soft tissue window to look at these. Then I go back through with a bone window to look at the bones.

Neck Vessels

For the vessels of the neck, I use an approach that first does anterior vessels and then posterior vessels, moving from right to left. I follow the right common carotid artery through the bifurcation, and then follow the internal carotid to the skull base. I then repeat this pattern for the left carotid system. Then, I start from the right vertebral origin and follow it up to the skull base. Then the left vertebral artery. Once I’m finished, I restart at the skull base.

Head Vessels

For the vessels of the head, I follow a similar approach. I first follow the right ICA through the carotid terminus and then follow the right middle cerebral artery (MCA) and anterior cerebral artery(ACA). Once finished, I return to the skull base and repeat this pattern on the left. I then move to the posterior circulation, where I first follow the right vertebral artery, the basilar artery, and the right posterior cerebral artery (PCA). Then I repeat it on the left. My final search is to quickly look at the deep venous sinuses.

Summary

While others may have a different strategy, the most important part is to have a strategy and stick to it. This pattern of dividing the study into discrete sections will help you see all the findings and describe them accurately when reading cases on your own.

See all of the search pattern videos on the Search Pattern Playlist.

Imaging CNS autoimmune and inflammatory disease

Vascular Processes

This is the sixth and final lecture in a case based review of imaging of the brain and spine for autoimmune and inflammatory conditions. We will cover the MRI findings of some of the common conditions and some potential pitfalls and mimics.

This lecture covers intracranial vasculopathies, including central nervous system (CNS) vasculitis, Moya Moya disease, CADASIL, and MELAS. These vasculopathies can have a similar imaging appearance.

CNS vasculitis

CNS vasculitis is a process affecting the vessels which supply the brain with blood/oxygen. This can be a primary CNS process or can be associated with other systemic vasculopathies, such as lupus. The imaging manifestations are unexpected infarcts that are out of proportion for age and other causes of infarct. On vascular imaging, you will see areas of narrowing followed by areas of dilation or normal caliber, almost like beads on a string. While this can be caused by atherosclerotic disease, usually it will be out of proportion for age.

Vessel wall imaging

Vessel wall imaging is a specialized technique to look for inflammation in the walls of intracranial vessels. This consists of specialized sequences that suppress both fat and flow so you can see enhancement in the walls. On vessel wall imaging, vasculitis tends to enhance circumferentially while atherosclerotic disease enhancement is more eccentric. This is a useful advanced technique.

Moya Moya disease

Moya moya disease is a primary obliterative angiopathy which primarily occurs in young Asian women. In this disease, the large vessels of the circle of Willis, namely the middle cerebral artery, are obliterated and replaced with a number of abnormal collateral vessesl. This leads to a characteristic “puff of smoke” appearance on angiography. Patients may present with multiple strokes or hemorrhage and can be treated with ECA/ICA bypass. There are other causes of a moya moya like appearance, as it can happen with anything that causes chronic obliterative angiopathy, like sickle cell disease. However, although the terms are used interchangeably, this is really a moya moya syndrome, not the primary disease..

CADASIL

CADASIL, or cerebral autosomal dominant arteriopathy with subcortical infarcts and leukencephalopathy, is a genetic condition associated with the NOTCH3 gene abnormality. These patients have small and middle vessel abnormalities which manifest as a number of subcortical strokes and white matter abnormality in the bilateral temporal lobes. If you see abnormal subcortical temporal white matter, think about CADASIL.

MELAS

MELAS, or mitochondrial encephalopathy with lactic acidosis and stroke-like symptoms, is a similar syndrome where you get stroke-like episodes often preferentially involving the temporal and parietal lobes. They can often improve with time, but it can mimic other vasculopathies and strokes.

Summary and Conclusion

There are a number of vasculopathies which can affect the brain, with the most common being CNS vasculitis and moya moya disease or syndrome. CADASIL and MELAS can also have a similar appearance. This is the last lecture in this series. Please be sure to check out the other lectures in this series.

The level of this lecture is appropriate for radiology residents, radiology fellows, and trainees in other specialties, such as neurology, who have an interest in neuroradiology or may see patients with CNS demyelinating or inflammatory conditions.

Other videos on the autoimmune and demyelinating playlist are found here

Imaging CNS autoimmune and inflammatory disease

Amyloid related disease

This is the fifth lecture in a case based review of imaging of the brain and spine for autoimmune and inflammatory conditions. We will cover the MRI findings of some of the common conditions and some potential pitfalls and mimics.

This lecture covers three central nervous system (CNS) manifestations of amyloid disease: cerebral amyloid angiopathy (CAA), inflammatory amyloidosis, and amyloidomas. While the pathology is similar, the imaging manifestations are markedly different.

Cerebral amyloid angiopathy

Cerebral amyloid angiopathy is a small vessel vasculitis caused by deposition of amyloid beta in the walls of the vessels. The result is a vasculitis manifested by repeat hemorrhages, often in the periphery of the brain or at gray/white junctions, with relative sparing of areas often affected by hypertensive hemorrhage (such as the basal ganglia, thalamus, and pons). Patients are usually over 70 and may have progressive mental decline out of proportion for age. Imaging findings are most visible on gradient or susceptibility weighted T2 images, where you can see the sequelae of chronic hemorrhage. CAA is more common in patients with Alzheimer’s disease and Down’s syndrome, which are also amyloid related diseases.

Inflammatory amyloidosis

Inflammatory amyloidosis is another intracranial manifestation of amyloid disease that may affect slightly younger patients. Imaging findings are similar in that small areas of microhemorrhage can be seen, but the major difference is in the amount of cerebral edema as best characterized on FLAIR and T2 weighted images. Patients with inflammatory amyloid may present with headache, altered mental status, or focal neurologic symptoms. It can be challenging to diagnose, particularly if areas of hemorrhage are not clearly seen, and biopsy may be required.

Amyloidoma

Amyloidomas are tumor-like conditions in which the patients often present with focal neurologic symptoms and an intracranial mass. It often has surrounding edema, but a key feature is its internal T2 hypointensity. On post-contrast imaging, it can mimic a high grade glioma or metastasis because it can enhance avidly. Often resection or biopsy is required because they look so tumor-like.

Summary and Conclusion

Amyloid related disease in the CNS is uncommon, with the most common manifestation a vasculopathy from amyloid deposition in vessels. If accompanied by edema and inflammation, it is called inflammatory amyloid. Masses of amyloid deposition within the brain are uncommon but in rare cases can mimic tumors. All of these disease can be hard to diagnose and can frequently require a biopsy.

The level of this lecture is appropriate for radiology residents, radiology fellows, and trainees in other specialties, such as neurology, who have an interest in neuroradiology or may see patients with CNS demyelinating or inflammatory conditions.

Other videos on the autoimmune and demyelinating playlist are found here

Imaging CNS autoimmune and inflammatory disease

Spine Inflammatory Disease

This is the fourth lecture in a case based review of imaging of the brain and spine for autoimmune and inflammatory conditions. We will cover the MRI findings of some of the common conditions and some potential pitfalls and mimics.

This lecture covers two inflammatory diseases which can occur in the spinal cord: transverse myelitis and sarcoidosis. Multiple sclerosis can also cause an inflammatory myelitis, but it usually is associated with intracranial MS and has shorter segment lesions.

Transverse myelitis 

Transverse myelitis is a common infectious or inflammatory cause of myelopathy in the cervical or thoracic spine. This is most commonly manifested with long segment T2 abnormality (more than one vertebral body in length). It is commonly central and may have enhancement, particularly in the acute phase. It is often associated with a recent viral illness and can be caused by direct viral infection or as inflammatory post-viral syndrome. Treatment is largely limited to symptomatic control and immune suppression similar to treatment of multiple sclerosis.

Sarcoidosis

Sarcoid can affect the spine although it is less common that involvement of the brain. The most common manifestation in the spine is long segment T2 hyperintensity with associated enhancement. The enhancement pattern is often nodular and peripheral, which can help differentiate it from other causes of abnormal cord signal. As with sarcoidosis in the brain, you may also see nodular areas of enhancement or sarcoidomas. The diagnostic workup is similar. You should start by imaging the brain and chest to look for other potential areas of sarcoid involvement. ACE levels or IL-2 surface antigen can also be useful when available.  

Summary and Conclusion

In summary, when you have longer segment T2 hyperintense lesions in the spine, you should think about transverse myelitis or sarcoidosis. There is a broader differential which includes multiple sclerosis, lymphoma, and other tumors (such as astrocytoma or ependymoma). You may not be able to tell without other diagnostic clues, which makes imaging of the brain and correlation with the clinical scenario important.

The level of this lecture is appropriate for radiology residents, radiology fellows, and trainees in other specialties, such as neurology, who have an interest in neuroradiology or may see patients with CNS demyelinating or inflammatory conditions.

Other videos on the autoimmune and demyelinating playlist are found here

Imaging CNS autoimmune and inflammatory disease

Masslike inflammatory disease

This is the third lecture in a case based review of imaging of the brain and spine for autoimmune and inflammatory conditions. We will cover the MRI findings of some of the common conditions and some potential pitfalls and mimics.

This lecture covers two masslike inflammatory diseases which can occur in the orbit and brain. These don’t really fit well into other categories with the exception that they are more likely to have a mass and adjacent expansion.

Orbital inflammatory disease

Orbital inflammatory disease is an infiltrative disease most often seen in the orbit and anterior skull base. It is characterized by masslike replacement of the orbital contents, sometimes with extension in the orbits. It is often T2 intermediate to dark and has avid enhancement. Many cases are associated with IgG4 abnormalities, while other cases are purely idiopathic. This disease was previously called orbital pseudotumor, but it is more exact now to call it IgG4 orbital disease or idiopathic orbital inflammation. The differential diagnosis for this appearance includes metastatic disease, lymphoma, and sarcoidosis.

Sarcoidosis

Sarcoid can also affect the brain, orbits, and spine, and when it does is referred to as neurosarcoidosis. The most common manifestation is leptomeningeal enhancement, but it can be accompanied by parenchymal nodules. It preferentially affects the basal cisterns and skull base. When you have a basilar meningitis, the differential includes metastatic disease (leptomeningeal carcinomatosis), unusual infections (such as fungi, tuberculosis, and other atypical organisms), and sarcoidosis, as was the case here.

Summary and Conclusion

In summary, when you have nodular masslike enhancement centered in the skull base or orbits, there is a pretty limited differential diagnosis. The inflammatory differential includes sarcoidosis and orbital inflammatory disease. Other things such as metastatic disease and atypical infections are also considerations.

The level of this lecture is appropriate for radiology residents, radiology fellows, and trainees in other specialties, such as neurology, who have an interest in neuroradiology or may see patients with CNS demyelinating or inflammatory conditions.

Imaging CNS autoimmune and inflammatory disease

Encephalitis

This is the second lecture in a case based review of imaging of the brain and spine for autoimmune and inflammatory conditions. We will cover the MRI findings of some of the common conditions and some potential pitfalls and mimics.

This second lecture covers causes of encephalitis, including inflammatory and autoimmune etiology. This section also covers infectious encephalitis, which is the most common mimic.

Limbic encephalitis

Limbic encephalitis is an immune mediated encephalitis often associated with neoplasm and a variety of circulating antibodies. It most commonly is manifested as bilateral (asymmetric or symmetric) temporal lobe FLAIR/T2 abnormalities. Enhancement is variable but less common than seen in herpes encephalitis.

Chronic limbic encephalitis

Over time, chronic limbic encephalitis can result in temporal lobe sclerosis and atrophy. Volumetric analysis of the brain and temporal lobes may be useful in highlighting the differences over time.

Lupus encephalitis

Lupus is a systemic autoimmune condition which can be associated with intracranial findings, including encephalitis, vasculitis, and posterior reversible encephalopathy syndrome (PRES). Vessel imaging may be normal, as it tends to affect the small vessels of the brain.

Viral encephalitis

Viral encephalitis has a nonspecific imaging appearance with patchy white matter FLAIR/T2 abnormalities, often involving the temporal lobes. There are a number of causes of viral encephalitis, including herpes, west nile virus, St. Louis encephalitis, and others.

Herpes encephalitis

Herpes encephalitis is the most dreaded of the encephalitis causes because it has high morbidity and mortality. Compared to nonspecific viral and inflammatory encephalitis, it tends to have more enhancement and more DWI abnormality. Patients suspected of having herpes encephalitis should be started empirically on treatment immediately to improve the prognosis.

Summary and Conclusion

The level of this lecture is appropriate for radiology residents, radiology fellows, and trainees in other specialties, such as neurology, who have an interest in neuroradiology or may see patients with CNS demyelinating or inflammatory conditions.

Imaging CNS autoimmune and inflammatory disease

Introduction/Demyelinating disease

This is the first lecture in a case based review of imaging of the brain and spine for autoimmune and inflammatory conditions. We will cover the MRI findings of some of the common conditions and some potential pitfalls and mimics.

This first lecture covers demyelinating disease, with the most common being multiple sclerosis (or MS), neuromyelitis optica (NMO), and acute disseminated encephalomyelitis (ADEM). These are all demyelinating/autoimmune conditions in which the brain loses its normal myelination.

Multiple sclerosis

MS is the most common demyelinating disease, affecting women more than men, with 2 age distribution peaks in younger and middle age women. MS commonly presents with optic nerve or visual symptoms, affects the brain more commonly than the spine, and can result in short segment spine lesions.

Neuromyelitis optica

Neuromyelitis optica, or NMO, is an autoimmune disease characterized by predominantly optic nerve and spine lesions. It is often associated with an antibody to aquaporin 4.

Acute disseminated encephalomyelitis (ADEM)

ADEM is an acute fulminant demyelinating syndrome characterized by acute onset and often many supratentorial lesions. The majority of patients recover, although some may have residual symptoms and it can even progress to death.

Acute hemorrhagic encephalomyelitis (AHEM)

AHEM is a closely related variant of ADEM which is associated with hemorrhage.

Susac syndrome

Susac syndrome is a small vessel vasculitis with small vessel infarcts, most commonly in the retina, cochlea, and periventricular white matter and corpus callosum. It can frequently mimic demyelinating disease because the distribution of lesions is similar.

Summary and Conclusion

The level of this lecture is appropriate for radiology residents, radiology fellows, and trainees in other specialties, such as neurology, who have an interest in neuroradiology or may see patients with CNS demyelinating or inflammatory conditions.

Imaging CNS autoimmune and inflammatory disease

This playlist is a case-based review of autoimmune and inflammatory conditions that can be seen in neuroradiology. MRI findings in the brain and spine are discussed. Common conditions are covered, including demyelinating disease, encephalitis, masslike disease like sarcoid and orbital inflammatory disease, spine inflammatory disease, amyloid, and vascular processes.

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

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 .

Noncontrast MRI cervical spine search pattern

Magnetic resonance imaging (MRI) of the cervical spine is a very commonly encountered test which can be performed for a variety of indications, including degenerative disease, trauma, demyelinating disease, and metastatic disease. Most of these cases will be done without contrast, as most of the information is there on a non-contrast exam.

This video will walk you through a step-by-step approach to evaluating an MRI of the cervical spine. The optimal approach is to use select sequences to evaluate each part of the study in the following order:

Alignment
Vertebral bodies
Marrow signal
Intervertebral discs
Spinal cord/canal
Soft tissues
Individual levels

Each sequence in the study has strengths at looking at one or more of these things. As we walk through, we’ll take a look at how to use each one.

The level of this lecture is appropriate for medical students, junior residents, and trainees in other specialties who have an interest in neuroradiology or may see patients with spine diseases.

See this and other videos on our Youtube channel.