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.

Intracranial infections – 5 – Other

There are a few other infectious considerations which have special imaging appearances and which you should keep in mind. This includes neurocysticercosis and Creutzfeldt-Jakob disease (CJD).

This lecture is the final in a series of 5 about imaging intracranial infection and covers diffuse brain infections. The series of videos will cover:
1) General considerations
2) Diffuse infections
3) Focal infection
4) Immunocompromised patients
5) Other considerations

Neurocysticercosis is a brain infection caused by the pork tapeworm. It is a common infection in Latin America and is a common acquired cause of seizure. While the imaging appearance varies with stage, it most commonly has a cystic lesion in the brain parenchyma with peripheral enhancement and surrounding edema. Racemose cysticercosis can involve the CSF spaces, including the ventricles or sylvian fissures. Chronic cysticercosis commonly has punctate peripheral calcification, which can be a clue in patients with this infection.

Creutzfeldt-Jakob disease (CJD) is a prion disease which is commonly thought of as infection because of its association with contaminated beef (bovine spongiform encephalopathy), but most cases (approximately 85%) are spontaneous, with the remainder familial/inherited. Image findings include bilateral symmetric abnormalities of the basal ganglia and thalamus, including signs such as the pulvinar sign or hockey stick (describing thalamic involvement). Cortical linear involvement, or cortical ribboning, is also common.

In summary, there are a variety of infections in the brain ranging from meningitis/encephalitis through focal infections such as abscess and PML. Awareness of these infections is necessary to make an appropriate diagnosis in these patients.

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

Other videos on the intracranial infection playlist are found here.

 

Intracranial infections – 4 – Immunocompromise

Immunocompromised patients have special considerations for infection of the brain, including HIV encephalopathy, toxoplasmosis, cryptococcus, and progressive multifocal leukoencephalopathy (PML).

This lecture is the fourth in a series of 5 about imaging intracranial infection and covers special considerations in immunocompromised patients. The series of videos will cover:
1) General considerations
2) Diffuse infections
3) Focal infection
4) Immunocompromised patients
5) Other considerations

HIV encephalopathy is a result of direct infection of the white matter in the brain by the HIV virus. It is bilateral, symmetric, and tends to progress over time. There is usually no enhancement.

Toxoplasmosis is the most common opportunistic infection of the brain in HIV patients. Common imaging findings include multifocal masses and enhancement, often involving the basal ganglia. The “target sign”, or bullseye like appearance of the enhancing lesions, is common. The imaging appearance of toxoplasmosis overlaps a great deal with lymphoma, which tends to be more solidly enhancing and involves the periventricular white matter more. Often a treatment trial for toxoplasmosis is begun with short term follow-up imaging to see if the patient improves.

Cryptococcus is also a common brain infection in immunocompromised patients. It’s most common manifestation is enlargement of the perivascular spaces of the basal ganglia, or gelatinous pseudocysts. This typically does not have much, if any, postcontrast enhancement.

Finally, progressive multifocal leukoencephalopathy (PML) is an infection caused by reactivation of a virus (JC virus) in the brain parenchyma in the setting of immune suppression, either because of HIV or immunosuppressive medications. It is manifested by bilateral, subcortical, asymmetric white matter abnormalities without enhancement. Treatment is restoration of the immune system, but outcomes are poor.

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

Other videos on the intracranial infection playlist are found here.

 

Intracranial infections – 3 – Focal Infections

Focal infections are those infections of the brain which are walled off either within the brain parenchyma or in the extra-axial space, such as subdural or epidural abscess.

This lecture is the third in a series of 5 about imaging intracranial infection and covers focal brain infections. The series of videos will cover:
1) General considerations
2) Diffuse infections
3) Focal infection
4) Immunocompromised patients
5) Other considerations

Abscess in the brain, regardless of location, is characterized by hyperintensity on diffusion weighted imaging. There is often mass effect, surrounding edema, and a peripherally enhancing fluid collection. Abscess can arise from local infection, such as a surgery or sinusitis, or can occur from hematogenous spread.

Ventriculitis is a highly morbid complication of intracranial abscess, as can be found when pus spills into the ventricle. Sinus thrombosis is also a potential complication of intracranial abscess.

One key feature which separates the diffusion restriction of abscess from lymphoma is that the abnormal DWI is in the center of a peripherally enhancing collection, whereas in lymphoma it is the enhancing portion itself which is restricted.

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

Other videos on the intracranial infection playlist are found here.

 

Intracranial infections – 2 – Diffuse infections

Diffuse infections are those infections of the brain which affect large regions of the brain or affect the brain diffusely. This includes meningitis, encephalitis, and ventriculitis.

This lecture is the second in a series of 5 about imaging intracranial infection and covers diffuse brain infections. The series of videos will cover:
1) General considerations
2) Diffuse infections
3) Focal infection
4) Immunocompromised patients
5) Other considerations

Meningitis is infection centered in the surfaces of the brain, particularly the pia and subarachnoid space. This can be caused by bacteria, viruses, or other unusual pathogens like tuberculosis or fungi. Imaging findings include incomplete FLAIR suppression and leptomeningeal enhancement. Basilar meningitis is a special subset of meningitis affecting the spaces around the brainstem and skull base. It is special because it is more likely to be an unusual pathogen. Sarcoidosis and leptomeningeal metastases can also mimic an infectious meningitis.

Encephalitis is similar to meningitis, although it is centered in the brain parenchyma. There is a great deal of overlap between these conditions and they can often be seen together (meningoencephalitis). Compared to meningitis, encephalitis is even more likely to be viral. The medial temporal lobes are commonly involved, and when they are a diagnosis of herpes encephalitis should be considered. This encephalitis caused by HSV can be rapidly debilitating or fatal. Encephalitis can also be autoimmune or inflammatory, mimicking infection.

Finally, ventriculitis is infection within the CSF of the ventricles themselves. This is often seen by abnormal FLAIR or diffusion in the ventricles, sometimes with periventricular enhancement. This can be from a primary pathogen with sparing of the parenchyma or as a complication of meningitis or abscess. Ventriculitis also has somewhat poor prognosis.

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

Other videos on the intracranial infection playlist are found here.

 

Intracranial infections

Intracranial infections are a common consideration in neuroradiology. Patients can present with altered mental status and may have systemic signs such as fever. The radiologist needs to know how to evaluate these findings on imaging and correlate them with systemic tests, such as lumbar puncture and echocardiogram.

This lecture is divided into 5 parts:
General considerations
Diffuse infections
Focal infection
Immunocompromised patients
Other considerations

Be sure to watch them all to get the complete overview of imaging intracranial infection.

Intracranial infections – 1 – General principles

Intracranial infections are a common consideration in neuroradiology. Patients often present with altered mental status, often with a fever or systemic symptoms. The radiologist needs to know how to proceed in those instances, both in terms of what types of imaging to perform and how imaging findings might relate to the systemic findings.

This lecture is the first in a series of 5 about intracranial infection and covers general principles behind imaging the patient with suspected intracranial infection. The subsequent 4 videos cover additional more specific considerations.

The two main imaging techniques used in imaging intracranial infection are CT and MRI. CT is a rapid screening test which can detect edema, hemorrhage, midline shift, and prominent masses. It is available in the vast majority of hospitals (at least in the US, but also many abroad), and doesn’t require much compliance from the patient. It also requires no screening for metallic implants and other MRI considerations.

MRI is much better at evaluating intracranial infection however. Key sequences include DWI, FLAIR, T2, and T1 postcontrast. DWI is ideal for seeing pus and infarct. FLAIR is ideal for imaging edema. T2 can give you some unique clues, as a few diseases such as lymphoma, tuberculosis, and abscess can be T2 dark. Many infections also cause breakdown of the blood brain barrier, which shows up as enhancement on postcontrast MRI.

Lumbar puncture and echocardiogram are the two main systemic tests which may help you determine if an intracranial infection is present. LP directly assesses for infections agents and inflammatory cells in the CSF, while echocardiogram indirectly assesses for bacterial endocarditis, which can spread to the CSF through emboli.

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

Other videos on the intracranial infection playlist are found here.

CT (computed tomography) face radiology search pattern

When you start taking call as a radiology resident, a common test you are going to encounter is a maxillofacial CT, or face CT. This is especially true if you are taking call at a level 1 or level 2 trauma center. A lot of times, this is done in conjunction with a head and/or cervical spine CT. This is an extremely common test in the setting of trauma, including assault and car accidents (MVA or MVC). The key in these settings is to rule out a significant fracture or soft tissue injury to the face.

Because there are a lot of structures, it is important to have a useful search pattern. Reconstructions, especially the coronal reconstruction, are key when interpreting CT of the face. These allow you to see key structures that are parallel to the slice plane on axial images. Symmetry is extremely helpful, as the left should match the right. Additionally, making sure all the fat and fascia planes are clean is very useful.

This video will walk you through a step-by-step approach to evaluating a CT of the face. I recommend a pattern where you start with the coronals at the cranial (top) part of the image, and then work your way down. In this way, you can look at the brain, orbits, sinuses, palate, mandible, and so forth, minimizing the risk of missing a significant finding. Then you can repeat the pattern with the axial images. Finally, the sagittal images are a nice troubleshooting tool, especially for the mandible and cervical spine. As you practice, you will find you can move more quickly through your search without necessarily focusing on each individual element for too long.

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 be involved with patients with facial injuries and other abnormalities.

 

See this and other videos on our Youtube channel.