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.
Introduction
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
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
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
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.
Tumor
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
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.
Summary
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.