Local cerebral lesion with a ring on CT scan is caused by –
**Core Concept**
A ring-enhancing lesion on a CT scan indicates a localized area of brain tissue damage surrounded by an area of edema, inflammation, or infection. This type of lesion is often associated with a mass effect, which can lead to increased intracranial pressure and neurological symptoms.
**Why the Correct Answer is Right**
The most common cause of a ring-enhancing lesion on a CT scan is a brain abscess. A brain abscess is a collection of pus that forms in the brain tissue, usually as a result of bacterial or fungal infection. The abscess is characterized by a central area of necrotic tissue surrounded by a ring of inflammatory cells, which enhances with contrast on a CT scan. The abscess is often caused by hematogenous spread of infection from a distant site, such as the lungs or heart.
**Why Each Wrong Option is Incorrect**
**Option A:** Cerebral lymphoma is a type of cancer that can cause a ring-enhancing lesion on a CT scan, but it is less common than a brain abscess and typically does not have a central area of necrotic tissue.
**Option B:** Meningioma is a type of tumor that can cause a ring-enhancing lesion on a CT scan, but it is usually located near the surface of the brain and is less likely to cause a mass effect.
**Option C:** Infarct is a type of brain tissue damage caused by a lack of blood flow, which can cause a ring-enhancing lesion on a CT scan, but it is typically not associated with a mass effect or increased intracranial pressure.
**Clinical Pearl / High-Yield Fact**
A ring-enhancing lesion on a CT scan is often associated with a mass effect, which can lead to increased intracranial pressure and neurological symptoms. It is essential to consider the patient's history, physical examination, and laboratory results to determine the underlying cause of the lesion.
**Correct Answer: B. Meningioma.**