What are Rushton bodies?
**Core Concept**
Rushton bodies are small, eosinophilic, intranuclear inclusions observed in the neurons of the brain, particularly in the Purkinje cells of the cerebellum and the pyramidal cells of the hippocampus. They are a type of cellular inclusion, which are abnormal structures within cells that can be seen under a microscope.
**Why the Correct Answer is Right**
Rushton bodies are composed of aggregates of RNA and proteins that accumulate within the nucleus of neurons due to viral infections, particularly those caused by the herpes simplex virus (HSV) and varicella-zoster virus (VZV). The presence of Rushton bodies is a hallmark of viral encephalitis and is often seen in the context of herpes simplex encephalitis. They are thought to be a result of the viral replication process and the subsequent disruption of normal cellular function.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as Rushton bodies are not associated with Alzheimer's disease pathology. While Alzheimer's disease does involve the accumulation of abnormal proteins within neurons, Rushton bodies are a distinct entity that is more closely linked to viral infections.
**Option B:** This option is incorrect as Lewy bodies are a different type of cellular inclusion that are characteristic of Parkinson's disease and Lewy body dementia. Lewy bodies are composed of abnormal protein aggregates, whereas Rushton bodies are composed of RNA and proteins.
**Option C:** This option is incorrect as Negri bodies are a type of cellular inclusion that are associated with rabies virus infection. While both Rushton bodies and Negri bodies are types of viral inclusions, they are distinct entities that are associated with different viruses.
**Option D:** This option is incorrect as corpora amylacea are a type of cellular inclusion that are composed of amyloid and are found in the brains of individuals with aging and neurodegenerative diseases. They are distinct from Rushton bodies in terms of their composition and location.
**Clinical Pearl / High-Yield Fact**
Rushton bodies are an important diagnostic feature of herpes simplex encephalitis, a medical emergency that requires prompt recognition and treatment. In the context of viral encephalitis, the presence of Rushton bodies can help differentiate between different etiologies and guide appropriate management.
**Correct Answer: C. Negri bodies are a type of cellular inclusion that are associated with rabies virus infection.