Rosh Pediatrics Practice Exam

What is the most likely diagnosis for a child with fever, stiff neck, and a cerebrospinal fluid showing mononuclear dominance?

1. Autoimmune encephalitis

2. Bacterial meningitis

3. Viral encephalitis

4. Viral meningitis

The correct answer is: Viral meningitis

The scenario presented involves a child exhibiting fever, stiff neck, and cerebrospinal fluid (CSF) that shows mononuclear dominance. These clinical features are characteristic of viral meningitis, where you often see an increased white blood cell count predominantly consisting of lymphocytes (mononuclear cells) in the CSF. Viral meningitis commonly leads to symptoms such as fever and neck stiffness, similar to those seen in bacterial meningitis. However, the key differentiator in this case is the finding in the CSF; viral infections typically result in mononuclear pleocytosis rather than the neutrophilic predominance seen in bacterial meningitis. Further contextualizing the options: autoimmune encephalitis often presents with a combination of neurological symptoms but may have different CSF findings, such as oligoclonal bands or specific antibodies. Bacterial meningitis would present with a different CSF profile that typically shows elevated neutrophils, decreased glucose levels, and increased protein levels. Viral encephalitis, while presenting similarly to viral meningitis, tends to have more severe neurological symptoms, and specific pathogen identification is often necessary for diagnosis. In summary, the combination of fever, stiff neck, and mononuclear dominance in the CSF strongly