Which statement best differentiates meningitis from encephalitis clinically and with basic tests?

• A. Meningitis presents with fever and meningismus; encephalitis presents with altered mental status; CSF in meningitis shows neutrophilic predominance and low glucose, while encephalitis shows lymphocytic predominance with normal or mildly reduced glucose.
• B. Meningitis presents with fever and meningismus; encephalitis presents with altered mental status.
• C. CSF in meningitis shows lymphocytic predominance.
• D. Encephalitis presents with seizures only.

Answer: (A)

Understanding the distinction between meningitis and encephalitis rests on where the infection primarily lies and how that affects symptoms and CSF findings. Meningitis mainly involves the meninges, so patients commonly have fever and meningismus (stiff neck, photophobia, headache). Encephalitis involves the brain tissue itself, so patients more often have altered mental status, confusion, sometimes behavioral changes, or seizures.

The CSF patterns reinforce this: bacterial meningitis typically shows neutrophilic predominance with low glucose due to consumption by bacteria and high protein. Viral processes, including viral meningitis or encephalitis, more often yield a lymphocytic predominance with normal or only mildly reduced glucose and elevated protein modestly.

The best statement ties these clinically distinct pictures together and pairs them with the classic CSF profiles, making it the most complete and accurate differentiation. Other options lack either the full clinical picture or the characteristic CSF findings.