Create a ten‑item multiple‑choice questionnaire on central nervous system infections for medical students.

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CNS Infection MCQ for Medical Students

Question 1: Initial Diagnostic Workup

A 28-year-old woman presents to the ED with fever, severe headache, and neck stiffness for 12 hours. She is alert and has no focal neurologic deficits. What is the most appropriate next step?

A. Obtain CT head before lumbar puncture
B. Start empiric antibiotics and defer lumbar puncture
C. Perform lumbar puncture immediately after blood cultures
D. Obtain MRI brain to rule out meningitis

Correct Answer: C
Explanation: In patients without altered consciousness or focal neurologic signs, lumbar puncture should be performed immediately without prior imaging 1. CT is only needed to exclude contraindications like mass lesions in patients WITH focal findings 1. Blood cultures should be obtained first, then immediate LP 2.

Question 2: CSF Analysis Interpretation

A 45-year-old man undergoes LP for suspected meningitis. CSF shows: WBC 450/μL (85% lymphocytes), protein 120 mg/dL, glucose 35 mg/dL (serum glucose 90 mg/dL). Gram stain is negative. What is the most appropriate immediate management?

A. Start acyclovir only and await HSV PCR results
B. Start acyclovir, vancomycin, ceftriaxone, and ampicillin immediately
C. Observe and repeat LP in 24 hours
D. Start tuberculosis therapy only

Correct Answer: B
Explanation: Mononuclear predominance with low glucose requires immediate empiric treatment with IV acyclovir 10 mg/kg q8h PLUS vancomycin, ceftriaxone, and ampicillin 2. Partially treated bacterial meningitis and Listeria can show lymphocytic predominance 2. Never assume viral meningitis based on cell type alone 2.

Question 3: HSV Encephalitis Management

A 32-year-old woman with fever, confusion, and temporal lobe abnormalities on MRI has negative CSF HSV PCR at 24 hours. Clinical suspicion for HSV encephalitis remains high. What should you do?

A. Stop acyclovir since PCR is negative
B. Continue acyclovir and repeat LP at 24-48 hours
C. Switch to empiric antibiotics only
D. Obtain brain biopsy immediately

Correct Answer: B
Explanation: Never stop acyclovir based on a single negative CSF PCR if clinical suspicion remains high; repeat LP at 24-48 hours 2. CSF PCR sensitivity for HSV is 95% but can be negative early 3. Acyclovir is the single most important treatment and delays significantly increase mortality 2.

Question 4: Bacterial Meningitis Empiric Therapy

A 65-year-old diabetic man presents with fever, confusion, and meningismus. CT head shows no mass effect. You plan LP but it will be delayed 2 hours. What should you do NOW?

A. Wait for LP results before starting antibiotics
B. Start vancomycin and ceftriaxone after blood cultures
C. Start vancomycin, ceftriaxone, and ampicillin after blood cultures
D. Start acyclovir only

Correct Answer: C
Explanation: If LP is delayed for any reason, start empirical antibiotics (vancomycin plus ceftriaxone plus ampicillin) immediately after blood cultures 1, 2. Ampicillin is essential in patients >50 years or immunocompromised to cover Listeria 2. Delays in treatment worsen outcomes 3.

Question 5: CSF Volume for Testing

You are performing LP on a patient with suspected encephalitis. What is the minimum CSF volume you should collect for comprehensive testing?

A. 5 mL
B. 10 mL
C. 15 mL
D. 22 mL

Correct Answer: D
Explanation: The Infectious Diseases Society of America recommends collecting at least 22 mL of CSF for comprehensive testing 1. This allows for cell count, protein, glucose, Gram stain, culture, and multiple PCR tests 3.

Question 6: Excluding Meningitis

A 30-year-old immunocompetent woman has LP performed for fever and headache. CSF shows: opening pressure 12 cm H₂O, WBC 2/μL, protein 35 mg/dL, glucose 65 mg/dL. What can you conclude?

A. Viral meningitis is likely
B. Bacterial meningitis is excluded
C. Tuberculous meningitis is possible
D. Repeat LP is mandatory

Correct Answer: B
Explanation: Normal opening pressure, <5 WBC/μL, and normal CSF protein essentially exclude meningitis in immunologically normal hosts 1. This CSF profile makes CNS infection highly unlikely 1.

Question 7: Temporal Lobe Encephalitis Differential

A 25-year-old man presents with behavioral changes, seizures, and MRI showing bilateral temporal lobe hyperintensities. CSF shows lymphocytic pleocytosis. Which tests should you order FIRST?

A. HSV-1/2 PCR and anti-NMDAR antibodies
B. Bacterial culture only
C. Fungal culture and cryptococcal antigen
D. Arbovirus serology only

Correct Answer: A
Explanation: Temporal lobe involvement suggests HSV encephalitis or autoimmune limbic encephalitis 3. CSF PCR for HSV-1/2 (sensitivity 95%) and anti-NMDAR antibodies should be obtained immediately 3. HHV6/7 PCR should also be considered 3.

Question 8: Dexamethasone in Bacterial Meningitis

A 40-year-old man is diagnosed with pneumococcal meningitis. When should dexamethasone be administered?

A. After 24 hours of antibiotics
B. Only if hearing loss develops
C. Before or with the first antibiotic dose
D. Dexamethasone is contraindicated

Correct Answer: C
Explanation: Dexamethasone has beneficial effects on death, functional outcome, and hearing loss in bacterial meningitis when given before or with the first antibiotic dose 3. Delayed administration reduces efficacy 3.

Question 9: CSF Eosinophilia Workup

A 35-year-old immigrant presents with headache and confusion. CSF shows 200 WBC/μL with 40% eosinophils. Which organisms should you test for?

A. HSV and VZV only
B. Mycobacterium tuberculosis, fungi, and parasites
C. Streptococcus pneumoniae and Neisseria meningitidis
D. Enterovirus and arbovirus

Correct Answer: B
Explanation: CSF eosinophilia suggests MTB, fungal infections, or parasitic infections including Baylisascaris procyonis, Angiostrongylus cantonensis, and Gnathostoma species 3. Routine bacterial pathogens do not cause eosinophilic meningitis 3.

Question 10: Brainstem Encephalitis Evaluation

A 50-year-old woman presents with diplopia, ataxia, and altered mental status. MRI shows brainstem hyperintensities. Which pathogens should be considered FIRST?

A. HSV-1 only
B. Arboviruses, Listeria, and Mycobacterium tuberculosis
C. Cryptococcus only
D. Enterovirus only

Correct Answer: B
Explanation: Brainstem involvement suggests arbovirus testing, Listeria PCR (if available), Brucella antibody, and MTB testing 3. Respiratory virus testing should also be performed 3. Neurosarcoidosis and Behçet disease are non-infectious considerations 3.

References

1
Guideline

Diagnostic Approach to Central Nervous System Infections

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2025

2
Guideline

Immediate Empiric Treatment for Suspected Meningoencephalitis

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2026

3
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

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This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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