What is the best next step for a patient presenting with severe headache, photophobia, neck stiffness, and fever?

Best Next Step: CT Scan Before Lumbar Puncture

In a patient presenting with severe headache, photophobia, neck stiffness, and fever, the best next step is CT scan of the head (option b) to rule out contraindications before proceeding to lumbar puncture for definitive diagnosis of meningitis. 1, 2

Clinical Reasoning

This patient presents with classic meningeal signs (neck stiffness, photophobia, severe headache) plus fever, creating high suspicion for bacterial meningitis. However, imaging must precede lumbar puncture to assess for mass effect, herniation risk, or other contraindications. 2, 3

Why CT First, Not Immediate Lumbar Puncture

• Neuroimaging is indicated before lumbar puncture when patients have neurologic signs such as nuchal rigidity or altered consciousness to prevent herniation complications 1
• The European Society of Clinical Microbiology and Infectious Diseases strongly recommends obtaining CT before LP to assess for herniation risk, with 90% specificity for identifying dangerous mass effect 2
• Non-contrast head CT should be obtained immediately as the first imaging study, with 98% sensitivity for detecting acute pathology within the first hours 1, 2

The Complete Diagnostic Algorithm

1. Obtain emergent non-contrast head CT immediately 1, 2

   • Sensitivity of 98-100% for subarachnoid hemorrhage in first 6-12 hours 1, 2
   • Rules out mass lesions, hemorrhage, and contraindications to LP 2, 3

2. If CT is negative, proceed immediately to lumbar puncture 1, 2, 4

   • CSF analysis is the principal diagnostic contributor for bacterial meningitis 1, 4
   • Analyze for cell count/differential, glucose ratio, protein, Gram stain, and culture 2, 4
   • Opening pressure measurement is critical 4

3. Initiate empiric antibiotics within 1 hour if meningitis suspected, even before LP if there will be any delay 4

   • Ceftriaxone plus vancomycin for suspected pneumococcal meningitis 4
   • Add dexamethasone to reduce mortality and neurological sequelae 4

Critical Pitfalls to Avoid

• Do not perform lumbar puncture before imaging in patients with meningeal signs - this risks cerebral herniation if mass effect is present 2, 3
• Do not delay antibiotics waiting for imaging or LP - treatment should begin within 1 hour of presentation if bacterial meningitis is strongly suspected 4
• Do not assume absence of fever rules out meningitis - clinical characteristics have limited diagnostic accuracy, and bacterial meningitis can present without fever 1, 3
• Do not dismiss this as migraine - the classic triad of fever, headache, photophobia, and neck stiffness mandates aggressive workup even though it's present in <50% of bacterial meningitis cases 5

Why Not the Other Options

• MRI brain (option a): Too time-consuming in acute setting; CT is faster and adequate for ruling out contraindications to LP 1
• Lumbar puncture first (option c): Dangerous without prior imaging when meningeal signs present due to herniation risk 2, 3
• EEG (option d): Not indicated for meningitis diagnosis; only useful if seizures are the primary concern 1

Expected CSF Findings in Bacterial Meningitis

Once LP is safely performed after negative CT:

• Polymorphonucleocyte predominance (neutrophilic pleocytosis) 4
• CSF/blood glucose ratio <0.4 (typically 0.27 in bacterial meningitis) 4
• Elevated protein (usually >45 mg/dL) 4
• Elevated opening pressure (>25 cm H₂O) 4

The mortality rate for bacterial meningitis is 20-30%, increasing with diagnostic delays, making this systematic approach critical for reducing morbidity and mortality. 1, 5