Meningismus + photophobia
CSF: Bacterial vs Viral
TriadFever + meningismus + AMS + photophobia
EmpiricVanc + ceftriaxone + dexamethasone
Add ampicillinAge ≥50 / pregnant / immunocompromised (Listeria)
Dexamethasone0.15 mg/kg q6h ×4 d, before/with 1st abx
Suspected bacterial meningitis? Antibiotics + dexamethasone FIRST — never delay for the CT/LP.
CSF profile — bacterial vs viral
| Bacterial | Viral | |
|---|---|---|
| Opening pressure | ↑↑ (200–500+) | Normal–mildly ↑ |
| WBC / diff | 1,000–10,000+ PMNs | 10–500 lymphocytes |
| Glucose | ↓↓ (<40 or <2/3 serum) | Normal |
| Protein | ↑↑ (100–500+) | Normal–mildly ↑ |
| Gram stain / other | Gram stain, culture, latex agglutination | PCR (enterovirus, HSV) |
◆ Signature clue
PMN-predominant CSF + low glucose = bacterial until proven otherwise. Early viral can be PMN-predominant — a repeat LP in 6–12 h shows the lymphocytic shift.
Diagnosis
LP for CSF cell count, glucose, protein, Gram stain & culture. If focal deficit / papilledema / ↓consciousness → CT first, but do NOT delay antibiotics for imaging.
Management
Vancomycin + ceftriaxone + dexamethasone; add ampicillin if ≥50 / pregnant / immunocompromised (Listeria). Dexamethasone 0.15 mg/kg q6h ×4 d before/with the first antibiotic dose.