Key Concept: CSF glucose is consumed by bacteria → low in bacterial & TB meningitis, normal in viral & GBS. Protein rises with inflammation severity. Albuminocytologic dissociation (high protein, normal WBC) is the hallmark of GBS. Bacterial = PMNs; Viral & TB = lymphocytes.
Diagnosis
Key Features
Bacterial Meningitis
WBC count >1,000/mm³
Glucose <40 mg/dL (markedly low)
Protein >250 mg/dL (markedly elevated)
Rapid onset with high fever, neck stiffness
Gram stain / culture often positive
Neutrophil (PMN) predominance in CSF
Viral Meningitis
WBC count 10–500/mm³
Glucose 40–70 mg/dL (normal)
Protein <150 mg/dL (mildly elevated)
Lymphocyte predominance in CSF
Common causes: enteroviruses, mumps, HSV-2
Self-limited course; supportive care
TB Meningitis
WBC count 100–500/mm³
Glucose <45 mg/dL (low)
Protein 100–500 mg/dL (significantly elevated)
Subacute / insidious onset over weeks
AFB stain positive; culture on Löwenstein-Jensen media
Cranial nerve palsies (especially CN VI)
Guillain-Barré Syndrome
WBC count 0–5/mm³ (normal)
Glucose 40–70 mg/dL (normal)
Protein 45–1,000 mg/dL (albuminocytologic dissociation)
Elevated protein WITHOUT pleocytosis (albuminocytologic dissociation)