Infection type	Differential	Glucose level	Opening pressure	Protein level	White blood cell count	Other studies
Bacterial (typical)*	Usually 80% to 90% PMNs; > 50% lymphocytes possible	< 40 mg per dL (2.22 mmol per L) in 50% to 60% of cases; CSF:serum glucose ratio < 0.4 is 80% sensitive and 98% specific	Adults and children 8 years and older: 200 to 500 mm H2O Children younger than 8 years can have lower pressures	Almost always elevated	Usually 1,000 to 5,000 per μL 99% of children have > 100 per μL	Gram stain, CSF culture, CSF lactate (> 35.1 mg per dL [3.9 mmol per L]), PCR testing; latex agglutination if Gram stain is negative and antibiotics were given before lumbar puncture
Cryptococcal	Lymphocyte predominance	Usually > 40 mg per dL	> 250 mm H2O in severe cases; serial lumbar punctures or ventriculoperitoneal shunt required to drain CSF if pressure persistently > 250 mm H2O	Usually < 40 mg per dL (400 mg per L)	Usually mildly elevated; normal count possible, especially in patients with HIV infection	CSF culture, CSF cryptococcal antigen test, India ink capsule stain, latex agglutination, enzyme immunoassay, lateral flow assay, HIV test
Fungal (excluding cryptococcal)	Possible early PMNs progressing to lymphocyte predominance; eosinophils possible	Significant decrease possible	Variable	50 to 250 mg per dL (500 to 2,500 mg per L)	Usually elevated, up to several hundred per μL	CSF (1–3)-beta-D-glucan (elevated level is 95% to 100% sensitive and 83% to 99% specific), CSF fungal culture, Gram stain (hyphae); PCR test is only 29% sensitive
Neurosyphilis	Variable	Possibly decreased	Usually elevated in immunocompetent patients; may not be elevated in immunocompromised patients	> 45 mg per dL (450 mg per L)	Early stage: 10 to 400 per μL Late stage: 5 to 100 per μL Declines over decades	HIV test, CSF Venereal Disease Research Laboratory test (30% to 75% sensitive and 100% specific†), CSF fluorescent treponemal antibody absorption test (100% sensitive and 50% to 70% specific)
Parasitic	Eosinophilia (> 10 eosinophils per μL or > 10% of total cells)	Usually low normal or normal	Variable but can be persistently elevated, requiring CSF draining	Usually elevated	150 to 2,000 per μL	PCR test; enzyme-linked immunosorbent assay for Angiostrongylus cantonensis, Gnathostoma spinigerum, and Baylisascaris procyonis
Tuberculosis	Early lymphocyte and PMN predominance progressing to lymphocyte predominance	Median: 40 mg per dL; lower in advanced stages	Variable depending on stage	Usually 100 to 200 mg per dL (1,000 to 2,000 mg per L)	Usually 5 to 300 per μL; 500 to 1,000 per μL in 20% of cases	Multiple cultures with acid-fast stain; PCR test (56% sensitive and 98% specific), CSF adenosine deaminase (> 10 U per L [166.67 nkat per L]); “pellicle” appearance of CSF‡
Viral	Lymphocyte predominance; possible PMN predominance in early infection	Usually normal; decreased in 25% of patients with mumps; mild decrease possible in patients with HIV infection	Usually normal	Normal or mildly elevated	Usually 100 to 1,000 per μL; higher in patients with enterovirus infection (elevated red blood cell count possible in patients with herpes infection)	PCR test preferred; other tests include CSF lactate (low), Gram stain, CSF or serum immunoglobulin M antibodies for arboviruses, electroencephalography or other neuroimaging for suspected encephalitis