What does cerebrospinal fluid (CSF) cell count indicate in meningitis?

Updated: Jul 16, 2019
  • Author: Rodrigo Hasbun, MD, MPH; Chief Editor: Michael Stuart Bronze, MD  more...
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Answer

The CSF cell count varies according to the offending pathogen (see Tables 5 and 6 below). It is usually in the few hundreds (100-1000/µL) with a predominance of lymphocytes in patients with viral meningitis. Some cases of echovirus, mumps, and HSV meningitis may produce a neutrophilic picture early in the course of disease. (See Lumbar Puncture.)

Table 5. CSF Findings in Meningitis by Etiologic Agent (Open Table in a new window)

Agent

Opening Pressure (mm H2 O)

WBC count (cells/µL)

Glucose (mg/dL)

Protein (mg/dL)

Microbiology

Bacterial meningitis

200-300

100-5000; >80% PMNs

< 40

>100

Specific pathogen demonstrated in 60% of Gram stains and 80% of cultures

Viral meningitis

90-200

10-300; lymphocytes

Normal, reduced in LCM and mumps

Normal but may be slightly elevated

Viral isolation, PCR assays

Tuberculous meningitis

180-300

100-500; lymphocytes

Reduced, < 40

Elevated, >100

Acid-fast bacillus stain, culture, PCR

Cryptococcal meningitis

180-300

10-200; lymphocytes

Reduced

50-200

India ink, cryptococcal antigen, culture

Aseptic meningitis

90-200

10-300; lymphocytes

Normal

Normal but may be slightly elevated

Negative findings on workup

Normal values

80-200

0-5; lymphocytes

50-75

15-40

Negative findings on workup

LCM = lymphocytic choriomeningitis; PCR = polymerase chain reaction; PMN = polymorphonuclear leukocyte; WBC = white blood cell.

Table 6. Comparison of CSF Findings by Type of Organism (Open Table in a new window)

Normal Finding

Bacterial Meningitis

Viral Meningitis*

Fungal Meningitis**

Pressure (mm H2 O)

50-150

Increased

Normal or mildly increased

Normal or mildly increased in tuberculous meningitis; may be increased in fungal; AIDS patients with cryptococcal meningitis have increased risk of blindness and death unless kept below 300 mm H2 O

Cell count (mononuclear cells/µL)

Preterm: 0-25

Term: 0-22

>6 months: 0-5

No cell count result can exclude bacterial meningitis; PMN count typically in 1000s but may be less dramatic or even normal (classically, in very early meningococcal meningitis and in extremely ill neonates); lymphocytosis with normal CSF chemistries seen in 15-25%, especially when cell counts < 1000 or with partial treatment; ~90% of patients with ventriculoperitoneal shunts who have CSF WBC count >100 are infected; CSF glucose is usually normal, and organisms are less pathogenic; cell count and chemistries normalize slowly (over days) with antibiotics

Cell count usually < 500, nearly 100% mononuclear; up to 48 hours, significant PMN pleocytosis may be indistinguishable from early bacterial meningitis; this is particularly true with eastern equine encephalitis; presence of nontraumatic RBCs in 80% of HSV meningoencephalitis, though 10% have normal CSF results

Hundreds of mononuclear cells

Microscopy

No organisms

Gram stain 80% sensitive; inadequate decolorization may mistake Haemophilus influenzae for gram-positive cocci; pretreatment with antibiotics may affect stain uptake, causing gram-positive organisms to appear gram-negative and decrease culture yield by average of 20%

No organism

India ink is 50% sensitive for fungi; cryptococcal antigen is 95% sensitive; AFB stain is 40% sensitive for tuberculosis (increase yield by staining supernatant from at least 5 mL CSF)

Glucose

Euglycemia: >50% serum

Hyperglycemia: >30% serum

Wait 4 hr after glucose load

Decreased

Normal

Sometimes decreased; aside from fulminant bacterial meningitis, lowest levels of CSF glucose are seen in tuberculous meningitis, primary amebic meningoencephalitis, and neurocysticercosis

Protein (mg/dL)

Preterm: 65-150

Term: 20-170

>6 months: 15-45

Usually >150, may be >1000

Mildly increased

Increased; >1000 with relatively benign clinical presentation suggestive of fungal disease

AFB = acid-fast bacillus; CSF = cerebrospinal fluid; HSV = herpes simplex virus; RBC = red blood cell; PMN = polymorphonuclear leukocyte.

*Some bacteria (eg, Mycoplasma, Listeria, Leptospira spp, Borrelia burgdorferi [Lyme], and spirochetes) produce spinal fluid alterations that resemble the viral profile. An aseptic profile also is typical of partially treated bacterial infections (>33% of patients have received antimicrobial treatment, especially children) and the 2 most common causes of encephalitis—the potentially curable HSV and arboviruses.

**In contrast, tuberculous meningitis and parasites resemble the fungal profile more closely.


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