Table 3 Mimics of Meningitis
Meningeal mimics Differential features and diagnostic clues
.Enteroviral meningitis Seasonal distribution: summer (recent fresh water/sick person exposure)
History: sore throat, facial/maculopapular rash, loose stools/diarrhea
Onset: subacute; not as ill as bacterial meningitis
CSF:
Gram stain:
Lactic acid: normal (<3 mmol/L)
.Partially treated
bacterial meningitis
(usually 2 8 to
influenzae)
History: meningitis symptomsþprevious antibiotic therapy
Onset: subacute
CSF:
Gram stain:
Lactic acid: mildly:(4–6 mmol/L).HSV-1 Season: nonseasonal
History: antecedent herpes labialis (not concurrent)
Onset: aseptic meningitis/meningoencephalitis (subacute); encephalitis (acute)
Presentation: viral/aseptic meningitis, meningoencephalitis, or encephalitis
EEG: unilateral temporal lobe focus
Head MRI/CT scan: unilateral temporal lobe focus (negative early)
CSF:
Gram stain:
RBCs (negative early; present later)
:PMNs ( may be>90%)
Glucose may be;/normal
:Lactic acid*RBCs in CSF
.Meningeal
carcinomatosis
History: leukemias, lymphomas, carcinomas, or without known primary neoplasm;
mental status changes:
Onset: subacute
Presentation: 80% have cranial nerve involvement, (CNs III, IV, VI, VII, or VIII
most common)
CSF:
Gram stain:
RBCs:
protein: highly:
lactic acid: variably:
Cytology: abnormal in 90%.Amebic
meningoencephalitis
(Naegleria fowleri)
History: recent swimming in fresh water
Onset: rapid
Presentation: olfactory/gustatory abnormalities: early
Head MRI/CT: mass lesions
CSF:
RBCs:þ
glucose:;
lactic acid: variably:
Gram stain: “motile WBCs” (ameba) on wet prep.Brain abscess (with
ventricular leak)
History: source usuallysuppurative lung disease (bronchiectasis),cyanotic heart disease
Onset: acute (R?L shunts), mastoiditis, dental abscess, etc.
Presentation: meningitis
Head MRI/CT: mass lesions
CSF: mimics bacterial meningitis (with ventricular leak)
Protein: highly:
Without leak: usually<200 WBCs
With leak:100,000 WBCs
.Leptospirosis History: water/rat urine exposure
Onset: acute
Presentation: clinically ill, jaundiced, conjunctival suffusion,:SGOT/SGPT. Usually
associated with severe leptospirosis (Weil’s syndrome)
CSF:
Bacterial profile
CSF::bilirubin (>serum bilirubin)
RBCs:þ
.Tuberculous/fungal
meningitis
History: TB exposure
Onset: subacute
Presentation: basilar meningitis, usually with evidence of primary infection. Lung
lesions not always apparent in TB (chest X ray negative in 50%).
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