Pediatric Aseptic Meningitis Workup

Updated: Mar 15, 2019
  • Author: Daniel Owens, BM, MRCPCH(UK); Chief Editor: Russell W Steele, MD  more...
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Workup

Other Tests

When the clinical presentation of aseptic meningitis is typical, imaging studies (ie, early computed tomography [CT] or magnetic resonance imaging [MRI]) are rarely required for initial management,  unless (1) other pathology must be ruled out before lumbar puncture or (2) focal neurologic signs are present. [37]  Imaging may be useful to check for abscesses, subdural effusions, empyema, or hydrocephalus. Normal CT findings do not rule out increased intracranial pressure (ICP).

EEG

Electroencephalography (EEG) may be considered if atypical febrile seizures have occurred. A neuroimaging study is required for complicated cases, including children with meningoencephalitis.

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Laboratory Studies

The following studies are indicated in patients with suspected aseptic meningitis:

White blood cell (WBC) count

C-reactive protein (CRP) – one study suggests that a CRP of >80 is associated with bacterial meningitis. [54]

Procalcitonin (PCT) – PCT is a potentially useful predictor for distinguishing between bacterial and aseptic meningitis  and is increasingly available. It rises faster than CRP thus making it potentially more useful in early diagnosis of bacterial meningitis. [55, 56]

Blood glucose (to compare with CSF glucose)

Blood culture to exclude bacterial meningitis

Viral culture of throat swab, nasopharyngeal aspirate, and stool sample

Serology – Save serum for paired convalescent sample comparison of serology at 2-3 weeks following acute illness

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Lumbar Puncture and CSF Analysis

The most important laboratory study is examination of the cerebrospinal fluid (CSF). Accordingly, lumbar puncture should be considered in the absence of contraindications (see below). CSF evaluation should include opening and closing pressures, as well as the following:

Cell count

Gram stain

Culture and sensitivity

Glucose

Viral PCR

Protein and antigen

Acid-fast bacillus

Fungal stains

Typical findings include the following:

CSF pressure that is within the reference range or increased

WBC count that is usually below 500/µL, with greater than 50% lymphocytes; although the lymphocytic predominance in the CSF is typical, neutrophils can predominate in the early stages The white cell count can be normal in viral meningitis. [57, 6]  If the white cell count is normal it may indicate that the primary infection is systemic rather than meningitic.

CSF protein concentration of 0.5-2 g/L

CSF glucose concentration that is within the reference range (>66% blood glucose level) or low

Negative Gram stain results

CSF interleukin (IL)-6 and IL-12 levels are significantly higher in bacterial meningitis and are therefore useful markers for distinguishing this condition from aseptic meningitis.

CSF lactate has been proposed as a useful differentiator between viral and bacterial meningitis in adults. [58]  Its use alongside the Bacterial Meningitis score has been trialed with promising results however further data is needed. [59]

If bleeding occurs during the lumbar puncture and the CSF is contaminated with blood, interpretation becomes more difficult. In such situations, it is better to treat and wait for the results of the CSF culture. In very bloody lumbar punctures, a drop of the fluid on the sterile dressing usually will produce a double ring if there is CSF present. When in doubt, treat and attempt the lumbar puncture again later.

Formulas to adjust for the WBC count in the CSF analysis have not increased the specificity or sensitivity in traumatic lumbar puncture and still risk misclassifying patients. [60]

Polymerase chain reaction (PCR) assay for many of the common etiologic agents of aseptic meningitis is increasingly available through state health departments, the Centers for Disease Control and Prevention (CDC), and research laboratories.

PCR assay for enteroviruses (EVs) is specific and faster and more sensitive than viral culture. It should be considered as an initial investigation where available. Culture is no longer necessary for clinical diagnosis and is recommended only in patients with PCR-positive results to obtain isolates for typing purposes. [61, 62] , [63]

Routine CSF EV PCR testing has been shown to reduce the length of hospitalization and the duration of antibiotics in pediatric patients with suspected aseptic meningitis. [64]  Its use also reduces hospital costs, one Dutch study showed an average reduction of more than US$1450 of mean sots per patient. [65]

PCR assay of CSF can detect as few as 10 copies of viral nucleic acid. The ability to amplify DNA from herpes simplex virus (HSV)–1 and HSV-2, varicella-zoster virus (VZV), cytomegalovirus (CMV), human herpesvirus 6A (HHV6A) and HHV6B, and Epstein-Barr virus (EBV) in a single reaction has revolutionized diagnosis of EV and other viral infections (eg, HHV7 and West Nile virus). PCR assay of CSF in EV 71 infection can often yield negative results; higher diagnostic yields are obtained from PCR of respiratory and gastrointestinal (GI) tract specimens. [66]

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