Pediatric Aseptic Meningitis Workup

Updated: Mar 05, 2015
  • Author: Saul N Faust, MBBS, PhD, MA, MRCPCH(UK); Chief Editor: Russell W Steele, MD  more...
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Workup

Other Tests

CT and MRI

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. 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)
  • Procalcitonin (PCT) – PCT has been suggested as a potentially useful predictor for distinguishing between bacterial and aseptic meningitis but is not yet widely available [41]
  • 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
  • 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. [42]

Avoid lumbar puncture in patients with depressed levels of consciousness, shock, or any significant contraindications for the procedure, and immediately begin treatment in these patients. Contraindications for lumbar puncture include the following:

  • Prolonged or focal seizures
  • Focal neurologic signs
  • Widespread purpuric or petechial rash
  • Glasgow Coma Scale score lower than 13
  • Pupillary dilatation or asymmetry
  • Impaired oculocephalic reflexes (doll’s-eye reflex)
  • Abnormal posture or movement - Decerebrate or decorticate movement or cycling
  • Signs of impending brain herniation (eg, inappropriate low pulse, raised blood pressure, or irregular respiration)
  • Coagulation disorder
  • Papilledema
  • Clinical or radiological signs of raised intracranial pressure
  • Shock
  • After convulsions until stabilized
  • Clotting study results (if obtained) outside the normal range
  • Platelet count below 100 x 10 9/L
  • On Anticoagulant therapy
  • Local superficial infection at puncture site
  • Respiratory insufficiency

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. [43]

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. [44, 45, 46]

Routine CSF EV PCR testing has been shown to reduce the length of hospitalization in pediatric patients with suspected aseptic meningitis. [47] In one study, children with positive EV PCR results had shorter hospitalization stays than children with negative PCR results or children who were not tested. [23]

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. [3]

In a study from the Netherlands, the introduction of a rapid enterovirus molecular test in children with enterovirus meningitis led to reductions in the median duration of hospitalization and the duration of antibiotic administration (to 2 days and 1 day, respectively). [1] Mean costs per patient calculation showed an average reduction of more than US$1450.

There has been recent discussion about whether CSF lactate is a good marker for differentiating bacterial (>6 mmol/L from aseptic (< 2 mmol/L) menigitis. Some researchers have suggested that CSF lactate is a better marker than other standard markers used, whereas others have suggested that it does not add any useful information to the conventional CSF markers. [48]

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