Meningitis%20-%20acute,%20bacterial%20(pediatric) Diagnosis

• Perform a complete neurologic exam, including a mental status exam if applicable
• May decide to delay lumbar puncture (LP) if contraindications are noted on assessment [signs of increased intracranial pressure (ICP), severe cardiopulmonary compromise and infection of the skin overlying the LP site]

Look for Signs of Meningeal Irritation

Neck Stiffness

• Examine the neck for rigidity by gentle forward flexion with the patient in supine position

Kernig Sign

• Position of patient: Supine, with the hip flexed at 90^o
• Positive when extension of the knee from this position elicits resistance or pain in the lower back or posterior thigh

Brudzinski Sign

• Position of patient: Supine
• Positive when passive neck flexion results in flexion of the knees and hips

• Position of patient: Supine
• Positive when passive flexion of one hip and knee causes flexion of the contralateral leg

Look for Signs of Increased Intracranial Pressure (ICP)

• Headache
• Emesis
• Bulging fontanel or diastasis (widening) of the sutures
• Ocular movement disorders (eg Abducens nerve palsy)
• Hypertension with bradycardia
• Apnea or hyperventilation
• Altered state of consciousness (eg coma) 
• Decorticate or decerebrate posturing

Other Signs and Symptoms

Neonates

• Neonates with bacterial meningitis usually do not have meningismus
• They can present with temperature instability, jaundice, vomiting, diarrhea, respiratory distress, high-pitched crying, irritability, lethargy, refusal to eat and changes in affect and state of alertness
• Bulging fontanelle may occur late in the illness
• Seizures commonly reported among those with group B streptococcal meningitis

Children 1-4 Years Old

• May also suffer antecedent or concurrent respiratory infections
• Fever, chills, vomiting, photophobia, severe headache and nuchal rigidity are the most common initial symptoms

Lumbar Puncture (LP) and Cerebrospinal Fluid (CSF) Exams

• Perform LP promptly and send CSF specimens for exams, to facilitate initiation of appropriate therapy
• A positive CSF culture is diagnostic of bacterial meningitis
• Determine if there are contraindications for a STAT LP
  
  • Thrombocytopenia is a relative contraindication if patient is immunosuppressed
• CSF formula: Cell count, glucose, protein
• Extent of CSF abnormalities depend on causative agent

Findings Suggestive of Bacterial/Purulent Meningitis

• Elevated opening pressure
• Elevated protein levels
• Decreased glucose
• Neutrophilic pleocytosis
• Elevated lactate levels

• 10⁵ CFU/mL of bacteria should be present for Gram stain to be reliable

• Eg pneumococcal bacterial antigen test (BAT), latex agglutination test, cryptococcal antigen latex agglutination system (CALAS), immunochromatographic antigen test
  • Make use of serum containing bacterial antibodies or commercially available antisera directed against capsular polysaccharides of meningeal pathogens
• BAT is reserved for patients whose initial CSF Gram stain is negative or CSF culture is negative after 48 hours of incubation
  • Pneumococcal BAT have a sensitivity for pneumococcal meningitis between 67%-100% and a specificity of >95%
• Latex agglutination is a rapid diagnostic tool to determine the causative pathogen
  • Sensitivity varies for each causative pathogen: 78-100% for H influenzae, 22-93% for N meningitidis, and 59-100%f or S pneumoniae
  • Sensitivity decreases when empiric treatment is started before lumbar puncture

Other Tests, as Warranted

• Acid fast bacilli (AFB) smear and tuberculosis (TB) culture, India ink, latex antigen techniques, polymerase chain reaction (PCR), tissue culture, Limulus lysate test, counter immunoelectrophoresis

Blood Cultures (BC)

• Obtain BC preferably before instituting empiric antibiotic therapy
• May be done first if with contraindications for a STAT LP

• Blood glucose (during lumbar puncture) 
• Blood urea nitrogen (BUN), serum sodium, chloride, potassium and bicarbonate
• Urine output and specific gravity
• Complete blood count and platelet counts
  • In the presence of petechiae, purpura or abnormal bleeding, measure of coagulation function may also be assessed

Cranial Imaging (Computed Tomography [CT], Magnetic Resonance Imaging [MRI])

• Criteria for performing cranial imaging prior to LP include presence of focal neurologic deficits, new-onset seizures, severe altered mental status (Glasgow Coma Scale <10), and severely compromised immune system (ie transplant patients, HIV-positive patients)
• Magnetic resonance imaging with gadolinium enhancement and diffusion-weighted imaging may be used for patients with meningitis secondary to medical devices (eg CSF shunt, CSF drain, intrathecal drug therapy)