Paediatrics: Meningitis

Meningitis

75% of cases of meningitis are believed to occur in those <15yrs of age. Three organisms (Streptococcus pneumoniae, Neisseria meningitides (mainly group B in the UK) and Haemophilus influenzae type b) account for 80% of the cases. H. influenzae and meningococcal group C have declined very significantly since the introduction of routine immunization in infancy.

Three important practice points to remember are:

•   Infants do not get classical symptoms of meningism with meningitis and there should be an extremely low threshold for doing a lumbar puncture as part of the septic screen in infants with unexplained fever or seizures.

•   Co-existing septicaemia in 20–30% is often the treatment priority to prevent death.

•   Do not forget possibility of tuberculous meningitis.

Pathogenesis

The sequence of pathology involves:

•   Colonization and invasion of the nasopharyngeal epithelium.

•   Invasion of the blood stream.

•   Attachment to and invasion of the meninges.

•   Induction of inflammation with leak of proteins leading to cerebral oedema.

•   Alteration in cerebral blood flow and metabolism.

•   Cerebral vasculitis.

Symptoms and signs

In younger children symptoms may be non-specific including fever, poor feeding, lethargy. Rash and seizures may or may not be present. In older children, fever with headache and neck stiffness. Other features include:

•   General: fever, vomiting, and anorexia.

•   Central: irritability, disorientation, altered mental state.

•   Seizures: occur in 30%. Focal seizures suggest localized infarction or subdural collection. Do not assume ‘febrile convulsion’ in child under 1yr of age or over 1yr of age with additional symptoms.

•   Neck stiffness: more common in older children.

•   Neurology: focal cranial nerve signs are more common in children with tuberculous or cryptococcal meningitis.

•   Eyes: papilloedema is a late sign and not a reliable indicator of raised intracranial pressure. Retinal hemorrhages may be present and may indicate sagittal venous thrombosis or coagulopathy. However, these are rare and in the infant the possibility of non-accidental or inflicted head injury should be considered.

Lumbar puncture

Lumbar puncture is a useful procedure to make the diagnosis of meningitis and identify the organism and it is generally safe. However, patients with bacterial meningitis may have raised ICP so if there is a clinical suspicion of this problem (low heart rate with raised blood pressure, often first sign of which are transient changes seen on cardiac monitors) then the procedure

should be deferred. (The cellular and chemical changes of meningitis will remain in the CSF for several days). The contraindications are:

• shock or cardiovascular instability;

• signs of raised intracranial pressure

·focal neurological signs or focal seizures

• infection of the skin at the lumbar puncture site (rare);

• evidence of coagulopathy;

• acute meningococcal disease

Treatment

Suspected cases of meningococcal meningitis in the community should receive IV benzylpenicillin (IM if no IV access) as an initial single dose.

• Children  10yrs, 1g.

• 1–9yr olds, 600mg.

• <1yr, 300mg.

Suspected cases in hospital should receive 80mg/kg/od ceftriaxone (or cefotaxime 50mg/kg/tds). A management algorithm for health profession-als based on the NICE clinical guideline 102 is available at M www.nice. org.uk/CG102

Steroids

In bacterial meningitis

·Do note use corticosteroids in children younger than 3mths

• There is benefit from the use of dexamethasone and the dosing schedule is 0.15mg/kg qds for 4 days to reduce the severity of neurological sequelae, particularly deafness, after bacterial meningitis (M www.nice.org.uk/CG102).

• If dexamethasone was not given before the first dose of antibiotics, but was indicated, try to give the first dose within 4hr of starting antibiotics, but do not start dexamethasone more than 12 hours after starting antibiotics.

In meningococcal septicemia

·Do not use the meningitic dosing of dexamethasone.

• In children with shock that is not responding to fluids and inotropes, physiological replacement of hydrocortisone (25mg/m² qds) should be considered after discussion with the intensive care team.