Paediatric meningitis
Definition
Meningitis is inflammation of the meninges.
(This may seem obvious but there are two things which meningitis gets confused with: encephalitis and meningococcal sepsis. Encephalitis is inflammation of the brain parenchyma (i.e. the actual brain), not the meninges. Meningococcal sepsis is a sepsis where the pathogen is meningococcus (or N. meningitidis).)
Epidemiology
Viral meningitis is the commonest cause (though not as serious). Bacterial meningitis has an incidence of 2-3 per 100,000.
Pathophysiology
There are a variety of pathogens which cause bacterial meningitis. Also listed are the age groups in which the organism is common:
- Neisseria meningitidis (or meningococcus): all age groups except neonates. This is the most common cause
- Streptococcus pneumoniae" (or pneumococcus): all except neonates
- Group B streptococci: newborns
- Listeria monocytogenes: those with poor immune systems i.e. newborns and the immunocompromised.
- Haemophilus influezae type B (or Hib): unvaccinated children
- Tuberculosis: rare but associated with HIV
Risk Factors
- Contact with others who infected
- Immune compromise
- Various illnesses: endocarditis, diabetes, thalassaemia and CF
Clinical Features
Meningitis is a rapid-onset, fatal disease. Being able to detect it clinically, especially in children where the clinical features tend to be less specific, is incredibly important. These are some of the features of meningitis:
- Headache
- Nausea
- Fever
Below are signs which are considered to be of meningism. This is just a clever word for "signs of meningeal irritation".
Meningism
- Neck stiffness: aka nuchal ridigidity
- Kernig's sign: pain on extending the knee during hip flexion
- photophobia: aversion to bright light. This sign is unreliable.
- Brudzinski's sign: bending head forward causes hip flexion
(I only use the term "meningism" because consultants who think they're clever will use it with you, mostly just to confuse you. You can now turn the tables and use the word - correctly - when talking to them. HAHA! This will fool them into thinking you are clever which, given you're a medical student, you probably are not.)
Sepsis
Have a look at paediatric sepsis for some information on sepsis. Though I have stated that meningococcal sepsis and meningitis are different conditions, the latter can lead to the former. So you do need to be aware of sepsis with meningitis children.
Investigations
Lumbar puncture
This is a dangerous test to do in a child with meningitis as it can lead to coning or brain herniation. Any neurological signs (focal;GCS<13;dilated pupils;doll's eye reflex;papilloedema) or BP↑are signs of imminent herniation. DIC and purpura are contraindications.
Bloods
- FBC - WCC↑ are a sign of infection
- CRP - normal in viral, raised in bacterial
- U+Es - measure dehydration, rule out UTI
- Blood culture - identify pathogen if initial treatment fails
Imaging
- CXR - rule out pneumonia
Other tests
- Dipstick urine - rule out UTI
- Nasal swabs - rule out nasal infection
- Stool culture
Management
Blood cultures take 48 hours to come back. If you wait for them, there's a good chance your patient will be dead. This is bad and knowing what bacteria killed a child is of little consolation to a parent (or so studies have shown). Thus, most of the management of meningitis in children is done without knowing the pathogen.
General treatment
ABC
- Protect airway
- Give high-flow O2
- IVI colloid 10-20ml/kg bolus
Antibiotics
In a situation where bloods cannot be done quickly and meningitis is suspected, give benzylpenicillin IM 300mg (<1yrs)/600mg (1-9yrs)/1200mg (>10yrs)
- Ceftriaxone 80mg/kg/day IV over 30 mins (reduced to 50 over 1h if <7 days)
OR
- Benzylpenicillin 50mg/kg/4h slowly IV (/8h aged 1wk-1mo.) AND Cefotaxime 50mg/kg/6h IV over 15 minutes
- Netilmicin possible in neonates slowly IV 3mg/kg/12h (2.5 aged >1wk.)
- Add ampicillin in listeria
- Treat cryptococcus if HIV +ve.
'Raised Intracranial Pressure'
- Use mannitol 20% 2.5-5mL/kg IVI