The 3-week-old with a bulging fontanelle and a normal lumbar puncture
A 3-week-old girl, born at term, presents with poor feeding for 2 days and a bulging anterior fontanelle. She is afebrile (36.9°C), irritable when handled, and has had one episode of vomiting. She was discharged at 48 hours after an uncomplicated delivery; maternal group B streptococcus status was unknown and no antibiotics were given in labour. On examination she is alert but jittery, with a full fontanelle, no neck stiffness, and normal tone and reflexes. A lumbar puncture is performed: CSF white cells 8 × 10⁶/L (60% lymphocytes), red cells 2 × 10⁶/L, protein 0.55 g/L, glucose 3.1 mmol/L (serum 4.8 mmol/L). Gram stain is negative. Blood culture is pending.
1. Does the CSF result exclude bacterial meningitis? Justify your answer.
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No - a 'normal' CSF does not exclude bacterial meningitis in a neonate.
- Neonatal CSF has different reference values: protein is normally higher (up to ~1.5 g/L in the first weeks) and glucose lower than in older children, so a protein of 0.55 g/L and glucose of 3.1 mmol/L are not reassuring in isolation - they are within the normal range but do not exclude infection.
- A cell count of 8 × 10⁶/L is within the normal neonatal range (up to ~20 × 10⁶/L), but the differential and the clinical picture matter more than the number.
- Gram stain is negative in a substantial proportion of culture-proven neonatal meningitis, and the sensitivity is lower after any prior antibiotics (even intrapartum prophylaxis).
- The clinical signs are the key: a bulging fontanelle, irritability on handling, poor feeding and vomiting in a 3-week-old are red flags for meningitis. The absence of fever and neck stiffness is typical of neonates, in whom signs are subtle.
- Group B streptococcus is the leading cause in this age group, and late-onset disease can present at 3 weeks.
Therefore treat empirically and do not be reassured by the CSF. Repeat the LP if the first was traumatic or if the clinical course is atypical.
2. Outline your empirical management and the investigations you would send.
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Empirical antibiotics (start immediately, do not wait for cultures):
- Ampicillin (or amoxicillin) plus gentamicin is the standard neonatal regimen, covering GBS, Listeria, and Gram-negative organisms.
- Add cefotaxime (not ceftriaxone, which displaces bilirubin and risks kernicterus in neonates) if Gram-negative meningitis is suspected or the infant is deteriorating.
- Dose according to postnatal and gestational age; check local guidelines.
Investigations:
- Blood culture (already sent), CSF culture and repeat cell count if possible, urine culture.
- Full blood count, CRP, blood gas with lactate, glucose, electrolytes, and liver function.
- Consider CSF PCR for GBS, E. coli, and enteroviruses (enterovirus can mimic bacterial sepsis in neonates).
- Cranial ultrasound to look for ventriculitis, infarction, or hydrocephalus.
Supportive care: maintain glucose and perfusion, monitor for seizures, and involve neonatal/paediatric intensive care if there is any deterioration. Review the lumbar puncture site and repeat the LP at 24–48 hours if the infant is not improving, to confirm sterilisation of CSF.
3. The blood and CSF cultures grow group B streptococcus at 36 hours. Discuss duration of therapy and the surveillance the infant needs before discharge.
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Duration: uncomplicated GBS meningitis is treated for at least 14–21 days of intravenous therapy, guided by clinical response and repeat CSF culture (which should be sterile at 24–48 hours). Meningitis is treated longer than bacteraemia without a focus (which is typically 10 days).
Surveillance before discharge:
- Audiology - sensorineural hearing loss is a recognised sequela of neonatal meningitis; arrange hearing assessment (automated auditory brainstem response) before discharge or shortly after.
- Neurodevelopmental follow-up - formal review at 6–12 months and beyond, looking for motor, cognitive and behavioural sequelae.
- Cranial imaging - ultrasound or MRI to look for hydrocephalus, ventriculitis, or infarction, particularly if the head circumference is crossing centiles.
- Head circumference measurement at every visit.
- Seizure surveillance - counsel the parents about signs of seizures.
Prevention counselling: discuss that GBS disease in a future pregnancy warrants intrapartum antibiotic prophylaxis, and that the family should mention this to their obstetrician. Ensure the infant completes the full course and that follow-up is booked before discharge - do not rely on the family to arrange it.