Meningitis and encephalitis: Case

This neonate presents at 19 days of life with poor feeding, irritability, fever, a bulging fontanelle, and a focal seizure, which together make bacterial meningitis the working diagnosis until proven otherwise. Infants at this age are the great masqueraders: the absence of neck stiffness and the non-specific nature of the signs must never reassure the clinician, because a bulging fontanelle and a seizure in a febrile neonate strongly suggest central nervous system infection. [1]

Clinical findings

The key findings are the bulging fontanelle signalling raised intracranial pressure, the focal seizure suggesting parenchymal involvement, and the fever with irritability. The differential includes bacterial meningitis, viral meningoencephalitis including herpes simplex, and a metabolic or structural cause of neonatal seizures. A full septic workup is mandatory: blood culture, urine culture, and lumbar puncture for cerebrospinal fluid analysis, with cell count, glucose and protein, Gram stain, culture, and viral studies including herpes simplex polymerase chain reaction. [1]

Because he has had a seizure and signs of raised pressure, perform neuroimaging before lumbar puncture and give empiric antibiotics and aciclovir immediately, before the scan. The expected cerebrospinal fluid pattern in neonatal bacterial meningitis is a neutrophilic pleocytosis with low glucose and high protein, and a Gram stain positive for Gram-positive cocci in chains would point to group B Streptococcus. [1]

Management

The neonatal empiric regimen is ampicillin plus an aminoglycoside such as gentamicin, or ampicillin plus cefotaxime, because third-generation cephalosporins alone do not reliably treat Listeria monocytogenes. Add aciclovir 20 mg per kilogram intravenously 8-hourly whenever herpes simplex encephalitis or disseminated neonatal herpes is plausible, because the cost of a missed diagnosis is catastrophic. Give dexamethasone only if the unit policy supports it, as the neonatal evidence is weaker than in older children. [1]

Once group B Streptococcus is confirmed, tailor therapy. Group B streptococcal meningitis requires 14 to 21 days of intravenous therapy with an aminoglycoside for synergy in the first days, and a repeat lumbar puncture after 24 to 48 hours is advocated by some units to document sterilisation. Treat the seizure with an age-appropriate anticonvulsant and manage raised intracranial pressure with head elevation and, if needed, hypertonic saline. [3]

Complications and follow-up

Neonatal bacterial meningitis carries the worst prognosis of any age group, with permanent neurodevelopmental disability in up to half of survivors. Sensorineural hearing loss affects 10 to 30 per cent of children after bacterial meningitis and may be progressive, and the paediatric evidence that dexamethasone or glycerol reliably relieves this hearing burden is limited. [2]

This infant needs an audiology assessment before discharge and structured developmental and neurological surveillance at corrected ages 6 and 12 months, with early intervention services for any identified delay. Counsel the family about the prognosis honestly, acknowledge the uncertainty, and provide a clear safety-net for re-presentation, because the consequences of a missed complication such as progressive hydrocephalus or late seizures are severe. [2]