Indications for and Outcomes of Lumbar Punctures Performed in Infants less than 3 Months Old

Background: Infants under 3 months often present with nonspecific signs and symptoms making it a challenge to diagnose CNS infection in this population. Yet missing the diagnosis can result in significant mortality and morbidity. A recent large review showed low rates of bacterial meningitis (BM) in the under two month population, contributing to increased interest in whether low risk infants can be identified to reduce the need for invasive investigations.

Objectives: To look at indications for and results of LP in the less than 3 months population presenting to our hospital and determine whether features exist to aid in stratifying infants as low risk of BM.

Methods: Data was retrospectively collected on all infants under 3 months who had LP performed between September 2017 and September 2018. Using the hospital's electronic database we gathered demographic data, initial observations, presenting features and documented indication for LP alongside results from biochemical and bacteriological investigations.

Results: 134 LP were performed, 43 in the less than 1 month group and 91 in the 1-3 months group. There were no positive bacteriology results with 26 (19.4%) confirmed cases of viral meningitis. 3 (0.02%) patients were treated for presumed BM (1 was clinically suspected with no LP performed, 1 had raised WCC with positive CSF microscopy and 1 was found to have meningeal thickening on cranial ultrasound scan). See chart 1 for summary of diagnosis at time of discharge.

Chart 1: Diagnosis at the time of discharge for all infants under 3 months of age on whom an LP was performed between September 2017 and 2018

Conclusion: This data adds to a growing body of evidence of low rates of positive results from LP in the under 3 month group. Further research is required to better stratify this population and avoid unnecessary invasive investigation without missing the diagnosis in the small proportion of infants who do have BM possibly allowing a more individualised approach to febrile under 3 month old patients.