Written by Jonathan Brewer
Spoon Feed
Ultrasound is a useful tool to identify the optimal approach for lumbar punctures in young infants, though the optimal space may be more cephalad than commonly taught.
Baby got back
This study aimed to evaluate the spinal anatomy of young infants, utilizing ultrasound to identify optimal lumbar puncture (LP) sites. It analyzed potential LP sites from L2/L3 through L5/S1 to determine differences in needle insertion depth (NID), spinal canal width (SCW), and subarachnoid fluid width (SAW), while also identifying the location of the conus medullaris (as infant spines are not entirely ossified) and attempting to predict the NID based on certain variables (age, gestational age, height, and weight).
In this prospective study of 50 infants aged 0–6 months, the authors noted that NID was consistent (~1 cm) across sites. However, SCW and SAW were larger at cephalad sites (Mean L2/L3 SCW = 8.6 mm, SAW = 3.5 mm compared to L4/L5 SCW = 6.0, SAW = 1.9). Among all the predictive variables analyzed, weight alone significantly predicted NID (β = 1.01–1.35 mm/kg, p < 0.05). Notably, while the conus medullaris is generally located between the T12-L3 vertebral interspaces in infants, one participant in this study had an identifiable conus medullaris that extended below the L2 spinous process.
How will this change my practice?
Ultrasound is already utilized in adults for both static and dynamic guidance of lumbar punctures. As we continue to increase our skill with point-of-care ultrasound for procedural guidance, I will be using this for my next infant LP. I will probably analyze the L3/L4 space initially, but if the conus medullaris is superior to L2, I may look at attempting the L2/L3 space.
Source
Spinal Anatomy Ultrasound in Young Infants With Implications for Lumbar Puncture. Pediatr Emerg Care. 2024 Dec 12. doi: 10.1097/PEC.0000000000003313. Epub ahead of print. PMID: 39665465
