Background The aim of this article was to provide a detailed description of the neonatal anatomy related to the erector spinae plane block and to report the spread of the dye within the fascial planes and potential dermatomal coverage.

Methods Using ultrasound guidance, the bony landmarks and anatomy of the erector spinae fascial plane space were identified. The erector spinae plane block was then replicated unilaterally in two fresh unembalmed neonatal cadavers. Using methylene blue dye, the block was performed at vertebral levels T5—using 0.5 mL in cadaver 1—and T8—using 0.2 mL in cadaver 2. The craniocaudal spread of dye was tracked within the space on the ultrasound screen and further confirmed on dissection.

Results Craniocaudal spread was noted from vertebral levels T3 to T6 when the dye was introduced at vertebral level T5 and from vertebral levels T7 to T11 when the dye was introduced at vertebral level T8. Furthermore, the methylene blue spread was found anteriorly in the paravertebral and epidural spaces, staining both the dorsal and ventral rami of the spinal nerves T2 to T12. Small amounts of dye were also found in the intercostal spaces.

Conclusion In two neonatal fresh cadavers, the dye was found to spread to multiple levels and key anatomic locations.