Dura to spinal cord distance at different vertebral levels in children and its implications on epidural analgesia: A retrospective MRI-based study

Abstract

Background: The distance from the dura to spinal cord is not uniform at different vertebral levels. The dura to spinal cord distance may be a critical factor in avoiding the potential for neurological injury caused by needle trauma after a dural puncture. Typically, the greater the dura to spinal cord distance, the larger the potential safety margin. The objective of our study is to measure dura to spinal cord distance at two thoracic levels T₆ -₇ , T₉ -₁₀ , and one lumbar level L₁ -₂ using MRI images.

Methods: Eighty-eight children under the age of 8 years old qualified for the study. The distance from dural side of ligamentum flavum to the posterior margin of the spinal cord was defined as dura to spinal cord distance. Sagittal T₂ -weighted images of the thoracic and lumbar spine were used to measure the dura to spinal cord distance at the T_6-7 , T_9-10 , and L_1-2 interspaces. Measurements were taken perpendicular to long axis of the vertebral body at each level.

Results: The dura to spinal cord distance was 5.9 ± 1.6 mm at T_6-7 (range: 1.4-9.9 mm), 5.0 ± 1.6 mm at T_9-10 (1.2-8.1 mm), and 3.6 ± 1.2 mm at L_1-2 (1.2-6.8 mm). There were no evident differences in dura to spinal cord distance by gender, age, height, or weight.

Conclusion: The present study reports that the largest dura to spinal cord distance is found at the T_5-6 level, and the shortest dura to spinal cord distance at the L_1-2 level. There appears to be substantially more room in the dorsal subarachnoid space at the thoracic level. The risk of spinal cord damage resulting from accidental epidural needle advancement may be greater in the lumbar region due to a more dorsal location of the spinal cord in the vertebral canal compared to the thoracic region.

Keywords: epidural anesthesia; ligamentum flavum; lumbar spine; neuraxial block; postoperative analgesia; thoracic spine.