Distance from Dura mater to spinal cord at the thoracic vertebral level: An introductory study on local subdural geometry for thoracic epidural block

Dura-to-spinal cord distance at different vertebral levels in Indian children: A retrospective computerized tomography scan-based study

Background:

Neuraxial techniques provide good postoperative analgesia for painful procedures in the pediatric population. However, any injury to the spinal cord can lead to irreversible long-term effects.

Aims:

We aimed to evaluate dura-to-cord (DTC) distance from computerized tomography (CT) images of thoracolumbar spine in pediatric age group (1–16 years) at T_8–9, T_9–10, and L_1–2 interspaces to identify the safe space for epidural insertion in Asian children.

Settings and Design:

It was a retrospective study including 141 children aged 1–16 years who underwent routine CT scan of the thoracolumbar region for unrelated diagnostic indications.

Materials and Methods:

Patients with spinal abnormalities were excluded. Sagittal CT images of the thoracolumbar spine were obtained to calculate the DTC at T_8–9, T_9–10, and L_1–2 interspaces. The measurements at all levels were obtained perpendicular to the long axis of the vertebral body.

Statistical Analysis Used:

Continuous data were depicted as mean with standard deviations. The categorical data were presented as counts with percentages.

Results:

The mean DTC distance at T_8–9, T_9–10, and L_1–2 interspaces was 3.51 ± 0.98 mm (95% confidence interval [CI]: 3.35–3.67), 2.73 ± 0.94 mm (95% CI: 2.57–2.89), and 2.83 ± 1.08 mm (95% CI: 2.66–3.02), respectively. A significant difference was found between the genders at T_9–10 (P = 0.02) and L_1–2 levels (P = 0.04). No difference in DTC was found in toddlers, preschool children, school-going children, and adolescents. DTC at T_8–9 showed a significant correlation with age (R² = 0.0479; P = 0.04), weight (R² = 0.038; P = 0.02), and height (R² = 0.037; P = 0.03).

Conclusion:

Thoracic epidural space can be used in children and adolescents for epidural catheter placement. T_8–9 level showed maximum DTC distance and significant correlation with age, height, and weight in CT imaging in the present study.

Predictors of Intraspinal Pressure and Optimal Cord Perfusion Pressure After Traumatic Spinal Cord Injury

Background/Objectives

We recently developed techniques to monitor intraspinal pressure (ISP) and spinal cord perfusion pressure (SCPP) from the injury site to compute the optimum SCPP (SCPP_opt) in patients with acute traumatic spinal cord injury (TSCI). We hypothesized that ISP and SCPP_opt can be predicted using clinical factors instead of ISP monitoring.

Methods

Sixty-four TSCI patients, grades A–C (American spinal injuries association Impairment Scale, AIS), were analyzed. For 24 h after surgery, we monitored ISP and SCPP and computed SCPP_opt (SCPP that optimizes pressure reactivity). We studied how well 28 factors correlate with mean ISP or SCPP_opt including 7 patient-related, 3 injury-related, 6 management-related, and 12 preoperative MRI-related factors.

Results

All patients underwent surgery to restore normal spinal alignment within 72 h of injury. Fifty-one percentage had U-shaped sPRx versus SCPP curves, thus allowing SCPP_opt to be computed. Thirteen percentage, all AIS grade A or B, had no U-shaped sPRx versus SCPP curves. Thirty-six percentage (22/64) had U-shaped sPRx versus SCPP curves, but the SCPP did not reach the minimum of the curve, and thus, an exact SCPP_opt could not be calculated. In total 5/28 factors were associated with lower ISP: older age, excess alcohol consumption, nonconus medullaris injury, expansion duroplasty, and less intraoperative bleeding. In a multivariate logistic regression model, these 5 factors predicted ISP as normal or high with 73% accuracy. Only 2/28 factors correlated with lower SCPP_opt: higher mean ISP and conus medullaris injury. In an ordinal multivariate logistic regression model, these 2 factors predicted SCPP_opt as low, medium–low, medium–high, or high with only 42% accuracy. No MRI factors correlated with ISP or SCPP_opt.

Conclusions

Elevated ISP can be predicted by clinical factors. Modifiable factors that may lower ISP are: reducing surgical bleeding and performing expansion duroplasty. No factors accurately predict SCPP_opt; thus, invasive monitoring remains the only way to estimate SCPP_opt.

Electronic supplementary material

The online version of this article (10.1007/s12028-018-0616-7) contains supplementary material, which is available to authorized users.

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

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.