Abstract

Background: Anesthesiologists frequently give thoracic epidural blocks for a variety of surgeries. Magnetic Resonance Imaging (MRI) has provided studies of the nerves (cauda equina) inside the dural sac. But only a few correlate the spinal cord with the dura mater in the thoracic region. The aim of this study was to evaluate four measurements between the skin and the spinal cord in three thoracic segments.
Method: Retrospective study with 105 children aged 0 to 13 years in the supine position underwent MRI. Medial sagittal slices of the 2^nd, 5^th, and 10^th thoracic segments were measured for the relative distances through two devices from the Radiology Service. The following parameters were evaluated: spinal dura mater and the spinal cord distance; skin to spinal cord distance; needle entry angle between the skin and intervertebral space; and distance corrected by an angle between spinal dura mater and the spinal cord. For statistical analysis were used the following tests Chi-Square, Wilcoxon, Friedman, ANOVA, and Krukal-Wallis, and the significance level was set at 0.05.
Results: The posterior dural-spinal cord distance is significantly greater in the midthoracic region (5^th thoracic=5.61±1.61 mm) than at upper (2^nd thoracic=4.52±1.25 mm) and lower thoracic levels (10^th thoracic=4.68±1.38 mm) (p<0.015). There were no differences between interspaces T2 and T10. There was no correlation between the age and the measured distance between the dura mater and the spinal cord. The entry angle of the needle at T2 has observed a value of 27.16±5.12 degrees, at T5 was 38.68±6.10 degrees and at T10 was 39.08±5.23 degrees. These angles reflected an increase in the distance between the SDMSC in the three evaluated segments (T2=34%, T5=45%, T10=40%), reflecting in greater protection of the spinal cord.
Conclusions: This study demonstrated there is a greater depth of the posterior subarachnoid space at T2, T5, and T10 levels. The greater distance was found at T5. The correction of the entry angle of the needle increased the distance in the three interspaces. This distance between the dura mater and the spinal cord protects the spinal from damage in case of an accidental dural puncture during thoracic epidural attempts. It certainly will permit a spinal needle to provide segmental thoracic spinal anesthesia without damage.

Keywords

anatomy, intrathecal, MRI,neuraxial, spinal cord, thoracic spinal cord, pediatric, children