Variations of End Level of the Dural Sac

ABSTRACT

OBJECTIVE: To determine the normal variations of end level of the dural sac in Korean subjects by magnetic resonance imaging (MRI). METHOD: The corresponding vertebral level of termination of the dural sac was evaluated by MRIs in two hundred adult Koreans (118 males, 82 females). We excluded the subjects with spine fracture, significant spinal deformity or spinal stenosis. End level of the dural sac was described in terms of their corresponding vertebral level. The vertebral levels were further divided into upper, middle, lower level, and intervertebral disc levels from the L5 to S3 vertebra. RESULTS: The most frequent end level of the dural sac was at the S1-S2 intervertebral disc level (22.5%) which was followed by the upper portion of S2 (21.5%) and the middle portion of S2 (17.0%). There was no significant difference in end level of the dural sac between male and female subjects. CONCLUSION: The dural sac most frequently ended at the S1-S2 intervertebral level and the end level of dural sac were located from the L5-S1 intervertebral level to the mid-point of S3. In a clinical setting, variable levels of the dural sac termination should be considered in an unexpected dural puncture during a caudal anesthesia or injection.