Contrast flow characteristics in the cervical epidural space: an analysis of cervical epidurograms

A single-center prospective analysis of cervical epidurograms, using a crossover design.

To delineate the extent and pattern of spread of epidural contrast during cervical epidural steroid injections. To determine the volume of solution needed for effective cervical epidural steroid injections. To determine the most appropriate neck flexion angles for cervical epidural steroid injections. To determine the relationships between epidural spread, degree of neck flexion, and volume of solution used during cervical epidural steroid injections.

The decreased epidural space in the cervical region makes injections here liable to rare, but potentially serious, complications. The lower cervical (C6-C7, C7-T1) levels are thought to be safer because of the increased epidural space here, as compared with higher levels. There is, however, considerable controversy in the scientific literature regarding the levels at which cervical epidural injections should be performed. There is also no consensus regarding the volume of solution needed or the extent of neck flexion required for effective epidural spread. To date, no study has examined these questions.

Patients with lower cervical spine pathology who were referred for cervical epidural steroid injections were randomly assigned to have the injections performed at the C6-C7 or C7-T1 midline level. Volume of solutions used and degree of neck flexion were measured. Characteristics of epidural spread were recorded. Patients requiring repeat injections had the injections performed at the adjacent level with identical volume and angle of neck flexion using a goniometer. Contrast flow characteristics were again recorded. Extent of spread was correlated with the level of injection, volume of injectant, and degree of neck flexion.

No major or permanent complications were noted. The contrast was found to spread evenly throughout the entire dorsal cervical epidural space, on a consistent basis, in all cases. At C6-C7, it was found to spread an average of 3.61 +/- 0.84 levels; and at C7-T1, it spread an average of 3.88 +/- 1.01 levels. Using a three-way analysis of variance, the level at which the epidural was performed, the amount of contrast used, and the neck flexion angle did not affect the number of levels spread.

In cervical epidural steroid injections performed in the midline at C6-C7 and C7-T1, the contrast consistently covers the dorsal cervical epidural space bilaterally, irrespective of the volume used or neck flexion angle used. This suggests that solutions introduced here would cover the dorsal cervical epidural space. This questions the utility of performing potentially more dangerous injections at higher cervical levels or more invasive procedures, such as the use of epidural catheters.