Figure 1.

Modified classification of epidurography contrast patterns. (a) Grade 1: contrast spread to the medial or midline zone of the ipsilateral or contralateral epidural space, (b) grade 2: contrast spread to the lateral epidural space, proximal to the medial border of the neural foramen, (c) grade 3: contrast spread to the intraforaminal space, not extending to the lateral border of the neural foramen, (d) grade 4: contrast spread to the intraforaminal space, extending to but not crossing the lateral border of the neural foramen, and (e) grade 5: contrast spread beyond the lateral border of the neural foramen. Patients with grade 1, grade 2, and grade 3 patterns were assigned to a group exhibiting limited intracanal spread (IC group), while patients with grade 4 and grade 5 patterns were assigned to a group exhibiting extended extraforaminal spread (EF group).