Anatomy of Human Epidural Space using CT-epidurography

Suh, Soon Ae; Choi, Kyu Taek; Cheun, Jae Kyu

Abstract

The anatomy of the human epidural space was demonstrated in 8 patients by computed tomography (CT) examinations performed after epidural injection of water soluble radiographic contrast material into the L3-4 epidural space via Tuohy needle. The examinations showed the posterior epidural space to be divided by the plica mediana dorsalis and an additional transverse connective tissue plane. The compartmentalized nature of the space may be, at times, responsible for entrapment and coiling of epidural catheters, despite the satisfactory technical performance of catheterization for epidural anesthesia. All patients demonstrated a great amount of fatty tissue within the junction of the posterior midline epidural connective tissue structures, producing a triangular-shaped structure which might be an impediment to catheterization. The posterior epidural space is more easily filled with contrast media than the anterior epidural space. We also measured the depth of epidural space. The posterior epidural space was 2-6 mm deeper than the anterior epidural space. At the thoracic spine, the depth of the posterior epidural space was about 1-2 mm and the anterior space was under 1 mm or revealed trace. At the lumbar region, the depth of the posterior epidural space was about 4-7 mm. Air bubbles were noticed in the epidural space, especially around intervertebral foramen; therefore, it was suggested that the air bubbles can produce incomplete analgesia along the nerve roots.