11 Epiduroscopic Images of Spinal Anatomy Epiduroscopy has become a popular procedure for patients with low back pain and/or leg pain. As a direct three-dimensional imaging procedure, epiduroscopy allows the physician to explore the anatomic structures in the epidural space, such as spinal dura mater, epidural fat tissue, epidural blood vessels, spinal nerve roots, and posterior longitudinal ligament (PLL). The physician can diagnose the epidural pathology by an epiduroscope and treat it under direct vision at the same time. An understanding about static and functional anatomy of the epidural space is imperative to physicians who perform an epiduroscopy. However, the learning curve for epiduroscopy is very slow because the epidural space is narrow, especially in cases of spinal stenosis, and the epiduroscope is too small to observe the whole epidural space. During epiduroscopy, the structural view of the epidural space is changing because the dura is sloping around in the epidural space. To obtain a good view of the epidural space using the epiduroscope, the whole procedure should be taken with prudence to avoid injury of the blood vessels in the epidural space. Bleeding can occur easily, which can obscure the field of vision, making it difficult to differentiate the epidural structures. If there is severe adhesion in the epidural space, it may not be possible to distinguish each structure, and the scope cannot be advanced further. Understanding the anatomy of epidural space of the extradural space in the spinal canal is essential for understanding the epiduroscopic views of the epidural space. Epiduroscope can be advanced into the anterior epidural space as well as the posterior epidural space. Epiduroscopic view of the epidural space varies according to the angle from the anterior and posterior epidural space. Physicians should also know about the limitation of the epiduroscope, which can angulate only left and right, not up and down. The more we view the epidural space directly, the more we can understand the epidural pathology. This chapter discusses the normal epiduroscopic and pathologic images, and also mentions about instrumentation images under epiduroscopy. The boundaries of the epidural space are foramen magnum to the superior; sacrococcygeal membrane to the inferior; PLL, vertebral bodies, and disks to the anterior; pedicles and intervertebral foramen to the lateral; and ligamentum flavum, facet joint capsules, and lamina to the posterior ( Characteristics of the epiduroscopic images of epidural structures are summarized in The epidural fatty connective tissue is generally the first structure to be identified during the epiduroscopic procedure. The epidural fatty connective tissue appears as a greasy, yellow-colored bubble ( • The fatty tissue is often traversed by small blood vessels. • It is mainly located in the anterolateral and dorsomedial parts of the epidural space and acts as a lubricant for the movements of the nerve roots in the spinal canal. • The epidural fatty tissue is important for the nerves to be used up after chronic inflammatory processes; this can lead to involvement of the neural structures in the scar tissue being formed. • Spinal dura mater is important as an optical guide rail when navigating the epidural space. • In the epiduroscopic image, the dura mater appears as a blue-gray or gray-white connective tissue structure ( • The elasticity of the spinal dura mater is easy to determine by triggering “the tenting phenomenon,” which is only positive for the spinal dura mater. • The spinal dura mater has an average thickness of 0.321 (SD 0.127) mm with significant variations depending on the particular segment. Fig. 11.1 Boundaries of the epidural space. Table 11.1 Characteristics of structures observed in epiduroscopic images
11.1 Introduction
11.2 Boundaries of the Epidural Space
Fig. 11.1). The epidural space contains fatty connective tissue, the dural sac, spinal nerves, epidural blood vessels, and other types of connective tissue. Since the dural sac ends at the level of the S2 vertebral body, the tissues from S2 to sacrococcygeal membrane are epidural fatty tissue, filum terminale externum, and the proximal parts of the nerve roots of S2 to Cocc1.
11.3 Normal Epiduroscopic Anatomy
Table 11.1.
11.3.1 Fatty Connective Tissues
Fig. 11.2).
11.3.2 Dura
Fig. 11.3) with small blood vessels traversing it.
Structures | Characteristics |
Epidural fat | Glistening, white to yellowish, and often traversed by small blood vessels |
Dura mater | Blue-gray or gray-white, and traversed with small blood vessels Elasticity triggered with “the tenting phenomenon” |
Nerve root | White with a pin-yellow tinge containing of blood vessels Easily mistaken for fibrotic tracts |
Posterior longitudinal ligament | White with a fibrous structure without visible blood vessels Distinguished with the spinal dura mater by no vascularization and rarely elastic without “tenting phenomenon” |
Ligament flavum | White to yellowish concave surface without visible vessels |
Blood vessels | |
Adhesions | As tissue organized in strings and sheets of white fibers or the presence of impenetrable dense white tissue Generally avascular regardless of their severity |
Inflammation | Hyperemia observed as a discrete area of dura root sleeve, peridural membrane, or other epidural structure, as compared to normal appearing areas of the epidural space |
