Ariana M. Nelson1 and Honorio T. Benzon2 1 University of California Irvine School of Medicine, Irvine, CA, USA Cervical epidural steroid injection (CESI) is a commonly performed therapeutic interventional procedure to improve the pain control and functional status in patients with cervical radicular pain. Patients with cervical pain who fail to improve with non-interventional conservative treatments may experience analgesia with CESIs. However, due to the complexity and considerable variability in cervical spinal anatomy, severe complications may occur and interventionalists must observe proper precautions to safely perform this delicate procedure. The epidural space is the circumferential space located within the vertebral column and outside the dural sac. The space contains fat, a venous plexus, spinal branches of the segmental arteries, and lymphatic vessels. The nerve roots of the spinal cord also pass through the epidural space before exiting the canal through the intervertebral foramina, also termed the neuroforamina. The epidural space is bordered posteriorly by the ligamentum flavum and the periosteum of the vertebral column, anteriorly by the posterior longitudinal ligament, and laterally by the pedicles and intervertebral foramina. The anteroposterior diameter of the posterior cervical epidural space in neutral position is about 1–2 mm, but increases to 3–4 mm when the neck is in flexion [1]. The cervical epidural space is unique as it decreases in axial diameter at the more superior levels. Compared to the other vertebral segments, fat is almost absent at the cervical level. There is also a high incidence of midline gaps in the cervical ligamentum flavum, which has ramifications for the interlaminar approach to CESIs. [2]. Epidural lipomatosis is defined as the non-neoplastic overgrowth of adipose tissue within the epidural space [3]. It is most commonly associated with exogenous steroid use but CESI may also promote fat deposit in the epidural space leading to or further exacerbating epidural lipomatosis [4, 5]. There are several vessels of critical importance near the cervical spinal region. The paired vertebral arteries typically arise from the subclavian arteries, enter the intervertebral foramina at C6, and course vertically up the transverse foramina just anterior to the spinal ganglion. The deep cervical artery and ascending cervical artery anastomose with the vertebral artery posterior to the cervical spinal nerves [6]. Radicular medullary arteries also lie within the intervertebral foramina. They course through the cervical intervertebral foramina and anastomose with the anterior and posterior spinal arteries. However, these arteries have variable origins, which determine the location of these branches in relation to each intervertebral foramen. The vertebral artery is most commonly located along the anterior aspect of the foramina (Figure 19.1) but, in an unknown percent of patients, it is in close proximity to the posterior aspect of the intervertebral foramina (Figure 19.2). The posterior position of the vertebral artery within the foramen correlates with the severity of foraminal stenosis and loss of disc height [6, 7]. Anastomoses of the ascending and deep cervical arteries with the vertebral artery also demonstrate considerable variation, contributing to the overall significant anatomic divergence of the cervical spinal vessels [6]. Figure 19.1 Normal anterior anatomic position of the vertebral artery in relation to spinal nerves. Degree of neuroforaminal stenosis or other anatomic variability will influence likelihood of needle traversing vasculature during TF-CESI. Figure 19.2 Example of the vertebral artery positioned in the posterior foramen, a risk factor for an adverse event during TF-CESI. (Source: Beckworth et al. [8].) Chronic neck pain/upper extremity pain for >3 months resulting from: There are two approaches for injection of steroid in the cervical epidural space: the interlaminar (IL-CESI) approach and the transforaminal (TF-CESI) approach (Figure 19.3). The choice of approach should be made by the physician on a case-by-case basis after evaluating potential risks and benefits for each particular patient. The procedure is generally performed under fluoroscopic guidance, which allows a view from multiple projections, aiding with the localization of the injection needle. Alternative imaging guidance, including ultrasound (US), and computed tomography (CT), has also been described in the literature [15]. Figure 19.3 Transforaminal approach to the epidural space with a cutting tipped needle and the interlaminar approach to the epidural space using a blunt LOR needle. IL-CESI is favored as the first-line approach due to the association of TF-CESI with a greater risk of serious complications such as spinal and cerebral infarctions. However, the proceduralist may elect to perform a TF-CESI in patients with symptoms due to multilevel degenerative disease of the cervical spine at superior cervical levels. In multiple-level involvement, relief after a single-level TF-ESI can identify the culprit level(s) needing decompression to aid in surgical planning. It may also be favored in cases of failed IL-CESI, that is, if the interlaminar procedure is either aborted or a completed interlaminar procedure does not result in analgesia for the patient. Lastly, the proceduralist may elect to perform TF-CESI if IL-CESI is not possible due to prior posterior cervical fusion or laminectomy. Surgical manipulation of the posterior cervical space causes scarring of the potential space and therefore loss of resistance technique will have a high likelihood of inadvertently puncturing the dura [16]. Before injection of steroid, injection of nonionic, water-soluble, contrast medium under real-time fluoroscopy or digital subtraction imaging is recommended for both approaches. This step is especially crucial in the transforaminal approach due to the higher risk of intravascular injection leading to catastrophic complications. In contrast, because position within the epidural space is achieved primarily via tactile feedback in IL-CESI, the procedure may be performed without contrast [17]. However, it is typically only omitted in cases where the patient has a documented severe hypersensitivity reaction to contrast that is not amenable to pre-medication with prophylactic steroids and antihistamines. The interlaminar approach should only be performed at the C6–C7 level or more inferior spaces. Higher levels of the cervical epidural space are narrower, increasing susceptibility of the dural sac and the spinal cord to direct needle injury during injection. In addition to the larger epidural space diameter at C7–T1, the spinous process angulation is not as steep, allowing easier needle access. For lesions at superior levels of the spinal cord, a catheter can be threaded superiorly to deposit injectate closer to the pain-generating site. It is important to note, however, that LOR may be subtle or imperceptible due to the high incidence of midline gaps in the cervical ligamentum flavum and the use of small diameter needles [2]. Once the needle reaches the epidural space (slightly ventral to the spinolaminar line in lateral fluoroscopic view) and LOR is achieved, contrast medium is injected under fluoroscopy to confirm the position of the needle tip [2]. In the correct position, under contralateral oblique (CLO) view, the dorsal margin of the contrast should highlight the spinolaminar line as a well-defined or smudged convex single-line [1] (Figure 19.4). After confirming correct needle placement, steroid is injected. Figure 19.4 Contralateral oblique fluoroscopic view of contrast spread pattern in the cervical epidural space after IL-CESI. In the event of inadvertent dural puncture, intradural injection of contrast medium will show contrast accumulation in the ventral portion of the spinal column forming a CSF-contrast agent level. In AP view, a symmetric distribution of contrast material will be visualized as homogenously filling the space between facet columns [1, 18]. The choice of steroid used in CESIs has been widely discussed due to the association of particulate steroids and risk of infarction in TF-CESI. Particulate steroids, including triamcinolone, prednisolone, methylprednisolone, and betamethasone are no longer recommended for TF-CESI. They are, however, still utilized for IL-CESI in clinical practice. Dexamethasone is a nonparticulate steroid that has reduced morbidity in the case of accidental intravascular injections and has therefore become the steroid of choice for the transforaminal approach to CESI [19, 20]. Epidural injection of local anesthetics alone, or as a diluent during steroid injection, is common in practice. Although local anesthetics demonstrate moderate evidence for pain relief [10, 11], there are risks associated with their use. Unintentional placement of local anesthetics in the intrathecal or subdural space can result in high spinal block. High spinal block can lead to hypotension, bradycardia, apnea, loss of airway reflexes, and paralysis. There is debate as to whether local anesthetics as diluents to steroid can provide immediate decrease in pain following epidural injection. However, a recent study reported no substantial increase in immediate, clinically meaningful pain relief using low-dose lidocaine as a diluent [21]. In general, catastrophic complications are rare after CESIs. However, TF-CESIs have been associated with more significant complications compared to IL-CESIs. Infarction: Intravascular injection of steroids has been reported in TF-CESI. The mechanism behind injuries due to intravascular steroid injection is the use of particulate steroids resulting in embolic infarct [22, 23]. Particulate steroids can aggregate and form particles larger than the red blood cells (RBCs) in the bloodstream, leading to steroid occlusion or RBC aggregate occlusions. Of the particulate steroids, methylprednisolone forms the largest particles, triamcinolone intermediate, and betamethasone the smallest in size [24
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Complications of Cervical Epidural Steroid Injection
2 Northwestern Memorial Hospital, Feinberg School of Medicine, Chicago, IL, USA
Introduction
Anatomy
The Cervical Epidural Space and Vertebrae
Vasculature
Indications [9–11]
Contraindications [12–14]
Techniques
Interlaminar Cervical Epidural Steroid Injection
Injectate
Steroids
Local Anesthetics
Complications
Intravascular Injection
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