Specific indications for provocative discography include the following (Guyer and Ohnmeiss 1995; Bini et al. 2002; Fenton and Czervionke 2003; Guyer et al. 2003; Anderson 2004; Peh 2005):

Contraindications include (Tehranzadeh 1998; Fenton and Czervionke 2003; Anderson 2004; Peh 2005):

The patient should be interviewed about the type, location, and nature of the pain and any history of prior spinal surgery. Informed consent obtained prior to the procedure would include discussion regarding the nature and purpose of the pain provocation test as well as the possible risks and complications. Drug and contrast allergies should be elicited and addressed accordingly. MR discography with gadolinium contrast is an option for patients with severe iodine contrast allergy and has been shown to be accurate and safe (Huang et al. 2002; Slipman et al. 2002; Falco and Moran 2003; Streitparth et al. 2011). The patient’s medical records and prior imaging studies should be reviewed. Previous MRI studies are valuable for assessing overall disc morphology and for identification of a normal disc that can be used as a control. Careful pre-procedure evaluation with radiographs as well as MRI may be helpful to avoid ambiguity regarding transitional lumbar anatomy. Fasting for 6 h prior to the procedure is recommended (Peh 2005). Anticoagulant and antiplatelet medications such as warfarin and aspirin are withheld 5 days prior to the procedure to avoid possible bleeding. Pain medications, anti-inflammatory drugs, sedatives, and any medications that may alter the patient’s perception to pain should not be used on the day of the procedure to ensure integrity of test results. Some authors ­prescribe prophylactic intravenous antibiotics (cefazolin 1 g bolus or clindamycin 600 mg if allergic to cephalosporin or penicillin) to be administered within 1 h before commencement of the procedure. Blood pressure and pulse oximetry should be monitored throughout the procedure. A strictly aseptic technique is employed (Walker et al. 2008).

Provocative discography is best performed in an interventional suite within the diagnostic radiology department using a biplane fluoroscope or high-quality C-arm fluoroscope as an acceptable alternative if the prior is unavailable. For patients who are allergic to iodinated contrast agents, MR discography using intradiscal gadolinium-chelate is a viable alternative (Huang et al. 2002; Slipman et al. 2002; Falco and Moran 2003; Streitparth et al. 2011). There are variations in the size and type of needles used by different centers and practitioners. Some practitioners advocate the single-needle approach using a styleted needle that ranges in size from 18 to 22 gauge (Fenton and Czervionke 2003). Many practitioners adopt the double-needle approach which has been shown to result in a lower rate of discitis as the inner needle which enters the nucleus pulposus does not come in contact with the skin (Fraser et al. 1987; Peh 2005). The use of a thinner 26-gauge inner needle also decreases the size of the puncture hole in the annulus fibrosis, and having a pre-shaped curve at the distal end of the inner needle facilitates entry into center of the L5–S1 nucleus.

An example of a discography set consists of the following (Peh 2005):

Cervical discography is controversial, with some investigators recommending against the procedure as the information obtained from cervical discography does not outweigh the increased risks of complications that are reported to occur in up to 13 % of cases (Connor and Darden 1993). These complications include discitis, epidural abscess, hematoma, myelopathy, and quadriplegia (Zeidman et al. 1995). Other practitioners have found cervical discography to be a safe and useful procedure in selected patients with chronic intractable neck pain with negative or indeterminate imaging findings and who are being considered for surgery (Connor and Darden 1993; Zeidman et al. 1995; Grubb and Kelly 2000). A recent systematic review of cervical discography concluded that cervical discography performed according to the International Association for the Study of Pain (IASP) criteria may be a useful tool for evaluating chronic cervical pain, although not disc herniation or radiculitis. However, the level of evidence is limited by lack of large studies and consistent use of IASP standards (Manchikanti et al. 2009a).

The cervical disc cannot be approached posteriorly because of the spinal cord, anteriorly because of the airway, or posterolaterally because of the vertebral artery. As such, cervical discography is performed with an anterolateral approach with the patient supine and neck slightly hyperextended. A right-sided approach is preferred as most operators are right-handed, and it also decreases the likelihood of inadvertent puncture of the esophagus which lies slightly to the left. Careful technique and accurate surface localization are important to avoid injury to vital structures in the neck. The carotid sheath contents are protected by palpating the carotid pulse and displacing the carotid sheath laterally with the middle and index fingers. A 20-gauge 6.35 cm outer needle is introduced just medial to the fingertips following local anesthetic administration, at an angle of 40–45°, taking care to avoid the esophagus and trachea (Fig. 41.2). Under intermittent fluoroscopy, the needle tip is then slowly directed to the outer annulus fibrosis of the disc where it should be positioned in line with the anterior cortex of adjacent vertebral bodies on lateral projection and the ipsilateral pedicles on anteroposterior projection. The stylet is then removed and replaced by 26-gauge, 8.9 cm inner needle which is directed to the center of the disc space under fluoroscopy (Fig. 41.3) (Peh 2005).

There are very few indications for thoracic discography which is rarely performed or reported in the literature. Severe and disabling thoracic pain secondary to disc degeneration that requires discography has not been well studied (Tehranzadeh 1998; Fenton and Czervionke 2003). This procedure has been used to evaluate symptomatic Scheuermann disease (Winter and Schellhas 1996). Thoracic discs with prominent Schmorl nodes may be intensely painful on provocation, even in asymptomatic subjects, and thoracic discography may demonstrate disc pathology that is not seen on MRI (Wood et al. 1999). The technique is similar to lumbar discography described below, with selection of needle length based on the depth of the disc to be examined. The needle tip should be kept along the lateral aspect of the superior articular process on posteroanterior fluoroscopy to avoid entering the spinal canal. A pleural puncture is likewise avoided by keeping the needle tip medial to the costotransverse junction (Fenton and Czervionke 2003).

Provocative discography is most commonly performed for evaluation of the lower three lumbar discs. For lumbar discography, the patient may be placed in a prone or left lateral decubitus ­position, depending on operator preference. Some advocate the prone position in which the patient is more stable and immobile (Tehranzadeh 1998; Fenton and Czervionke 2003). The principal author prefers the left lateral decubitus position with the patient flexing his or her knees and a pillow placed beneath the waist to keep the spine straight. The skin puncture point is approximately 8–10 cm from the midline. After the patient is cleaned and draped, and local anesthesia administered, the outer discography needle is then inserted. The posterolateral extradural approach is preferred as it avoids puncturing the thecal sac (Tehranzadeh 1998; Fenton and Czervionke 2003; Anderson 2004). The outer needle is inserted with an obliquity of about 45–60º to the sagittal plane (Fig. 41.4).

Under intermittent fluoroscopic imaging in the AP and lateral directions, the outer needle is positioned so that its tip is placed at the right posterolateral corner of the annulus fibrosis of the target disc. The needle tip should lie in line with the posterior cortex of the adjacent vertebral bodies on the lateral projection and with the ipsilateral pedicles of the adjacent vertebral bodies on the anteroposterior projection (Fig. 41.5). For the L5–S1 disc, an additional caudal angulation of up to 40º is usually necessary, due to the overlying iliac crest. Pre-bending of the inner and outer needle or the use of a curved needle set may be necessary to facilitate entry into the disc in difficult cases at this level. Mild rubbery but firm resistance is felt when the needle tip comes into contact with the annulus fibrosis. The stylet of the outer needle is then removed and replaced by the longer inner needle. Under fluoroscopic guidance in two orthogonal directions, the tip of the inner needle is directed to the center of the nucleus pulposus. When the position of the inner needle is satisfactory, a test injection of 0.1 ml of nonionic contrast agent is made to confirm the needle position using a 1 ml tuberculin syringe with 0.1 ml markings (Peh 2009). If the position of the needle tip is suboptimal, adjustment of needle position and repeat fluoroscopic screening are required.

The injected contrast agent should form a rounded or curvilinear blob near the center of the disc space. Care should be taken to avoid injection into the annulus fibrosis which may lead to a false positive response. This is manifested by marked resistance to contrast instillation at the start of the injection and visualization of the contrast agent persisting between the needle tip and the edge of the disc (Peh 2009). In a normal disc, there is moderate resistance during contrast injection up to a volume of 1.5 ml which is the usual capacity of a nondegenerate disc. In a degenerate disc, there may be mild or no resistance to contrast injection with a typical volume of more than 2 ml. The volume of contrast agent injected should not exceed 3 ml for lumbar discography, 0.5 ml for cervical, and 1.0 ml for thoracic discography (Tehranzadeh 1998). The injection is usually terminated when very firm resistance is felt or if severe pain is produced (Fenton and Czervionke 2003). The volume of contrast agent injected at each level as well as the amount of resistance encountered should be documented.

Following removal of the needles and ensuring that there is no excessive bleeding, small adhesive bandages applied over the puncture sites are all that is required. After completing post-­discography imaging, the patient should be observed for up to 2 h in either a reclining or recumbent position with regular monitoring of vital signs. Upon discharge, most practitioners will give their patients a prescription of a non-narcotic painkiller, with an option of prescribing a short prophylactic course of oral broad-spectrum antibiotics (Fenton and Czervionke 2003; Peh 2005).

Disc morphology can be assessed with either radiographs or CT after intradiscal contrast injection. A normal disc maintains a normal height on both anteroposterior and lateral radiographs. The injected contrast agent remains in a central position within the nucleus pulposus, taking on a unilocular (“cotton ball” or rectangular) or bilocular (“hamburger bun”) configuration (Fig. 41.6). A Schmorl node is sometimes seen as focal protrusion of injected contrast agent into the adjacent vertebral end plate (Brightbill et al. 1994). A degenerated disc will show a reduced disc height with irregular fissures in the annulus fibrosis which may be complex or multiple. The peripheral annulus may remain intact or be torn. Contrast extravasation beyond the margins of the disc is indicative of an annular tear. A bulging disc may be seen with an intact peripheral annulus and is characterized by circumferential, diffuse, and symmetrical annular bulging. A disc protrusion refers to focal, often asymmetrical, posterior or posterolateral protrusion of disc material within an intact posterior longitudinal ligament. Superior or inferior migration of the nuclear material may give a “candle drip” appearance. A disc extrusion is a large disc protrusion that involves the posterior longitudinal ligament with contrast agent seen within the epidural space on discography. Extruded disc material in the extradural space which has separated from the parent disc is called a sequestrated disc (Figs. 41.7 and 41.8) (Peh 2005).

The Dallas discogram description is based on CT appearances and was originally classified into grades 0–3 (Sachs et al. 1987) and subsequently modified to four grades (Aprill and Bogduk 1992). Further modifications of the Dallas description included additional grades from 5 to 7 (Figs. 41.9 and 41.10).