127 Page 1 Provocation Discography Leonardo Kapural, M. D., Ph.D. Cleveland, Ohio Introduction: Nonspecific features of discogenic pain make clinical diagnosis of such pain difficult. Many practitioners use provocation discography in conjunction with magnetic resonance imaging (MRI) studies to substantiate a diagnosis of discogenic pain. The use of provocation discography is justified if it is used to identify symptomatic disc level as a preliminary test to spinal fusion/disc arthroplasty or as a preliminary test to any minimally invasive approaches to treat discogenic pain such as IDET, nucleoplasty or intradiscal biacuplasty (1). It can occasionaly be diagnostic test in symptomatic patients with negative MRI (1). Provocative discography, despite questioned reliability (2,3,4), remains only test to this date to relate pathologically changed MRI images to patient’s pain (5-8). Contemporary technique has increased the validity of discography by measuring concordant pain with small volume contrast under fluoroscopy, at least one negative control and ideally, in the absence of psychopathology (1-8). Technique: The technique of provocation discography requires insertion of a needle into the center of the disc under the guidance of fluoroscopy and subsequent injection of contrast into the disc (9). During provocation discography resistance on entry to the annulus, compliance of the disc nucleus on injection, and concordant or non-concordant pain provocation on injection is recorded. Spread of contrast with possible evidence of annular fissure or epidural leak and changes in intradiscal pressure are also documented or measured. A posterolateral extraspinal approach is frequently used with the patient in the prone position (9). The fluoroscope is used to guide the site of needle entry. The vertebral endplates should be aligned in the anteroposterior view and the C-arm of the fluoroscope then turned into the oblique position. Superior articular process (SAP) of the subjacent vertebra should project approximately to the middle third of the disc space. Local anesthetic is infiltrated and the needle is placed laterally to the SAP. Upon entry into the annulus, resistance will be noted. The needle is then advanced through the annulus and into the intervertebral disc nucleus using anteroposterior and lateral fluoroscopic images as guides. Water-soluble radiopaque contrast is then injected into the disc (9). Figure 1.Antero-posterior and lateral views of three-level provocation discography in progress. On the left two disc levels (L3-4 and L4-5) are injected with contrast, on the right, lateral fluoroscopic view showing all three discs containing contrast (including L5-S1). 127 Page 2 Patient’s response to injection is then classified as (6): - No pain or sensation of pressure only - Pain which is not the patient’s typical pain - Pain which is similar to the patient’s typical pain - Exact reproduction of the patient’s typical pain symptoms If the patient experiences pain that is similar in location, severity and quality to his or her “usual pain”, it is called concordant pain. Nonconcordant pain, on the other hand, suggests that the pain is dissimilar from the patient’s “usual pain”. Possible mechanisms for pain provocation during discography include stretching of the annular fibers with increased intradiscal pressure which may stimulate the nerve endings, biochemical or neurochemical stimulation which may cause pain or injection which can increase pressure at the end plates and vertebral body. To make additional diagnostic conclusions intradiscal pressure must be measured and disc compliance must be evaluated during discography(5). Opening pressure is characterized as pressure to overcome intradiscal pressure for contrast flow. Normal supine opening pressure is somewhere between 15 and 25 psi. Intradiscal pressure above 80 psi simulates sitting/standing intradiscal pressure. Abnormal disc opening pressure is low and such disc can take larger volume of contrast material. Frequently, concordant pain at low induced pressures concomitant with fissure filling is a positive provocation discogram. Derby et al.(5), characterized chemically sensitive discs if painful response develops at intradiscal pressure increase of less than 15 psi above the opening pressure. In mechanically sensitive discs, pain is provoked at pressure between 15 and 50 psi above the opening pressure while in indeterminate discs pain is experienced between 51 and 90 psi above the opening pressure. The reliability of the test is increased with painless disc-control (5). Furthermore, the International Spine Intervention Society (ISIS) developed their discography guidelines based on previous studies and combined pain scores, pressure measurements and provocation of concordant pain. ISIS labeled unequivocal discogenic pain if there is a reproduction of concordant pain at a level of 7/10 (verbal pain scale) or greater at a pressure of less than 15 psi above the opening pressures, when stimulation of two adjacent discs produces no pain at all. According to this classification definite discogenic pain exist when concordant pain develops at a level of 7/10 or greater, pain is reproduced at less than15psi above the opening pressure and stimulation of one adjacent disc produces no pain. Definite discogenic pain is also present if pain is reproduced at a pressure of less than 50psi above opening pressure and stimulation of two adjacent discs does not reproduce pain at all. Probable discogenic pain is defined as concordant pain of at least 7/10 at the pressure of <50psi above the opening pressure and when stimulation of one adjacent disc reproduces no pain at all while another adjacent disc produces pain at greater than 50psi but is not concordant. Finally, an indeterminate disc will not meet any of the above criteria yet still will produce pain. Clinical value: The reliability of provocation discography has been questioned from the very beginning of it’s use. Holt et al., in 1968 controversial study (10) injected intervertebral discs of 30 healthy inmates without history of lower back pain. 72 discs were injected satisfactorily out of 90, 11 degenerated and 16 ruptured discs were diagnosed. Overall, 37 % of volunteers reported back and leg pain. However, there were multiple problems with this study such as use of inmates as study subjects, using dye that can be irritating to tissues, and un-blinded provocation of concordant and nonconcordant pains (10). Other opponents of discography theorize that the internal disk disruption may not be the substrate for discogenic pain at all. A recent study indicated that the injury and subsequent repair of annulus fibrosus are causative factors in the degeneration of painful disc (11) that is formation of the area of vascularized granulation tissue joined by extensive innervation extending from the outer layer of the annulus fibrosus into the nucleus pulposus along the intradiscal fissure histologically characterizes painful disc (11,12). Multiplied macrophages and mast cells are also present in the same area (12). Majority of the recent studies support the use of discography for clinical diagnosis of discogenic pain and to select appropriate disc levels for planned surgical intervention (5, 13-19). A multicenter retrospective study of surgical outcomes in 96 patients showed that discography could predict successes of interbody/combined lumbar fusion (5). Other factors including workers compensation and psychometric profiles of the patients can influence results of provocation discography (20). 127 Page 3 Several minimally invasive treatments producing variable clinical results were introduced over the last 10 years. Annuloplasties using heat like IDET, radiofrequency single catheter annuloplasty and intradiscal biacuplasty all used discography as guidance for the patient selection. Our study could not predict success of the IDET procedure using discography and it is not yet clear if such diagnostic approach could influence success rates for those minimally invasive procedures (21). Complications: Complication rate of provocative lumbar discography is low (0-2.5%). Devastating complications are usually Infectious such as discitis, epidural abscess and bacterial meningitis (22-25). The prevalence of discitis ranges from 0% to 1.3% per disc and is usually due to penetration of contaminated needle with skin flora (23-25). Clinically, patients would complain of worsening back pain accompanied by laboratory findings of leukocytosis and elevated ESR (22). The occurrence of infectious discitis appears to be decreased with the use of intradiscal antibiotics (26). Intravenous administration of antibiotics may also bring selective intradiscal availability with frequently used cefazolin being at it’s highest intradiscal concentration 15-81 minutes after intravenous infusion (27). Another large study reported no complications of 1477 provocative discographies in 523 patients (28). Epidural abscess is a rare complication of provocative discography. There are a few case reports on epidural abscesses, one reporting on the patient’s bilateral leg pain after the procedure requiring lumbar laminectomy (29). The other epidural abscess occurred as a complication of computed tomography-guided discography when the discography needle pierced the trachea (30). Acute lumbar disc herniations precipitated by discography were described in four men and one woman, clinically manifested as an acute exacerbation of radicular leg pain and acute foot drop in one of the patients. Authors concluded that the annular deficiency may be a predisposing factor to discography-related disc herniation (31). Of other rare complications of the procedure, one case of urticaria in 750 discographic injections performed in 250 patients was reported (32). To avoid the majority of the above listed complications, it is recommended that lumbar discography be performed by a well-experienced physician, always in sterile conditions with a double-needle technique and fluoroscopic imaging used for the proper needle placement (1). Conclusions: Provocation discography remains controversial as diagnostic tool for discogenic pain. However, it still remains as the only test to relate pathologically changed MRI images to patient’s spinal pain. References: 1. 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