Anatomy

There is a gradual transition of disc morphology from the cervical spine, where movement is more relevant than loading, to the lower lumbar spine, where intervertebral movements are smaller, and load transfer is maximal.

The lumbar discs consist of a central NP surrounded by the AF which consists of concentric laminae of collagen fibers thickest anteriorly and laterally.³⁴ In contrast, cervical discs consist of a crescent-shaped anterior interosseous ligament with thick anterior collagen fibers that taper laterally toward the uncinate processes; they are essentially deficient posterolaterally where there is only a thin layer of paramedian, vertically orientated fibers.³⁵ The anterior longitudinal ligament covers the front of the cervical disc, and the posterior longitudinal ligament reinforces the deficient posterior AF with longitudinal and alar fibers.³⁵

Cervical discs have a different chemical morphology to thoracic and lumbar discs. In particular, they contain a higher collagen content in the NP and higher glycosaminoglycans content in the AF, both of which allow for the greater demands of bending and twisting movements in the cervical spine compared to other spinal regions.³⁶

Because discs are innervated, they have the capacity to be sources of pain.³⁷ The normal disc is avascular and aneural except for the outer third of the AF.^38,39 Lumbar discs are innervated by the lumbar sinuvertebral nerves, and branches of the lumbar ventral rami and grey rami comunicantes.^40–42 There are five types of nerve terminations found in the lumbar disc: these have various morphologies and include simple and complex free nerve endings that concentrate particularly in the lateral disc, with a smaller amount posteriorly and the least amount anteriorly.⁴³ The posterolateral portion of lumbar discs are innervated by the lumbar ventral rami that arise just lateral to the intervertebral foramen and by a branch of the grey rami communicans just before it connects with the ventral ramus.⁴⁰ The sinuvertebral nerves also innervate the posterior longitudinal ligament, and the grey rami communicantes also innervate the lateral disc and the anterior longitudinal ligament.^40,41 Additionally, the innervation by the grey rami communicantes is not a direct sympathetic innervation;⁴⁰ it has been postulated that somatic and afferent fibers from lumbar structures use the grey rami as transmission pathways only.⁴¹

Cervical discs are innervated laterally by branches of the vertebral nerve and more generally by branches of the cervical sinuvertebral nerves; these nerves penetrate as deeply as the outer third of the AF.^38,44 The end-plate adjacent to the NP is also innervated.⁴⁵

In discogram positive discs, histologic studies have shown that there is there is a more extensive and deeper innervation of the disc, with free nerve endings expressing substance P reaching into the outer part of the NP,^37,46,47 as well as the adjacent end plate and vertebral body.⁴⁸ The ingrowth of nerves in the discogram positive disc is within a region of vascularized and innervated granulation tissue that accompanies fissures extending from the AF to the outer part of the NP.⁴⁷ These nerves contain increased substance P (SP), neurofilament (NF), and vasointestinal peptide (VIP) immunoreac-tive nerve fibers, and are consistent with the concept of DP.⁴⁷

Disc Degeneration

Disc degeneration and similar morphologically descriptive terms including degenerative disc disease and zygapophysial joint spondylitis, are imaging-related labels that should not be used as diagnostic labels for a person presenting with NSSP. These terms describe mid- to late-stage degenerative change seen on imaging techniques. Although there may be a mild link between some imaging changes and NSSP,⁴⁹ there is at present no reliable or valid method to detect this relationship in any individual case.^50,51

Degeneration is an inevitable process. The process of degeneration consists of gradual structural change, which at times is accompanied by altered homeostasis and changes in innervation. Although such a process might be painful in its own right, or might determine that the whole intervertebral segment is prone to pain, there does not appear to be an inevitability that pain will appear. Thus, DD can be observed, but at this stage of science, little if any pain attribution can be assigned to it. Put simply, DD is not DP!

The IVDs are mainly composed of extracellular matrix molecules and have only about 1% by volume cell content, with the content of cells decreasing from the periphery inward, reflecting the relative avascularity of the disc.⁵² These cells are of vital importance for disc homeostasis because they regulate the synthesis and metabolism of the extracellular matrix.

DD is represented at a molecular level by a relative rise in the quantity of senescent cell population on the background of an overall fall in the total number of cells within the disc.⁵³ The percentage of senescent cells within a disc is also inversely related to the ability of other cells to proliferate, and the relative quantity of senescent and proliferating cells is independent of age.⁵³ DD ends with structural failure, represented macroscopically by thickened vertebral end plates, increased cracks and fissures in the matrix, and delamination and tears in the AF.⁵⁴ The radiologic endpoint of DD is disc space narrowing and osteophyte formation.⁵⁴

Cellular function within the disc is mediated by at least five major factors: genetics, nutrition (diffusion of nutrients and oxygen across the disc matrix), cell function regulation via IL-1, TNF-α and TNF-β, age and senescence, and mechanical loading.⁵⁵ The contribution to DD by genetic factors is highly significant; it may be as high as 80% in the cervical spine,⁵⁶ and general heritability for DD ranges from 34% to 61% in different regions of the spine.⁵⁷ In the lumbar spine, the genetic contribution is between 29% and 54%, with environmental influences of about equal importance.⁵⁸ For example, smoking has a moderate influence on the prevalence of DD,⁵⁹ presumably due to its effects on disc nutrition. This emphasizes that DD is not primarily or significantly due to aging⁶⁰ or to mechanically induced “wear and tear” processes.^57,61

Studies on symptomatic and asymptomatic populations with various imaging modalities emphasize that DD does not imply NSSP. In the cervical spine, radiologic DD is present in 13% of men and 5% of women during the third decade, in 85% to 90% of the population by the sixth decade, and nearly 100% by the age of 70.⁶² It occurs most commonly at C5-6, C6-7, and C4-5, respectively.^63,64 In people aged 60 to 65 years without neck pain, about 95% of men and 70% of women have at least one degenerative change on their cervical spine plain x-rays.⁶³ Although plain x-ray changes, including vertebral end-plate changes, disc space narrowing, spondylolisthesis, spondylolysis, sacral lumbarization, wedge vertebra, a sagittal diameter of less than 12 mm, and abnormal lumbar lordotic angle,^49,65,66 have some predictive value for low back pain, the relationship is mild at best,⁶⁷ and their detection is largely not helpful in the management of NSLBP because changes occur frequently in the asymptomatic population. As a consequence, plain x-rays should not be ordered unless there is suspicion of a red-flag condition.^68–71

The relevance of computed tomography (CT) scanning is similar to plain x-rays; it is an excellent test for some red-flag conditions, demonstrates DD well, but it is not helpful in the detection of DP. CT is better than MRI in detecting ZJ spondylitis,⁷² but this is of no particular clinical relevance. F-PET/CT (fluoride positron emission tomography with addition of CT) may have a role to play in that it is more likely to be positive in symptomatic patients, and in that it might identify the source of pain.⁷³

Plain x-rays combined with MRI provide the best method to detect DD.⁷⁴ Plain x-rays are perhaps better than MRI at detecting early stages of DD; MRI detects later stages of DD.⁷⁴ However, such information is only relevant to research because the detection of DD does not help in the diagnosis of NSSP. Studies of asymptomatic subjects have shown degenerative rates of more than 30% in the general population.⁷⁵

Discography is the best method to detect gross disc morphology. Fissures can be detected best on CT imaging postcontrast injection. However, although this component of discography detects degeneration, such a finding does not mean that the disc is a source of pain. For this reason, discography evolved from a purely morphologic test to one that attempts to detect whether or not the disc is painful. Discography, like other imaging modalities, should not be ordered in an effort to detect degeneration because degeneration is not a legitimate diagnosis for NSSP.

Discography and Pain

The relative uselessness of morphologic changes in the search for a source of pain has lead to the search for the painful source using two mechanisms; pain provocation and pain reduction.

Discography can theoretically cause pain from the disc itself by two fundamental mechanisms, annular distention and end-plate deflection. Annular distention during discography can initiate nociception because the peripheral AF is innervated. In vitro study has shown that in radiographically nondegenerated discs, discography causes measurable end-plate deflection ranging from 0.12 to 0.69 mm centrally and from 0.06 to 0.35 mm at locations between the center and the periphery of the end plate.⁷⁶ Hsu investigated 692 discs in patients with back pain; he showed that during PD end-plate disruption is uncommon (2% of all discograms) but that when it occurs even with lightly induced pressure, the prevalence of moderate or severe fully concordant pain is very high (in this series, 13/14 or 93%); in contrast, 42.3% of the remaining discs without end-plate disruption had moderate-to-severe fully concordant pain on PD, and 57.7% had either mild or zero pain.⁷⁷

Pain reproduction during the disc stimulation component of PD is considered integral to its validity. All discs, if provoked enough, will produce pain. However, a study on asymptomatic subjects revealed that even if grade 3 annular tears are present, pain induced on PD is likely to be mild—even at high manometric pressures.⁷⁸ From this study, pressures below which pain does not occur or it occurs at low intensity have been identified for asymptomatic subjects. The assumption is that this effect should be mirrored in studies of symptomatic patients, so that manometric pressure readings can be titrated against pain scores to set parameters above which the procedure can be called positive. For example, at a pressure of 50 psi any pain score above 6/10 is not seen in asymptomatic volunteers: at a pressure of 40 psi, the cut-off score is 5/10. Put another way, there is close to zero chance of an asymptomatic subject having any pain at 20 psi or less, and of having pain greater than 6/10 up to a pressure of 70 psi.⁷⁹ When the criterion for a positive PD pain response is 6/10 or more at 50 psi, the false-positive rates in asymptomatic subjects falls to 10%.⁷⁹

Derby and colleagues then found that there was a correlation between postdiscography CT scan levels of annular disruption and the pain score; using VAS of 6/10 or more at less or equal to 50 psi above opening pressure, they found that these parameters revealed negligible positive results at annular disruption below grade 3, and 44% positive results with grade 3 or greater annular disruption, with severe pain being proportional to the pressure in grade 4 and 5 discs.⁸⁰

Subsequent to this study, Carragee and coworkers found the false-positive rate of low-pressure painful disc stimulation injections in subjects without chronic NSLBP to be about 25%.²⁰ However, there were some drawbacks in this retrospective study including that some of these subjects had undergone previous back surgery. The conclusion from this study is that although the false-positive rate of PD may be as high as 25% in an imperfectly selected asymptomatic population, this figure is likely to be less in subjects who do not have a chronic pain state or who have not had previous spinal surgery.

In an effort to decrease the rate of false-positive findings, the methodology of discography is undergoing modification. The development currently is in AD, in which various local anesthetic agents are injected into the disc, and FAD, in which a balloon-tipped catheter is placed into the disc so that provocation maneuvers can be undertaken in the recovery room.^81,82

Referred Pain is not the Same as Radicular Pain

In presentations of axial pain, one major hurdle for the patient to overcome is the differentiation of referred pain from radicular pain. Most patients seem to consider that if the pain travels into the leg from the back that it is sciatica caused by a “pinched” nerve. It is important to understand the concept of referred pain because most pain in the limbs from the spine is referred pain. Radicular pain is relatively uncommon. One simple example of referred pain is angina, and this is a good model to discuss to indicate to the patient that limb pain can come from structures other than nerves.

Special Tests Rarely Substantiate a Diagnosis

As discussed earlier, MRI, the most morphologically accurate test, can be used to identify profiles that render a patient more likely to have a positive discogram or at least an increased likelihood of NSLBP. MRI and other tests cannot provide a definitive diagnosis of pain pathophysiology or source in a patient with NSSP. Most patients have had or want MRI, and most have had plain x-rays and CT scans. Often they have been provided with an imaging-derived morphologic diagnosis, such as disc degeneration or facet joint degeneration, or the more pejorative and equally illegitimate label, “disc degenerative disease.” Perhaps even worse, they might have been labeled with the more personally challenging negative finding; “we have not found anything at all wrong on these tests,” which might have the implication that the pain is invented or at least “psychological.” These tests should be understood for what they achieve. First, they have a varied ability to exclude red-flag conditions. Second, they are particularly useful as a tool to establish the cause of radicular pain. Third, by and large they cannot establish the cause of NSSP.

Diagnosis is Rarely Tissue or Pathology Specific

Diagnosis is particularly vexing; it needs to be accepted by all that in pain practice, diagnosis is often generalized to descriptions of the pain itself, and that illegitimate labels abound. NSSP is one label that can be used for a presentation of spinal somatic referred pain that is not caused by any other process or named condition. NSSP means pain, be it local or referred, that appears to derive from one of the locally innervated structures of the spine and does not derive from any known pathologic process.

The prime indication for discography is NSSP of sufficient longevity, dimension, and character that the clinician and the patient consider that some further step needs to be taken to achieve significant pain relief. There is no consensus regarding acceptable parameters above which discography might be performed. It is generally stated that a patient should have exhausted all conservative measures including multidisciplinary management, pain management programs, and rehabilitation before being considered for intervention including discography, and that the likely medium- to long-term scenario is for persistent substantial disability and pain.

The problem for the clinician is what to recommend to a patient with chronic disabling NSLBP. Discography is useful only from an interventional perspective if it rules in or rules out some form of treatment; options are confined to intradiscal procedures and spinal surgery. But these treatments have not been shown to be effective for the general population of patients with DP established on PD. Conversely, rehabilitation and pain management programs also have not had significant impact on the management of NSSP,^83–86 although exercise programs combined with fear-avoidance application have proven merit in the prevention of chronicity,^87–91 and pain management programs are often recommended as being more effective than traditional medical conservative treatment for chronic pain in general.⁹² In any case, the decision to move into interventional management for any patient typically occurs after such attempts have failed.

Predicting long-term outcome is probably impossible in individual cases. Trends exist: but the course of back pain is not as optimistic as has been conveyed.⁹³ Although about 76% of patients with a history of recent (within 6 months) low back pain recover or have low levels of pain, 14% have persistent, high disability with moderate-to-severe limitation of function.⁹⁴

Will the patient with severe disabling back pain ever get better? Many do not; however, some do. Smith performed a retrospective study of 25 NSLBP patients with positive PD in whom surgery was considered to be indicated yet was not undertaken.⁹⁵ At a mean follow-up time of 5 years, 68% had improved, 8% were the same, and 24% had worsened. Of those who had become worse, 67% had psychiatric disease. As an aside, in this study 80% of those receiving workers’ compensation improved.

If the patient does go to surgery consequent upon PD, what will be the long-term result? Knox and Chapman performed a retrospective study on 22 patients who had anterior lumbar interbody fusion for discogram-concordant lower back pain and found that all double level fusions did poorly and in single level fusions, 35% had good, 18% fair, and 47% poor results, with previous surgery and workers’ compensation doing the worst.⁹⁶ Parker prospectively studied 23 patients treated by a single surgeon with posterolateral fusion.⁹⁷ All underwent preoperative discography and were monitored for an average of 4 years postoperatively, at which time 39% had a good-to-excellent result, 13% a fair result, and 48% a poor result, with 90% of those on compensation having a poor result. Wetzel performed a retrospective review of 48 patients with low back pain who had discogram/CT, then lumbar arthrodesis, with a success rate (good outcome) of 46%.⁹⁸ Carragee performed total discectomy and fusion on patients with positive discography and achieved highly effective outcome in 27% of patients, and minimally acceptable or better outcome in 43%.⁹⁹

Is discography useful to detect pain possibly derived from discs adjacent to another disc that is to be fused? Willems found that PD adjacent to an intended to be fused segment (determined by temporary external transpedicular fixation) in patients with persistent back pain was not helpful and that patient outcomes after lumbar fusion were the same whether or not the adjacent disc was normal or degenerated.¹⁰⁰

Discography has also been used as a pretest for intradiscal procedures including intradiscal electrothermal therapy (IDET) and nucleoplasty. Results from these procedures suggest that there may be cohorts within the IDD subtype that do well.^101,102

What tests such as discography try to do is to develop a model that will predict which diagnostic subtype in which clinical scenario will do best with a particular treatment. It is a test that is not commonly performed; it is performed only on the most difficult presentations, and is done in interventional settings on a minimal number of patients presenting with spinal pain.

How Useful is MRI in the Assessment of NSSP and IDD?

MRI changes occur in the asymptomatic population.^51,103,104 In the lumbar spine, Boden and colleagues studied subjects with no past history of LBP and sciatica; in those younger than age 60, 20% had a herniated disc; in the 60 years and older group, 36% had a herniated disc and 21% had spinal stenosis. Disc degeneration or bulging at one or more levels occurred in 35% of subjects between 20 and 39 years, and in all but one of the subjects aged 60 to 80 years.¹⁰³ MRI findings are common in asymptomatic individuals and the extent of changes is not predictive of the development or duration of future back pain.¹⁰⁴

In the evolution of PD, attempts have been made to ascertain whether or not MRI can be used to predict PD outcome because PD is not without morbidity.^105,106 Although MRI is somewhat predictive of a positive PD test when a high intensity zone (HIZ) or Modic type I or II changes are found, it is somewhat insensitive.

The HIZ, defined on sagittal MRI as a very bright signal (equal to or brighter than CSF on T2 weighted scans) contained within the posterior AF,¹⁷ has been shown to have appreciable but variable correlation with positive PD in patients presenting with NSLBP.⁷⁹ The initial study showed that an HIZ increases the odds that PD will be positive in that patient at that level by a factor of 6.5.¹⁷ Studies on the HIZ since that time have all shown that HIZ is highly specific (range 0.74 to 0.93)^107–111 but variable sensitivity, from as low as 0.09,¹⁰⁸ to as high as 0.78.¹¹⁰ Thus, it is uncommon for an HIZ to occur in a disc that is not painful to PD, and the calculated likelihood ratios (ranging from 1.3 to 6.5 and averaging 4.1) indicate that an HIZ increases the odds that a PD will be positive by at least 50%.⁷⁹ Additionally, although HIZs are present in both asymptomatic and symptomatic subjects, they are found significantly more in symptomatic (prevalence 60% ± 15%) than asymptomatic subjects (24% ± 11%).¹¹²

Modic changes have also been studied in relationship to NSLBP and PD.^113,114 The overall rate of vertebral end-plate signal changes (VEPSC) is about 43% in patients with NSLBP and 6% in those without.¹¹⁵ The most common association of VEPSC and NSLBP is extensive Modic type I changes at L5-S1.¹¹⁶

Overall, VEPSCs are relatively insensitive, but quite specific, for the diagnosis of IDD established by discography, with sensitivity of 23.2%, specificity 96.8%, PPV 91.3%, and NPV 46.5% in one study.²⁵ When Modic changes are studied according to type, the type I end plate has the highest PPV for positive PD at 81% (±7%).¹¹⁴

It is possible for PD to be positive in the presence of a normal MRI. Zucherman reported on 18 symptomatic patients who had positive PD an average of 2.5 months after a normal MRI; positive meant production of concordant pain and abnormal disc morphology.¹¹⁷ This study was performed more than 20 years ago and whether or not this applies with current MRI technology is unknown.

Can Clinical Tests Predict IDD?

The prevalence of IDD in a population of NSLBP patients thought to have sufficient pain and disability to undergo PD is about 35%.^118,119 The prevalence of IDD in a group of patients with positive clinical indicators increases to 52% to 69%.¹¹⁸ The centralization phenomenon, or pain centralization, which is the retreat of referred pain toward the spinal midline during specified clinical examination, a history of persistent pain between acute episodes, a significant loss of extension and a subjective report of so-named “vulnerability in the neutral zone” individually and in combination increase the likelihood of an eventual diagnosis of IDD in a group of highly disabled and psychosocially distressed patients with otherwise diagnosed NSLBP.^118,120 Additionally, if vibration applied over individual spinous processes is considered a positive test, then the odds of a positive PD increases significantly.^121,122

Interpretation of Discography

There are three cardinal components that need to be recorded separately but viewed collectively; (1) provocation/analgesia, (2) disc manometry, and (3) disc morphology. These three different aspects are required to write a discogram report, and all three elements are still evolving.

The International Spine Intervention Society (ISIS) describes positive PD as follows:⁴⁹ (1) reproduction of the patient’s pain by stimulation of the affected disc; (2) such that the evoked pain has an intensity of at least 7 on a 10-point scale; and (3) pain is reproduced at a pressure of stimulation of <15 psi; (4) provided that stimulation of adjacent discs does not reproduce pain; and (5) postdiscography CT demonstrates a grade 3 or 4 fissure.

Provocation/Analgesia Assessment

Although this phase occurs as the last step in discography, it is the most important aspect to record because it, above all, is the component that separates discography from other tests. Because this phase requires the patient to report subjective pain responses, it is open to reporting bias and other error.

The optimal setting for the provocation component of discography is as follows: (1) the patient needs to be calm and comfortable, (2) the person recording the information from the patient should not be the injector, (3) that person and the patient should be blinded to the disc being injected.

The degree of pain production should be recorded. It is not possible in many instances to use a visual analog scale in the operating room during the procedure. If so, a verbal pain rating is used. The patient should understand beforehand that this is to be used and it should be ascertained that the patient understands how to communicate pain with 0 to 10 as being no pain and 10 of 10 being the most severe pain that he or she can imagine.

An example of the recording that can be used for PD is:

Disc Manometry

Disc manometry is an estimate of the hydrodynamic competence of a disc. It is formally measured with manometric pressure systems.^13,123,124 In IDD, NP pressure decreases irregularly, and AF stresses rise. The depressurization of the NP reflects the degradation of the nuclear matrix, which can no longer retain water efficiently, to sustain axial loading. This results in extra load having to be borne by the posterior AF. Both of these findings correlate with a positive provocation component.¹²⁵

Disc Morphology

The morphology of the disc is revealed during the contrast injection phase of discography. Under image intensification, AP and lateral views are used routinely. In a normal discogram, contrast remains contained within the NP, and it has smooth, regular margins. When abnormal, contrast is seen to flow from the NP into the AF, and when the disc is ruptured it flows into the epidural space.

Postdiscography CT scan performed within 3 hours of the procedure provides more information about disc morphology and is said to improve diagnostic accuracy, at least for disc prolapse.¹²⁶ CT-discography importantly provides a better ability to subtype PD according to the Dallas system.¹⁶ Where CT is not available, caudad gantry views can show the discs close to AP.

Cervical and Thoracic Discography

It is not possible to determine if a cervical disc is a major source of pain using MRI or other imaging techniques, particularly as MRI findings do not correlate well even with advanced histologic DD.^127,128 However, the cervical disc is likely to be a source of pain. If cervical DP is diagnosed, the ability of such knowledge to improve outcome in the management of neck pain is questionable.^129–136 Cervical discography has hardly been studied,¹³⁷ but has advocates. A review of cervical provocation discography, which includes disc stimulation and morphologic evaluation, found that there were few studies of good standard, and concluded the cervical discography is a useful tool for evaluating chronic cervical pain, without disc herniation or radiculitis, with the strength of evidence for diagnostic accuracy being at Level II-2.¹³⁸ However, because the morphology of the cervical disc is substantially different from the lumbar disc, no comparative conclusions can be made from the studies on lumbar discography. The cervical AF does not consist of concentric laminae of collagen fibers as in lumbar discs; it is a crescentic mass of collagen that is thick anteriorly and tapers laterally toward the uncinate processes, and is deficient posterolaterally.¹¹⁴ There are no established postdiscography CT scan findings such as is seen in the Dallas description of these in the lumbar spine. There are no clinicopathologic correlations that underpin cervical, or thoracic, discography.

The technique of cervical provocation discography was first published in 1957,¹³⁹ having been pioneered by Cloward,¹⁴⁰ and subsequently developed.^141–144 In the lumbar spine, abnormal morphology and precise pain reproduction are two of the more important components that contribute to a positive discogram.¹⁴⁵ This is not the case in the cervical spine because fissuring of cervical discs is not reflective of trauma but of normal anatomy and aging,^146–149 and, hence, extravasation of contrast from the disc in cervical discography cannot be considered to be indicative of an abnormal disc.^149–152 The essential component of cervical discography is, therefore, not morphologic, but it is in what happens during the injection or “stimulation” phase because stimulation of cervical discs in asymptomatic volunteers is painless or only minimally painful,¹⁴⁸ meaning that cervical disc stimulation has at least some negative predictive value: if the disc does not hurt when stimulated, it is unlikely to be a source of pain. Additionally, to diminish the possibility of false positives, subsequent opinion and study has discerned that adjacent structures should be similarly stimulated to ensure that pain is not apparent in multiple sites.

If cervical discography is used, it should be understood that it is in the very experimental stage of evolution. If performed, the recommended protocol is to perform multilevel procedures that stimulate pain: positive disc stimulation occurs when: (1) provocation of the target disc reproduces the patient’s (concordant) pain, and (2) adjacent site stimulation does not reproduce pain.¹⁵³

It is evident from the use of cervical facet joint blocks and disc stimulation that more than one source of pain can be detected at any one cervical intervertebral segment.¹⁵⁴ As a consequence, when disc stimulation is used, a positive test requires: (1) reproduction of the patient’s concordant pain at a magnitude of at least 7 on a 10-point VAS, (2) exclusion of cervical facet joint pain at any segmental level where disc stimulation is positive because the false-positive rate without exclusion is 67%,¹⁵⁴ and (3) not finding reproduction of the patient’s pain in adjacent structures.

Thoracic discography is even less studied. In a study on 10 asymptomatic subjects and 10 patients with chronic thoracic pain undergoing PD, it was found that: (1) even in asymptomatic people, thoracic discography could be intensely painful, especially when prominent Schmorl nodes were present, (2) MRI changes did not always correlate with disc morphology on discography, and (3) in the symptomatic group, 50% of studied discs were concordantly painful.¹⁵⁵

Discitis

The use of sterile technique and single- or double-needle technique seem to be the minimum requirements for the prevention of infection. Prophylactic antibiotics may decrease the incidence of discitis.

Discitis is a nasty complication. A review of cases revealed the following:¹⁵⁶

There are no randomized or controlled trials on the efficacy of prophylactic antibiotics.¹⁵⁸ Based on animal experiments,¹⁰⁶ the incidence of postdiscography discitis is lowered with the use of cefazolin given intravenously or in the intradiscal suspension injection. In high concentrations, contrast medium can itself inhibit bacterial growth at least to some degree, and it does not reduce the inhibitory effect of antibiotics.¹⁵⁹ A follow-up of 127 consecutive patients having lumbar discography with contrast containing cefazolin 1 mg/mL revealed no cases of discitis.¹²¹ Willems and colleagues had no cases of discitis when they performed two-needle technique discography without preemptive antibiotics on 200 patients and followed them all for a minimum period of 3 months.¹⁶⁰ The reported overall incidence of discitis without prophylactic antibiotics is in the region of 0.25% of all patients or 0.094% of all discograms.¹⁶⁰

It is of course important to know where the injectate is going. Initial injection of antibiotic containing material should not be made if the needle tip site is unknown. For example, intrathecal administration of cefazolin can be fatal.¹⁶¹

Can Discography Cause Harm?

Experimental animal studies have revealed that disc puncture can induce accelerated disc degeneration. Carragee followed two matched cohorts of 75 each without serious LBP “illness.”¹⁰⁵ Each subject was assessed with MRI and one group underwent L3-4, L4-5, and L5-S1 discography examination in 1997. Between 7 and 10 years after enrollment, each subject underwent a further MRI: 50 discography subjects and 52 control subjects were reassessed. The results were summarized as follows: (1) in all graded or measured parameters, discs that had been exposed to puncture and injection had greater progression of degenerative findings compared to control (noninjected) discs: progression of disc degeneration, 54 discs (35%) in the discography group compared to 21 (14%) in the control group; 55 new disc herniations in the discography group compared to 22 in the control group (2) new disc herniations were disproportionately found on the side of the AF puncture, (3) the quantitative measures of disc height and disc signal also showed significantly greater loss of disc height and signal intensity in the discography disc compared to the control disc.

Additionally, discography can produce long-term pain in subjects with abnormal psychological profiles. A 12-month follow up of subjects without LBP revealed that no subject with normal psychometric testing had persistent pain after discography, but pain of those with abnormal psychometric test results reported significant new low back pain.¹⁶²

These facts mean that discography should not be undertaken unless there are strong indications that the results will substantially alter the management and that the management changes have a reasonable chance of producing a far better outcome than might be obtained otherwise. The second part of this chapter discusses the technical and radiographic aspects of discography.

Contraindications

Absolute contraindications to the performance of discography at any level include (1) the patient being unable or unwilling to consent to the procedure; (2) inability to assess the patient response to the procedure, including sedation, significant analgesic use, or psychiatric overlay; (3) significant localized or systemic infection; and (4) pregnancy. Relative contraindications include (1) anticoagulant therapy or bleeding diathesis; (2) allergy to radiographic contrast, local anesthetic, or antibiotic; (3) anatomic derangements that would compromise the safe and successful conduct of the procedure.

In regard to cervical discography, further contraindications exist. A case of iatrogenic quadriplegia has been reported² owing to iatrogenic disc herniation and severe cord compression resulting from a disc injection at a level with little reserve space secondary to spinal stenosis. An anterior-posterior (AP) spinal canal diameter of less than 10 mm is an absolute contraindication, whereas an AP diameter of less than 11 mm constitutes a relative contraindication, to the performance of cervical discography at the specific or adjacent levels. To ascertain whether cervical discography is safe, the physician injectionist must personally interpret a recent MRI or CT scan to ensure that the cervical canal is ample.

Complications

Prior to the routine use of prophylactic antibiotics, discitis was the most feared, although nonlife threatening, complication to disc access. However, with precautions as will be detailed subsequently, this problem has become exceedingly rare. A comprehensive discussion of complications attributable to discography, mild to severe, is beyond the scope of this chapter, and the reader is directed to several excellent reviews and papers on the subject.^12–19

Equipment and Training

Fluoroscopy equipment allowing for the requisite excellent imaging is a basic requirement for access to the intervertebral discs. The fluoroscopic instrument of choice is the C-arm, which can be moved in any plane to provide optimum imaging to direct needle insertion and to verify, and document, final needle position and contrast spread. C-arms, which can accommodate a 55-degree contralateral oblique provide greater and easier access and the ability to target either side. Radiation-saving modalities, such as low-dose, pulsed mode, collimation, and saving of last image are essential and ensure safe practice. Digital subtraction imaging (DSI) capability can often provide useful information, especially if the patient has undergone previous surgery with metallic hardware implanted.

It is imperative that all physicians performing discography have training in the interpretation of real time fluoroscopic images whether cervical, thoracic, or lumbar. This training must be beyond the level of a residency and most current “pain” fellowships. Expertise in radiologic interpretation is far beyond the training and proficiency of nurse anesthetists (CRNAs), physician assistants (PAs), and other so-called “mid level nonphysician providers.”

To use the C-arm, an x-ray compatible procedure table is required. Although some operating room tables may suffice, most have metal incorporated into their structure which limits certain fluoroscopic projections. Carbon fiber tables, with the pedestal at the foot, are now quite affordable, and provide unlimited access and unrestricted imaging possibilities.

Radiation safety precautions as discussed in Chapter 5 should be followed.

In regard to radiographic guidance, although the use of computed tomography (CT), guidance has been advocated by a minority of practitioners,²⁰ this technique should be avoided. Using CT allows one to accurately delineate the skin entry point, however the advancement of the needle toward the target is accomplished crudely, without imaging assistance. This adds to the physical discomfort of the patient, the time required to complete the procedure, and the chance for needle misadventures. CT necessitates the injection of contrast for verification of needle placement without the benefit of active, real time imaging. Therefore, during the injection phase of the procedure (i.e., disc stimulation) the emerging contrast pattern cannot be monitored for disruption of the annulus, end-plate ruptures, and increase in height of the disc. In addition, vascular injections will, in all likelihood, escape detection owing to the rapid “washout” of contrast secondary to blood flow within the vein or artery. Marked increase in total radiation exposure to the patient is inherent in CT and should be of concern to all involved. There is no literary evidence indicating any benefit to the use of CT for discography. Specialty group guidelines published by the International Spine Intervention Society (ISIS)²¹ and the Physiatric Association of Spine, Sports, and Occupational Rehabilitation (PASSOR),²² specifically do not mention CT for use with disc access.

A historical record of all procedures must be archived with hard or digital images. Multiple images must clearly identify that the needle is in safe position in AP and lateral projections prior to injection of contrast, and after disc stimulation by contrast injection.

Miscellaneous Supplies

A variety of needles and syringes are required and vary as to the specific procedure level. This will be presented in the subsequent discussions. In addition to the specific procedure needles, a 25-gauge, 1.5-inch needle for skin localization and an 18-gauge needle for drawing up medications are used. A sterile, long, 8- to 12-inch, radio-opaque pointer, combined with a skin marking pen enables the injectionist to mark the proposed skin entry site in a sterile and radiation-safe manner.

As of this date, only lumbar discography requires the use of manometry, although in rare cases, a 3 mL syringe may be considered appropriate but far short of the ideal. Many manometers both digital and analog can be purchased. Most are accurate to the degree required. Automated systems, which inject and record, are available but expensive and provide questionable benefit. For cervical and thoracic procedures, a 3 mL syringe fitted with short, low-volume, small-bore extension tube is used: syringes smaller than 3 mL can exert too much pressure, whereas a 5 to 10 mL syringe is limited to the pressure that can be generated.

Monitoring devices, such as pulse oximetry, noninvasive blood pressure, and ECG, must at the least be immediately available, and their use is required if any sedation is contemplated. An ongoing conversation with the patient is always an appropriate and accurate monitor of the patient’s comfort, level of consciousness, cardiac, and respiratory status pre-, peri-, and postprocedure. Whether the procedure is performed in an office, ambulatory surgery center, or hospital setting, emergency equipment, pharmaceuticals, oxygen, airway supplies, suction, and other resuscitation provisions must be immediately available and checked regularly to ensure proper functioning. In addition, trained personnel must be available in case of an emergency.

Intravenous Access

Intravenous (IV) access is considered essential for discography. Although rare, emergent situations do occur and time restraints may not be ample to initiate IV access. Intravenous antibiotics (cefazolin 1 gram, gentamicin 80 mg, ciprofloxacin 400 mg) 15 to 30 minutes prior to needle insertion is standard of care. Although exceedingly rare, complications requiring the use of IV medications (allergic reactions, severe vasovagal reactions) do occur and IV access provides the possibility of nearly immediate treatment. In addition, discography is considered by many to be a highly stressful procedure and mild sedation is often provided.

Medications

For patient comfort and acceptance, anesthetizing the skin and underlying tissues with lidocaine (Xylocaine) 1% prior to needle insertion is suggested. In cervical discography, for the majority of patients, the target structure lies within 1 inch of the skin surface. In this case, for needles larger than 25 gauge, a skin wheal alone will suffice. For lumbar and thoracic procedures however, when 18- or 22-gauge introducer needles are positioned close to the disc itself, a track of local anesthetic to the depth of the superior articular process provides excellent working conditions. This can be easily accomplished using a 25-gauge, 3.5 inch Quincke or Chiba spinal needle.

In that the very name discography indicates an imaging study of the intervertebral disc, contrast is required to detail the internal disc architecture. Only nonionic, water-soluble contrast media should be used. Iohexol (Omnipaque) or iopamidol (Isovue) in concentrations of 180 to 240 mg/mL are safe with allergic reactions occurring in the 1:500,000 range. Contrast of the 300 mg/mL concentration, may be useful in cervical discography where the small volumes used may require a higher concentration for good visualization with fluoroscopy. Today, the addition of antibiotics to the contrast medium should be considered routine. The excellent paper by Klessig and colleagues²³ details this practice. Gentamicin and cefazolin in a concentration of 1 mg/mL of contrast, or clindamycin 7.5 mg/mL exceeds the minimum inhibitory concentration of Staphylococcus aureus, Staphylococcus epidermidis, and Escherichia coli, the three most commonly implicated organisms in discitis events.

Sedation

Although discography is an uncomfortable procedure, in competent hands, optimum sedation is often attained using minimal doses of pharmaceutical agents. Providing the patient with a detailed, honest account of the anticipated procedure during the consent phase of the interaction, “talking the patient through” the procedure (i.e., assuring that he/she is aware prior to any sensory stimulation, engaging the patient in conversation, and perhaps using music, or other sensory stimulation as a mild distraction) is imperative to creating a compliant, relaxed patient. At all times during the course of the procedure, the patient must be able to converse with the attending physician. If not obtunded prior to any untoward event, the patient will often give a vocal warning of unintentional misplacement of the needle. However, when carried to a point where the patient is unresponsive or minimally responsive to painful stimuli, this degree of sedation must be considered as dangerous and is never appropriate.

Intravenous midazolam is considered by many to be the perfect agent to provide a patient who is mildly sedated, but compliant. Excellent sedation is seen at doses in the range of 2.0 and 5.0 mg, often with a profound amnestic effect. Although not the choice of the author, some injectionists with an anesthesia background use the ultra–short-acting hypnotic, propofol. When given appropriately, the short half-life of this drug produces rapid, profound sedation for needle insertion, but rapid recovery for disc stimulation. It must be taken into consideration that high doses of any medication may lead to dysphoria, inability to respond to instructions, and noncompliant behavior. Unfortunately in many instances, sedation is used to conceal poor operator technique. Sedation can never take the place of technical competence.

The use of opioids as a pre- and/or periprocedure medication for discography is a contentious subject. The essential endpoint of mechanical disc stimulation is the patient’s perception of significant concordant pain. By their very nature, opioids blunt the perception of pain. The provocation of pain during discography must be accurately assessed, compared and quantified by the patient. The primary action of opioids will therefore lower the pain threshold, and the discomfort will be perceived as less severe. This may significantly alter the results of this diagnostic test. Therefore, use of even low-dose analgesic medications during discography will ensure a higher rate of false negatives. Conversely, some argue that providing a “small dose” of narcotics (fentanyl 50 mcg, meperidine 50 mg, or morphine 5 mg) prior to the procedure will help to decrease the rate of false positives in patients with clinically insignificant discogenic pain. For the sake of accuracy, possibly raising the standard for a positive discogram, from a VAS from 7/10 to 8/10, might be a more advantageous technique than through the use of unpredictable medications with wide variability in patient response. A diagnostic test is only as reliable as its accuracy, and opioids in any quantity degrade this quantitative data in an unpredictable manner.

One often overlooked aspect concerning the use of significant sedation during discography is the expectation created by their use. During the consent phase prior to the procedure, the detailing of marked sedation provides validation of the patient’s expectation of a painful, brutal procedure, and creates the perception that the planned procedure is inherently excruciating to such a degree that significant sedation is required; this belief is self-fulfilling. In addition, the psychological overlay, often seen as a comorbid condition in the chronic pain patient, validates the patient’s idea of the extreme severity of the condition, in that a procedure that requires sedation must be unbearable.

One problem facing discographers is that patients on chronic opioid therapy have developed some degree of altered pain response, including hyperalgesia and allodynia because of their long and often questionable narcotic treatment. Having these patients withdrawn entirely from their medications is often not an option. In this patient subset, provocation discography can be performed using their present state of medication load as a baseline pain level. Although quantification of their pain response might be difficult, determination of pain response to specific disc levels is often easily accomplished. When presenting these results to the referring physician or surgeon, the outcome must be understood in the context of the patient response to mild-to-moderate pain, such as creation of the local anesthetic skin wheal with a 25-gauge needle.

Preparation and Drapes

Although the incidence of discitis is low, precautions must be taken, and a clean procedure or operating room is imperative. Aseptic technique must be adhered to using a sterile skin preparation with povidone-iodine, iodophor-alcohol (DuraPrep), or chlorhexidine and alcohol. Draping with sterile towels and fenestrated drapes provides a sterile field. Clean scrub suits for all those in attendance, and surgical caps and masks for those in proximity to the patient are prudent. Most discographers scrub, gown, and glove as for an open surgical procedure. A sterile cover for the C-arm image intensifier allows the physician to directly orient the image intensifier during the periprocedural period, and prevents contaminating detritus from falling onto the sterile field from the equipment.

Techniques

Prior to beginning a discographic study, a decision as to what levels need to be included must be made. This selection is based on the physical examination, imaging studies, and patient symptomatology. Accurate pain referral maps are available for the cervical^24–26 and thoracic^27,28 regions and, although based on induced zygapophysial joint pain, appear to be accurate for intervertebral disc-mediated pain as well. In that negative control levels rostral and caudal to any substantiated painful disc provide an internal negative control validation, the suspected intervertebral disc and the two adjoining discs should be included. Although extraordinary exceptions may exist, disc stimulation of more than four levels is rarely indicated.

Postprocedure

Following the procedure, the patient is taken to recovery. Results of the procedure are discussed realizing that the medications used for sedation may render the patient amnestic. If positive concordant pain was noted at any level, a CT scan to document grade of annular disruption can be considered (see Fig. 38-19).

Although at one point, CT postdiscography was the norm, with discography becoming routine, and being performed in offices and ambulatory surgery centers without CT capabilities, CT imaging can no longer be thought of as an absolute requirement. However, if significant concordant pain is noted during disc stimulation, but disruption of the annulus is not evident with fluoroscopy, a CT scan is mandated because occasionally, a very small tear is not evident on fluoroscopy but is apparent on axial CT views.

When stable, the patient is discharged from the facility with postprocedure instructions. Driving should be curtailed for the day of the procedure. Some mild increase in the patient’s basal low back pain level is to be expected for a day or two. This increase is rarely severe and can be well managed with a prescription for a small amount of oral analgesics. The patient is provided with instructions for discussion of procedure results with the injectionist or the referring physician.

As with all medical procedures, a true and accurate post procedure report must be generated by the discographer. This record must include all pertinent information and be of such detail that a reviewing physician can appreciate what actually occurred during the procedure itself. If a postprocedure CT was ordered, interpretation of this by the discographer is required. Correlation between the provocation discography and the CT images is essential and has validity only if performed by that physician involved with actually stimulating the intervertebral discs and evaluating the patient during the procedure. Interpretation by a noninvolved radiologist, separated by time and distance, is at best meaningless and inappropriate. See example in Appendix A.

Equipment and Supplies

Thoracic discography requires the same basic equipment and supplies as for lumbar, with a few changes. No literature exists as to the diagnostic benefit of using manometry in the thoracic spine. Unless the lower thoracic levels are a continuation of an upper lumbar study, manometry is merely an unproven option. However, it appears intuitive that a disc evidencing concordant pain at low pressure is of more significance than one requiring high pressure to elicit a response. Dual needle techniques are rarely used in the thoracic spine. Secondary to the anatomy, 3.5- or 5-inch needles can be used to access most thoracic intervertebral discs unless a patient of very large body habitus is being studied.

Procedure

The patient is positioned prone on a radiolucent procedure table. Monitors are attached, IV antibiotic is provided, and mild sedation as above is initiated. Depending on the chosen procedure levels, the corresponding thoracic region is prepared and draped. In that most of the twelve thoracic levels are difficult to differentiate from each other, meticulous care must be taken to identify the targeted intervertebral discs. Counting down from T1, and then up from T12, should provided an identical answer. At each level to be studied, the end plates surrounding the disc are aligned so as to be parallel to the x-ray beam by using cephalocaudal tilt of the image intensifier (see Fig. 38-21). The end plates will evidence a linear rather than an oval appearance. As with the lumbar procedure, an oblique view is then used contralateral to the dominant pain (see Fig. 38-22, A).

Figure 38-21 Scout anteroposterior (AP) midthoracic spine. T6-7 disc end plates parallel to x-ray beam, arrows. Pedicle (P).

Figure 38-22 Right oblique. A, End plates of the T6-7 disc are parallel to the x-ray beam, arrows. Pedicle (P). Lateral pedicular and medial rib headlines are indicated by broken linesB, Open arrow points to target “box”. Needle is in position at T7-8. C, Magnified right oblique thoracic spine. Needles are in position at T8-9 and T7-8.

As the C-arm is rotated, the spinous process will appear to move toward the contralateral side, followed by the pedicle and rib head of the infrasegmental level. A hyperlucent rectangle, or “box,” will become distinct over the target disc. When the pedicle is seen to be positioned approximately 30% to 40% across the vertebral body further rotation should cease. The hyperlucent “magic box” will appear, and is easily identified over the disc with its sides defined rostrally by the inferior end plate of the vertebral body above; caudally by the superior end plate of the vertebral body below; laterally by the medial rib head line (i.e., a line oriented rostral-caudal connecting the medial aspect of the rib heads; and medially by the medial pedicular line which approximates the superior articular process and lamina which is at times quite indistinct (see Fig. 38-22, B).

The skin is marked over the hyperlucent “box” and a local anesthetic skin wheal is made. A 25-gauge, 3.5-inch needle can now be advanced through the wheal toward the target and a local anesthetic track can be injected during withdrawal. A puncture can be made with an 18-gauge needle so that the disc puncture needle need not pierce and potentially carry skin and detritus into the disc. Depending on level and body habitus, a 22-gauge, 5-inch, or 25-gauge, 3.5-inch disc puncture needle, with slight bend at the tip opposite the bevel, is introduced and using the “tunnel vision,” down the beam approach, guided toward the target “box” (see Fig. 38-22, C).

The needle is incrementally advanced using intermittent fluoroscopy to make corrections. It is important to stay medial to the medial rib head line, the costovertebral joint, because the lung lies just lateral. Os is often contacted during needle advancement because the needle is transiting a space between rib head and superior articular process (see Fig. 38-20). If contact is made, withdrawing the needle tip from os 1 to 2 mm, rotating the needle and reinserting slowly, the bent needle tip will allow one passage through this narrow space with minimal difficulty. Needle advancement is stopped when the intervertebral disc annulus is contacted as can be appreciated by its unique tactile feeling. The other levels are now accessed to the point of disc contact. When all needles are positioned in proximity to the discs (see Fig. 38-23), the C-arm is positioned for a lateral view, and the needles will be seen as aligned parallel to the respective vertebral end plates in the infraneural, caudal position within their foramen. The needles are then advanced slowly using active lateral fluoroscopy, using rotation to provide directional control secondary to the bent needle tips. The disc is felt and seen to be entered, and the needles are inserted sequentially into the center of the intervertebral discs.

Figure 38-23 Right oblique thoracic spine. Needles are in position within the lateral annulus of intervertebral discs T6-7, T7-8, T8-9, and T9-10.

Needle position within the nucleus pulposus is then verified, and documentary AP and lateral images are saved (see Fig. 38-24).

Figure 38-24 A, Lateral view thoracic spine. Needles have been advanced into the center of each disc. B, Anteroposterior (AP) view of thoracic spine. Needles are noted to lie in the center of each disc.

Injection of contrast with antibiotic is then made into each disc using active lateral imaging. The disc felt most likely to be positive by MRI pathology should be injected last. The patient is blinded as to level and onset of stimulation. As discussed previously, either a manometer is used, or 3 mL syringes with a small-bore, low-volume extension tubing. Tubing length must be limited in that perceived pressure increases in proportion to length. The injected volume into a thoracic disc will range from 0.5 to 2.5 mL depending on level, the more rostral discs resembling a cervical disc and accepting little volume. During injection, if a manometer is used, the same objective data as collected for lumbar discography is recorded. If one elects to use 3 mL syringes, approximate pressure generated, and characteristic of the endpoint (soft or firm) are recorded in lieu of opening and final pressure as determined with a manometer. AP and lateral images postcontrast are then saved (see Fig. 38-25, A and B). A true and exact, detailed procedure record of the entire procedure must be produced by the discographer as a historical documentation of the study. Postprocedure care is identical to that for lumbar discography. CT imaging postthoracic discography although never validated as having diagnostic utility, might be obtained if beneficial information is expected (see Fig. 38-25, C-E).

Figure 38-25 A, Anteroposterior (AP) view of thoracic spine. Injection into (i.e., stimulation of) each disc has been completed. Concordant pain (+); No pain (−). B, Lateral view of thoracic spine. Injection into (i.e., stimulation of) each disc has been completed. Concordant pain (+); No pain (−). C, CT image T6-7. Disc stimulation (−). Note internal disc disruption (IDD) with negative stimulation. D, CT image T7-8. Disc stimulation (+) with IDD. E, CT image T8-9. Disc stimulation (+) with IDD. F, CT image T9-10. Disc stimulation (+) with IDD.

Equipment and Supplies

As with all spinal injection techniques, cervical discography requires the use of a quality fluoroscope. Some physicians elect to place the fluoroscope at the head of the table rather than the side. This allows unrestricted positioning of the C-arm and excellent visualization of the cervical region in any plane. However, an x-ray compatible procedure table with the pedestal at the foot, allowing for unfettered, 360 degree access to the head of the bed must be available if this technique is used.

Only the rare discographer elects to use manometry in the performance of cervical discography. Volumes are small, and the unique anatomy of the cervical intervertebral disc lends itself to manual pressurization. For each level to be injected, a 3 mL syringe with small-bore, low-volume extension tubing is used. Quincke tip spinal needles (25-gauge, 3.5 inches) are the ideal instrument for accessing the cervical intervertebral disc. Although in most cases the disc can be entered using a 2-inch needle, the longer needle provides the benefit of allowing ease of tubing attachment to the hub with less chance of needle displacement. Whereas iohexol or iopamidol contrast in the 200 to 240 concentration are acceptable, the 300 variety provides somewhat better visualization with the very small volumes used with this procedure.

Procedure

The patient is placed in supine position with a pillow under the shoulders to slightly extend the neck and the head is rotated slightly to the left. Monitors are attached, IV antibiotic is provided, and mild sedation as detailed earlier is initiated.

After positioning, preprocedure fluoroscopic screening ensures adequate visualization of all planned levels in AP, lateral, and oblique views. Beards prevent adequate sterile preparation of the skin and must be removed before the procedure, preferably the day before. The cervical region is prepared and draped in a sterile manner. A wide preparation is advisable and should include the entire anterior and lateral neck, extend down to the clavicles, and include the mandibular area. Both shoulders are incorporated so that the discographer can push the shoulders down manually if adequate visualization so demands. As with all spinal procedures, “An ounce of prevention is worth a pound of cure”. ⁴⁵

Excellent discogenic pain referral maps for the cervical region are available,⁴⁶ and will help guide the discographer; however, multilevel discogenic pain is common⁴⁷ and a minimum of four levels should be studied to prevent omitting a painful disc and providing unreliable information. If pain is noted as referred into the occiput, C2-3 must be studied, whereas if scapular pain is present C6-7 is included.

Unlike the thoracic and lumbar procedures, in cases of cervical pain, the zygapophysial joint must be evaluated prior to proceeding with provocation discography. An extraordinarily high false-positive rate (68%) has been noted by Bogduk and Aprill,⁴⁸ when cervical discography was not preceded by cervical medial branch anesthetic injections to block the segmental zygapophysial joints.

In that the esophagus is prominent on the left, needle insertion is always from the right independent as to side of dominant pain. The skin entry will be approximately along the medial border of the sternocleidomastoid muscle (see Fig. 38-26) but will vary slightly with the individual level. At the C6-7 level the apex of the lung, the thyroid, and common carotid arteries require a slight medial approach. The thyroid cartilage is present at C5-6 and will be readily evident if contacted on insertion, whereas a somewhat more lateral needle insertion is used at C2-3 to prevent entry and passage through a possibly distended hypopharynx.

Figure 38-26 Axial MRI T2 WI at C6-7 level with illustration of needle insertion. C, Carotid; E, Esophagus; IJ, Internal jugular; T, Trachea; Th, Thyroid; SCM, Sternocleidomastoid muscle.

In the cervical region, due to the short distance between skin and intervertebral disc a dual needle technique is not advised. A slight bend on the 25-gauge procedure needle allows the operator to control direction during insertion. In addition, intradiscal manipulation is impossible without this needle modification. Any local anesthetic used must be limited to the skin because deeper infiltration may track along the cervical plexus or sympathetic chain and cause alteration in any pain response.

With the patient positioned as above, the fluoroscope is obliqued toward the right into the so-called “foraminal view” where the foramen are seen at their widest extent in both the cephalocaudal and ventral-dorsal dimensions. This is the same view advocated for cervical transforaminal and cervicothoracic (stellate) ganglion injections. The objective disc is identified by counting down from the readily identifiable C2-3 level, and the C-arm is manipulated so that end plates of the contiguous vertebral bodies are seen to be parallel to the x-ray beam. It must be emphasized that the course of the vertebral artery runs in a cephalocaudal orientation over the uncinate line (see Fig. 38-27).

Figure 38-27 Scout image cervical spine “foraminal” view. Note inferior end plate of C5 and superior end plate of C6 are parallel to x-ray beam. Light dashed lines represent the position of the vertebral artery.

A target point is selected over the disc approximately one third the distance between the uncinate process and the apparent ventral disc margin (see Fig. 38-28, B). The skin entry site is marked, and will be seen to be medial to the sternocleidomastoid and carotid artery, which can be easily palpated. If desired, a small skin wheal is made with local anesthetic. Using a blunt sterile instrument, pressure is then applied over the insertion site to decrease the distance between the skin and disc and also to distract vulnerable soft tissue structures away from the needle track. The patient is asked to refrain from vocalization, swallowing, or coughing, and the needle is then quickly advanced over the tip of the blunt instrument, and using active fluoroscopy is maneuvered toward the disc in one fluid movement (see Fig. 38-28, C). Resistance to further insertion is noted as the needle enters the disc, and needle advancement is halted when purchase in the disc is accomplished. Total time elapsed between needle skin puncture and disc entry is often less than 2 seconds. During needle insertion, the bend on the needle tip allows precise directional control by rotation. Some radiation of the dominant hand is inevitable; however, using pulsed 8/second, and low-dose fluoroscopic modes, it is minimal and an acceptable risk.

Figure 38-28 Cervical spine “foraminal” view. Needles have been previously placed in the C4-5 and C5-6 intervertebral discs. A, Image for C3-4 intervertebral disc access. Note inferior end plate of C3 and superior end plate of C4 are square to beam. B, Skin entry site is marked by pointer (i.e., blunt instrument). Target is in center of image to prevent insertion error due to parallax. C, To reduce the insertional distance, pressure is applied with the blunt instrument while the needle is quickly advanced into the C3-4 disc using active fluoroscopy. This allows for continuous directional control by rotation of the bent needle and prevents needle misadventure into potentially dangerous structures. D, Needle placed in lateral aspect of C3-4 intervertebral disc.

When needles are positioned in the periphery of all levels to be studied (see Fig. 38-28, D) the fluoroscope is rotated into a lateral view. Using active lateral fluoroscopy the needles are advanced into the approximate center of each disc and the position is verified in AP view. Care must be taken to ensure that the needle is not advanced through the disc, which could involve entry into the spinal canal and probable cord penetration. AP and lateral views are then saved to document-safe needle position (see Fig. 38-29). At C6-7, if body habitus prevents adequate lateral visualization, AP, ipsilateral oblique, and contralateral oblique images can be substituted on the rare occasion.

Figure 38-29 A, Anteroposterior (AP) view of the cervical spine with needles in the center of the intervertebral discs prior to injection of contrast. B, Lateral view of the cervical spine with needles in the center of the intervertebral discs prior to injection of contrast.

After the needle stylets are removed, the 3 mL syringes filled with contrast solution are connected to the hubs using the small-bore, minimal volume extension tubing, with Luer-Lok connections. Care must be taken to ensure that the needles are not advanced during the connection process.

Active lateral fluoroscopy is the used during disc stimulation (i.e., injection of contrast). The patient is blinded as to level and onset of stimulation. Pressure of injection is slowly increased until the intrinsic internal pressure within the disc is overcome and a small amount of contrast is seen within the disc. At this point, injection is halted. Occasionally, some momentary pain will be felt by the patient at opening pressure. This is usually transient and is probably a response to enlargement of a fissure. If high pressure is evident without intradiscal contrast noted, the needle opening may be lodged in dense discal material. Slight withdrawal of the needle and repositioning within the disc will often rectify this problem. Prior to reinjection, safe needle position must be verified. When opening pressure has been noted, slow injection of contrast can proceed. Often firm resistance or pain will be noted with injection of as little as 0.2 mL. Injection into any nonpathologic cervical intervertebral disc will be limited to less than 0.5 mL and high pressure noted.⁴⁹ Cervical intervertebral discs that appear to hold more than 0.5 mL will invariably be noted to have pathology on imaging. In normal discs, the endplates will be seen to separate owing to an increase in disc height during injection. AP and lateral images for the permanent medical record must be archived (see Fig. 38-31).

Figure 38-31 A, Lateral image of cervical spine following disc stimulation. At C5-6, note marked spread in the uncovertebral fissure (i.e., joint of Luschka), evidence of disc maturation (arrows). B, Anteroposterior (AP) image of cervical spine following disc stimulation. At C5-6, note marked spread in the uncovertebral fissure (i.e., joint of Luschka), arrows.

During disc stimulation, the parameters of the injection are recorded on a standardized form by operating room personnel. At a minimum, volume of injectate, endpoint pressure (soft or firm), pain response (vocal or physical), pain intensity, and pain concordance are assessed.

Endpoints of stimulation as per the ISIS guidelines cited previously include: concordant pain reproduced at a VAS of ≥7;

Figure 38-30 A, C2-3 injection of contrast (i.e., disc stimulation). Note this is not a true lateral view in that the zygapophysial/facet joints and the neural arches show nonalignment of bone margins (arrows). B, True lateral image of C3-4 with injection of contrast (i.e., disc stimulation).

significant nonconcordant pain; neurologic symptoms experienced by the patient; contrast escaping from the disc; displacement of the vertebral body end plates; or firm resistance to injection.

A positive level for discogenic pain is noted if concordant pain is evidenced with at least one asymptomatic, negative control level. Almost all cervical discs when stimulated to a sufficient level can produce pain whether pathologic or not. Evaluation of the procedure in regard to the patient’s response often requires experience beyond the technical considerations. Patients vary greatly in pain tolerance and psychological overlay, necessitating in the study results a certain degree of subjectivity by the discographer.

Analgesic discography although first described in the cervical region as referenced earlier,²⁶ has not been validated as providing accurate information on which to base clinical decisions. Bogduk and Aprill³⁴ were able to provide analgesia in only 7 of 34 (21%) of discs evidencing pain on stimulation, which only comes close to the level of placebo effect. Further study is needed.

Various patterns of contrast spread are expected even in asymptomatic cervical discs. In that the majority of mature cervical intervertebral discs evidence fissures and other pathology of the internal disc architecture, this is of little consequence and does not enter into the evaluation. For this reason, in the majority of cases, postcervical discography CT scans are not indicated.

Following the procedure an all-inclusive, highly detailed, individualized record of the procedure must be produced and archived. Post procedure care requires a prudent recovery period, and general instructions as noted for the lumbar procedure.