Low back pain (LBP) has been described as a global health concern with a point prevalence estimated at 7.5% of the global population, or around 577.0 million people in 2017. It has been the leading cause of years lived with disability (YLDs) at least from 1990 to 2017. Chronic LBP is the second leading cause of adult disability in the United States, and its prevalence increases with age. While the ancient Greeks and Egyptians suspected a relationship between disease in the lumbar spine and leg symptoms, the modern understanding of lumbar disk herniation did not arise until the mid-1700s, and the first lumbar discectomy was performed by Mixter and Barr in 1932. Discography was first described in 1948 with the early technique performed via a transdural approach. The ensuing decades have seen considerable progress from manual subjective discography to manual and automated injection manometers. Modern imaging studies, especially magnetic resonance imaging (MRI), are likely to show degeneration of multiple levels that may or may not be of any clinical significance to the presenting back and leg pain symptoms. The loss of proteoglycans from the disc gradually increases with age, especially in males, so that around 10% of 50-year-old discs and 60% of 70-year-old discs have severely degenerated. This leaves a fundamental question of what symptomatic pathology is and what is simply age-related degenerative changes of the spine. Provocative discography is a diagnostic modality that potentially has a unique role in answering this question. It should be noted that there are two distinct forms of disc degeneration: "Endplate-driven" disc degeneration involves endplate defects and inwards collapse of the annulus showing inflammatory endplate changes and Schmorl's nodes, and "annulus-driven" disc degeneration involves a radial fissure and/or a disc prolapse, which is well described in the Modified Dallas Classification System. It has even been shown that the presence of a high-intensity zone on MRI is only a suggestive and screening indication for the diagnosis of discogenic LBP and cannot replace the gold standard of discography. Pressure-controlled manometric discography using certain criteria may be the only way to distinguish asymptomatic discs among morphologically abnormal discs with Grade 3 annular tears in patients with clinical LBP, but manometry is not a mandatory requirement for discography. In addition to the disc itself, many structures can be responsible for varying degrees of axial spine pain with and without radicular features, and it may be challenging to discern which structures are involved in the clinical LBP syndrome. In addition to primary discogenic pain, which is heterogeneous in and of itself, facet arthritis, medial branch nerve entrapment, endplate edema, Schmorl's nodes, myofascial pain, spinal enthesitis, and sacroiliac joint dysfunction, to name a few, can be responsible for similar patient presentations. Provocative discography still has a role in particular cases. A "sham" injection may also have a role in teasing out non-physiologic complaints and/or obtaining insight into secondary gain issues. A discography is a diagnostic option that may link a patient’s subjective complaints of spinal pain to symptomatic disc disease when non-invasive imaging, such as MRI, does not indicate clear structural abnormalities. Post-discogram CT can also provide reasonable anatomic imaging for surgical decision-making. However, this procedure can be uncomfortable, and medical clearance should be considered in medically complex patients with cardiovascular or other high-risk comorbidities. Consideration should also be given to renal function due to the use of a radiographic contrast agent. With a number of regenerative medicine options, such as platelet-rich plasma and other "stem cell" treatments, available and coming on the market, provocative discography is seeing an empiric use in pre-injection planning. Additionally, minimally invasive intradiscal treatments, such as endoscopic diskectomy and intradiscal electrothermal procedures, often benefit from pre-procedure discograms, and/or pre-procedure discograms may be required by third-party payors. There are 2 classifications for the discogram: the original Dallas discogram description and the modified Dallas discogram description. Original Dallas Classification System based on contrast extravasation and was originally developed in the pre-CT era. It is still noted at the time of discogram and may be used when CT scanning is not available. This Original Classification System is graded 0-3 as follows: 0: no extravasation "cotton ball " appearance of the intact nucleus, 1: contrast into the inner annulus, 2: contrast into the outer annulus. 3: contrast beyond the outer annulus, commonly running into the anterior epidural space. The Modified Dallas Classification system is based on contrast extravasation seen on coronal CT imaging through the disc itself. There are six possible categories in the Modified Dallas Discogram Classification that describe the severity of the radial annular tear. : Grade 0 is a normal disc—no contrast material leaks from the nucleus. . Grade 1 tear will leak contrast material into the inner 1/3 of the annulus. . Grade 2 tear will leak contrast through the inner 1/3 and into the middle 1/3 of the disc. . Grade 3 tear will leak contrast through the inner and middle annulus. The contrast spills into the outer 1/3 of the annulus. Grade 4 tear includes a grade 3 tear, and the contrast is also seen spreading concentrically around the disc. The concentric spread must be greater than 30 degrees. A full-thickness radial tear and concentric annular tear merge together. . Grade 5 tear ('evil' grade) includes a grade 3 or grade 4 radial tear that has completely ruptured the outer layers of the disc and is leaking contract material out of the disc. This type of tear is felt to be associated with "chemical radiculopathy," with the low pH of the nuclear material theoretically irritating nerve roots directly.
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