Discography an investigative technique for Herniated nucleus pulposus. Since that time, new imaging techniques that are more appropriate for this diagnosis have been developed. Discography is currently used to determine whether the disk is the source of pain in patients with predominantly axial back or neck pain.
During discography, contrast medium is injected into the disk and the patient’s response to the injection is noted; provocation of pain that is similar to the patient’s existing back or neck pain suggests that the disk might the source of the pain. Computed tomography (CT) is usually performed after discography to assess anatomical changes in the disk and to demonstrate intradiscal clefts and radial tears.
Early studies suggested that discography had a low specificity, but more recent studies have failed to induce pain in asymptomatic controls, suggesting that discography has utility in identifying patients with discogenic pain. Pain reproduction during discography in symptomatic individuals is variable, with a lower incidence of pain reproduction in patients with Disk Degeneration than in those with posterior tears of the Anulus fibrosus or significant Disk Bulges.
Discs form the main connection between vertebrae. Their size varies depending on the adjacent vertebrae size and comprises approximately one quarter the length of the vertebral column.
These disks are composed of 4 parts: the Nucleus Pulposus in the middle, the Annulus fibrosis surrounding the nucleus, and 2 End plates that are attached to the adjacent vertebral bodies They serve as force dissipators, transmitting compressive loads throughout a range of motion. The disks are thicker anteriorly and therefore contribute to normal cervical lordosis.
Discography should be performed only if adequate attempts at conservative therapy and Noninvasive diagnostic tests, such as MRI, have failed to reveal the etiology of back pain.
Specific indications for discography include the following:
Evaluation of Abnormal Disks or Recurrent pain from a previously operated disk or lateral disk herniation
Assessment of patients in whom surgery has failed, to determine whether pseudoarthrosis or a symptomatic disk in a posteriorly viewed segment could be the source of pain
Assessment of disks prior to fusion to determine whether the disks of the proposed fusion segment are symptomatic and whether the disks adjacent to this segment can support a fusion
Assessment of candidates for minimally invasive surgery who have a confirmed disk herniation
Prophylactic antibiotics should be considered.
Double-needle technique always should be used.
The injection should be performed with water-soluble contrast medium.
Accurate needle placement is required to avoid annular injections, which could produce false-positive results.
Injection against the vertebral end plate can cause a false-positive response.
Discography should be followed by CT scanning if possible
The information recorded should include the following:
Very careful attention should be paid to interpreting the pain response during the injection of each disk, including whether the pain is similar to or exactly like the symptoms for which the patient seeks relief. The location of the pain and its intensity should be noted.
Pain at low pressures is most likely due to chemical irritation. Low resistance generally is associated with a tear through the outer annulus. Pain at high pressures may be due to mechanical irritation, end-plate deflection, or stimulation of pressure receptors.
Generally, if a large volume of contrast can be injected, the disk is degenerated or has a fissure extending through the outer annular wall.
The specificity of discography findings could be increased if CT scanning findings are correlated. Annular disruption reaching the outer annulus fibrosus is a key factor in pain generation. Disk morphology, including annular disruptions extending beyond the outer annulus, may permit increased discography specificity.