Chapter 64 Discography

Question 1

Discography has been called

Answer 1

a “test in search of an indication,” and a “solution in need of a problem

Question 2

Pain originating from the spine commonly manifests as

pain in the

Answer 2

low back and neck, and less frequently as pain

in the mid-back.

Question 3

Several factors make the identification of spinal

pain generators challenging

Answer 3

First, back pain can originate
not only from various spinal column components, but can
also be referred from structures adjacent to the spine such as abdominal or pelvic viscera, sacroiliac joints, and so on. Second, pain can be difficult to localize due to multisegmental, predominantly autonomic spinal innervation, with resultant convergence in the spinal cord. The diagnosis of spinal pain is further complicated by the concurrent presenceand overlapping clinical features of various spinal disorders, especially degenerative conditions.

Question 4

term internal disc disruption (IDD)

Answer 4

to describe a disc that is considered the main

source of patient’s pain but appears functionally intact on spinal imaging

Question 5

Isolated degenerative

disc pathology

Answer 5

one or two discs show profound degeneration in the presence of other relatively normal appearing discs

Question 6

discogenic pain (DP)

Answer 6

describes a clinical
state in which the disc is considered a main source of a
patient’s spinal pain

Question 7

A normal disc

Answer 7

grossly compartmentalized
into nucleus pulposus (NP) and annulus fibrosus(AF). Interspersed in an abundant intercellular matrix in the two disc compartments are sparsely present cells. The cells populating the NP are chondrocyte-like, while those
comprising the AF are fibrocyte-like.3 The intercellular
matrix in the NP is a “jelly-like” substance containing high concentrations of water and proteoglycans, while the matrix in the AF consists predominantly of Type I and
II collagen fibers.

Question 8

The compressive forces

applied to the disc are borne directly by the

Answer 8

NP, and are distributed as a tensile force to the annular collagen

Question 9

The incompressibility exhibited by a normal NP is due to its

Answer 9

high water content, which in turn is maintained by the

hydrostatic pressure generated by proteoglycans

Question 10

The normal NP proteoglycan content is a function of the

delicate balance between

Answer 10

anabolic and catabolic enzymatic

activities.

Question 11

The vascularity of a normal intervertebral disc

Answer 11

limited to the outer third of the AF. In addition, the disc is separated from the vascular vertebral body by avascular cartilaginous end plates.

Question 12

Consequently, the metabolic needs of the NP and inner AF are met almost entirely by

Answer 12

diffusion from the capillary plexuses in the adjacent vertebral bodies and outer AF. This process is facilitated by circadian changes in intradiscal pressure; lower nighttime pressure facilitates the flow of fluids into the disc, while higher daytime pressure forces the fluids out of the disc.

Question 13

The end
products of the NP cellular metabolic activities are also
removed by

Answer 13

the diffusion. the disc lacks scavenger cells, so that degradative products tend to accumulate over time, which can interfere with normal homeostatic
functions.

Question 14

The innervation of the normal disc

Answer 14

predominantly limited to the outer third of the AF. Disc innervation is mostly in the form of mechanoreceptors, which originate from plexuses along the anterior and posterior longitudinal ligaments. The posterior plexus receives its input from the sinuvertebral nerve and gray rami communicans, while the anterior plexus receives contributions mainly from gray rami communicans.

Question 15

degenerated disc disease most likely the result of

Answer 15

a decline in the number and function of viable disc cells, enhanced matrix
metalloproteinase (MMP) activity, and increased activity
of discal cytokines and other proinflammatory mediators. These metabolic derangements can result in a reduction of nuclear proteoglycans and loss of discal water content.

Question 16

The diminished NP hydrostatic pressure leads to

Answer 16

increased NP compressibility, which exposes the AF to direct compressive forces.

Question 17

In addition to mechanical stress, the AF
also undergoes degenerative changes similar to the NP.
These combined insults result in

Answer 17

the loss of annular collagen,
mechanical failure, and the development of annular
fissures that spread outward towards the periphery.

Question 18

Annular fissures

Answer 18

hallmark of discogenic pain. These tears are zones of highly vascularized and richly
innervated granulation tissue. The two types of nerve
fibers found in these granulation zones are vasoregulatory nerves that accompany neovascularization, and free nerve endings high in substance P concentration

Question 19

“chemically sensitized.”

Answer 19

state has been linked to the painful response associated with minimal pressure
elevation. annular tears are abundant in mononuclear cell infiltrates, which release nerve growth factors that contribute to nerve in-growth and accelerated degeneration. Disrupted discs also contain high concentrations of pro-inflammatory mediators, which serve to sensitize nerve endings and maintain a state of hyperalgesia

Question 20

In the long-term, changes in the disc morphology may

Answer 20

alter spinal mechanics, increase stress on adjacent spinal structures, and lead to sclerosis and auto-fusion. This
may lead to further disc and vertebral end plate degeneration, sacroiliac and facet joint pathology, and spinal
stenosis.

Question 21

The rationale for discography is based on three factors

Answer 21

the high prevalence of spine pain, the high prevalence rate of abnormal MRI findings at asymptomatic levels, and the low success rate for surgical interventions for degenerative spondylosis.

Question 22

the main criticism surrounding discography is the

Answer 22

high rate of false-positive (FP) results

Question 23

The issue of “false-negative” discograms has received far

less attention, but can lead to

Answer 23

inaccurate diagnoses, unnecessary interventions, and withholding beneficial treatment(s) from otherwise good candidates.

Question 24

several reasons

for this phenomenon of “false-negative”

Answer 24

failure to detect an inadequate
rise in intradiscal pressure because of the lack of pressure monitoring, injecting too slow, excessive sedation,
overzealous use of local anesthetic, and extensive contrast extravasation in severely degenerated discs.

Question 25

factors that may

increase the risk of FP discograms include

Answer 25

extreme anxiety,
performing disc stimulation before allowing previously
provoked pain to return to baseline, inadvertent annular injection, contrast-induced irritation of nervous tissue, end
plate deflection resulting from suboptimal needle placement, and rapid or over-disc pressurization

Question 26

If discography is conducted in these individuals at risk of FP,
one should consider obtaining two adjacent control
discs, and correlating reported pain with

Answer 26

heart rate measurements

and/or facial expressions.

Question 27

MRI,

Answer 27

the most sensitive test for disc pathology,

and lumbar discographic findings

Question 28

Can provocation discography

results be predicted by radiologic imaging?

Answer 28

whereas a significant correlation between concordant pain provocation and MRI findings has been demonstrated, the high FP and false-negative rates suggest the need for a reliable means to ascertain which abnormalities are pain generators.

Question 29

EFFECT of discography ON

SPINAL ARTHRODESIS

Answer 29

the results are conflicting as to whether pre-operative discography is an effective screening tool in identifying candidates or treatment levels for spinal fusion

Question 30

indications for lumbar disc replacement include

Answer 30

one- or two-level mechanical discogenic back pain without radiculopathy or significant facet pathology.

Question 31

ndications for cervical disc replacement include

Answer 31

Unlike the indications for lumbar disc replacement, cervical discs are implanted in patients with or without neurologic symptoms

Question 32

The purported advantage of anesthetic discography is that

Answer 32

it may reduce the high incidence of FP results obtained

with provocative discography

Question 33

the most important aspect of discography.

Answer 33

The patient’s subjective pain response to intradiscal injection

Question 34

Discography is predicated on the fact that

Answer 34

normal discs are sparsely
innervated, while disrupted discs are relatively richly innervated and have been rendered hyperalgesic from nociceptor exposure to inflammatory mediators.

Question 35

The foundation for

discography stems from three premises.

Answer 35

The first is that painful stimulation of any kind can provoke symptoms in a
chronic pain patient, including pressurization of a nonpainful
disc.
The second assumption is that pain caused by stimulation
of a nonpainful disc will be different than the patient’s usual pain.

Third, it is assumed that “minor” or nondebilitating pain can be evoked from stimulation of a nonpainful disc.

Question 36

A true control disc is present only when

Answer 36

pressurization fails to elicit a typical pain response
in a nontargeted disc. Both the IASP and ISIS consider the
presence of two control disc levels in conjunction with one painful disc level to be highly indicative of DP

Question 37

considered pivotal to diagnosis

Answer 37

amount of pressure needed to evoke pain. The key rationale
behind discography is that pain can be evoked by minimal
pressurization of a disrupted disc (akin to allodynia or
hyperalgesia), whereas higher intradiscal pressures would
be painless in a normal disc.

Question 38

pressure discography

Answer 38

The intradiscal pressure at
which the contrast flow is first observed in the disc is the
opening pressure, while the maximum pressure achieved
during a disc injection is referred to as the peak pressure

Question 39

Physiologic variations in disc pressures

Answer 39

intradiscal pressures are higher in upright

position and lower in the recumbent position.

Question 40

According to most guidelines, asymptomatic lumbar

discs are highly unlikely to evoke pain at pressures

Answer 40

below 15 psi. Therefore, pain evoked at pressure below

this level is considered highly suggestive of lumbar DP (i.e., a chemically sensitive disc)

Question 41

even a normal disc can provoke pain when

the peak pressure is raised too high

Answer 41

(i.e., above 90 psi). Pressures above 100 psi
are considered detrimental to disc integrity, so that one
potential advantage of pressure discography may be
avoidance of disc injury

Question 42

In the cervical and thoracic spine, manometry is

Answer 42

not commonly used due to risk of disc rupture

Question 43

The volumetric measurements made during discography

include the amount of contrast injected and the various endpoints. Normal lumbar discs typically accept

Answer 43

less than 1 ml of contrast before firm resistance is
reached—a firm endpoint. In cervical and thoracic discs,
these volumes are approximately 0.25 and 0.5 ml,
respectively. Degenerated discs typically accept larger contrast volumes and only moderate resistance to the
injection is encountered—a lower pressure or soft endpoint

Question 44

In the presence of a complete annular tear where

the disc communicates with the epidural space, how much volume?

Answer 44

an unlimited volume of the contrast may be injected with little or no resistance—a volume endpoint.

Question 45

Provocation of significant

pain should result in

Answer 45

cessation of any disc injection— a pain endpoint. It should be recognized that severely disrupted discs may evoke no pain or resistance on
injection.

Question 46

Grades of Morphologic patterns of contrast spread

Answer 46

grade 0 describes a normal lumbar disc in
which contrast is limited to the NP;
grades 1 to 3 designate
discs in which contrast extends to the inner, middle,
and outer third of the AF respectively;
grade 4 describes
a diffusely degenerated disc in which several annular
tears extend to the periphery of the annulus; and
grade 5
depicts a large tear that results in contrast extending
circumferentially to more than 30% of the disc circumference.

Question 47

Correlation of contrast spread and pain

Answer 47

Grade 3 tears
usually provoke concordant pain, 
grade 2 disruptions
reproduce pain infrequently, and 
grade 0 and 1 discs
rarely evoke pain.

Question 48

The avascular nature of the disc renders it vulnerable to the

Answer 48

iatrogenic innoculation of bacteria difficult to treat with

antibiotics. These factors make discitis the most feared complication of discography.

Question 49

any patient who experiences a new neurologic finding or continues to complain of persistent pain 1 week postprocedure warrants re-evaluation. At minimum, the postdiscography work-up should include a

Answer 49

focused history, physical exam, and laboratory screening tests that include erythrocyte sedimentation rate, C-reactive protein, and white blood cell count. If the erythrocyte sedimentation rate is more than 50, then a high-resolution
MRI focusing on the end plates is needed.

Question 50

caution should be exercised even when manometry is utilized, as there are several reports o

Answer 50

discography-induced lumbar disc herniation occurring at

lower pressures.

Question 51

Other complications

of discography include

Answer 51

headache, convulsions attributed to
contrast, nausea and vomiting, severe back pain, hematoma,
meningitis, arachnoiditis, nerve root injury, paravertebral
muscle spasm, vaso-vagal reactions, and allergic
reactions.