Flashcards in Chapter 64 Discography Deck (51):
Discography has been called
a “test in search of an indication,” and a “solution in need of a problem
Pain originating from the spine commonly manifests as
pain in the
low back and neck, and less frequently as pain
in the mid-back.
Several factors make the identification of spinal
pain generators challenging
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.
term internal disc disruption (IDD)
to describe a disc that is considered the main
source of patient’s pain but appears functionally intact on spinal imaging
one or two discs show profound degeneration in the presence of other relatively normal appearing discs
discogenic pain (DP)
describes a clinical
state in which the disc is considered a main source of a
patient’s spinal pain
A normal disc
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.
The compressive forces
applied to the disc are borne directly by the
NP, and are distributed as a tensile force to the annular collagen
The incompressibility exhibited by a normal NP is due to its
high water content, which in turn is maintained by the
hydrostatic pressure generated by proteoglycans
The normal NP proteoglycan content is a function of the
delicate balance between
anabolic and catabolic enzymatic
The vascularity of a normal intervertebral disc
limited to the outer third of the AF. In addition, the disc is separated from the vascular vertebral body by avascular cartilaginous end plates.
Consequently, the metabolic needs of the NP and inner AF are met almost entirely by
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.
products of the NP cellular metabolic activities are also
the diffusion. the disc lacks scavenger cells, so that degradative products tend to accumulate over time, which can interfere with normal homeostatic
The innervation of the normal disc
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.
degenerated disc disease most likely the result of
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.
The diminished NP hydrostatic pressure leads to
increased NP compressibility, which exposes the AF to direct compressive forces.
In addition to mechanical stress, the AF
also undergoes degenerative changes similar to the NP.
These combined insults result in
the loss of annular collagen,
mechanical failure, and the development of annular
fissures that spread outward towards the periphery.
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
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
In the long-term, changes in the disc morphology may
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
The rationale for discography is based on three factors
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.
the main criticism surrounding discography is the
high rate of false-positive (FP) results
The issue of “false-negative” discograms has received far
less attention, but can lead to
inaccurate diagnoses, unnecessary interventions, and withholding beneficial treatment(s) from otherwise good candidates.
for this phenomenon of “false-negative”
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.
factors that may
increase the risk of FP discograms include
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
If discography is conducted in these individuals at risk of FP,
one should consider obtaining two adjacent control
discs, and correlating reported pain with
heart rate measurements
and/or facial expressions.
the most sensitive test for disc pathology,
and lumbar discographic findings
Can provocation discography
results be predicted by radiologic imaging?
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.
EFFECT of discography ON
the results are conflicting as to whether pre-operative discography is an effective screening tool in identifying candidates or treatment levels for spinal fusion
indications for lumbar disc replacement include
one- or two-level mechanical discogenic back pain without radiculopathy or significant facet pathology.
ndications for cervical disc replacement include
Unlike the indications for lumbar disc replacement, cervical discs are implanted in patients with or without neurologic symptoms
The purported advantage of anesthetic discography is that
it may reduce the high incidence of FP results obtained
with provocative discography
the most important aspect of discography.
The patient’s subjective pain response to intradiscal injection
Discography is predicated on the fact that
normal discs are sparsely
innervated, while disrupted discs are relatively richly innervated and have been rendered hyperalgesic from nociceptor exposure to inflammatory mediators.
The foundation for
discography stems from three premises.
The first is that painful stimulation of any kind can provoke symptoms in a
chronic pain patient, including pressurization of a nonpainful
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.
A true control disc is present only when
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
considered pivotal to diagnosis
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.
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
Physiologic variations in disc pressures
intradiscal pressures are higher in upright
position and lower in the recumbent position.
According to most guidelines, asymptomatic lumbar
discs are highly unlikely to evoke pain at pressures
below 15 psi. Therefore, pain evoked at pressure below
this level is considered highly suggestive of lumbar DP (i.e., a chemically sensitive disc)
even a normal disc can provoke pain when
the peak pressure is raised too high
(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
In the cervical and thoracic spine, manometry is
not commonly used due to risk of disc rupture
The volumetric measurements made during discography
include the amount of contrast injected and the various endpoints. Normal lumbar discs typically accept
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
In the presence of a complete annular tear where
the disc communicates with the epidural space, how much volume?
an unlimited volume of the contrast may be injected with little or no resistance—a volume endpoint.
Provocation of significant
pain should result in
cessation of any disc injection— a pain endpoint. It should be recognized that severely disrupted discs may evoke no pain or resistance on
Grades of Morphologic patterns of contrast spread
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
depicts a large tear that results in contrast extending
circumferentially to more than 30% of the disc circumference.
Correlation of contrast spread and pain
Grade 3 tears
usually provoke concordant pain,
grade 2 disruptions
reproduce pain infrequently, and
grade 0 and 1 discs
rarely evoke pain.
The avascular nature of the disc renders it vulnerable to the
iatrogenic innoculation of bacteria difficult to treat with
antibiotics. These factors make discitis the most feared complication of discography.
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
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.
caution should be exercised even when manometry is utilized, as there are several reports o
discography-induced lumbar disc herniation occurring at