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Chapter 13 Spine Imaging 203
SECTION
II
A
FIG. 13.2 Foraminal stenosis. (A) Axial computed tomographic (CT) scan after myelography shows severe right
bony foraminal stenosis with no evidence of central stenosis or herniations (arrow). (B) Sagittal reformat of CT
data also shows severe foraminal narrowing, in contrast to more normal superior foramen.
that can directly image bone marrow. Since the beginning of
its clinical use in the early 1980s, MRI technology has progressed with improved quality and decreased examination
18-21
times.
Routine Magnetic Resonance Imaging
Pulse sequences that constitute a routine spine MR exam
include axial gradient recalled echo or T2, T1, and sagittal T2,
T1, and short-tau inversion recovery (STIR). Depending on
the imaging indication T1-weighted images can also be
obtained with gadolinium contrast agents, especially when
there is a concern of infection or when there has been a history
of spine surgery.
musculoskeletal pathology (Fig. 13.3).
22-30
STIR has shown a high sensitivity for
31-33
STIR has been
favorably compared with T1-weighted and T2-weighted fast
spin-echo (FSE), conventional spin-echo, and fat-saturated
FSE in the detection of vertebral metastatic disease.
34-36
STIR
may also be used for intramedullary cord lesions. Each examination also includes a scout image that, depending on the type
of image, can include much of the abdomen or chest in the
eld of view (Fig. 13.4).
Dynamic Magnetic Resonance Imaging
CT and MRI are typically obtained with the patient positioned
supine. Radiographs can be more readily obtained with the
patient standing or in exion or extension. e rationale for
MRI with patients in a sitting position, in exion or extension,
or with axial loading is that these positions are believed to be
the positions in which the patient is the most symptomatic. In
extension the lumbar spinal canal decreases, as does the cervical spinal canal (Fig. 13.5).
to decrease the diameter of the lumbar spine.41 In a study of
200 patients with symptoms of spinal stenosis who underwent
MRI with axial loading, 20 showed a decreased diameter of
37-40
Axial loading has been shown
B
AB
FIG. 13.3 Multiple osteoporotic compression fractures. (A) Sagittal
T1-weighted magnetic resonance image through thoracic spine shows
multiple collapsed bodies with central low signal reecting prior
vertebroplasties (small arrows). The marrow adjacent to methacrylate shows
normal fatty signal intensity. (B) T12 body (large arrow) shows low signal on
T1-weighted image and increased signal on sagittal short-tau inversion
recovery image consistent with acute age.
the canal with axial loading. Of those 20 patients, the plan of
care was changed in ve patients because of the added infor-
mation of axial loading images.
42
Magnetic Resonance Myelography
MR myelography can be obtained for evaluation for cerebrospinal uid (CSF) leak in conditions such as intracranial
204 DIAGNOSIS
FIG. 13.4 Half-Fourier acquisition single-shot turbo spin-echo scout image
obtained during a routine lumbar spine examination demonstrates an
unsuspected right upper lobe lung mass (arrow), a possible malignancy.
hypotension. Radionuclide cisternography and conventional
CT myelography both use ionizing radiation and are invasive.
e technique of MR myelography involves the use of heavy
T2-weighted sequences43 and can readily identify paravertebral
uid collections or spinal diverticuli. Sensitivities for radionuclide cisternography, CT myelography, and MR myelography
have been reported to be 55%, 67%, and 86%, respectively.
44-46
Additionally, there has been use of intrathecal gadolinium,
although o-label and not approved by the US Food and Drug
Administration (FDA), with subsequent MRI that has been
shown to be advantageous by multiple authors.
47,48
Magnetic Resonance Neurography
For evaluation of the peripheral nerves, MRI using
T1-weighted images and fat-saturated T2 or STIR images can
be used to evaluate for neoplasm (Fig. 13.6), entrapment, or
nerve injury.49 Severity of nerve injury can be evaluated from
mild injury (neurapraxia) where there is mild nerve enlargement and T2 hyperintensity to complete nerve transection
where the separation of the nerve can be visualized.49 MR
neurography is also useful for evaluation of diuse peripheral
nerve lesions such as neurobromatosis or the inammatory
or hereditary neuropathies.
50
A
FIG. 13.5 Sagittal T2-weighted images of the cervical spine demonstrate developmental fusion of C2 and C3
vertebral bodies. Images are obtained in (A) exion, (B) neutral, and (C) extension. There is ligamentous
buckling with extension resulting in more profound canal compromise (arrow) compared with neutral and
exion positioning.
B
C
Chapter 13 Spine Imaging 205
AB
FIG. 13.6 (A) Axial fat-saturated contrast-enhanced T1-weighted images demonstrate asymmetric enlargement
and enhancement of the right sciatic nerve (arrow), representing neoplastic inltration in this patient with
leukemia. (B) Normal sciatic nerve for comparison (arrow).
SECTION
II
Diusion-Weighted Imaging
Diusion-weighted imaging (DWI) is routinely used for brain
imaging. However, its use for spine imaging is not routine
secondary to multiple technical limitations, including motion
artifact and the relatively small size of the spinal cord.51 Similar
caveats apply to diusion tensor imaging (DTI), in which the
diusivity of water molecules can imply the course of white
matter tracts.
52
DWI of the spine can be applied to the vertebral bodies as
well as the spinal cord. Multiple studies have been performed
looking at the ability to discriminate benign versus pathologic
compression fractures based on DWI; however, the results
have been conicting.
or ischemia using DWI has also been described.
53-57
Evaluation of spinal cord neoplasm
58
DTI of the spine is also fraught with technical diculties.
Applications in regard to suspected neoplasm include both
lesion characterization and evaluation of the lesion’s margins
for surgical planning purposes.
59,60
In cases of cord compression
DTI has demonstrated cord injury that is not accompanied by
T2-weighted signal abnormalities.61 In addition, DTI has been
shown to be more sensitive than T2-weighted imaging for
evaluation of spinal cord inammation.
62
Cerebrospinal Fluid Flow Imaging
CSF imaging demonstrates biphasic pulsatile CSF ow with
caudal systolic and cranial diastolic ow. Applications include
Chiari malformations or evaluation of spinal cord syrinx cavities or tethered cord.
63-66
Magnetic Resonance Spectroscopy
1
H-MR spectroscopy (MRS) uses a conventional MR machine
to evaluate metabolites in an area of interest and has been
extensively used with brain imaging. MRS for spinal imaging
is met with extensive technical challenges, including motion,
small size of the spinal cord, distance of the spinal cord from
surface coils, and the inherent composition of the immediately
surrounding so tissues and osseous structures, which can
result in distortion of the magnetic eld.67 Clinical applica-
tions include demyelination68 and neoplasm.
69
Magnetic Resonance Imaging Safety and Patient Issues
e specic and important aspects of MRI safety (including
patient exposure to the magnetic eld and gadolinium-based
contrast media) are widely available on multiple websites, and
the interested reader is referred to them for detailed answers
(e.g., www.MRIsafety.com). Certain implants or metallic
foreign bodies can increase in temperature or move, potentially leading to patient harm—hence the need for all patients
to ll out a safety screening form before placement in the MRI
machine.70 Recently MRI-compatible pacemakers, although
with some stipulations, have been developed.
Bleicher and colleagues72 found a serious complication rate
of approximately 0.03% of gadolinium contrast agents when
reviewing records of more than 23,000 patients, attesting to
the overall favorable safety prole of gadolinium contrast
agents. However, there are two important issues: gadolinium
deposition in patients with normal renal function and nephrogenic systemic brosis (NSF).
In 2014 Kanda and colleagues73 correlated a dose-dependent
T1 hyperintensity in certain structures intracranially in
patients with a history of gadolinium administration. McDonald and coworkers74 conrmed the presence of gadolinium in
the globus pallidus, pons, dentate nucleus, and thalamus in
autopsy specimens of 13 patients with normal renal function
who all underwent a minimum of four gadolinium contrastenhanced examinations. Whether the intracranial accumulation of gadolinium is harmful is not clear at this point.
NSF, previously called nephrogenic brosing dermopathy,
is a systemic disorder of widespread brosis that has been tied
to prior administration of gadolinium-based contrast agents
in the setting of renal disease. e incidence of NSF in the
setting of severe renal dysfunction is approximately 1% to
7% aer exposure to gadolinium-based contrast material. e
FDA has asked manufacturers to include a new boxed warning
71
75
206 DIAGNOSIS
on the product labeling of all gadolinium-based contrast
agents used to enhance the quality of MRI. e warning states
that patients with severe kidney insuciency who receive
gadolinium-based agents are at risk for developing NSF, a
debilitating and potentially fatal disease.
76,77
Also, patients
just before or just aer liver transplantation and patients with
chronic liver disease are at risk for developing NSF if they are
experiencing kidney insuciency of any severity. e risk of
a patient developing NSF may be minimized by the following
76,78-81
steps
:
1. Identify patients with a glomerular ltration rate less than
30 mL/min/1.73 m2 as at risk.
2. Administer contrast medium to a patient at risk for devel-
oping NSF only when the expected benet clearly outweighs
the risk of administration.
3. Perform unenhanced MRI rst with proper monitoring
so that unnecessary contrast medium administration is
avoided.
4. Use the lowest dose of gadolinium-based contrast medium
that is feasible for the examination.
Spinal Angiography
Spinal angiography is extremely useful for spinal vascular
malformations for the delineation of the vascular supply
and for therapeutic treatment.
used in the pretherapeutic workup of suspected vascular
neoplasms involving the vertebral bodies, posterior elements,
and spinal canal and is coupled with preoperative or palliative
embolization. Spinal angiography should address three areas
for the surgeon or interventionalist: (1) the exact location
and conguration of the lesion, (2) vascularity of the lesion,
including feeding and draining vessels, and (3) regional vascular anatomy.
84
Spinal vascular malformations are a very heterogeneous
group of lesions that have had a wide variety of classication
schemes applied to them. One common classication system
is from Anson and Spetzler,85 who classied them as types
1 to 4:
Type 1: spinal dural arteriovenous stula between the dural
branch of the spinal ramus of the radicular artery and
intradural medullary vein
Type 2: spinal cord arteriovenous malformation with shunting
across an interposed vascular nidus (intramedullary
glomus malformation)
Type 3: complex spinal arteriovenous malformation with
metameric extension (juvenile malformation)
Type 4: direct arteriovenous stula (intradural perimedullary
stula)
e most common spinal vascular lesion is a dural
arteriovenous stula (Fig. 13.7). ese lesions are thought to
be acquired and are particularly present in the thoracic and
lower lumbar spine. Spinal dural arteriovenous stulas are
more common in men. ere is oen a delay from symptom
onset to time of diagnosis, averaging 27 months. Clinical ndings include weakness (55%), a progressive clinical course
(100%), and myelopathy on examination (84%). In the spine,
82,83
Spinal angiography is also
nidus of the stula is most oen located between T6 and T12
or in the sacrum. In 1977, Kendall and Logue86 denitively
identied the site of the arteriovenous shunting within the
root sleeve. e symptoms are a result of intramedullary
edema and ischemia secondary to increased venous backpressure within the varicose coronal veins. Gilbertson and colleagues87 and Masaryk and colleagues88 identied increased
signal intensity on T2-weighted images within the cord as the
most sensitive imaging nding in spinal dural stula.
Although imaging, in particular MRI, has become a
mainstay for the evaluation of vascular malformations,
spinal angiography remains a crucial technique for precise
denition of the type of lesion, the overall morphology, the
ow characteristics, and the identication of specic feeding
vessels.89 Arterial and delayed venous imaging may be necessary to appreciate fully the venous drainage of the vascular
pathology, particularly in arteriovenous malformations and
dural stulas. Arterial lms allow examination of abnormal
blush or arteriovenous shunting. e normal vascular supply
to the cord, in particular the artery of Adamkiewicz, should
be dened. In addition to the usual general complications of
angiography, embolization to the anterior spinal artery could
occur aer angiography, which may lead to an ascending
paralysis. In general complications are rare, given the small
catheters used, nonionic contrast medium, and an improved
speed of the examination with digital subtraction angiography.
Technologic advances have allowed high-resolution, highcontrast discrimination MR or CT imaging for evaluation of
the spinal arteries, with the goal of minimizing the need for
conventional catheter angiography for identication of spinal
vascular disease.
90-92
e size of the anterior spinal artery
(0.2 to 0.8 mm) and the close approximation of the spinal
veins necessitate a sophisticated MRI sequence with bolus
gadolinium–based intravenous contrast medium administration. Although various techniques may be used, the three main
requirements are a large eld of view, high spatial resolution,
and high temporal resolution.
In a series of 34 patients, Mull and colleagues92 showed that
contrast-enhanced spinal MR angiography (MRA) could reliably
detect or exclude spinal cord arteriovenous abnormalities with
a 100% predictive value. e main arterial feeder can be reliably
dened by MRA, but small secondary feeders may be missed.
e main reasons for obtaining MRA would be for primary
identication of a vascular abnormality and to pinpoint the
likely site of a feeder for conventional catheter angiography.
CT angiography can also dene normal and abnormal spinal
vasculature.
93,94
e technique requires a multidetector row CT
scanner (generally 16) and 1-mm section thickness.
Discography
Discography was originally conceived as a morphologic study
of disc herniation but then morphed into a useful but limited
test relying on pain provocation through disc pressurization.
Although discography can accurately dene disc degeneration,
this procedure is now seen as a physiologic evaluation of the
disc consisting of volumetric, manometric, radiographic, and
pain provocative challenge.
97,98
is procedure remains quite
95,96
Chapter 13 Spine Imaging 207
SECTION
II
A
FIG. 13.7 Dural stula. (A) Sagittal T2-weighted
magnetic resonance (MR) image shows diuse
abnormal increased signal from the central aspect of
thoracic cord, sparing a small rind of peripheral cord.
There are faint serpentine areas of ow void along the
dorsal aspect of the thoracic cord (arrows). (B) Single
slice from a three-dimensional gradient-echo dynamic
enhanced MR angiogram shows multiple dilated
intradural vessels primarily along the dorsal surface of
the cord (arrows). (C) Coronal reformat of MR
angiogram shows dorsal enlarged vessels and small
nidus of vessels on the left at T9 (arrow). (D)
Anteroposterior view of a spinal angiogram at the left
T9 intercostal level shows a stula at the foraminal
level (arrow), with shunting to intraspinal dilated veins
(large arrow).
B
C
D
controversial; it has enthusiastic supporters and detractors
and has generated a voluminous literature. Some authors see
discography as helpful in identifying internal disc disruption
and in verifying painful disc levels before surgery (particularly
fusion), whereas others see it as unproven and of questionable
99-106
benet.
Discography is an invasive procedure and is not performed
as a screening technique. Discography is most accurate when
the diagnosis of discogenic pain is probable based on appropriate history, physical examination, and imaging.96 is test
is always limited in sensitivity and specicity owing to the
subjective report of pain type and location by the patient.
According to Tehranzadeh and others,
107-109
indications for
discography include the following:
1. Negative MRI, CT, or myelography ndings with equivocal
ndings for disc disease
208 DIAGNOSIS
2. Cases with positive MRI, CT, or myelography ndings with
disc disease at multiple levels
3. Presence of equivocal MRI, CT, or myelography ndings
4. Recurrent back pain in postsurgical patients with diculty
in evaluating scar versus disc
5. Cases of failed back surgery to evaluate painful pseudarthrosis or symptomatic disc
6. Evaluation of spinal fusion disc above or below the fusion
level
7. erapeutic injection of corticosteroid or anesthetic into
the disc itself
Nuclear Medicine Examinations
Nuclear medicine examinations commonly performed for
spine imaging include bone scintigraphy using technetium
99m
99m (
tomography (PET) imaging. Other radiotracers are also available, including somatostatin analogs, that are useful with
neuroendocrine tumors and meningiomas.
osteoblastic activity and are less useful for aggressive lytic
metastases. Sensitivity and specicity range from 62% to 100%
and 78% to 100%, respectively. Bone scans require a 5% to 10%
change for abnormalities to be detected. Trauma, degenerative
changes, infection, and other conditions can also show uptake
on bone scans.
and is more sensitive for lytic rather than sclerotic metastatic
disease.
uptake in nonneoplastic conditions such as inammation,
infection, or degenerative change.
matory changes of the spine are
gallium (67Ga) citrate, and indium-111 (
blood cells. Although scintigraphy with
pounds is sensitive to infection, it is also nonspecic. Healing
fractures, degenerative arthritis, sterile inammatory reactions,
tumors, and loosened prosthetic devices can show increased
uptake.
radionuclides, including higher target-to-background ratios,
better image quality (compared with 67Ga), and more intense
uptake by abscesses. Its main disadvantage is its accumulation
within any inammatory lesion, whether infectious or not.
e radionuclide study also takes hours to days to perform.
Tc) and 18F-uorodeoxyglucose positron emission
110
For evaluation of metastatic disease, bone scans image
111,112
PET imaging measures metabolic uptake
111,113,114
Similar to bone scans, PET imaging can show
115
Radionuclides most commonly used for detecting inam-
99m
Tc phosphate complexes,
111
In)–labeled white
99m
Tc and 67Ga com-
116-118 111
In has several advantages compared with other
119
FIG. 13.8 Metal artifact. This sagittal T1-weighted magnetic resonance
image is severely degraded by xation hardware (four-level pedicle screws)
that does not allow adequate evaluation of the neural foramen.
important factors that determine the magnitude of image
artifact. Titanium wires exhibit the least artifact on CT and
MRI compared with cobalt chrome or stainless steel.
MRI studies may be severely compromised in the presence
of spinal instrumentation, and there can be potential safety
and biologic considerations (Fig. 13.8). Many strategies can
reduce susceptibility artifacts on MRI, including the use of
spin-echo techniques, especially FSE variants over gradient
echo; larger elds of view; higher readout bandwidths; smaller
voxel sizes; and appropriate geometric orientation of the
frequency-encoded direction in relationship to metallic objects
(Fig. 13.9).
120,121
Additional MR artifacts can be present, such
as motion artifact (Fig. 13.10), ow-related artifact, chemical
shi, Gibb’s artifact, and aliasing or wrap-around artifact.
Pathology
122
Imaging Artifacts
Artifacts invariably occur during spine imaging and can either
obscure or simulate pathology. Stainless steel implants are
known to generate substantial metal artifact with MRI and CT.
On CT, metal causes severe x-ray attenuation (missing data)
in selected planes. ese missing data or hollow projections
cause classic “starburst” or streak artifacts during image
reconstruction. e resulting distortions oen render these
studies useless. Materials with lower x-ray attenuation coecients (plastic, titanium, tantalum, stainless steel, cobalt
chrome) produce fewer distortions. Metal composition, mass,
orientation, and position of the implant in the body all are
When interpreting a radiographic examination of the spine,
the rst step is to identify the abnormality and then arrive at
a diagnosis or reasonable dierential diagnosis. One of the
most critical pieces of imaging information regarding spinal
pathology used in forming a dierential diagnosis involves
determination of whether the lesion is intramedullary, intradural extramedullary, or extradural.
Degenerative Disc Disease
e morphologic ndings of degenerative disc are well documented and demonstrated, especially with MRI. ere are,
Chapter 13 Spine Imaging 209
AB
FIG. 13.9 (A) Extensive artifact from posterior instrumentation in this T1-weighted image obscures evaluation
of the spinal canal. (B) T1-weighted image with contrast and metal reduction technique demonstrates
improved evaluation of the canal with epidural extension of disease (asterisk).
SECTION
II
FIG. 13.10 Sagittal contrast-enhanced T1-weighted image of the cervical
spine demonstrates apparent signal abnormality/enhancement of the cord
at level of C3 (arrow). However, this is motion artifact from swallowing/
epiglottis movement with a similar morphologic abnormality tracking
outside the cervical spinal cord (arrowheads) conforming to the shape of
the epiglottis.
however, many factors to consider before imaging patients
who present with uncomplicated low back pain, including that
the ndings of degenerative disc disease are common in
asymptomatic individuals, degenerative disc disease has a
favorable natural history, and there is a potential impact on
clinical decision making.
123
e presence of degenerative changes within the cervical
and lumbar spine has been shown to be age related and equally
present in asymptomatic and symptomatic individuals.
124,125
By the h decade of life, 25% of asymptomatic patients have
degenerative changes in the intervertebral disc spaces. By the
seventh decade, 75% have degenerative changes.
126
grams performed in patients without symptoms revealed
abnormalities in 24% of the exams,
124
and MR exams in
patients without symptoms demonstrated normal exams in
only 36% of cases.
127
Overall, the natural history of low back pain is favorable,
with most patients experiencing improvement within 4 weeks
regardless of whether they are imaged.
128,129
Over time, disc
herniations can improve or decrease in size and new extrusions can occur aer the onset of original symptoms.
Multiple studies have shown that imaging in cases of
uncomplicated low back pain does not positively aect patient
management and that imaging can actually be harmful.
Studies of radiographic evaluations have shown that there
is little eect on patient management.
133,134
Treatment and
diagnosis were not dierent in patients who were not imaged
as opposed to patients who underwent advanced imaging.
When comparing patients with low back pain receiving either
radiographs or an abbreviated MR imaging protocol, there was
no advantage to the MR imaging group.
136
Gillan et al. found
no treatment dierence between imaging versus no imaging
in patients with low back pain.
135
Imaging for low back pain
can be associated with potential harm, including radiation
exposure if CT imaging is used,
of spine surgery,
138-140
and the potential for patients to have a
lesser sense of well-being.
137
potential for increased rates
141
Multiple authors suggest that an imaging study is indicated
in the evaluation of a patient with sciatica when (1) true
radicular symptoms are present, (2) there is objective evidence
of nerve root irritation on physical examination (i.e., positive
straight-leg raise test), and (3) the patient has not responded
to “conservative management” of 4 to 6 weeks’ duration.
Earlier imaging is considered appropriate if clinical features
raise concern regarding malignant or infectious causes or if
neurologic ndings worsen during observation. ese recommendations are based on several studies of successful nonoperative treatment of sciatica.
145-150
Imaging is recommended
only for the remaining minority of patients with persistent
signs and symptoms who are believed to be surgical candidates
or in whom diagnostic uncertainty remains. In the 2009
American College of Radiology appropriateness criteria for
Myelo-
130-132
135
142-144
210 DIAGNOSIS
imaging patients with low back pain, imaging patients was
noted to be inappropriate if the following were absent: trauma
in patients older than 50 years of age, unexplained fever or
weight loss, immunosuppression, history of cancer or intravenous drug use, steroid use, age greater than 70 years, progressive neurologic symptoms or loss of function, or symptoms
being present for longer than 6 weeks.
151
Intervertebral Disc
Because of its inherent contrast sensitivity, MRI reveals morphologic abnormalities well and also provides insight into the
biochemical changes of the degenerating disc. With aging and
degeneration, there is gradual narrowing of the disc space and
loss of the normal high intradiscal signal intensity on
T2-weighted images. e latter is believed to be secondary to
changes in proteoglycan composition within the disc rather
than to absolute changes in water content.
progresses, small uid-lled ssures or cracks may develop
that manifest as intradiscal areas of linear high signal on
T2-weighted images.
153-155
Gas and calcication can also
develop within a degenerating disc.
Fissures (tears) of the anulus brosus can also be visualized with MRI. ey appear as small areas of increased
signal on T2-weighted images and can enhance aer contrast
agent administration, presumably secondary to the ingrowth
of granulation tissue into the ssure as a consequence of
healing.
156
ree types of anular ssures have been described,
depending on their orientation relative to the concentric
anular bers.
157
e high frequency of anular ssures seen in
association with large disc bulges challenges the concept that
the anulus brosus is intact in bulging discs but ruptured in
herniated discs. e clinical signicance of anular ssures is
unknown. In patients without nerve root compression, back
pain may be secondary to irritation of the nerve endings in
the peripheral anulus either from scar tissue within an anular
ssure or from a disc herniation; this is referred to as discogenic
pain. Although this concept is oen used to ascribe clinical
signicance to these lesions, many asymptomatic patients
harbor anular ssures.
ere is no universally accepted classication system
describing degenerative disc disease. A multispecialty task
force released recommendations for disc nomenclature spanning the orthopedic, neurosurgical, and radiologic communi-
158
ties.
is group has dened a protrusion as a herniation that
maintains contact with the disc of origin by a bridge as wide
as, or wider than, any diameter of the displaced material (Fig.
13.11). An extruded disc is a larger herniation in which the
diameter of the disc material beyond the interspace is wider
than the bridge, if any, that connects it to the disc of origin
(Fig. 13.12). A sequestered (free) disc fragment is an extrusion
that is no longer contiguous with the parent disc. It may reside
either anterior or posterior to the posterior longitudinal ligament or rarely may be intradural (Figs. 13.13 and 13.14). A
free fragment may be located at the disc level or may migrate
superiorly or inferiorly, oen lateralized by the thin, sagittally
oriented midline septum seen in the lower anterior epidural
space.
152
As degeneration
FIG. 13.11 Lateral disc herniation. Axial T1-weighted magnetic resonance
image shows well-dened right lateral herniation with no thecal sac
compromise (arrow).
FIG. 13.12 Cervical disc extrusion. Sagittal T2-weighted magnetic
resonance image shows large disc extrusion at C6–C7 severely eacing the
anterior thecal sac and cord. Signal intensity of the cord is normal.
Degenerative Endplate Changes
In addition to these observed changes within the degenerating
disc, vertebral marrow signal abnormalities adjacent to the
degenerating disc are common.
manifests as decreased marrow signal paralleling the endplates
on T1-weighted images and increased signal on T2-weighted
images. ese changes reect replacement of normal fatty
marrow with brovascular marrow, which has greater water
159
Type 1 endplate change
Chapter 13 Spine Imaging 211
SECTION
II
A
C
FIG. 13.13 Disc extrusion with free fragment. (A) Sagittal and (B) axial T1-weighted magnetic resonance
images show a large central extrusion at L5–S1 extending dorsally and inferiorly, suggesting a free fragment.
There is severe eacement of caudal thecal sac. (C) Sagittal and (D) axial T2-weighted images show extrusion as
intermediate signal and conrm mass eect on sac.
B
D
content. Type 2 endplate changes are slightly more common
than type 1 changes, showing increased signal on T1-weighted
images and isointense to slightly increased signal on
T2-weighted images. Histologically, these changes correlate
with fatty marrow replacement. ese changes may be pre-
ceded by type 1 changes, and oen these changes exist in
combination at the same level or dierent levels. Type 3 end-
plate changes show decreased marrow signal on T1-weighted
and T2-weighted images, a nding that correlates with endplate sclerosis seen radiographically.
159
Recent researchers have suggested that type 1 endplate
changes can be secondary to a low-grade infection,
160,161
with
one study showing that patients with type 1 endplate changes
treated with antibiotics showed improvement over the placebo
162
group.
Lumbar Stenosis
As an anatomic entity, spinal stenosis refers to narrowing of
the central spinal canal, neural foramina, or lateral recesses.
Most commonly, it is acquired secondary to degenerative
disease of the intervertebral disc or facets or both, although
developmentally shortened pedicles are an important component of symptomatic spinal stenosis in patients with otherwise
mild degenerative changes (Figs. 13.15 and 13.16).
the development of MRI, plain lms and CT were used to
diagnose spinal stenosis by measuring the dimensions of the
bony canal. At present, such measurements are not commonly
performed. ese measurements do not take into account the
normal anatomic variation between patients or the role of the
disc and ligamentum avum in spinal stenosis and are inaccurate predictors of clinical symptoms. MRI accurately depicts
163
Before
212 DIAGNOSIS
A
FIG. 13.14 Cervical disc herniation. (A) Axial computed tomographic scan and (B) sagittal reformat after
myelography show well-dened extradural lesion at C4–C5 eacing the anterior thecal sac and touching the
cord. A small osteophyte is present at C5–C6 with no cord compromise.
FIG. 13.15 Lumbar canal stenosis. Axial computed tomographic scan at
L4–L5 shows marked bony central canal stenosis with mild anterior
osteophyte and marked facet hypertrophic degenerative change. The disc is
degenerated with vacuum phenomenon.
the degree and cause of thecal sac narrowing in patients with
central canal stenosis. Such narrowing is most commonly due
to bony and ligamentous hypertrophy.
In addition to central canal stenosis, stenosis of the lateral
recess is an important cause of lower extremity pain and
paresthesias. e lateral recess is bordered anteriorly by the
posterior aspect of the vertebral body and disc, laterally by
the pedicle, and posteriorly by the superior articular facet.
e root sleeve within the lateral recess is oen compressed by
bony hypertrophy of the superior facet, oen in combination
with disc bulging and osteophyte along the anterior border of
the lateral recess. Lateral recess pathology can clinically mimic
disc herniation. MRI allows dierentiation between central
B
and lateral recess stenosis and provides important information
for presurgical planning.
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Facet Disease
Degenerative disease of the facet joints typically occurs in
combination with degenerative disc disease, although facet
disease alone may be responsible for symptoms of back pain
and radiculopathy. As with any synovial-lined joint, facet
joints are susceptible to the development of joint space loss,
subchondral sclerosis and cyst formation, osteophytosis, and
subluxation. Because of the richly innervated synovium and
joint capsule, these changes alone can be a source of pain, or
alternatively they can contribute to nerve root impingement
by causing spinal stenosis or foraminal compromise. On MRI,
degenerated facets appear hypertrophied, sclerotic, and irregular. Enlarged ligamentum avum is commonly present. Facet
degeneration can lead to the formation of synovial cysts that
can compress the thecal sac and roots from a posterior direction. Synovial cysts are best depicted on axial images and
appear as posterolateral epidural masses adjacent to a degenerated facet, most commonly at the L4–L5 level. Synovial cysts
have variable signal characteristics secondary to varying cyst
uid composition and associated hemorrhage, calcication, or
gas within the cyst (Fig. 13.17).
165
A peripheral hypointense
rim on T2-weighted images related to calcication may be
seen. Intravenous contrast medium is useful in suspected
cases to dene better the lesion and its relationship to the
adjacent facet joint and thecal sac.
Instability
e most frequently seen alignment abnormality is spondylolisthesis, which is dened as ventral slippage of a vertebra relative to the vertebrae below. e two most common causes of