Myelopathy can be caused by either intrinsic spinal cord disease
or extrinsic compression. In the individual case, it may be
impossible to clinically distinguish between the two. While
myelopathy has traditionally been evaluated with myelography, this
technique is both more invasive and less sensitive than MRI.
MRI has revolutionized the imaging of myelopathy. Not only is
MRI more sensitive than CT or myelography for detection of disease,
it is also more specific for the characterization of disease. This
issue of Applied Imaging discusses the most common diseases of the
spinal cord that can be diagnosed with MRI.
William G. Bradley, Jr., MD, PhD, FACR
Myelopathy is produced by disease of the spinal cord.
It can present with sensory or motor abnormalities. Sensory
abnormalities include pain, numbness, or paresthesias from
involvement of the spinothalamic tracts, or loss of position
sense/proprioception from involvement of the dorsal columns.
Sensory abnormality can be one-sided (e.g., Brown-Séquard) or
bilateral, with a definable sensory level that is either fixed
(e.g., transverse myelitis) or variable (e.g., ascending
Motor findings due to cord disease include loss of motor
function to both legs (paraparesis) for lesions involving the
thoracic cord and conus, or loss of motor function in the arms and
legs (quadriparesis) due to lesions of the cervical cord. Lesions
involving only one side of the body (hemiparesis, hemiplegia)
typically arise in the brain, not the spinal cord.
Over the past 2 decades, magnetic resonance imaging (MRI) has
proven to be the premier imaging technique for the evaluation of
myelopathy. Older techniques, such as myelography, were limited to
evaluation of the cord contour (which was both insensitive and
nonspecific). While computed tomography (CT) continues to be useful
for evaluation of the bony spine (e.g., in cases of trauma,
spondylosis, or tumor), it is less sensitive for demonstrating the
This issue of Applied Imaging focuses on the use of MRI to
evaluate the symptoms of myelopathy. It is organized along classic
lines: intramedullary (cord), intradural-extramedullary (outside
the cord but within the thecal sac), and extradural disease
(originating outside the thecal sac) with secondary cord
Initially, cord gliomas are seen as focal areas of
hyperintensity on T
-weighted images that may or may not enhance with gadolinium on T
-weighted images (Figure 1), similar to their appearance in the
With time, they enlarge and a contour abnormality can also be
detected. Cord gliomas are most often of two types: astrocytomas
Astrocytomas of the cord tend to involve the cervical region but
may involve any part of the cord. They tend to be infiltrative and
difficult to remove surgically. These lesions tend not to respond
to radiation therapy.
Ependymomas of the cord are more often found in the lower
thoracic cord and conus.
They tend to be more easily resected and are more radiosensitive
There also is a tendency for ependymomas to be more vascular and
more prone to hemorrhage.
Thus, they are more likely to enhance with gadolinium.
Multiple sclerosis (MS) of the cord can simulate a cord tumor
(Figure 2). In milder cases, the only finding may be focal
hyperintensity (Figure 3) on a T
Tumefactive MS presents with cord swelling (Figure 2) and may
enhance just like a tumor. In patients undergoing an initial
evaluation of myelopathic symptoms, it may be useful to obtain
images of the brain to detect subclinical MS. In such cases,
thin-slice, sagittal, fast fluid attenuated inversion recovery
(FLAIR) images have proven to be particularly useful.
While MS plaques may be indistinguishable from tumors on an
individual basis, they tend to be more longitudinally elongated and
flame-shaped (Figure 3) than tumors (which tend to be more
rounded). Involvement is most common in the posterolateral aspects
of the upper cord, decreasing in frequency in the thoracic cord and
MS of the cord can present with transverse myelitis, although
these symptoms are not specific. Viral myelitis and acute
disseminated encephalomyelitis (ADEM), a monophasic autoimmune
demyelinating process, can produce similar symptoms. Any of these
inflammatory conditions can cause cord swelling (Figure 2) and
simulate a cord tumor.
Syringohydromyelia is a term encompassing almost any cystic
lesion of the cord.
When these are associated with a Chiari I malformation (extension
of the cerebellar tonsils at least 3 mm below the foramen magnum),
the appropriate term is "hydromyelia" (Figure 4). This represents
enlargement of the central canal; therefore, hydromyelic cysts are
lined by ependyma.
The term "syringomyelia" technically refers to cystic lesions of
the cord other than those due to dilatation of the central canal.
Such cysts may be seen following trauma or arachnoiditis. They may
also be seen in conjunction with a cord tumor. The tumor can be
intra- or extramedullary and located either above or below the
syrinx (Figure 5). Syringes are lined by glia.
It follows from the above that syringohydromyelia presenting
without a Chiari I malformation requires further evaluation for the
presence of a tumor. Such patients should be given gadolinium at
the time of MR imaging.
A third kind of spinal cord cyst is that due to a cystic
neoplasm (Figure 1). Such cysts are lined by tumor cells and tend
to be filled with fluid that is more proteinaceous than CSF. This
causes them to appear brighter than CSF, particularly on T
-weighted and proton density-weighted images.
The lesions in this compartment originate outside the cord and
within the thecal sac. Generally, they produce myelopathy only when
they interrupt the blood supply to or the venous drainage from the
cord, or when they become large enough to compress the cord.
Meningioma is the most common tumor in this compartment, most
often found in the thoracic and cervical spine.
This lesion tends to arise from the arachnoid villi near the
In the cervical spine, these tend to be anterolateral; in the
thoracic spine, they are posterolateral.
Like meningiomas in the brain, lesions in the spine tend to be
isointense with normal neural tissue on both T
- and T
-weighted images and to enhance intensely with gadolinium (Figure
6). Spinal meningiomas may have a dural tail. Because they are
generally slow growing, they may cause considerable cord
compression before the patient seeks medical attention.
Schwannomas tend to be more common in the cervical than the
thoracic region. Unlike meningiomas, they tend to be brighter than
neural tissue on T
-weighted images and darker on T
-weighted images. Like meningiomas, they enhance intensely with
Since schwannomas generally arise from nerve roots, they tend to be
positioned more laterally and may extend into the ipsilateral
neural foramen. Because they are slow growing, they often remodel
the bone with subsequent widening of the foramen. With continued
growth, they will expand lateral to the foramen as well, leading to
the classic "dumbbell" appearance.
Leptomeningeal carcinomatosis most often results from
hematogenous spread of carcinoma of the lung or breast, or from
lymphoma. It may also result from CSF spread of such intracranial
malignancies as high grade gliomas and primitive neuroectodermal
The latter "drop metastases" generally present first with
radiculopathy due to involvement of lumbosacral nerve roots;
however, over time, lesions in the cervical and thoracic region can
enlarge to sufficient size to compress the cord (Figure 7).
It is important to realize that early spinal leptomeningeal
carcinomatosis can only be detected on MRI with gadolinium and that
many of these patients have already had craniospinal irradiation.
This irradiation will result in enlargement of the vessels over the
surface of the cord, potentially simulating leptomeningeal
In such cases, it is important to ascertain that the apparent drop
metastases do not actually represent multiple cross-sections of the
same dilated vessel on sequential axial slices. Additionally, in
one form of leptomeningeal carcinomatosis, there is a thin coating
of tumor over the surface of the cord known as "zuckerguss" (German
for "sugar coating"). On T
-weighted images, the cord may appear enlarged and to have
increased signal intensity, simulating a primary glioma. It is
important to administer gadolinium to these patients to detect the
thin layer of enhancement on the surface of the cord and, thereby,
make the correct diagnosis (Figure 8). Although uncommon, this form
of leptomeningeal carcinomatosis can be seen with lymphoma,
metastatic breast carcinoma, and CSF spread of medulloblastoma.
Fungal meningitis can simulate the appearance of leptomeningeal
carcinomatosis, leading to enhancing nodules over the surface of
The most common cause of extradural disease that produces cord
compression and myelopathy is bony metastatic disease.
While most metastatic disease goes to the vertebral bodies
initially, lymphoma can go directly to the epidural space, thereby
producing cord compression without bony destruction.
In older patients with osteoporosis, compression fractures may lead
to a retropulsed fragment that compresses the cord, producing
In younger patients without osteoporosis, the same effect can be
produced by trauma. In a similar fashion, disk extrusions in the
cervical and thoracic region can acutely compress the cord. In
particular, flexion-extension injuries of the cervical spine
(whiplash) can result in traumatic disk extrusion with secondary
cord compression, cord edema, and myelomalacia.
Thus, in the setting of myelopathy following spine trauma, it is
important to perform MRI to determine whether the cord compression
is secondary to transient buckling of the posterior longitudinal
ligament from hyperextension (which does not require surgery) or
acute disk extrusion or fracture (which may require surgery).
In addition, common masses such as schwannomas and meningiomas
can be found in the epidural space or in both the epidural and the
intradural extramedullary compartments. Regardless, when such
masses achieve sufficient size within the confines of the bony
spine to compress the cord, myelopathy ensues. Similarly, bony
spinal stenosis due to degenerative disk disease can cause
myelopathy (Figure 9).
While CT may have applications in the setting of primary or
metastatic disease of the bony spine or trauma, it is not effective
for visualizing the cord itself due to the dense beam hardening
(Hounsfield) artifact produced by the surrounding bone. Therefore,
MRI, with and without contrast, should be the initial imaging
evaluation for myelopathy.
Clinical Quiz: True or False
1. When MRI is available, there is no reason to perform CT or
myelography for evaluation of myelopathy.
2. Spinal masses show up so well on MRI that contrast is not
3. The evaluation of syringomyelia does not require the use of
4. While myelopathy is usually produced by diseases of the cord
itself, it can also be produced by lesions outside the cord.
5. It is possible for an extramedullary mass to have compressed
the cord and caused myelopathic symptoms, and not be visible on an
MRI study several hours later.
1. False. CT is often useful for the evaluation of diseases
involving bone. Post-myelography CT may be useful if there is too
much patient motion or local metallic artifact on the MRI study. In
addition, patients with pacemakers and ferromagnetic intracranial
aneurysm clips can never undergo MRI.
2. False. Leptomeningeal carcinomatosis can often be seen only
with gadolinium, and small meningiomas and schwannomas may only be
revealed on the basis of their enhancement.
3. False. When syringomyelia is seen without an associated
Chiari I malformation, gadolinium should be given to detect an
otherwise unseen cord tumor, which may be producing the syrinx.
4. True. Lesions that are large enough to compress the cord can
5. True. In the setting of whiplash injury, the posterior
longitudinal ligament can acutely buckle due to hyperextension,
bruise the cord, and then return to its normal position.