AJR 2002; 179:515-521
© American Roentgen Ray Society
High-Resolution Single-Slice MR Myelography
Masako Nagayama1,
Yuji Watanabe,
Akira Okumura,
Yoshiki Amoh,
Satoru Nakashita and
Yoshihiro Dodo
1 All authors: Department of Radiology, Kurashiki Central Hospital, 1-1-1 Miwa,
Kurashiki, Okayama 710-8602, Japan.
Received December 4, 2001;
accepted after revision January 24, 2002.
Address correspondence to M. Nagayama.
Introduction
MR myelography is a noninvasive technique that can provide anatomic
information about the subarachnoid space. Major advantages of MR myelography
over conventional radiographic myelography include its lack of ionizing
radiation, noninvasive nature, and lack of need for intrathecal contrast
material [1]. Two techniques,
based on slice selection, are currently in use: multislice MR myelography and
single-slice MR myelography. Multislice MR myelography requires a relatively
long imaging time. The image quality is often degraded by artifacts arising
from cerebrospinal fluid pulsatile flow and background signal contributed by
fat or paravertebral veins. Reconstructed images created using maximum
intensity projection can obscure small intrathecal structures that are
surrounded by hyperintense cerebrospinal fluid
[1,2,3,4].
Single-slice MR myelography, which is performed using a single thick slice
and requires no postprocessing, provides a projection image with excellent
suppression of background signals
[5,
6]. Because its imaging time is
much shorter than that of multislice techniques, single-slice MR myelography
can be readily added to a routine MR examination of the spine.
In this pictorial essay, we illustrate findings of various spinal diseases
on high-resolution single-slice MR myelography, which can provide important
additional information to conventional MR imaging.
Technique
Single-slice MR myelography was performed using a single-shot turbo
spin-echo sequence with extremely long effective TE. The imaging parameters
for the cervicothoracic spine were TR/TE, infinite/1200-1400; echo-train
length, 256; signal averaged, one; and imaging time, 2.8 sec. In the lumbar
spine, an inversion pulse was applied to completely suppress the fat signal.
The scan parameters were TR/TE, infinite/1200-1600; inversion time, 150;
echo-train length, 256; signals averaged, four; and imaging time, 32 sec. The
spatial resolution (pixel size) for the cervicothoracic and lumbar spine were
0.98 x 0.98 mm and 0.55 x 0.55 mm, respectively. In each patient,
three images (in coronal and in bilateral oblique coronal directions) were
obtained with a slice thickness of 40-60 mm. Single-slice MR myelographic
images were displayed with midsagittal T2-weighted MR images, which allow
better anatomic resolution. All MR imaging was performed with a 1.5-T unit
(Gyroscan ACS-NT or Intera; Philips Medical Systems, Best, The
Netherlands).
Characteristics of Single-Slice MR Myelography
Single-slice MR myelography provides a fluoroscopic view similar to that of
a conventional radiographic myelogram. Our technique yields extremely heavily
T2-weighted images with excellent signal contrast, high spatial resolution,
and less artifact arising from cerebrospinal fluid flow than seen on
multislice MR myelography. Thecal sac filled with cerebrospinal fluid shows
markedly high signal intensity, whereas background signals including fat and
paravertebral veins are almost completely suppressed. Intrathecal structures
such as spinal cord, nerve roots, and vessels are imaged as filling defects
outlined by hyperintense cerebrospinal fluid, whose margins appear smooth and
clear (Fig.
1A,1B).
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Fig. 1A. —Single-slice MR myelography in healthy 35-year-old male
volunteer. Cervical spine single-slice MR myelogram obtained in posterior view
shows spinal cord as filling defect in thecal sac containing hyperintense
cerebrospinal fluid. Nerve root sleeves are shown as symmetric tentlike or
sleevelike protrusions from thecal sac margin (arrows).
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Fig. 1B. —Single-slice MR myelography in healthy 35-year-old male
volunteer. Lumbar spine single-slice MR myelogram obtained in posterior view
shows individual nerve roots (arrows) extending from spinal cord to
nerve root sleeves and cauda equina.
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Single-slice MR myelography can provide an overview of the thecal sac, even
if the presence of a spinal block due to spinal stenosis or intrathecal
adhesion results in a myelographic block on radiographic myelography
[5]. The degree of the spinal
stenosis can be overestimated on single-slice MR myelography because of
relatively low signal-to-noise ratio. Although the findings of single-slice MR
myelography such as intrathecal abnormal filling defects and contour
abnormalities of thecal sac margin may not be specific, when combined with
conventional MR images they can help characterize and diagnose the lesions
specifically.
Normal Variations
Conjoined nerve root is a normal variant, in which two nerve roots share a
common proximal root sleeve before separating to exit through their respective
neural foramina. Single-slice MR myelography shows that the proximal nerve
root sleeve of two nerve roots are conjoined in an asymmetric manner
(Fig. 2). Cystic dilatations of
nerve root sleeves are often seen as saccular structures beside the thecal
sac. Nerve roots typically appear to be contained in the saccular cystic
dilatation (Fig. 3).
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Fig. 2. —Conjoined nerve root in 39-year-old man. Single-slice MR
myelogram reveals that two nerve roots (arrow) of right side share
common proximal sleeve at level of sacrum. Tortuous fine vessel
(arrowheads) on surface of lumbosacral spinal cord is normal
finding.
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Fig. 3. —Cystic dilatation of nerve root sleeves in 74-year-old woman.
Single-slice MR myelogram reveals cystic dilatation of nerve root sleeves
(long arrows) as round protrusions from thecal sac margin containing
nerve roots (short arrows). Bilateral lobulated round cysts
(arrowheads) at sacral level are thought to be cystic dilatation of
nerve roots or perineural cysts.
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Congenital Anomalies
A tethered spinal cord can cause several clinical manifestations, including
bladder dysfunction, lower extremity weakness, abnormal reflexes, and back
pain. The spinal cord is fixed (tethered) by one or more abnormalities such as
a short, thickened film terminale, a lipoma, or fibrous adhesions. The
diagnosis of tethered cord is made when the conus medullaris lies below the
level of L2 [6]. On sagittal MR
images, however, it may be difficult to distinguish between cauda equina and
conus medullaris [6]. With
single-slice MR myelography, it is easy to identify the caudal end of the
conus medullaris and make the diagnosis of tethered cord (Figs.
4A,4B
and
5A,5B).
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Fig. 4A. —Tethered spinal cord and lipomyelocele in 33-year-old man.
Sagittal heavily T2-weighted routine MR image illustrates difficulty of
identifying exact location of conus medullaris. Filling defect
(arrowhead) consistent with lipoma is seen at termination of spinal
canal.
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Fig. 4B. —Tethered spinal cord and lipomyelocele in 33-year-old man.
Single-slice MR myelogram obtained in posterior view shows conus medullaris at
its tethered site (arrow) more clearly than A. Note dilated
thecal sac and filling defect of intradural and extradural lipoma
(arrowhead), which corresponds to lesion seen in A.
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Fig. 5A. —Syrinx cavity, tethered cord, and lipomyelocele in
18-month-old boy. Cervicothoracic spine single-slice MR myelogram obtained in
posterior view reveals syrinx as spindle-shaped or segmented tubular
hyperintense areas (arrows) with cerebrospinal fluid—intense
signal in spinal cord.
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Fig. 5B. —Syrinx cavity, tethered cord, and lipomyelocele in
18-month-old boy. Thoracolumbar spine single-slice MR myelogram obtained in
posterior view shows dilatation of lumbosacral thecal sac and conus medullaris
(long arrow) terminating at filling defect site (arrowheads)
representing lipoma. Syrinx is seen as spindle-shaped or segmented tubular
hyperintense areas (short arrows) as in A. Asterisk indicates
urinary bladder.
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A syrinx cavity is a cystic cavitation in the spinal cord associated with
congenital anomalies such as Chiari's malformation and with tumor, trauma, and
arachnoiditis. Single-slice MR myelography clearly shows a syrinx cavity as
spindlelike or tubular high signal intensity similar to that of cerebrospinal
fluid in the spinal cord (Fig.
5A,5B).
Posttraumatic Pseudomeningoceles
Traction injury of the brachial plexus is often caused by motorcycle
collisions and leads to avulsion of the spinal nerve roots. Preganglionic
nerve root avulsion is accompanied by injury of the nerve root sleeve, which
results in the pseudomeningocele
[2]. Single-slice MR
myelography can depict a pseudomeningocele as a tubular or oval cystic mass
protruding from the thecal sac into the neural foramen, often extending into
the paravertebral space (Fig.
6).
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Fig. 6. —22-year-old woman with posttraumatic pseudomeningocele caused
by traffic collision. Single-slice MR myelogram obtained in posterior view
clearly shows pseudomeningoceles (arrows) at C7—T1 as long
sleevelike hyperintense structure extending into paravertebral space.
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Adhesive Arachnoiditis
Adhesive arachnoiditis is associated with the previous history of
infection, surgery, trauma, intrathecal hemorrhage, and Pantopaque
(iophendylate; Alcon Surgical, Fort Worth, TX) radiographic myelography
[7]. Adhesion of nerve roots
and cauda equina can be well recognized on single-slice MR myelograms. As
reported on X-ray myelograms, characteristic findings such as irregular
contour of the thecal sac, root sleeve obliteration (root sleeveless
appearance), central clumping or peripheral adhesions of the nerve roots, and
filling defects [7] are shown
on single-slice MR myelograms. Among them, central clumping or peripheral
adhesion of the cauda equina are well identified on axial heavily T2-weighted
images (Fig.
7A,7B,7C,7D).
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Fig. 7B. —Adhesive arachnoiditis in 73-year-old man. Single-slice MR
myelogram obtained in posterior view clearly shows thickening and fusion of
nerve roots, irregular contour of thecal sac, and obliteration of nerve root
sleeve.
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Spinal Tumors
Single-slice MR myelography clearly shows intradural extramedullary tumors
as abnormal filling defects sharply outlined by cerebrospinal fluid
(Fig. 8). In spinal stenosis
caused by extradural tumor, single-slice MR myelography shows deformity of the
thecal sac margin due to extrinsic compression (Fig.
9A,9B,9C).
Intramedullary tumor may appear as diffuse, smooth enlargement of the spinal
cord on single-slice MR myelography (Fig.
10A,10B).
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Fig. 8. —Meningeal metastasis from lung cancer in 64-year-old man.
Single-slice MR myelogram obtained in posterior view clearly shows multiple,
small intradural extramedullary metastatic nodules (arrows) as
filling defects sharply outlined by cerebrospinal fluid.
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Fig. 9A. —Multiple bone metastases from parotid gland cancer in
65-year-old man. Single-slice MR myelogram obtained in posterior view shows
stenosis of thecal sac and minimal deviation of spinal cord (arrow)
due to left-sided extrinsic compression at T3. Bandlike filling defects
(arrowheads) are due to pathologic compression fracture of T1 and
cervical degenerative changes.
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Fig. 9B. —Multiple bone metastases from parotid gland cancer in
65-year-old man. Sagittal unenhanced T1-weighted image shows multiple
hypointense bone metastases (arrows). At T3, both vertebral body and
spinous process show hypointensity.
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Fig. 9C. —Multiple bone metastases from parotid gland cancer in
65-year-old man. Axial T2-weighted image at T3 reveals metastatic tumor
(arrowheads) occupying left pedicle, transverse process, and proximal
part of third rib. Tumor expands into spinal canal and is close to spinal
cord.
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Fig. 10B. —Intramedullary tumor with syrinx in 73-year-old man.
Single-slice MR myelogram obtained in posterior view shows diffuse, smooth
enlargement of cervical spinal cord. Solid part of tumor (long arrow)
is depicted as hypointense relative to cystic areas (arrowheads) and
syrinx (short arrows). Bandlike filling defects at C3-C4 and C4-C5
are associated with degenerative changes.
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Disk Herniation
Single-slice MR myelography shows focal deformity of thecal sac margin due
to disk herniation. Oblique single-slice MR myelography reveals extrinsic
deformity of lateral recess of the thecal sac margin due to posterolateral
disk hernia (Fig.
11A,11B,11C).
Far lateral disk hernia, which does not affect the thecal sac, cannot be
detected on single-slice MR myelography.
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Fig. 11B. —Posterolateral disk herniation in 36-year-old man. Oblique
single-slice MR myelogram clearly shows right posterolateral compressive
deformity of thecal sac margin (arrow) and displacement of nerve
roots.
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Fig. 11C. —Posterolateral disk herniation in 36-year-old man. Axial
heavily T2-weighted MR image at L4-L5 shows right posterolateral disk
herniation (arrowhead) that has resulted in stenosis of right side of
spinal canal, lateral recess, and neural foramen.
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Degenerative Spinal Stenosis
In spinal stenosis due to degenerative disease, single-slice MR myelography
shows bandlike filling defects or wavelike deformity of the thecal sac by
extrinsic compression. The degrees of the spinal stenoses can be readily
compared at each level (Fig.
12A,12B).
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Fig. 12A. —Degenerative spinal stenosis with redundant nerve roots in
74-year-old man. Sagittal fat-suppressed T2-weighted MR image shows severe
degenerative spinal stenosis at L2-L3 through L4-L5.
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Fig. 12B. —Degenerative spinal stenosis with redundant nerve roots in
74-year-old man. Single-slice MR myelogram shows wavelike deformity with
diffuse stenosis of thecal sac and bandlike filling defects
(arrowheads). Stenoses are more severe at L3-L4 and L4-L5, which are
seen as complete block. Multiple serpentine filing defects on cephalic side of
stenosis at L2-L3 indicate redundant nerve roots (arrows).
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Redundant nerve roots are associated with severe spinal stenosis and may be
seen on the cephalic side of the block in the lumbar region
[8]. Single-slice MR
myelography clearly depicts tortuous, elongated nerve roots (Fig.
12A,12B).
Spinal Arteriovenous Malformation
Dural arteriovenous fistulas are usually seen as serpentine vessels
coursing in a craniocaudad direction in the spinal canal surrounded by
cerebrospinal fluid. Single-slice MR myelography can clearly depict the
dilated abnormal vessels as serpentine filling defects with good continuity
around the spinal cord (Fig.
13A,13B).
In a patient with associated subarachnoid hemorrhage, abnormal vessels may be
obscured on single-slice MR myelography because the signal intensity of
cerebrospinal fluid is decreased as a result of the hemorrhage
[3].
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Fig. 13B. —Spinal arteriovenous malformation in 77-year-old man.
Single-slice MR myelogram reveals enlarged abnormal vessels as serpentine
filling defects (arrowheads) around spinal cord with good
continuity.
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References
- Figueroa RE, Stone JA. MR imaging of degenerative spine disease: MR
myelography and imaging of the posterior spinal elements. In: Castillo M., ed.
Spinal imaging, state of art. Philadelphia: Hanley
& Belfus 2001:105
-122
- el Gammal TAM, Crews CE. MR myelography of the cervical spine.
RadioGraphics
1996;16:77
-88[Abstract/Free Full Text]
- el Gammal T, Brooks BS, Freedy RM, Crews CE. MR myelography:
imaging findings. AJR
1995;164:173
-177[Abstract/Free Full Text]
- Krudy AG. MR myelography using heavily T2-weighted fast spin-echo
pulse sequences with fat presaturation. AJR
1992;159:1315
-1320[Abstract/Free Full Text]
- Demaerel P, Bosmans H, Wilms G, et al. Rapid lumbar spine MR
myelography using rapid acquisition with relaxation enhancement.
AJR
1997;168:377
-378[Free Full Text]
- Osbom AG. Diagnostic neuroradiology. St.
Louis: Mosby-Year Book, 1994:807
-808
- Ross JS, Masaryk TJ, Modic MT, et al. MR imaging of lumbar
arachnoiditis. AJR
1987;149:1025
-1032[Abstract/Free Full Text]
- Hacker DA, Latchaw RE, Yock DH Jr, Ghosharjura K, Gold LH.
Redundant lumbar nerve root syndrome: myelographic features.
Radiology
1982;143:457
-461[Abstract/Free Full Text]
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Introduction
Technique
