AJR 2001; 176:969-972
© American Roentgen Ray Society
Giant Cystic Schmorl's Nodes
Imaging Findings in Six Patients
Olivier Hauger1,
Anne Cotten2,
Jean-François Chateil1,
Olivier Borg3,
Maryse Moinard1 and
François Diard1
1
Service de Radiologie A, Groupe Hospitalier Pellegrin, CHRU Bordeaux, Place
Amélie Raba
Léon, 33076 Bordeaux Cedex, France.
2
Service de Radiologie, Hôpital B, CHRU Lille,
Blvd. de Pr. J. Leclerc, 59037 Lille Cedex, France.
3
Service de Radiologie, Hôpital Jean Bernard,
CHRU Poiters, BP 577, 86021 Poiters Cedex, France.
Received August 2, 2000;
accepted after revision September 18, 2000.
Address correspondence to F. Diard.
Abstract
OBJECTIVE. We describe the imaging findings of an unusual type of
Schmorl's node appearing as giant cystlike lesion of the vertebral bodies.
CONCLUSION. Giant cystic Schmorl's nodes are unusual entities; their
radiologic appearance differs dramatically from the classic description and is
diagnostically challenging. However, the appearance of these nodes on
conventional radiographs and especially on MR images is characteristic.
Knowledge of this entity would help to eliminate unnecessary invasive
diagnostic or therapeutic procedures.
Introduction
Cartilaginous or Schmorl's nodes are common and are related to prolapse of
intervertebral disk material into the vertebral body. These nodes can be
produced by any process that weakens either the cartilaginous endplate of the
vertebral body or subchondral trabeculae of the vertebra. Their radiographic
appearance is typical, and diagnosis is usually easy because they appear as
irregularities of the vertebral contours or small radiolucent lesions of the
vertebral bodies limited by reactive sclerosis and connected with the
intervertebral disk. However, Schmorl's nodes can have another radiographic
appearance that differs dramatically from the classic one—a
diagnostically challenging large cystic lesion that may be confused with other
cystlike lesions of the vertebral body. However, Schmorl's nodes have a
characteristic radiographic appearance unlike that of the other, more
aggressive cystlike lesions of the vertebral bodies and should be known in
order to prevent inappropriate invasive diagnostic or therapeutic
procedures.
Although some reports [1,
2] have included single cases
of large Schmorl's nodes, to our knowledge there has been no focused imaging
description of such lesions in the radiology literature. Therefore, the
purpose of this study is to describe the radiographic features of these
lesions on conventional radiographs, CT scans, and MR images in six patients,
one of whom had a follow-up examination after 2 years.
Subjects and Methods
The six patients in this study (one man, five women) were 17-24 years old
(mean age, 20 years). All had experienced lower back pain for 5-24 months
(mean, 10 months), with no history of specific trauma with the exception of
one patient who had fallen on her back 4 years earlier. Three of the five
women were tall (>1.75 m). Two participated in sports regularly.
All six patients underwent conventional radiography of the lumbar region,
five underwent CT (in three patients after diskography), five underwent MR
imaging, and one underwent radionuclide bone scanning. MR imaging protocols
varied, depending on the center at which the examination was performed.
However, for each patient, MR parameters included sagittal spin-echo
T1-weighted (TR range/TE range, 500-575/10-20) and sagittal and axial fast
spin-echo T2-weighted images (TR range/TEeff range,
2941-4000/90-120). In three patients, additional fat-suppressed spin-echo
T1-weighted sequences (TR range/TE range, 560-605/12-15) were performed in the
sagittal and axial planes after injection of gadolinium.
Three patients were contacted 2 years later, and conventional radiography
and MR imaging were performed again on one patient.
Results
On conventional radiographs, giant Schmorl's nodes were located in the
lower lumbar region, particularly the vertebral bodies of L3 (three patients)
and L4 (three patients). They appeared as well-demarcated, sharply
circumscribed lytic lesions occupying between one half and the whole vertebral
body height (18-25 mm) in contact with the superior intervertebral space
(Fig. 1). The nodes were
surrounded by a thin sclerotic margin suggesting a nonaggressive lesion.
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Fig. 1. —17-year-old girl with 2-year history of lower back pain. No
history of specific trauma except fall on her back during childhood.
Radiograph shows well-damarcated, sharply circumscribed lytic lesion of
vertebral body of L3 in contact with superior intervertebral space
(arrow).
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CT findings confirmed a well-delineated, slightly lateralized central
osteolytic lesion of the vertebral body that was surrounded by a sclerotic rim
and in contact with the superior surface of the vertebral body. The
interruption of the superior vertebral endplate was clearly visualized on
sagittal two-dimensional reconstructions (Fig.
2A,2B).
The density of the lesion was between 0 and 20 H, suggesting a fluid
content.
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Fig. 2A. —19-year-old woman, a basketball player, with 2-year history
of lower back pain and evidence of Scheuermann's disease sequelae. Axial CT
scan shows well-delineated osteolytic lesion of vertebral body of L3
surrounded by sclerotic rim.
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Fig. 2B. —19-year-old woman, a basketball player, with 2-year history
of lower back pain and evidence of Scheuermann's disease sequelae. Sagittal
two-dimensional reconstruction of CT scan reveals contact of lesion with
interrupted superior surface of vertebral body.
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Direct communication between the disk and the lesion was visualized by
diskography, which showed the leakage of the contrast material from the disk
into the cystic lesion. Moreover, a fluid—contrast material level was
observed, confirming the fluid content of the lesion and its cystic nature
(Fig.
3A,3B,3C).
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Fig. 3A. —24-year-old woman with 6-month history of lower back pain and
evidence of lytic lesion of vertebral body of L4. Diskograph shows leakage of
contrast material from disk into lesion, confirming hypothesis of Schmorl's
node. Note fluid—fluid level (arrow). Patient is in lateral
position.
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Fig. 3B. —24-year-old woman with 6-month history of lower back pain and
evidence of lytic lesion of vertebral body of L4. Axial CT scan after
diskography shows presence of contrast material in lesion with
fluid—fluid level (arrow). Presence of air (arrowhead)
on top of lesion is attributable to procedure.
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Fig. 3C. —24-year-old woman with 6-month history of lower back pain and
evidence of lytic lesion of vertebral body of L4. Sagittal two-dimensional
reconstruction of CT scan after diskography more clearly reveals leakage of
contrast material from disk into lesion. Again, fluid—fluid level
(arrowheads) confirms cystic nature of lesion.
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The MR results in all patients showed low-signal-intensity lesions on
T1-weighted images. On T2-weighted images the signal intensity became high,
again suggesting a fluid content, with a surrounding wall of lower signal
intensity and of variable thickness showing an enhancement after contrast
medium injection. All the lesions were connected to a degenerative superior
intervertebral disk (Fig.
4A,4B,4C,4D).
The disk was considered to be degenerative if there were both a narrowing of
the intervertebral disk and a decrease of the nuclear signal on T2-weighted MR
images caused by dehydration of the nucleus pulposus. A bone scan obtained in
one patient showed no uptake in the vertebral body, again suggesting a
nonevolutive benign lesion. When we performed a 2-year control examination of
one patient, we found no change in the appearance of the lesion (Fig.
5A,5B).
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Fig. 4A. —Lumbar spine images of 20-year-old woman hospitalized for
febrile meningeal syndrome. Incidental finding of typical giant cystic
Schmorl's node occupying total height of L4 vertebral body. Sagittal
two-dimensional reconstruction of CT scan reveals interruption of superior
surface of vertebral body.
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Fig. 4B. —Lumbar spine images of 20-year-old woman hospitalized for
febrile meningeal syndrome. Incidental finding of typical giant cystic
Schmorl's node occupying total height of L4 vertebral body. On sagittal
T1-weighted MR image (TR/TE, 550/20), lesion appears as low signal
intensity.
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Fig. 4C. —Lumbar spine images of 20-year-old woman hospitalized for
febrile meningeal syndrome. Incidental finding of typical giant cystic
Schmorl's node occupying total height of L4 vertebral body. On sagittal
T2-weighted image (3500/110), center of lesion appears lobulated and has high
signal intensity. Lesion has lower intensity wall. Note degenerative pattern
of adjacent intervertebral disks.
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Fig. 4D. —Lumbar spine images of 20-year-old woman hospitalized for
febrile meningeal syndrome. Incidental finding of typical giant cystic
Schmorl's node occupying total height of L4 vertebral body. Axial
fat-suppressed T1-weighted MR image (605/15) after gadolinium injection shows
thin peripheral enhancement likely to be related to presence of granulation
tissue. Note epidural enhancement next to iterative lumbar punctures
(arrow).
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Fig. 5A. —Lumbar spine of 21-year-old woman with lower back pain.
Sagittal T2-weighted MR image (TR/TE, 3000/90) shows cystic Schmorl's node
occupying two thirds of third vertebral body height. Again, there is high
signal centrally and surrounding wall of lower signal intensity. Note contact
of lesion with superior vertebral surface and degenerative pattern of superior
intervertebral disk.
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Fig. 5B. —Lumbar spine of 21-year-old woman with lower back pain.
Sagittal T2-weighted MR image (2800/120) obtained 2 years after A does
not show any change in appearance of lesion except that surrounding wall
appears slightly thinner. At time of examination, patient no longer complained
of lower back pain.
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Discussion
Cartilaginous or Schmorl's nodes represent intravertebral herniation of
disk material through the cartilaginous endplate. Such cartilaginous endplate
disruption can be produced by an abnormality of the plate itself or by
alterations in the subchondral bone of the vertebral body. The cartilaginous
endplate can be weakened by peculiarities related to its development, such as
an indentation left by the regression of the chorda dorsalis, the presence of
an "ossification gap"
[3], the perforation of
nutrient vessels, an abnormal pressure of a turgor nucleus pulposus, or the
presence of specific disorders, especially Scheuermann's disease. These
peculiarities are present in children but disappear in adults, thus explaining
the higher frequency of such lesions in children.
Other disorders including trauma, degenerative disk disease, and metabolic
and neoplastic diseases may also produce weakening of the cartilaginous
endplate or subchondral bone and thus initiate Schmorl's node formation, but
these disorders are usually seen in an older population.
The extension in the vertebral body of an idiopathic Schmorl's node (not
related to known vertebral body or disk disease) is usually limited because
trabecular sclerosis occurs in the surrounding bone. Calcification and
ossification of the protruded disk may be noted, and granulation tissue
extends from the marrow into the disk. Unlike this classic description, the
Schmorl's nodes observed in these patients appeared as large cystic lesions
occupying at least one half of the vertebral body height.
There is a strong resemblance between the Schmorl's nodes presented in this
study and the subchondral cysts described as being found in other joints,
particularly as sequelae of bone injury
[4]. The precise mechanism of
the latter lesions is not known. One possibility is that the occurrence of
trauma leads to trabecular fracture with secondary hemorrhage and cystic
degeneration. Another possibility is that the occurrence of altered mechanical
stress leads to intramedullary vascular disturbance, with consequent foci of
bone necrosis that heal by fibroblastic proliferation and mucoid degeneration
of connective tissue [5]. These
hypotheses could be applied to the diskovertebral junction because, as noted
by Resnick and Niwayama [6],
similarities exist between the cartilaginous joints at the diskovertebral
junction and synovial joints elsewhere in the body. Both cartilaginous joints
and synovial joints have bone covered with hyaline cartilage and surrounding
fibrous tissue. The gelatinous nucleus pulposus has similarities with synovial
fluid.
Because of the degeneration of the disk and the leakage of contrast
material from the disk into the cystic lesion of the vertebral body at
diskography, intravertebral disk herniation is likely to be the initial
phenomenon leading to giant cystic lesions. One possibility is that after this
herniation, trabecular hemorrhage occurs, preventing chondrification and thus
leading to cystic degeneration.
The reason that certain Schmorl's nodes evolve to giant cystic lesions
remains unclear. In the classic description
[7], typical Schmorl's nodes
are most commonly found in the lower thoracic and upper lumbar spine. They
usually involve the inferior endplate and are more common in men than in
women. It is of interest that the lesions described in this study have
specific peculiarities that differ in every respect from the classic
description. In our study, cystic Schmorl's nodes were exclusively found in
the lower lumbar spine (L3 or L4), involved the superior endplate, and
appeared to be far more common in women than in men (5/6 lesions were found in
young women). In the histories of our patients, we did not find any specific
event that could have contributed to the development of such lesions. Disk
abnormalities associated with Scheuermann's disease were observed in one
patient. One patient had a significant history of trauma, whereas four
patients had no history of significant injury. Nor did we notice any
significant spinal deformity such as hyperlordosis that could have caused
mechanical stress on the vertebral bodies. Moreover, the location of the
lesions on the vertebral bodies of L3 or L4 suggests that the lesions are not
related to acute trauma, which generally involves the T8-L1 region
[8].
Considering the rarity of these lesions, it is unlikely that the female
predominance observed in our study is a coincidence. To our knowledge, there
is no mention in the literature of any peripubertal hormonal profile that may
weaken the bone and cause fracture of the vertebral endplate or hemorrhage
into the trabecular bone.
Another peculiarity of the giant cystic Schmorl's nodes found in this study
is that they were related to lower back pain in all patients. Besides the
radiologic pattern, this symptom represents another similarity with the
posttraumatic subchondral cysts observed in peripheral joints. Indeed, in the
peripheral joints a radiolucent lesion associated with pain becomes evident
over a period of months (or years) after the traumatic episode. Subsequently,
the lesion stabilizes and the pain disappears. In the present study, three
patients contacted 2 years after the initial consultation described the
disappearance of the symptoms without any specific treatment. The imaging
features seen in one of these patients on conventional radiographs and MR
images did not show any changes in the appearance of the lesion. Pain is
likely to be a predominant symptom as the cyst develops and is likely to
disappear once the lesion stabilizes. Such maturation of a Schmorl's node over
a 3-year period has been reported in one patient
[2]. In this case, the authors
described an initial severe lower back pain, probably caused by the fracture
of the endplate or surrounding bone, without major radiographic abnormalities.
The authors reported that in their patient, the pain was followed 10 months
later by the development of a typical Schmorl's node with a 50% reduction of
the pain. After 3 years, the lesion stabilized, and the patient was
symptom-free.
Knowledge of the outcome of these lesions has important implications for
both diagnosis and therapeutic attitudes. As for the diagnostic exploration,
the initial examination of a patient should include conventional radiography
and MR imaging. When the radiologic pattern of the lesion is typical and
consists of a large well-delineated cystic lesion of the vertebral body
connected to a degenerative superior intervertebral disk, as evidenced by
narrowing and low signal intensity on T2-weighted MR images, no further
investigation is required. If the communication between the cystic lesion and
the intervertebral disk is not clearly revealed, diskography (coupled with CT
or MR imaging) is the procedure that will allow the most accurate diagnosis.
In a patient with a typical radiologic presentation, which was the case for
all our patients, the diagnosis is evident, and the radiologic findings
preclude the need for any further investigation, particularly any
histopathologic confirmation (a 2-year follow-up in one of our patients
confirmed the stabilization of the lesion with time). However, if all these
criteria are not present, other diagnoses have to be considered, and
histopathologic confirmation by biopsy may be needed. These diagnoses,
corresponding to cystlike lesions of the vertebral body during the second and
third decades of life, principally include cystic hemangioma, fibrous
dysplasia, giant cell tumor, and chondroma. Aneurysmal bone cysts and
osteoblastoma, which involve the posterior neural arch, may extend to the
vertebral body but are rarely localized within it. Plasmocytoma and metastasis
appear in older patients. MR imaging can easily differentiate these lesions
from giant cystic Schmorl's nodes because of the diffuse enhancement of their
tissue component on contrastenhanced sequences. A peripheral enhancement of
variable thickness, probably caused by the presence of granulation tissue, is
commonly observed in Schmorl's nodes, but it never appears diffuse.
As for therapy, no invasive treatment is required considering the benignity
and the stabilization with time of these lesions. Because it is likely that
the pain disappears as the lesion stabilizes, only symptomatic treatment is
required.
Giant cystic Schmorl's nodes are rare entities with a radiologic appearance
that differs dramatically from the classic description and that is
diagnostically challenging. However, the appearance of these nodes on
conventional radiographs and especially on MR images is characteristic.
Knowledge of this entity will help to prevent unnecessary invasive diagnostic
or therapeutic procedures.
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Abstract
Introduction
