DOI:10.2214/AJR.04.1874
AJR 2006; 186:1256-1259
© American Roentgen Ray Society
Multiple Posterior Vertebral Fusion Abnormalities: A Case Report and Review of the Literature
Joseph J. Chen1,
Barton F. Branstetter, IV1,2 and
William C. Welch3
1 Department of Radiology, University of Pittsburgh, 200 Lothrop St., PUH Rm.
D132, Pittsburgh, PA 15213.
2 Department of Otolaryngology, University of Pittsburgh, Pittsburgh, PA
15213.
3 Department of Neurological Surgery, University of Pittsburgh, Pittsburgh, PA
15213.
Received December 9, 2004;
accepted after revision February 28, 2005.
Address correspondence to B. F. Branstetter IV
(bfb1{at}pitt.edu).
Keywords: congenital anomaly • CT • radiography • spine • trauma • vertebral column
Introduction
Congenital vertebral anomalies of the posterior spine can be difficult to
distinguish from acute traumatic injuries on CT and conventional radiography
[1]. To ensure that patients
with congenital anomalies are not treated unnecessarily for spinal fractures,
radiologists need a thorough understanding of the embryology of the spinal
column and the potential manifestations of fusion failure. We present an
unusual patient with multiple neural arch clefts of the spine that were
initially misdiagnosed as traumatic injuries. We discuss the expected
locations of congenital vertebral clefts and review the pertinent radiology
literature.
Case Report
A healthy 25-year-old man with no history of back pain was rear-ended in a
low-speed motor vehicle collision. He was restrained and had no loss of
consciousness. Two days later, the patient presented to a community emergency
department complaining of neck and lower back pain. On examination, there were
no clinical signs of neurologic trauma and no focal neurologic defects. The
patient complained of moderate tenderness to palpation along the cervical,
thoracic, and lumbar vertebrae and paravertebral areas.
At the community emergency department, the patient underwent conventional
radiography of the cervical and lumbar spine (Figs.
1A and
1B) and CT of the cervical
spine (Figs. 1C,
1D, and
1E). The imaging findings were
suggestive of acute fractures, and the patient was referred to our trauma
center for further evaluation. The images were reevaluated at the trauma
center, and the diagnosis of multiple congenital vertebral arch clefts was
made. The patient was diagnosed with muscular strain and was treated
conservatively. He had follow-up examinations in the neurosurgery clinic and
has recovered completely.
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Fig. 1A —25-year-old man with no history of back pain who was rearended in
low-speed motor vehicle collision 2 days earlier presented to community
emergency department complaining of neck and lower back pain. On examination,
there were no clinical signs of neurologic trauma and no focal neurologic
defects. Patient complained of moderate tenderness to palpation along
cervical, thoracic, and lumbar vertebrae and paravertebral areas. Lateral
radiograph of cervical spine shows linear radiolucency (arrows)
through posterior elements of C2 vertebra. This finding was initially
interpreted as acute fracture.
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Fig. 1B —25-year-old man with no history of back pain who was rearended in
low-speed motor vehicle collision 2 days earlier presented to community
emergency department complaining of neck and lower back pain. On examination,
there were no clinical signs of neurologic trauma and no focal neurologic
defects. Patient complained of moderate tenderness to palpation along
cervical, thoracic, and lumbar vertebrae and paravertebral areas. Lateral
radiograph of lumbar spine shows linear radiolucency (arrows) through
pars interarticularis of L3 vertebra.
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Fig. 1C —25-year-old man with no history of back pain who was rearended in
low-speed motor vehicle collision 2 days earlier presented to community
emergency department complaining of neck and lower back pain. On examination,
there were no clinical signs of neurologic trauma and no focal neurologic
defects. Patient complained of moderate tenderness to palpation along
cervical, thoracic, and lumbar vertebrae and paravertebral areas. Multiple
fusion abnormalities seen on unenhanced axial CT: spinous cleft (spina bifida
occulta, arrows, C) of C2 vertebra (C), retrosomatic
cleft (arrows, D) of C5 vertebra (D), and spondylolysis
(arrows, E) of C2 vertebra (E).
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Fig. 1D —25-year-old man with no history of back pain who was rearended in
low-speed motor vehicle collision 2 days earlier presented to community
emergency department complaining of neck and lower back pain. On examination,
there were no clinical signs of neurologic trauma and no focal neurologic
defects. Patient complained of moderate tenderness to palpation along
cervical, thoracic, and lumbar vertebrae and paravertebral areas. Multiple
fusion abnormalities seen on unenhanced axial CT: spinous cleft (spina bifida
occulta, arrows, C) of C2 vertebra (C), retrosomatic
cleft (arrows, D) of C5 vertebra (D), and spondylolysis
(arrows, E) of C2 vertebra (E).
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Fig. 1E —25-year-old man with no history of back pain who was rearended in
low-speed motor vehicle collision 2 days earlier presented to community
emergency department complaining of neck and lower back pain. On examination,
there were no clinical signs of neurologic trauma and no focal neurologic
defects. Patient complained of moderate tenderness to palpation along
cervical, thoracic, and lumbar vertebrae and paravertebral areas. Multiple
fusion abnormalities seen on unenhanced axial CT: spinous cleft (spina bifida
occulta, arrows, C) of C2 vertebra (C), retrosomatic
cleft (arrows, D) of C5 vertebra (D), and spondylolysis
(arrows, E) of C2 vertebra (E).
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Discussion
Patients with suspected spinal trauma have historically been screened with
conventional radiography of the spine. However, CT is increasingly being used
as a screening tool [2].
Although CT provides a more detailed analysis of bone anatomy, congenital
anomalies still represent a potential source of false-positive findings.
The human vertebral system forms from somites, which are segmented mesoderm
derivatives found in the embryo during early gestation
[3]. These somites
differentiate into three parts: the dermatome, which becomes the dermis; the
myotome, which becomes the skeletal muscles of the posterolateral body wall;
and the sclerotome, which becomes the vertebrae and ribs. Initially, these
segmented somites consist of only mesenchymal tissue, but by week 6 of fetal
development, six chondrification centers appear in each somite
[3]
(Fig. 2).
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Fig. 2 —Illustration shows developmental landmarks in idealized vertebra:
primary ossification centers (dark gray), secondary ossification
centers (black), and chondrification centers (light
gray).
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The chondrification centers fuse, and by week 8, the mesenchymal vertebral
body has been replaced by a cartilaginous vertebral body. The cartilaginous
vertebral body then begins the process of ossification
[3]. Although different
sections of the spine ossify in slightly different ways, the process
essentially involves three ossification centers—one in the anterior arch
and one on each side of the neural arch
(Fig. 2). By the age of 7
years, most of these centers have fused, replacing the previous cartilage
model with bone. Each vertebral body also has secondary ossification centers
that form rings on the superior and inferior surfaces
[3]. These rings appear at
puberty and fuse with the vertebral body by the age of 25 years.
There are six types of posterior neural arch defects
(Fig. 3). Their origins are
congenital, acquired, or a predisposition to defects based on a congenital
weakness. The embryology of the vertebral column explains three of the six
types of neural arch defects—neurocentral synchondroses, paraspinous
clefts, and spinous clefts
[4-6].
The remaining three defects either have an unknown cause or are presumed to be
caused by overuse (e.g., spondylolysis)
[7-13].
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Fig. 3 —Illustration shows six types of posterior neural arch defects:
neurocentral synchondrosis (1), retrosomatic cleft (2), spondylolysis (3),
retroisthmic cleft (4), paraspinous cleft (5), and spina bifida occulta (6).
(Adapted from [10])
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The first type of defect, persistent neurocentral synchondrosis, results
from the failure of the vertebral body growth plates to transform into bone
(Fig. 3). At birth, almost the
entire vertebral body and arch have converted from cartilage into bone. The
neurocentral joints and the spinous process and costovertebral joints remain
as cartilaginous growth plates to allow the vertebral arch to grow in response
to the growing spinal cord. Normally, by the age of 3-6 years, these
cartilaginous neurocentral joints fuse
[4]. By the age of 6-14 years,
evidence of these cartilage segments can no longer be observed on MR images
[5]. Neurocentral synchondrosis
is thought to be an ossification failure of these cartilage segments
[4].
The second type of defect, the retrosomatic cleft, is a hypoplasia or
aplasia of the vertebral pedicle
[7,
8]
(Fig. 3). The origin of this
defect has not been elucidated. Possible causes include neurofibroma,
vertebral artery erosion, neoplastic disease, or fracture of the neural arch
[9]. Other studies have
suggested that the abnormality is of congenital origin
[10].
The third type of defect, spondylolysis, is a cleft that passes through the
pars interarticularis, which connects the superior and inferior articular
facets (Fig. 3). Although these
defects have been classified into congenital and acquired defects, it is
widely believed that most are acquired due to repeated microtrauma and
overuse, eventually causing stress fractures of the pars interarticularis
[11,
12]. As such, they are seen
more frequently in athletes and soldiers who underwent strenuous training
during World War II [12,
14]. The overall prevalence of
spondylolysis is estimated to be 7.2%
[15]. The L5 vertebral body
accounts for 90% of the cases
[15].
The fourth type of defect is the retroisthmic cleft. This defect has been
described as "laminolysis" because the defect is through the
lamina. Unlike spondylolysis, the defect is dorsal to the inferior articular
facet (Fig. 3). The origin of
this defect is inconclusive, but researchers have suggested stress fracture
from chronic mechanical overload
[13]. Retroisthmic cleft is
the rarest of the six posterior fusion defects.
The fifth and sixth types of defect are the paraspinous cleft and the
spinous cleft (spina bifida occulta) (Fig.
3). Although most of these defects occur in the lumbar spine, they
may occur anywhere along the spinal column. The defects are due to the failure
of neural tube closure during development, preventing muscle and bone from
growing around the gap [7]. The
incidence of neural tube defects in the United States is approximately 1 of
every 2,000 births [16].
Congenital vertebral anomalies of the posterior spine can cause confusion
in the assessment of patients with suspected spine trauma. A greater knowledge
of the location and imaging characteristics of potential fusion defects will
assist the radiologist in distinguishing congenital defects from acute
injuries.
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- Guanciale AF, Dillin WH, Watkins RG. Back pain in children and
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Curr Probl Pediatr 2000;30
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Introduction
Case Report
