congenital vertebral anomaly. Congenital vertebral anomalies are a collection of malformations of the spine. Most, around 85%, are not clinically significant, but they can cause compression of the spinal cord by deforming the vertebral canal or causing instability. This condition occurs in the womb.

1. 2020
Congenital vertebral
anomaly
Saad Salih Mahdi
Group: A
‫ﻣﮭدي‬ ‫ﺻﺎﻟﺢ‬ ‫ﺳﻌد‬
Second stage
saadiylep@ced.nahrainuniv.edu.iq
Dear Department of Embryology

2. Congenital Vertebral Anomalies
Congenital vertebral anomalies are relatively common disorders, ranging from simple,
asymptomatic “block” vertebrae to complex combinations of anomalies involving
multiple vertebral levels. They can occur anywhere from the craniovertebral junction
to the coccyx. Congenital vertebral anomalies may be associated with other birth
defects, and awareness of these associations is important. To manage patients with
congenital vertebral anomalies effectively, a firm grasp of the relevant embryology,
classification, natural history, clinical evaluation, and treatment principles is essential.
Embryogenesis
The sequential stages of the development of the spine. In the first six embryonic weeks
set the stage for early vertebral development in a process known as primary neurulation.
In that period, also known as the mesenchymal stage, the notochord develops in the
first few embryonic weeks from cells within the Hensen node. Somitic mesodermal
cells migrate from a position just caudal to the Hensen node and ultimately lie just
lateral to the midline notochord. These cells coalesce into paired somites in a rostral to
caudal direction, all under the influence of the notochord, the neural tube, homeobox
genes, and cell adhesion proteins. The somites ultimately divide into sclerotomes and
dermomyotomes, with each of the bilaterally paired sclerotomes giving rise to a single
vertebral body and single set of posterior elements during a migrational phase in the
fourth and fifth embryonic weeks.
Although this process of primary neurulation accounts for the formation of the vertebral
column and spinal cord down to the lumbosacral junction, most sacral and coccygeal
vertebrae develop from the caudal eminence in a poorly understood process called
secondary neurulation. The caudal eminence is a mass of undifferentiated cells at the
caudal end of the primary neural tube. Secondary neurulation begins at approximately
the fourth embryonic week and is responsible for the formation of the spinal cord, nerve
roots, and vertebral column of the sacral and coccygeal areas. New insights into the
complex manifestations of secondary neurulation are provided by Pang et al.
During the sixth embryonic week, the chondrification stage begins with the formation
of three paired chondrification centers within a vertebra. One set of chondrification
centers develops anteriorly to form the vertebral body, and two sets develop posteriorly
to form the posterior elements. This process develops in a cranial and caudal direction
from the cervicothoracic junction and is responsible for rapid vertebral column
growth. It culminates at approximately the ninth embryonic week. Ossification of the
cartilaginous elements begins shortly thereafter and ultimately ends somewhere
between the 14th and 18th years of life. The intervertebral disk develops from tissue
derived from perinotochordal mesenchymal cells and begins its formation in the
chondrification stage.

3. Etiology
Congenital vertebral anomalies commonly result from abnormal development during
the first trimester of pregnancy. The nature and timing of the insult to the embryonic
vertebral column determine the type of congenital abnormality that is produced.
Hemivertebrae and hypoplastic vertebrae arise during the mesenchymal stage, with a
disruption of the primary chondrification centers and a pairing defect of the responsible
sclerotomes, respectively. Some authors have proposed that vertebral body hypoplasia
and aplasia, both common causes of kyphotic abnormalities, arise during the
chondrification stage, possibly as a consequence of absent centrum vascularization.
Environmental factors, including infections such as tuberculosis, can also result in
hypoplastic vertebrae and congenital scoliosis.
The etiology of osseous malformations in the cervical spine is probably
multifactorial. Autosomal-dominant inheritance of cervical ribs has been reported, and
the congenital cervical fusions occurring with abnormalities such as the Apert and
Crouzon syndromes are probably based on autosomal-recessive and autosomal-
dominant inheritance patterns, respectively. Genetic inheritance does not account for
many of these lesions, however, and there is some evidence to suggest that congenital
vertebral anomalies result from vascular occlusions during development.
Some authors have suggested a subclavian artery supply disruption sequence to explain
the pathogenesis of Klippel-Feil and other vertebral anomalies. They hypothesize that
cervical fusions result from the disruption of intersegmental vessels arising from the
vertebral arteries at the time of resegmentation of the sclerotomes. Specific refinements
of this hypothesis have been forwarded by Tredwell et al, who reported that the fetal
alcohol syndrome variant of the Klippel-Feil anomaly is always associated with a single
level of congenital fusion. In contrast, other cases of Klippel-Feil have only a 20% rate
of single-level fusion. They relate this finding to a specific teratogenic insult occurring
between the 24th and 28th days of embryonic life.
Vascular occlusion may be only one of several causes of congenital vertebral
anomalies. failure of development of the zygapophyseal joint appeared to cause
vertebral body fusions, or block vertebrae.
The etiology of more complex vertebral anomalies, such as congenital vertebral
dislocation, segmental spinal dysgenesis, and medial spinal aplasia, is currently poorly
understood.
Classification
Congenital anomalies of the spine classified according to:-
Classification of Congenital Vertebral Anomalies
1-Disorders of formation
• Wedge vertebrae
• Hemivertebrae
• Caudal agenesis
• OEIS syndrome
• VACTERL syndrome
2- Disorders of segmentation
• Block vertebrae

4. • Segmental bars
3- Combination disorders
4- Special disorders
• Congenital vertebral dislocation (deformation disorder)
• Segmental spinal dysgenesis (probable disorder of formation)
• Medial spinal aplasia (probable disorder of formation)
Abbreviations: OEIS, omphalocele, cloacal exstrophy, imperforate anus, and spinal
deformities; VACTERL, vertebral anomalies, anorectal malformations, cardiac
malformations, tracheoesophageal fistula, renal anomalies, and limb anomalies.
1-Disorders of vertebral formation are regarded as failures in development of any
part of the vertebral column. They may be either complete or partial and may be
unilateral or bilateral.
a- a wedge vertebra result from Incomplete formation of a vertebral body, with one
side hypoplastic and with an asymmetric appearance.
b- a hemivertebra result If one pedicle and the adjacent vertebral body are absent,
. A hemivertebra can be further classified depending on whether it is fused to one or
both adjacent vertebrae.
-An unsegmented hemivertebra is fused to the adjacent vertebrae above and below,
-a partially segmented hemivertebra is fused to one vertebra above or below
-a segmented hemivertebra is separated by a disk space from each adjacent vertebra.
***In the sacrococcygeal area, a more complex example of these disorders is the
caudal agenesis syndrome.
a Coronal MRI, b coronal reconstruction CT and c anteroposterior direct X-ray
graphs showing a segmented
hemivertebra of a MMC patient (black arrows). Note also the intervertebral discs
both above and below the hemivertebra

5. Butterfly Vertebra
Butterfly vertebrae have a cleft through the body of the vertebrae and a funnel shape
at the ends. This gives the appearance of a butterfly on X-ray. It is caused by
persistence of the notochord (which usually only remains as the center of the
interverebral disc) during vertebrae formation. Constriction of the vertebral body
happens centrally, probably after incomplete fusion of two chondral centers with
hypoplasia at the junctional site.
A funnel-like defect divides the vertebra into right and left halves. There are usually
no symptoms.
Missing Vertebra (Vertebral Aplasia)
Total aplasia of a vertebral body may also occur. The condition will most likely lead
to kyphosis. The embryologic insult which leads to this abnormality is still unclear,
but it may occur during the late chondrification or early ossification phase of
formation
of the vertebral body centrum. As the remainder of the spinal segment develops from
separate chondrificationcenters, these portions are usually not affected. Rarely the
entire vertebral body segment may fail to develop or the vertebral maldevelopment
may occur at multiple levels.
2-Disorders of vertebral segmentation give rise to failures of vertebral separation and
different degrees of intersegmental fusion . These disorders include block vertebrae and
unilateral unsegmented bars.
a--Block vertebrae may be the best example of a segmentation failure resulting from
the failure of a somite segment to separate into cephalic and caudal halves, creating one
large block with no intervening disk.
b-- a unilateral unsegmented bar. A similar defect occurring on one side of the
developing spinal column.
The term unsegmented bar describes a bony bar that fuses the disk space and facet
joints of one or more adjacent vertebral levels. The fusion may exist in the anterior
spinal column, posterior spinal column, or both and may exist alone or in combination
with other disorders.
Vertebral growth proceeds on the segmented side only, a condition that often leads to
severe scoliosis.
A segmentation failure across the anterior portion of adjacent segments with normal
development of the posterior portion of the vertebra leads to progressive kyphosis.
Lateral segmentation anomalies are presumed to begin in the membranous and
cartilaginous phases of vertebral development.

6. In contrast, vertebral body segmentation anomalies are thought to arise as a result of
disordered ossification.
Schematic drawings representing defects of segmentation and formation.
4-Special disorders
a-Congenital vertebral dislocation :-
• Involved vertebrae malformed
• Superior vertebrae: elongated posterior elements with abnormally large spinal
canal, bifid or incomplete laminae
• Inferior vertebrae: misshapen, may be either smaller or larger than normal,
posterior elements typically normal, spinal canal normal at this level
• Spinal cord: intact, displaced by bony elements
b-Atlantal hemiring
• Bony discontinuity of the C1 ring in conjunction with lateral displacement of the
C1 lateral masses

7. • Associated with occipital condyle abnormalities and absence of the transverse
ligament
• Often causes or leads to significant craniovertebral instability
c-Segmental spinal dysgenesis
• Multilevel congenital spinal stenosis, hourglass shape of spinal canal
• Absent pedicles, neurocentral junctions and transverse processes at involved
levels
• Stenotic posterior osseous ring encircling the spinal cord, separated from the
posterior vertebral cortex by fat-filled space
• Absent nerve roots at level of the stenosis
• Normal vertebrae above and below the malformation
• Spinal cord present cranial and caudal to the malformation
• Generally normal sensorimotor function or incomplete neurologic deficits
• High incidence of associated anomalies: tethered spinal cord, equinovarus
deformities, Klippel-Feil syndrome, crossover rib, renal agenesis or duplication,
situs inversus, and tetralogy of Fallot
d-Medial spinal aplasia
• Segmental or suspended agenesis of between 3 and 11 thoracic and/or lumbar
vertebrae without associated lumbosacral agenesis
• Spinal cord agenesis caudal to the malformation
• Complete congenital paraplegia below the level of malformation
• Severe orthopedic deformities with “Buddha-like” posture
Spina bifida
is characterized by a midline cleft in the vertebral arch. It usually causes
no symptoms in dogs. It is seen most commonly in Bulldogs and Manx
cats.[5] In Manx it accompanies a condition known as sacrocaudal
dysgenesis that gives these cats their characteristic tailless or stumpy tail
appearance. It is inherited in Manx as an autosomal dominant trait

8. Clinical Presentation and Evaluation
The clinical presentation of congenital vertebral anomalies is highly variable. Although
1-pain is the most frequent presenting symptom among adults, Pain may predominate
in the midline or in a radicular fashion
2- incidental findings, association with other syndromes, and abnormal posture (e.g.,
torticollis) are the major pathways to diagnosis among children.
3-. Weakness and sensory changes can also be in a radicular pattern or can be part of a
myelopathic syndrome involving a specific vertebral level. Autonomic disturbances,
including bowel and bladder changes, may occur, with urinary incontinence often
presenting early.
Many patients with congenital vertebral body anomalies have symmetric fusions or
blocked vertebrae and so present with no obvious spinal deformity. Indeed, if the fusion
exists at one or two levels only, these individuals may not even be aware of its existence
until it is revealed by radiographs taken for unrelated causes.
Other individuals, however, can have much more obvious deformities that are detected
at any time from birth to early adulthood.
The physical examination of a patient with suspected congenital vertebral anomaly
should begin with general observations.
-- A low-lying hairline or web neck deformity typical of Klippel-Feil syndrome
--- abnormalities of the ears or palate associated with Goldenhar syndrome
--- Dwarfism without evidence of mental retardation may suggest achondroplasia,
spondyloepiphyseal dysplasia, or some other type of skeletal dysplasia.
Careful examination of the skin on the back is important to detect cutaneous stigmata
of spinal dysraphism, including hairy patches, skin discoloration, dimples, lipomas,
hemangiomas, and other findings.
Examination of the extremities may reveal ligamentous laxity associated with Ehlers-
Danlos syndrome or Larsen syndrome.
Physical findings in the feet may include high arches or cavus deformity, which are
common in Friedreich ataxia.
The association of both foot and spine deformities strongly suggests spinal dysraphism
or a generalized neuromuscular disorder.
Limb length discrepancy is present if the patient is standing and the pelvis is out of the
horizontal plane; this can be quantified by placing blocks of variable thickness under
the short leg until the pelvis is level. The patient, dressed comfortably in an examination
gown, should be standing during the examination of the spine, which should proceed in
a cranial to caudal direction in a systematic fashion.
In general, a “physiologic” curve is convex to the right, whereas a “pathologic” curve
is convex to the left. Tenderness over the spine should be sought, as well as a
determination of the range of motion. A complete neurologic examination should also
be performed, with particular emphasis on the cranial nerves, sensorimotor function,
and deep tendon reflexes. The patient’s gait and station may provide subtle clues for
the presence of lower extremity or truncal weakness.
Cervical Region
Torticollis, a twisting of the neck with the head tilted toward the involved muscle and
the chin rotated toward the opposite side (“cock robin” posture), is a common physical
finding among children. Torticollis usually results from unilateral contracture and
fibrosis of the sternocleidomastoid muscle; however, a retrospective study of 288
patients documented (18.4%) with torticollis of nonmuscular causes. Although the

9. majority of these had neurologic causes, almost a third were associated with vertebral
anomalies. We routinely order plain cervical spine radiographs for children who present
with torticollis to exclude vertebral anomalies before the initiation of physical therapy.
In selected patients (e.g., those with vertebral anomalies or with severe deformity), thin-
cut computed tomographic (CT) scans with two-dimensional reconstructions are
ordered to further investigate the bony anatomy. Although torticollis usually responds
to physical therapy, it must be carefully monitored because it may lead to severe,
progressive problems.
Although the majority of congenital vertebral anomalies in children are asymptomatic,
several anomalies should be considered when children present with neck pain or
torticollis. Atlantal hemirings and congenital upper cervical anomalies are relatively
frequent causes of torticollis in younger children. Cervical ribs, or anomalous ribs in
the cervical region that point downward, vary in size from tiny ossicles to fully formed
ribs. The ribs are usually asymptomatic unless they are large enough to compress nerves
or vessels. Symptoms of venous compression include pain in the ulnar distribution,
neck pain, and pain along the involved part of the brachial plexus.
Thoracolumbar Region
Except after trauma, neurologic dysfunction associated with spinal deformity of the thoracic
level is usually insidious in onset and slow in progression. Most cases are associated
with idiopathic or congenital spinal deformities, particularly kyphosis.
The terms kyphosis, lordosis, and scoliosis
kyphosis, refer to abnormally increased convexity in the curvature of the thoracic
spine (lateral view),
lordosis increased anterior concavity in the curvature of the cervical and lumbar spine
(lateral view),
scoliosis increased lateral deviation from the normally straight vertical line of the spine
(posterior view), Scoliosis of the thoracic and lumbar spine usually presents as a
painless deformity and has commonly been found in school screening programs.
Juvenile idiopathic scoliosis is defined as scoliosis detected in children between 3 and
10 years of age, and adolescent idiopathic scoliosis occurs between 10 and 18 years of
age.
The most sensitive diagnostic screening test for thoracolumbar spinal deformity is the
forward-bending test. As the patient bends forward, the presence of a rib prominence
or rotation is highly suggestive of an underlying curve and can be measured with a
horizontal inclinometer. A plumb line dropped from the center of the occiput to the
gluteal cleft is able to detect any lateral deviation of the trunk. Scoliotic curves should
be described by their apex and location, such as a right thoracic curve, left lumbar curve,
and so on. Sagittal plane deformity should also be assessed, with an evaluation for
excessive kyphosis or lordosis.
Lumbosacral Region
Segmentation anomalies are frequently found in the lumbar and sacral spine, but they rarely
produce neurologic symptoms or signs in children. Hemiblock and wedge vertebrae contribute
to scoliotic and kyphotic deformities.
Caudal agenesis encompasses numerous congenital malformations of the lumbosacral spine
ranging from simple anal atresia to the absence of sacral, lumbar, and possibly thoracic
vertebrae to the most severe segmentation failure of the lower extremities, sirenomelia.
Children with caudal agenesis generally show normal cognitive development but are often
paraplegic and seldom have associated treatable neurologic conditions, such as spinal stenosis
and tethered cord syndrome.

10. References
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2. Dorland's Medical Dictionary
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Disorders". Clinical Neurology in Small Animals: Localization,
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