The vertebral column is formed by condensation of the mesoderm surrounding the neural tube and no- tochord and subsequent segmentation of the primi- tive mesenchyme into 32–34 vertebral units. Each unit is represented primarily by a cartilaginous model, which is formed in turn by coalescence of two paired (right and left) chondrification centers:
two for the vertebral body and two for the neural arches. The intervertebral discs develop primarily from remnants of the notochord. Involution of the notochord occurs at the level of the vertebral bodies, while its persistence at the level of the intervertebral discs leads to what will become the nucleus pulpo- sus. Primary ossification centers appear in the carti- laginous vertebrae around the 10th week of gesta- tion. A single center, or less commonly two centers, will appear in each vertebral body. When two ossifi- cation centers appear, one may be anterior and the other posterior, in contrast to the side-to-side loca- tion of the chondrification centers. Single ossifica- tion centers also appear in the vertebral pedicles at each side. The correct development of the vertebral bodies and discs is also heavily dependent on an ad- equate blood supply from segmentary arteries and veins. Thus, anomalies of segmentary vessels can be directly responsible for certain types of vertebral malformations.
The primary ossification centers appear first in the lower thoracic and upper lumbar vertebrae, at about 3 months of gestation, and are present in all the ver- tebrae at about 5 months. They enlarge progressively during embryonic life, but at birth they are still sepa- rated from one another by unossified cartilage. In- deed, maturation of the vertebral column continues well beyond birth. Fusion between the ossification center in the body of each vertebra and that in each side of the posterior arch occurs at 3–6 years, while posterocaudal extension of the two centers in the arch toward the midline is complete by the age of ap- proximately 10 years. Secondary ossification centers appear in the cartilaginous rims at the superior and inferior edges of the vertebral body during puberty, while secondary centers for the superior and inferior
articular processes, transverse processes, and spin- ous processes appear around the age of 25 years (Sil- verman 1993).
Reference
Silverman FN. Introduction to the spine. In: Silverman FN, Kuhn JP: Caffey’s pediatric X-rays diagnosis. An integrated imaging approach. C.V. Mosby Company, St. Louis, 1993 (9th ed.), p. 117
Abnormal Shape or Size of Vertebrae
Congenital anomalies of the spine are relatively com- mon. Many are isolated defects of little, if any, clinical significance. Others are associated with neural tube defects, such as myelomeningocele and diastemato- myelia, or with nonspinal conditions, such as geni- tourinary abnormalities and congenital heart dis- ease. Still others are part of the malformation spec- trum of a number of skeletal dysplasias and syn- dromes. The vertebral bodies, posterior elements, and intervertebral discs can be affected, individually or in variable combinations. The defect(s) can be confined to a single spinal level or extend through multiple levels.
The subject of vertebral malformations is a com-
plex one. Failure of formation, segmentation, or
union of embryologic structures results in various
spinal anomalies, including aplastic, supernumerary,
partially formed, or blocked vertebrae. On the other
hand, several vertebral configuration abnormalities
are recognized in which none of the above mecha-
nisms is specifically involved, and the aberrant mor-
phology is then explained in the context of a general-
ized bone dysplasia or metabolic disorder or as a
response to well-defined primary causes. Given the
absence of unifying pathogenetic models, various
unrelated vertebral defects are grouped together here
based on the fact that all imply a change from the
normal vertebral shape or size. Emphasis is placed on
those structural abnormalities of the vertebral bod-
Alessandro Castriota-Scanderbeg, M.D.
ies whose recognition may be important in the diag- nosis of skeletal dysplasias and syndromes. Anom- alies of the neural arches, including hypoplasia/apla- sia, fusion defects (spina bifida), and segmentation failures (laminar and pediculate bars) are also sum- marized.
It is beyond the scope of this chapter to include all possible structural changes of vertebrae. Indeed, such vertebral configurations as fish-shaped, round, cuboid, wedged, squared, and spool-shaped verte- brae (and several others) are not detailed, although mention is made of these as appropriate throughout the chapter.
Tall Vertebrae
䉴
[Increased vertical dimensions of the vertebral bodies]
Tall vertebrae are often associated with conditions characterized by severe muscle hypotonia or requir- ing prolonged recumbency, reflecting diminished compressive forces on the potential longitudinal growth of the vertebral bodies (Donaldson et al.
1985). The resulting increase in the height index (i.e., the ratio of superoinferior diameter to anteroposteri- or diameter) is approximately proportional to the de- gree of inactivity (Resnick 1995; Houston and Zales- ki 1967). The increased height of the vertebrae bodies is associated with narrowing of the intervertebral discs (Taylor 1975).
Increased vertebral height may also reflect a pri- mary bone growth defect. Tall vertebrae are found in the lumbar spine in newborns with Down syndrome (OMIM 190685), suggesting a role of genetic factors in the development of this abnormality (Brandner 1972). Other vertebral anomalies reported in this syndrome include atlanto-axial and atlanto-occipital instability associated with asymmetry of the occipi- tal condyles, scoliosis, blocked vertebrae, and flatten- ing of the cervical vertebrae with premature osteo- arthritic changes (Martel and Tishler 1966; Cros et al.
2000; Rosenbaum et al. 1986). In Melnick-Needles syndrome (osteodysplasty OMIM 249420) vertebral changes include increased height with anterior scal- loping, enlarged spinal canal with thinned laminae in the lumbar segment, and kyphoscoliosis (Bartolozzi et al. 1983; ter Haar et al. 1982) (Fig. 3.1). Spinal changes in nevoid basal cell carcinoma syndrome (Gorlin syndrome, OMIM 109400) include kypho- scoliosis, spina bifida occulta, cervical spondylolis- thesis, blocked vertebrae, hemivertebrae, and in-
Fig. 3.1. Melnick-Needles syndrome. Note increased height of the vertebral bodies, which have an irregular squared-off ap- pearance. Also note posterior scalloping, most prominent in the lumbar vertebrae
Fig. 3.2. Freeman-Sheldon syndrome. The vertebrae are tall, with mild anterior scalloping
creased superoinferior vertebral diameter resulting in squared vertebral bodies (Barnes et al. 1982; Ki- monis et al. 1997; Lile et al. 1968). An increase in the height ratio is also found in Freeman-Sheldon syn- drome (OMIM 193700), in which it is associated with kyphoscoliosis and spina bifida occulta (Fig.
3.2). Proteus syndrome (OMIM 176920), a congenital hamartomatous syndrome characterized by regional gigantism and lymphangiomatous hamartomas, shows overgrowth of a variety of tissues, including the skin, connective and adipose tissue, endothelium, and bones. Overgrowth affects the tubular bones at one extremity, some of the tubular bones in the hands (macrodactyly), the skull, and the vertebral bodies, which appear high and wide, with irregular margins, and dysplastic pedicles and intervertebral discs (Azouz et al. 1987).
Tall vertebrae, together with slender and steeply angled (caudally directed) lower ribs, coxa vara, and gracile hand bones, are features in the rare Fuhr- mann dysplasia (dwarfism with tall vertebrae, OMIM 126950), which may be of autosomal dominant inher- itance (Fuhrmann et al. 1972). The increased height of the vertebral bodies in this disorder is thought to be secondary to severe muscular hypotonia. (This disorder must not be confused with Fuhrmann syn- drome (OMIM 228930), an autosomal recessive dis- order featuring cleft lip/palate, agenesis of fibula and ulna, bowing of femur, and joint contractures.) Tall vertebrae are also features in acro-cranio-facial dys- ostosis (OMIM 201050), a condition with prominent changes in the skull (craniosynostosis), facial bones (hypertelorism, proptosis, cleft palate, microgna- thia), and hands and feet (short 1st metacarpal and metatarsal) (Kaplan et al. 1988).
Radiographic Synopsis
1. Lateral projection: increase in the height index, calculated as the ratio between the largest super- oinferior and the smallest anteroposterior diame- ter. Reference values for the height index in the normal population are reported elsewhere (Kasai et al. 1996; Petterson and Ringertz 1991).
Associations
• Acrocraniofacial dysostosis
• Chromosomal abnormalities
• Down syndrome
• Freeman-Sheldon syndrome
• Fuhrmann dysplasia
• Infantile multisystem inflammatory disease
• Marfan syndrome
• Melnick-Needles syndrome
• Multiple pterygium syndrome (Escobar syndrome)
• Neuromuscular disorders
• Nevoid basal cell nevus syndrome (Gorlin syndrome)
• Proteus syndrome
• Spondylocostal dysplasia
References
Azouz EM, Costa T, Fitch N. Radiologic findings in the Proteus syndrome. Pediatr Radiol 1987; 17: 481–5
Barnes DA, Borns P, Pizzutillo PD. Cervical spondylolisthesis associated with the multiple nevoid basal cell carcinoma syndrome. Clin Orthop 1982; 162: 26–30
Bartolozzi P, Calabrese C, Falcini F, Giovannucci Uzzielli ML, Maggini M. Melnick-Needles syndrome: osteodysplasty with kyphoscoliosis. J Pediatr Orthop 1983; 3: 387–91 Brandner M. The diagnosis of trisomy 21 with the vertebral in-
dex in the newborn. Helv Paediatr Acta 1972; 21: 63–9 Cros T, Linares R, Castro A, Mansilla F. A radiological study of
the cervical alterations in Down syndrome. New findings on computerized tomography and three dimensional re- constructions. Rev Neurol 2000; 30: 1101–7
Donaldson JS, Gilsanz V, Gonzalez G, Wittel RA, Gilles F. Tall vertebrae at birth: a radiographic finding in flaccid infants.
AJR Am J Roentgenol 1985; 145: 1293–5
Fuhrmann W, Nagele E, Gugler R, Adili E. Dwarfism with dis- proportionately high vertebral bodies. Humangenetik 1972; 16: 271–82
Houston CS, Zaleski WA. The shape of vertebral bodies and femoral necks in relation to activity. Radiology 1967; 89:
59–66
Kaplan P, Plauchu H, Fitch N, Jequier S. A new acro-cranio-fa- cial dysostosis syndrome in sisters. Am J Med Genet 1988;
29: 95–106
Kasai T, Ikata T, Katoh S, Miyake R, Tsubo M. Growth of the cervical spine with special reference to its lordosis and mo- bility. Spine 1996; 21: 2067–73
Kimonis VE, Goldstein AM, Pastakia B, Yang ML, Kase R, DiGiovanna JJ, Bale AE, Bale SJ. Clinical manifestations in 105 persons with nevoid basal cell carcinoma syndrome.
Am J Med Genet 1997; 69: 299–308
Köhler A, Zimmer EA. Limiti del normale ed inizio del pato- logico nella diagnostica radiologica dello scheletro. Casa Editrice Ambrosiana, Milano, 1970 (11th ed.), p. 293 Lile HA, Rogers JF, Gerald B. The basal cell nevus syndrome.
AJR Am J Roentgenol 1968; 103: 214–7
Martel W, Tishler JM. Observations on the spine in mon- goloidism. Am J Roentgenol Radium Ther Nucl Med 1966;
97: 630–8
Petterson H, Ringertz H. Measurements in pediatric radiology.
Springer, Berlin Heidelberg New York, 1991, p. 31
Resnick D. Neuromuscular disorders. In: Resnick D (ed.) Diag- nosis of joint and bone disorders. W.B. Saunders Company, Philadelphia, 1995 (3rd ed.), p. 3371
Rosenbaum DM, Blumhagen JD, King HA. Atlantooccipital in- stability in Down syndrome. AJR Am J Roentgenol 1986;
146: 1269–72
Taylor JR. Growth of human intervertebral discs and vertebral bodies. J Anat 1975; 120: 49–68
Ter Haar B, Hamel B, Hendriks J, de Jager J. Melnick-Needles syndrome: indication for an autosomal recessive form. Am J Med Genet 1982; 13: 469–77
Beaked Vertebrae
䉴
[Anterior tongue-like protrusions of the vertebral bodies]
True beaked vertebrae are seen in a selected group of skeletal dysplasias and metabolic disorders and are therefore of critical importance for their recognition (Swischuk 1970). Anterior tongue-like projections are characteristic of dysostosis multiplex, a designa- tion used for the radiographic abnormalities of mu- copolysaccharidoses and mucolipidoses. Ovoid ver- tebral bodies pointing anteroinferiorly in the shape of small hooks and associated with gibbus deformity at the thoracolumbar junction typically occur in mu- copolysaccharidosis I-H (Hurler syndrome, OMIM 252800) (Chen et al. 1996) (Fig. 3.3). Several factors lead to gibbus deformities, including disturbances of vertebral body growth, poor truncal muscle tone, weight-bearing forces, and anterior disc herniation at the apex of the kyphotic curvature. In mucopoly- saccharidosis IV (Morquio syndrome, OMIM 253000), the vertebral bodies, which may be similar to those of Hurler syndrome in early infancy, develop universal platyspondyly, with irregular end-plates and tongue- like anterior protrusions, in later years (Fig. 3.4). In both conditions, odontoid hypoplasia and atlanto-ax- ial instability are additional anomalies affecting the spine. Vertebral abnormalities similar to, but milder than, those described above, including thoracolumbar gibbus deformity with ovoid, beaked vertebrae at the apex of the gibbus, also occur in mucopolysaccharido- sis II (Hunter syndrome, OMIM 309900) and III (Sanfil- ippo syndrome, OMIM 252900), aspartylglycosamin- uria (OMIM 208400) (Gehler et al. 1981), fucosidosis (OMIM 230000) (Taconis et al. 1976), mannosidosis (OMIM 248500), and gangliosidosis (OMIM 272800).
Vertebral anomalies resembling those of Hurler syn- drome, with a tendency to worsen in late infancy and childhood, are also observed in mucolipidoses (OMIM 252500, 252600, 252650, 256550) (Kuriyama et al.
1980).Among children with storage diseases and bone dysplasias, lumbar gibbus is most severe in those with Morquio syndrome, in which this feature is exaggerat-
Fig. 3.3. Mucopolysaccharidosis I-H (Hurler syndrome). Note the typical hooks (lower arrows) projecting from the anteroin- ferior aspect of ovoid (upper arrows) vertebrae, and the gibbus deformity at the thoracolumbar junction. These findings may be undistinguishable from those of patients with other types of dysostosis multiplex
Fig. 3.4. Mucopolysaccharidosis IV (Morquio syndrome). The vertebral bodies are markedly flat, with tongue-like anterior projections. The hook-shaped vertebrae and gibbus deformity at the thoracolumbar junction (lower part of the picture) mim- ic the findings in Hurler syndrome
ed by the sitting and standing positions, and may have neurological and orthopedic implications, including spinal cord compression and anterior herniation of the intervertebral discs at the apex of the curve (Levin et al. 1997).
In pseudoachondroplasia (OMIM 177170) the spine shows characteristic changes, including exag- geration of epiphyseal grooves of end-plates result- ing in superior and inferior humps, anterior tongue- like projections, and platyspondyly (Finidori et al.
1980). In Dyggve-Melchior-Clausen dysplasia (OMIM 223800) the vertebral bodies are flattened, pointed anteriorly, and often show notch-like defects of end-plates that lead to a ‘camel hump’ appearance (Spranger and Maroteaux 1975) (Fig. 3.5). Spondy- loepiphyseal dysplasia tarda (OMIM 313400) shows a typical vertebral configuration, with bulging in the central and posterior portions of the superior and in- ferior vertebral end-plates at the lumbar level, pro- ducing characteristic humps of dense bone. The ver- tebrae are flattened, while the intervertebral disc spaces are narrowed posteriorly and widened anteri- orly (Poker et al. 1965). Elongated tongue-like projec- tions of the vertebral body are seen in spondylometa- physeal dysplasia, Kozlowski type (OMIM 184252).
Anterior beaking is further exacerbated in the tho- racic tract by the spinal kyphosis. Marked vertebral flattening is also a striking feature. In thanatophoric dwarfism (OMIM 187600) there is severe platy-
Fig. 3.5. Dyggve-Melchior-Clausen dysplasia in a 14-month- old child. Note platyspondyly, anterior beaking of the vertebral bodies, and thoracolumbar kyphosis. The ‘camel hump’ ap- pearance typical of the condition is not present in this young patient (Courtesy of Dr. S. Fasanelli, Ospedale Bambino Gesu, Rome, Italy)
Fig. 3.6. Thanatophoric dwarfism in a newborn. Note flat and irregularly ossified vertebral bodies, with constriction of their midportions, and small hook-like anterior projections. An ir- regular pattern of ossification gives the vertebrae a band-like appearance
spondyly with notch-like ossification defects of the middle portion of the vertebral body and a band-like appearance of vertebrae. Central tongues may be seen projecting from the anterior aspects of the vertebral body (Fig. 3.6). Osteoglophonic dysplasia (OMIM 166250), a rhizomelic dwarfism of possible autosomal dominant inheritance, is characterized by severe craniofacial deformities (frontal bossing, hyper- telorism, severe mandibular prognathism), fibrous dysplasia of the mandible, abnormal dentition, cran- iosynostosis, gross multiple lucent metaphyseal de- fects, and flattening with anterior beaking of the ver- tebral bodies (Beighton et al. 1980; Kelley et al. 1983).
Anterior beaking of the vertebral body together with asymmetrical development of the vertebrae and kyphoscoliosis has been reported in children who have received radiation therapy for nephroblastoma (Smith et al. 1982).
Radiographic Synopsis
Lateral projection: the vertebral body points anterior- ly, with the anterior aspect of the vertebral body in the shape of a hook, or tongue-like projection
Associations
• Aspartylglycosaminuria
• Child abuse syndrome
• Diastrophic dysplasia
• Down syndrome
• Dyggve-Melchior-Clausen syndrome
• Fucosidosis
• Hypothyroidism
• Mannosidosis
• Marshall-Smith syndrome
• Mucolipidoses
• Mucopolysaccharidoses
• Niemann-Pick disease
• Osteoglophonic dysplasia
• Phenylketonuria
• Pseudoachondroplasia
• Radiation therapy
• SPONASTRIME dysplasia
• Spondyloepiphyseal dysplasia tarda
• Spondylometaphyseal dysplasia (Kozlowski type)
• Thanatophoric dysplasia
References
Beighton P, Cremin BJ, Kozlowski K. Osteoglophonic dwarf- ism. Pediatr Radiol 1980; 10: 46–50
Chen SJ, Li YW, Wang TR, Hsu JC. Bony changes in common mucopolysaccharidoses. Chung Hua Min Kuo Hsiao Erh Ko I Hsueh Hui Tsa Chih 1996; 37: 178–84
Finidori G, Rigault P, Maroteaux P, Padovani JP. Les déforma- tions osteo-articulaires dans la dysplasie pseudo-achon- droplastique. Chir Pediatr 1980; 21: 191–200
Gehler J, Sewell AC, Becker C, Spranger J, Hartmann J. As- partylglycosaminuria in an Italian family: clinical and biochemical characteristics. J Inherit Metab Dis 1981; 4:
229–30
Kelley RI, Borns PF, Nichols D, Zackai EH. Osteoglophonic dwarfism in two generations. J Med Genet 1983; 20: 436–40 Kuriyama M, Okada S, Tanaka Y, Umezaki H. Adult mucolipi- dosis with beta-galactosidase and neuraminidase deficien- cies. J Neurol Sci 1980; 46: 245–54
Levin TL, Berdon WE, Lachman RS, Anyane-Yeboa K, Ruzal- Shapiro C, Roye DP Jr. Lumbar gibbus in storage diseases and bone dysplasias. Pediatr Radiol 1997; 27: 289–94 Poker N, Finby N, Archibald RM. Spondyloepiphyseal dys-
plasia tarda: four cases in childhood and adolescence, and some considerations regarding platyspondyly. Radiology 1965; 85: 474–80
Smith R, Davidson JK, Flatman GE. Skeletal effects of ortho- voltage and megavoltage therapy following treatment of nephroblastoma. Clin Radiol 1982; 33: 601–13
Spranger J, Maroteaux P, Der Kaloustian VM. The Dyggve-Mel- chior-Clausen syndrome. Radiology 1975; 114: 415–21 Swischuk LE. The beaked, notched, or hooked vertebra: its sig-
nificance in infants and young children. Radiology 1970; 95:
661–4
Taconis WK, van Wiechen PJ, van Gemund JJ. Radiological findings in a case of type II fucosidosis. A case report.
Radiol Clin 1976; 45: 258–64
Scalloping of the Vertebral Body
䉴
[Exaggerated concavity of the anterior or posterior surface of the vertebral body]
The anterior and posterior margins of the vertebral body are smoothly concave in normal individuals.
An exaggeration of this concavity is referred to as scalloping of the vertebral body (Mitchell et al. 1967).
The dorsal side of the vertebral body is also the an- terior wall of the spinal canal. Therefore, posterior scalloping typically occurs in conditions associated with increased intradural pressure and dural ectasia.
The lumbosacral and sacral parts of the spinal canal
are most commonly involved, and several adjacent
vertebrae are affected. Hydrostatic pressure of the
cerebrospinal fluid on the dural sac is considered to
be related to scalloping on the medial sagittal plane of
the posterior vertebral wall, while pressure exerted by
the spinal nerves probably accounts for scalloping on
the lateral sagittal plane (Larsen 1985). In Marfan syn-
drome (OMIM 154700), posterior scalloping is attrib-
uted to dural ectasia. The dura is possibly weaker than
normal in these patients, owing to the generalized de-
fect of the connective tissue, and this means that it
tends to bulge against the posterior vertebral wall un-
der the pressure of the cerebrospinal fluid pulsations.
Again, the abnormalities are more conspicuous in the lumbar and sacral spine. They include focal widening of the spinal canal and neural foramina, with or with- out meningocele, and thinning of the pedicles and laminae (Pyeritz et al. 1988; Harkens and el-Khoury 1990). Posterior scalloping due to dural ectasia also occurs in homocystinuria (OMIM 236200) (Leonard 1973), a disorder resembling Marfan syndrome in many respects, and in Ehlers-Danlos syndrome (Mitchell et al. 1967). Whether scalloping of the lum- bar vertebrae in neurofibromatosis type 1 (OMIM 162200) is due to dural ectasia or to the primary mesodermal dysplasia is not known. Direct erosion resulting from local neurofibroma, though possible, is uncommon (Casselman and Mandell 1979). The ver- tebrae are also posteriorly concave in a number of skeletal dysplasias, including achondroplasia (OMIM 100800) (Fig. 3.7), and storage diseases (Fig. 3.8). The condition known as primary empty sella with general- ized dysplasia (OMIM 130720) is an association of empty sella (intrasellar extension of the subarachnoid space) and other anomalies, including osteosclerosis, short stature, widened spinal canal with multiple thoracic and lumbar meningoceles, posterior scallop- ing of the vertebral bodies, wormian bones, facial dysmorphisms resembling those of Treacher-Collins syndrome, and maldevelopment of the spinal cord, cerebellum, and cerebral cortex (Lehman et al.
1977). Duplication of the Xq13.3-q21.2 region has been described in a child with empty sella and growth hormone deficiency (Yokoyama et al. 1992). In spondylo-epi-metaphyseal dysplasia with multiple dislocations (OMIM 603546) posterior scalloping of the vertebrae occurs in association with vertebral end-plate irregularities, narrowing of the spinal canal, epiphyseal and metaphyseal abnormalities, characteristic changes in the hands, absent patellae, and joint laxity with dislocation of multiple joints (Hall et al. 1998). Posterior scalloping, often confined to one or two contiguous vertebrae, may also occur in association with ma sses arising from the epidural space, whether dysplastic or neoplastic in etio- logy (Tomlinson et al. 1991), and, less commonly, with disc herniation (Berthelot et al. 1995). Posterior scalloping of the vertebral body is common in acromegaly. In this condition, new bone is deposited on the anterior aspect of the vertebral body, while excessive resorption occurs on the posterior aspect of the vertebrae, giving rise to posterior scalloping.
Apposition is most prominent in the thoracic re- gion, while resorption dominates at the lumbar level (Stuber and Palacios 1971). Narrowing of the
Fig. 3.7. Achondroplasia. The vertebrae are mildly flat, poste- riorly concave, and anteriorly wedged. The pedicles are short, and the vertebral canal is narrowed
Fig. 3.8. Mucolipidosis III in a 9-year-old patient. Note marked posterior scalloping of the vertebral bodies. The first lumbar vertebra is hypoplastic and anteriorly wedged, result- ing in gibbus deformity. (From Levin et al. 1997)
spinal canal and secondary dural ectasia is another potential cause for posterior scalloping in acromegaly.
Indeed, cauda equina compression, a prominent sign of spinal canal stenosis, is frequently observed in this condition (Gelman 1974). By contrast, hyperplasia of the neighboring soft tissues, another feature accompa- nying acromegaly, seems to have only a minor role in the pathogenesis of vertebral posterior scalloping.
Anterior scalloping of the vertebral bodies most commonly occurs as a consequence of expansive mass- es arising in the retroperitoneal space or in the posteri- or mediastinum. More rarely, anterior scalloping re- flects a primary defect of the vertebral body. Notable examples are Melnick-Needles syndrome and Cock- ayne syndrome. In Melnick-Needles syndrome (os- teodysplasty, OMIM 249420), the vertebrae are tall and anteriorly concave, and the spinal canal is enlarged in the lumbar segment. Thinned laminae, especially in the lumbar spine, are also a feature (Moadel and Bryk 1977). In Cockayne syndrome (OMIM 216400) both an- terior and posterior scalloping occurs and the verte- bral body is ovoid in shape (Bensman et al. 1981).
Radiographic Synopsis
Lateral View: Exaggerated concavity of the ventral and dorsal surfaces of the vertebral body
Associations
• Achondroplasia
• Acromegaly
• Ankylosing spondylitis
• Aortic aneurysm
• Cockayne syndrome
• Communicating hydrocephalus
• Disc herniation
• Dyggve-Melchior-Clausen syndrome
• Ehlers-Danlos syndrome
• Homocystinuria
• Hypochondroplasia
• Marfan syndrome
• Melnick-Needles syndrome
• Meningocele
• Mucolipidoses
• Mucopolysaccharidoses
• Neurofibromatosis
• Platyspondyly with amelogenesis imperfecta
• Primary empty sella with generalized dysplasia
• Smith-McCort syndrome
• Spondyloepimetaphyseal dysplasia with multiple dislocations
• Syringohydromyelia
• Tumors (retroperitoneum, mediastinum, spinal canal)
References
Bensman A, Fraure C, Kaufmann HJ. The spectrum of x-ray manifestations in Cockayne’s syndrome. Skeletal Radiol 1981; 7: 173–7
Berthelot JM, Maugars Y, Bertrand-Vasseur A, Lalande S, Prost A. Dorsal scalloping by calcified disc herniation. Spine 1995; 20: 106–7
Casselman ES, Mandell GA.Vertebral scalloping in neurofibro- matosis. Radiology 1979; 131: 89–94
Gelman MI. Cauda equina compression in acromegaly. Radiol- ogy 1974; 112: 357–60
Hall CM, Elcioglu NH, Shaw DG. A distinct form of spondy- loepimetaphyseal dysplasia with multiple dislocations.
J Med Genet 1998; 35: 566–72
Harkens KL, el-Khoury GY. Intrasacral meningocele in a patient with Marfan syndrome. Case report. Spine 1990; 15:
610–2
Larsen JL. The posterior surface of the lumbar vertebral bod- ies. Part I. Spine 1985; 10: 50–8
Lehman RAW, Stears JC, Wesenberg RL, Nusbaum ED. Familial osteosclerosis with abnormalities of the nervous system and meninges. J Pediatr 1977; 90: 49–54
Leonard MS. Homocystinuria: a differential diagnosis of Mar- fan’s syndrome. Oral Surg Oral Med Oral Pathol 1973; 36:
214–9
Mitchell GE, Lourie H, Berne AS. The various causes of scal- loped vertebrae with notes on their pathogenesis. Radiolo- gy 1967; 89: 67–74
Moadel E, Bryk D. Osteodysplastia (Melnick-Needles syn- drome). Radiological quiz. Radiology 1977; 123: 154–206 Pyeritz RE, Fishman EK, Bernhardt BA, Siegelman SS. Dural
ectasia is a common feature of the Marfan syndrome. Am J Hum Genet 1988; 43: 726–32
Stuber JL, Palacios E. Vertebral scalloping in acromegaly. Am J Roentgenol Radium Ther Nucl Med 1971; 112: 397–400 Tomlinson FH, Scheithauer BW, Miller GM, Onofrio BM. Ex-
traosseous spinal chordoma. Case report. J Neurosurg 1991;
75: 980–4
Yokoyama Y, Narahara K, Tsuji K, Moriwake T, Kanzaki S, Murakami M, Namba H, Ninomiya S, Higuchi J, Seino Y.
Growth hormone deficiency and empty sella syndrome in a boy with dup(X)(q13.3-q21.2). Am J Med Genet 1992; 42:
660–4
Platyspondyly
䉴
[Abnormal flattening of the vertebral bodies]
Vertebral flattening can be congenital or acquired.
When it is acquired, a single vertebra, two adjacent
vertebrae, or several noncontiguous vertebrae may
be collapsed. Extreme flattening of a single vertebra
is referred to as vertebra plana. Acquired conditions
causing collapse of either single or multiple vertebral
bodies include trauma, osteoporosis, osteomalacia,
steroid or radiation therapy, and infections, as well as
focal (hemangioma, eosinophilic granuloma, giant
cell tumor, chordoma, etc.) and diffuse (plasma cell
myeloma, leukemia, lymphoma, metastases – espe- cially from breast, lung, and prostate carcinomas and from neuroblastoma, Paget disease, etc.) vertebral lesions.
Congenital flattening of the vertebral bodies can be generalized or confined to a given spinal level.
Occasionally, a more irregular distribution is ob- served, with involvement of several noncontiguous vertebrae alternating with unaffected vertebrae (Kozlowski et al. 1995).
In campomelic dysplasia (OMIM 114290) flatten- ing is confined to the cervical spine and is associated with scarcity of cervical ossification. Similarly, cervi- cal platyspondyly is seen in spondylocamptodactyly (OMIM 600000), a disorder inherited as an autoso- mal dominant mutation in which scoliosis and camp- todactyly are features (Lizcano-Gil et al. 1995). In children with homocystinuria (OMIM 236200) the vertebral bodies, especially in the thoracic spine, are flattened and anteroposteriorly elongated, and may be biconcave in shape. Scoliosis and generalized osteoporosis with compression fractures can be seen (Smith 1967). In Ehlers-Danlos syndrome, platyspondyly affecting only the lumbar spine is characteristic (Kozlowski et al. 1991) (Fig. 3.9 a, b).
The most likely cause of the flattening is muscular imbalance with increased stress on the lumbar
vertebrae. Additional spinal changes consistently ob- served in this condition include thoracolumbar kyphoscoliosis, which is often present at birth, ante- rior wedging of the vertebral bodies (in later years), spondylolysis with spondylolisthesis, and posterior scalloping of the vertebral bodies (Beighton and Thomas 1969). SPONASTRIME dysplasia (OMIM 271510), an association of spondylar and nasal alter- ations, and vertical striations in the metaphyses of the long bones, shows a peculiar pattern of lumbar spine involvement, characterized by a predictable evolution over time (Langer et al. 1997). In infancy, the vertebral bodies are very flat, with straight end- plates posteriorly, biconvex end-plates anteriorly, and anterior tonguing. With advancing age platy- spondyly tends to resolve, while a moderate deformi- ty of the vertebral bodies, consisting in smooth end- plate concavity posterior to the midpoint of the body, persists into adulthood (Fig. 3.10 a–d).
Generalized platyspondyly is a valuable radi- ographic sign of many skeletal dysplasias, metabolic disorders, and malformation syndromes. Universal platyspondyly, often of severe degree, develops with increasing age in patients with mucopolysaccharido- sis IV (Morquio syndrome, OMIM 253000), a condi- tion that has long been confused with Dyggve-Mel- chior-Clausen dysplasia owing to the association be- tween short-trunk dwarfism and platyspondyly. The vertebral end-plates are irregular, but usually not notched, and tongue-like protrusions arise from the anterior wall of the vertebral body, especially at the apex of the thoracolumbar gibbus deformity (Levin et al. 1997) (Fig. 3.11). In Dyggve-Melchior-Clausen dysplasia (OMIM 223800, 304950) there is general- ized platyspondyly, with anterior vertebral projec- tions and undulating defects in the end-plates (‘camel hump’ appearance) (Spranger et al. 1975) (Fig. 3.12). Marked vertebral flattening is a feature in spondylometaphyseal dysplasia, Kozlowski type (OMIM 184252) (Fig. 3.13). Elongated tongue-like projections of the vertebral body can be seen, the anterior beaking being further exacerbated in the thoracic tract by the spinal kyphosis. Other well-dif- ferentiated spondylometaphyseal dysplasias show mild to moderate platyspondyly (Kozlowski and Bellemore 1989; Kozlowski et al. 1988). In spondylo- epiphyseal dysplasia congenita (OMIM 183900) the skeletal changes, including those involving the spine, vary with age. In infancy flattening of the vertebral bodies with dorsal wedging (pear-shaped appear- ance) occurs in the thoracic and upper lumbar spine (Fig. 3.14). In childhood the vertebral bodies are flat and anteriorly pointed, especially at the thoracolum-
Fig. 3.9 a, b. Ehlers-Danlos syndrome in an 11-year-old boy.
aNote flattening of the lumbar vertebral bodies, most promi- nent from L-3 to L-5. b There is lumbar scoliosis, which is con- vex to the right. (From Kozlowski et al. 1991)
a b
bar junction. Odontoid hypoplasia also becomes ap- parent at this age. In adulthood the dorsal vertebrae are flat and irregular, with narrowing of the disc spaces, and wedged, with resultant kyphoscoliosis (Spranger and Langer 1970). Spondyloepiphyseal dys- plasia tarda, X-linked (OMIM 313400) shows a typi- cal vertebral configuration, which develops at the lumbar level in late childhood or early adolescence:
bulging in the central and posterior portions of the superior and inferior vertebral end-plates, producing
characteristic ‘humps.’ The intervertebral disc spaces are narrow posteriorly and wide anteriorly (Fig.
3.15). Platyspondyly with no end-plate humps and no tongue-like projections of the vertebral bodies is ob- served in spondyloepiphyseal dysplasia, Maroteaux type (OMIM 184095).Abnormalities in this condition are confined to the skeleton and include shortening of the hands and feet and genu valgum deformity (Doman et al. 1990). Multiple epiphyseal dysplasia (OMIM 132400) displays more irregular vertebral
Fig. 3.10 a–d. SPONASTRIME dysplasia in children at differ- ent ages. a In this newborn note severe platyspondyly of the lumbar spine. The shape of the vertebral bodies is charac- teristic: a posterior part with straight end-plates, an anteri- or part with convex end- plates, and a centrally located anterior bony protrusion. The pattern of ossification is irreg- ular, with lucent areas present.
b In this 13-month-old child the vertebral bodies are rela- tively taller than in the new- born. The anterior part is taller than the posterior part and has convex end-plates.
The posterior part has straight or slightly convex end-plates. c In this 36-month- old child the posterior part of the body has slightly convex end-plates that tilt, so that the junction between anterior and posterior parts is the narrow- est in the body. d In this 15- year-old patient the vertebral bodies are of normal height, and uniform in shape and size. The end-plate concavity is smooth, and its center is posterior to the midpoint of the body. (From Langer et al.
1997)
a b
c d
end-plates and a less severe degree of platyspondyly than spondyloepiphyseal dysplasia tarda. Additional distinguishing features in multiple epiphyseal dys- plasia include absence of the vertebral humps and a more severe degree of epiphyseal dysplasia in the dis- tal extremities (Murphy et al. 1973). ‘Brachyolmia’ is the designation for a heterogeneous group of condi- tions characterized clinically by short stature, and radiographically by generalized platyspondyly with minimal involvement of the limbs. Four types have been recognized. (1) Hobaek type (OMIM 271530) is associated with mild flattening of the vertebral bod- ies, irregular end-plates, and lateral projection of the vertebral profile beyond the pedicles. (2) In Toledo type (OMIM 271630) platyspondyly occurs in associ- ation with corneal opacities and precocious ossi- fication of the costal cartilages. (3) Maroteaux type (OMIM 271530) is characterized by a round aspect of the anterior and posterior vertebral borders, with mild lateral elongation. All these three disorders are caused by autosomal recessive mutations. (4) The existence of an autosomal dominant type character- ized by the most severe spinal changes (severe platy- spondyly, decreased interpediculate distance with vertebral bodies projecting laterally beyond the pedi- cles) has been suggested (Horton et al. 1983; Shohat et al. 1989; Darcan et al. 2000). Generalized, severe
platyspondyly with a distinctive shape of the verte- bral bodies occurs in metatropic dysplasia and parastremmatic dwarfism. Owing to defective ossifi- cation, the vertebral bodies in metatropic dysplasia (OMIM 250600) are underdeveloped (diamond- shaped), flattened, and anteriorly wedged, especially in the dorsal spine (Fig. 3.16 a, b). The precocious appearance of kyphoscoliosis, the severity of epiphy- seal changes, and the characteristic pelvic configura- tion (flaring of the iliac wings with marked hypo- plasia of the basilar portions) allow differentiation from spondylometaphyseal dysplasia, Kozlowski type (Kozlowski et al. 1976). Spinal changes in paras- tremmatic dwarfism (OMIM 168400) include flat and broad vertebral bodies, irregular ossification of the vertebral end-plates giving the bone a ‘flocky’ ap- pearance, and severe kyphoscoliosis (Fig. 3.17 a, b).
The irregular pattern of ossification (‘flocky bone’)
Fig. 3.11. Mucopolysaccharidosis IV (Morquio syndrome).
There is severe platyspondyly, marked irregularity of vertebral end-plates, and tongue-like projections from the anterior wall of the vertebral bodies (arrows). Note also thoracolumbar kyphosis and posterior scalloping of vertebral bodies
Fig. 3.12. Dyggve-Melchior-Clausen syndrome in a 17-year- old girl. Note platyspon-dyly and the unique verte- bral body configuration, with round anterior vertebral projec- tions and notch-like defects of superior and inferior end- plates, leading to a camel-hump appearance. (From Hall-Crag- gs and Chapman 1987)
affects the whole skeleton, notably the iliac wings, the scapulae, and the epiphyseal-metaphyseal junction of the tubular bones and tends to disappear in later adolescence and adulthood (Langer et al. 1970). Se- vere platyspondyly is also a feature in several lethal bone dysplasias, including thanatophoric dysplasia, fibrochondrogenesis, homozygous achondroplasia, and lethal short-limbed dysplasia with platyspondyly (San Diego, Torrance, Luton, Calgary, Yamagata, Perth, and Shiraz types) (Kozlowski et al. 1995). Pseu- dodiastrophic dysplasia (OMIM 264180), an early lethal bone dysplasia resembling diastrophic dyspla- sia in many respects, including the rhizomelic type of limb shortening and the severe clubfoot deformity (Burgio et al. 1974), show more pronounced platy- spondyly, interphalangeal and metacarpophalangeal joint dislocations, and absence of the ‘hitchhiker thumb’ (abduction of the hypermobile and proximal- ly inserted thumb) typical of diastrophic dysplasia.
Platyspondyly with hypoplastic, ‘wafer-thin’ verte- brae has been described in association with general-
Fig. 3.13. Spondylometaphyseal dysplasia, Kozlowski type.
There is severe platyspondyly with anteroposterior elongation of the vertebral bodies. The end-plates are irregular
Fig. 3.14. Spondyloepiphyseal dysplasia congenita. The verte- bral bodies are flattened and pear shaped. The intervertebral disc spaces are wider than normal
Fig. 3.15. Spondyloepiphyseal dysplasia tarda, X-linked.
Platyspondyly is associated with a typical configuration of lumbar vertebrae: bulging of the superior and inferior end- plates in the shape of characteristic humps
ized osteosclerosis in a unique form of sclerosing lethal skeletal dysplasia (Brodie et al. 1998).
Progressive pseudorheumatoid arthropathy (OMIM 208230) is a bone dysplasia whose clinical symptoms develop in children between 3 and 8 years of age and which is characterized by progressive arthropathy re- sembling rheumatoid arthritis, and platyspondyly.
Arthropathy manifests with painful swelling and joint stiffness involving the hips, the cervical spine, and the finger joints in the hands. Laboratory find- ings (negative rheumatoid factor, normal sedimenta- tion rate) and histology (normal synovium, nesting of chondrocytes in resting and proliferative carti- lage, loss of normal cell columnar organization in growth zones) exclude rheumatoid arthritis.Vertebral changes mimic those in Scheuermann disease, in- cluding flattening with anterior ossification defects.
Platyspondyly resulting in short stature, sometimes associated with kyphoscoliosis, is typical (Spranger et al. 1983). Abnormal epiphyses, with irregularity and flattening, are seen at multiple sites (Kaibara et al. 1983). In pseudoachondroplasia (OMIM 177170) there is moderate flattening of the vertebral bodies in
childhood, but they typically tend to recover during adolescence. The vertebrae show superior and in- ferior ‘humps,’ resulting in a biconvex appearance, end-plate irregularities, and anterior tongue-like projections of variable degree (Finidori et al. 1980) (Fig. 3.18).
Based on the observation of a father and son, both born to consanguineous parents, of which the boy had severe platyspondyly and metaphyseal manifes- tations of enchondromatosis (Ollier disease, OMIM 166000) and his father had moderate platyspondyly only, it was suggested that platyspondyly could repre- sent (1) a manifestation of the carrier state for an au- tosomal recessive trait, (2) a minor expression of the same autosomal recessive disease, or (3) less likely, the variable expression of an autosomal dominant trait (Halal and Azouz 1991). The condition, referred to as spondylo-enchondro-dysplasia (OMIM 271550), is characterized by an association of enchondro- matosis similar to that of Ollier disease, platyspondy- ly with end-plate irregularities (Fig. 3.19 a, b), multi- ple radiolucent defects (due to enchondromas) in the metaphyses of long and flat bones, and kyphoscolio-
Fig. 3.16 a, b. Metatropic dysplasia. Postmortem radiograph of a male infant who died 30 min after birth. a There is severe platyspondyly and midline nonunion of the posterior ele- ments. b Additional features include narrowing and elongation
of the thorax, shortening of long bones with marked metaphy- seal widening,‘battle-axe’ appearance of proximal femurs, epi- physeal ossification delay, short ilia with round margins and flat acetabula. (From Westvik and Lachman 1998)
a b
sis (Schorr et al. 1976; Frydman et al. 1986). Platy- spondyly associated with short stature, severe hip changes, distal shortening of ulna, and signs of pe- ripheral dysostosis, with short hands and feet, occurs in spondyloperipheral dysplasia with short ulna (OMIM 271700) (Kelly et al. 1977). A boxer-like face, sensorineural deafness and mental retardation are further features (Sorge et al. 1995). A previously un- reported form of skeletal dysplasia characterized by platyspondyly with amelogenesis imperfecta (OMIM 601216) has been described by Verloes et al. (1996) in two sibs born to consanguineous parents. In this autosomal recessive disorder the vertebrae are flat and rectangular, with posterior scalloping, short pedicles, and narrow interpediculate distances. Ab- sence of the enamel cap in the permanent teeth is a cardinal feature. Additional manifestations include short stature, short hands, and broad femoral necks.
A unique generalized bone dysplasia with severe platyspondyly and distinctive peripheral anomalies has been reported in two patients by Kozlowski et al.
(1999) (Fig. 3.20). The first patient showed short stature, short trunk, valgus deformity of the knees, short hands and feet, meta-epiphyseal changes of
Fig. 3.17 a, b. Parastremmatic dwarfism in a 9-year-old child. a Note flattening and marked end-plate irregulari- ties of the vertebral bodies.
The abnormal pattern of ossi- fication gives rise to a unique
‘flocky bone’ appearance of vertebral end-plates. b Note also thoracic scoliosis
b a
Fig. 3.18. Pseudoachondroplastic dysplasia in a 2-year-old child. Note superoinferior convexity (humps) of the lumbar vertebral bodies, with anterior tongue-like beaking. (From Unger et al. 2001 )
variable degree, and rectangular vertebrae. The sec- ond patient had some of the features seen in brachy- olmia, the most important phenotypic sign being shortening of the trunk. The vertebral bodies were flat, with thick and irregularly calcified ring apophy- ses. However, involvement of the long tubular bones and round bones, as well as pelvic and scapular in- volvement, delineates a previously unreported bone dysplasia.
A special type of collapsed vertebra, the ‘H- shaped’ vertebra, is typically seen in sickle cell ane- mia. This configuration is characterized by squared- off depression of the central portion of the end- plates, which is seen on lateral radiograms and is probably related to growth disturbances resulting from ischemia of the vertebral growth plate (Reynolds 1966). H-Shaped vertebrae are occasional- ly seen in other types of anemia, Gaucher’s disease (Hansen and Gold 1977), and osteoporosis (Fig. 3.21), although a smooth biconcave contour rather than a step-like depression of the vertebral end-plate is more typical in the latter conditions. An H-shaped vertebral configuration on frontal radiograms is observed in thanatophoric dysplasia.
Radiographic Synopsis AP and lateral projection
1. Decreased height of the vertebral bodies. Normal values for the vertebral body and disc space height are available (Brandner 1970; Remes et al. 2000).
Assessment of the vertebral body index provides an estimation of the vertebral body proportions [the vertebral body index is calculated as the ratio between the largest vertical (V) and the smallest anteroposterior (S) measurement of the vertebral body].
2. Narrowing of intervertebral disk space (infection, trauma).
3. Intervertebral space of normal height (bone dys- plasias).
Fig. 3.19 a, b. Spondylo-en- chondrodysplasia in a 14- year-old patient. Note a platy- spondyly of the thoracic ver- tebrae and b irregular end- plates with defects of the fron- tal parts of the thoracic and upper lumbar vertebrae. (From Uhlmann et al. 1998)
a b
Associations
• Achondrogenesis
• Achondroplasia (homozygous)
• Atelosteogenesis
• Brachyolmia
• Campomelic dysplasia
• Cephaloskeletal dysplasia (Taybi-Linder syndrome)
• Cushing syndrome
• De la Chapelle syndrome
• Diastrophic dysplasia
• Down syndrome
• Dyggve-Melchior-Clausen syndrome
• Dyschondrosclerosis
• Ehlers-Danlos syndrome
• Enchondromatosis
• Fibrochondrogenesis
• Freeman-Sheldon syndrome
• Fucosidosis
• Gaucher disease
• Gerodermia osteodysplastica hereditaria
• GM1 gangliosidosis
• Hallermann-Streiff syndrome
• Histiocytosis X
• Homocystinuria
• Hydrops-ectopic calcification-moth-eaten skeletal dysplasia
• Hyperphosphatasemia
Fig. 3.20. Severe platyspondyly and distinctive peripheral anomalies in a child aged 11 years and 6 months. Note severe platyspondyly with thick irregular ring apophyses. (From Ko- zlowski et al. 1999)
Fig. 3.21. Osteogenesis imperfecta tarda. Severe osteoporosis has resulted in central collapse of vertebral end-plates, produc- ing an ‘H’ or biconcave configuration of the vertebral bodies
• Hypertrichosis-osteochondrodysplasia
• Hypochondroplasia
• Hypophosphatasia
• Hypopituitarism (anterior lobe)
• Hypothyroidism
• Immune deficiency, severe combined (SCID) with ADA deficiency
• Kniest syndrome
• Larsen syndrome
• Lethal short-limbed dysplasia with platyspondyly
• Marshall-Smith syndrome
• Metatropic dysplasia
• Mucopolysaccharidosis IV-A (Morquio syndrome)
• Multiple epiphyseal dysplasia
• Opsismodysplasia
• Osteogenesis imperfecta
• Osteoglophonic dwarfism
• Osteoporosis
• Osteoporosis-pseudoglioma syndrome
• Oto-spondylo-megaepiphyseal dysplasia
• Parastremmatic dwarfism
• Patterson syndrome
• Platyspondyly with amelogenesis imperfecta
• Platyspondyly, severe, with peripheral anomalies
• Progressive pseudorheumatoid arthropathy
• Pseudoachondroplasia
• Pseudodiastrophic dysplasia
• Radiation therapy
• Rothmund-Thomson syndrome
• Schwartz-Jampel syndrome
• Sclerosing lethal skeletal dysplasia
• Short rib-polydactyly syndrome, type 1 (Saldino-Noonan)
• Smith-McCort syndrome
• Sotos syndrome
• Spondylocamptodactyly
• Spondyloenchondromatosis
• Spondylo-epimetaphyseal dysplasia
• Spondylo-epiphyseal dysplasia congenita
• Spondylo-epiphyseal dysplasia tarda
• Spondylometaphyseal dysplasia (Kozlowski type)
• Spondyloperipheral dysplasia with short ulna
• Stickler syndrome
• Thanatophoric dysplasia
• Ulnar metaphyseal dysplasia syndrome (Rosenberg)
• Wolcott-Rallison syndrome
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Hemivertebrae
䉴
[Absence of one half of the vertebral body]
Hemivertebrae are classified as lateral or dorsal and ventral, depending on whether the developmental defect consists in failure of the contralateral chondral center to develop (lateral hemivertebra) or in failure of the anterior and posterior centers to ossify (dorsal and ventral hemivertebrae, respectively). The first defect occurs at the prechondral stage, while the sec-
ond occurs at the ossification stage of vertebral de- velopment. The affected half of the vertebral body may be hypoplastic or absent, as is the pedicle and, at the thoracic level, the corresponding rib. Very often, the neural arch on the side of the affected half of the vertebral body shows a variable degree of fusion or segmentation defect (pediculate or laminar bars).
The pedicle on the side of the hemivertebra can be ei- ther normal or enlarged. The hemivertebra can exist in the place of a normal vertebra or can be a supernu- merary structure. Lateral hemivertebrae, which are by far the most common type, are often supernumer- ary. Ventral hemivertebrae are exceedingly rare.
Hemivertebrae can be fully segmented (nonincarcer- ated), semisegmented, or incarcerated. Fully seg- mented hemivertebrae are the most common type and usually produce the most severe degrees of spinal deformity, thus requiring prophylactic treat- ment (McMaster and David 1986) (Fig. 3.22). The so- called semisegmented hemivertebra is fused to one of the adjacent vertebrae above or below, giving rise to osseous fusions that are sometimes of bizarre shape (Fig. 3.23 a, b). In the fully segmented type the disc space is well developed above and below, allowing for differentiation from the acquired disorders, which cause destruction of the vertebral body. Dorsal
Fig. 3.22. Fully segmented hemivertebrae. Isolated lateral hemivertebra at L-3, producing significant structural scoliosis in the lumbar spine with the hemivertebra on the convexity of the curve. Note advanced degenerative osteophyte formation, especially on the concave side of the scoliosis. The inferior disc space is narrowed and the pedicle is enlarged
hemivertebrae resemble the anteriorly wedged, or cuneiform, vertebrae (Fig. 3.24). Wedging of the an- terior portion of the vertebral body can be primary or secondary to compression injuries or bone soften- ing. When primary, the defect is attributable to fail- ure of the anterior portion of the vertebral body to grow in height and is therefore a defect in formation similar to, although less severe than, a dorsal hemivertebra. Both produce similar effects on spinal alignment. The effects of hemivertebrae on spinal alignment are severe in most cases. Depending on
whether the hemivertebra is lateral or dorsal in loca- tion, spinal scoliosis or kyphosis, respectively, results (Zidorn et al. 1994). As discussed elsewhere in this section, kyphoscoliosis secondary to hemivertebrae is rapidly progressive in most cases, except when multiple hemivertebrae are present, displaying a bal- anced effect on spinal alignment (Nasca et al. 1975).
Hemivertebrae have been experimentally induced in fetuses of mice exposed to the teratogenic effect of valproic acid (Padmanabhan and Hameed 1994) and cadmium (Padmanabhan and Hameed 1986). The coexistence in both cases of exencephaly and facial abnormalities underscores the developmental inter- dependence of the neural plate and the paraxial mesoderm during normal morphogenesis. Failure of midline fusion of the two chondral centers for the vertebral body, possibly secondary to persistence of remnants of the fetal notochord, results in sagittal clefts, a developmental error occurring in early em- bryonic life (see section headed “Coronal Cleft Verte- brae”). Similarly, failure of midline fusion at the pre- chondral stage may result in a butterfly vertebra, in which two hemivertebrae are widely separated from each other by persistence of a central canal extending anteriorly and posteriorly on the sagittal plane through the vertebral body (Fig. 3.25). It has been suggested that overdistension of the neural tube soon after its closure (4th week of gestation) caused by an excess of cerebrospinal fluid may spread the develop- ing somite apart, resulting in bilateral hemivertebrae (Gardner 1980). In contrast to the thin fissure of ver- tebral sagittal clefts, the midline schisis in butterfly
Fig. 3.23 a, b. Semisegmented hemivertebra. a The lateral hemivertebra is fused with the next vertebra, giving a trape- zoid shape. b Note duplicated pedicles and transverse pro- cesses at L-2 owing to the presence of a semisegmented lateral hemivertebra. Scoliosis convex on the side of the hemivertebra is also apparent
a b
Fig. 3.24. Dorsal hemivertebrae. Isolated dorsal hemivertebra, resulting in gibbus deformity of the thoracolumbar junction
vertebrae is a wide cavity filled with cartilaginous tis- sue continuous with the intervertebral discs above and below. The two hemivertebrae resemble the wings of a butterfly, extending slightly beyond the lateral margins of the neighboring vertebrae, and show oblique superior and inferior end-plates so that they have a funnel-shaped appearance on frontal ra- diograms. Unlike hemivertebrae, butterfly vertebrae are not associated with segmentation rib defects. The pedicles may be broadened, and the interpediculate distance may be increased. This distinct vertebral configuration is commonly encountered in Alagille syndrome (arteriohepatic dysplasia, OMIM 118450) (Fig. 3.26), an autosomal dominant disorder due to mutation of the JAG1 (Jagged 1) gene at chromosome
20p12. Distinguishing features of the syndrome in- clude deep-set eyes, broad forehead, pointed mandible and bulbous tip of the nose, neonatal jaun- dice, growth retardation, and defects in the eyes, car- diovascular system (peripheral pulmonary artery stenosis), liver, and bones (vertebral and rib anom- alies). In addition to the butterfly-like shape, com- mon features in the spine include hemivertebrae, spina bifida occulta, and decreased interpediculate distance at the lumbar level. A striking histological feature in the liver is the paucity of intrahepatic in- terlobular bile ducts, resulting in chronic cholestasis (Watson and Miller 1973; Alagille et al. 1975; Rosen- field et al. 1980).
Hemivertebrae can be solitary defects or occur in association with other skeletal and nonskeletal ab- normalities. Solitary hemivertebrae are sporadic de- fects, carrying no risk to subsequent sibs (Wynne- Davies 1975). Moreover, isolated vertebral anomalies detected during fetal life usually have a favorable prognosis and are associated with normal karyotype.
By contrast, the presence of associated anomalies in the fetus increases the likelihood of lethality in the perinatal period (Zelop et al. 1993).
The cause and mode of inheritance of hemiverte- brae are unknown. The occurrence of a de novo reciprocal translocation, t(13;17)(q34;p11.2), in a girl with psychomotor developmental delay and congen- ital scoliosis due to segmented hemivertebra has raised the possibility that 17p11.2 is a candidate re- gion for a hemivertebra locus (Imaizumi et al. 1997).
This hypothesis derives credence from the obser- vation that some patients with Smith-Magenis syn- drome (OMIM 182290) have both congenital scoliosis and interstitial deletion at 17p11.2.
Hemivertebrae occurring alone or in combination with other anomalies of the spine, especially if located in the low cervical and upper thoracic spine, are com- monly associated with urinary tract malformations (Tori and Dickson 1980). Congenital hypoplasia of one lung is often accompanied by hemivertebrae (Silver- man 1993). Hemivertebrae are a common finding in subjects with myelomeningocele (Naik et al. 1978).
The acronym VATER (OMIM 192350) stands for a combination of vertebral defects, anal atresia, tracheoesophageal fistula with esophageal atresia, and radial dysplasia. No teratogen or chromosomal abnormality has been recognized, and all recorded cases have been sporadic. Vertebral anomalies are similar to those of spondylocostal dysplasia and include hemivertebrae and fused, hypoplastic, miss- ing, and ‘butterfly’ vertebrae (Quan and Smith 1972).
VACTERL is the acronym for the combination of
Fig. 3.25. Butterfly vertebra: conventional tomogram showing a typical butterfly vertebra at L-4
Fig. 3.26. Alagille syndrome. Note multiple butterfly vertebrae in the dorsal spine. (From Berrocal et al. 1997)
defects comprising, in addition to those of VATER as- sociation, cardiac malformations, renal anomalies in- cluding hydronephrosis and urethral atresia, and a wider range of limb anomalies, including hexadacty- ly, humeral hypoplasia, radial aplasia, and proximally placed thumb (Khoury et al. 1983). The designation
’dyssegmental’ dysplasia (OMIM 224400) refers to the extensive segmentation defects in the spine (Gorlin and Langer 1978) (Fig. 3.27 a, b). The vertebral bod- ies are of variable size (anisospondyly), with some vertebrae appearing oversized on lateral radiograms.
Vertebral aplasia, especially in the cervical spine, sagittal and coronal vertebral clefts, anterior wedg- ing, and lack of normal craniocaudal interpediculate widening in the lumbar spine are additional findings in the spine. Short and broad long tubular bones with dumbbell femurs, small and flared ilia, narrow chest, and reduced joint mobility are constant features. The autosomal recessive dyssegmental dysplasia of the
Silverman-Handmaker type (OMIM 224410) (Hand- maker et al. 1977) is early lethal and is characterized by more severe radiographic changes. The less severe Rolland-Desbuquois type (OMIM 224400) (Rolland et al. 1972) allows survival beyond the newborn period and is characterized by milder radiographic changes resembling those of Kniest dysplasia (OMIM 156550). A nosologically distinct disorder, dysseg- mental dysplasia with glaucoma (OMIM 601561), is associated with severe glaucoma, exophthalmos and corneal opacities (Maroteaux et al. 1996). Spinal dys- plasia, Anhalt type (OMIM 601344) resembles dyssegmental dysplasia in some respects, but is a dis- tinct disorder with short stature and significant anomalies in the spine, including hemivertebrae, flat vertebrae, narrow anterior-posterior diameter of the vertebral bodies, and absence of the normal spinous processes (Anhalt et al. 1995).
Fig. 3.27 a, b. Dyssegmental dysplasia, Silverman type in a stillborn. a Anteroposterior and b lateral radiograms. Note extremely irregular pattern of ossification of the vertebrae, multiple segmentation defects, and anisospondyly. There are hemivertebrae, wedged, over- sized, and missing vertebrae, coronal clefts, and lumbos- acral kyphosis.
(From Fasanelli et al. 1985)
b a
