Presenter : Dr. Charusmita Chaudhary Moderator: Dr R. K. Gogoi
In the spine, the most common congenital lesions presenting to medical attention are the diverse forms of spinal dysraphism diverse forms of caudal spinal anomalies:diagnosed:::: Prenatally at birth in early childhood in adulthood
Techniques of imaging Radiography Computed Tomography Magnetic Resonance Imaging Ultrasonography Nuclear Imaging
EtiologyMultifactorial genetic, environmental influences, folic acid deficiency in the mothers. Ultrasonography is performed in high-riskpregnancies.
Spinal Cord Development can be summarized in three basic embryologic stages1. The first stage : Gastrulation (the 2 or 3 week) conversion of the embryonic disk from a bilaminar disk to a trilaminar disk.1. The second stage : primary neurulation (weeks 3–4) the notochord and overlying ectoderm interact to form the neural plate. The neural plate bends and folds to form the neural tube, which then closes bidirectional in a zipperlike manner2. The final stage : secondary neurulation (weeks 5–6), a secondary neural tube is formed by the caudal cell mass. The secondary neural tube is initially solid and subsequently cavitation, eventually forming the tip of the conus medullaris and filum terminale by a process called retrogressive differentiation. Abnormalities at steps can lead to spine or spinal cord malformations the cephalic and caudal portions of the spinal cord form by distinctly different mechanisms, they exhibit distinctly different types of malformation
Gastrulation. a Dorsal view and btransverse view of thebilaminar embryonic disk. Firstingressing cells at Hensen’s nodemove anterior to form headprocesses and notochord. Cellsingressingthrough primitive streak migrateventrally and laterally to formmesodermal a and endodermalprecursors
NEURULATION AND DERANGEMENTS OF NEURULATION four stages of neurulation Formation Shaping of Bending of of the the Neural the Neural Fusion Neural Plate Plate Plate
Primary neurulation. Formation of the Neural Plate Shaping of the Neural Plate Bending of the Neural Plate FusionIllustrations of primary neurulation.Notochord (circle) interacts with overlyingectoderm to form neural plate (dark green),which then bends to form neural tube thatultimately closes in zipperlike fashion
Canalization and retrogressivedifferentiation (synonym: secondaryneurulation). Diagrammatic representationof proposed embryogenesis.
Categorization of Spinal Dysraphisms Spinal dysraphisms open and closed types In an open spinal dysraphism there is a defect in the overlying skin, and the neural tissue is exposed to the environment. In a closed spinal dysraphism, the neural tissue is covered by skin. Closed spinal dysraphisms can be further subcategorized on the basis of the presence or absence of a subcutaneous mass.
Open spinal dysraphism (OSD; characterized by exposure of nervous tissue through a congenital Defect Almost 99% are myelomeningoceles Variable degree of sensorimotor deficits,bowel and bladder dysfunction All patients with OSD have Chiari II Role of MRI: anatomic characterization;presurgical evaluation; identification of cord splitting when present
Deranged Neurulation Spina Bifida Aperta: Myelocele and Myelomeningocele spina bifida aperta designates those forms of spinal dysraphism in which the neural tissue and/or meninges are exposed to the environment because the skin, fascia, muscle, and bone are deficient in the midline of the back
Open Spinal Dysraphisms Myelomeningocele and Hemimyelomeningocele and myelocele hemimyelocele Myelomeningoceles and myeloceles are caused by defective closure of the primary neural tube Hemimyelomeningoceles and hemimyeloceles can also Exposure of the neural placode through a midline skin defect on occur but are extremely rare . the back. These conditions occur when Myelomeningoceles account for a myelomeningocele or more than 98% of open spinal myelocele is associated with dysraphisms diastematomyelia (cord Myeloceles are rare. splitting) and one hemicord fails to neurulate.
Open spinal dysraphisms are often diagnosed clinically, so imaging is not always performed. When imaging is performed, The main differentiating feature between a myelomeningocele and myelocele is the position of the neural placode relative to the skin surface The neural placode protrudes above the skin surface with a myelomeningocele and is flush with the skin surface with a myelocele
Myelomeningocele. Axial schematic of Myelomeningocele. Axial T2-myelomeningocele shows neural weighted MR image Myelomeningocele. Sagittal T2-placode (star) protruding above skin weighted MR image).surface due to expansion of underlyingsubarachnoid space (arrow).
Myelocele. Axial T2-weighted MRMyelocele. Axial schematic of myelocele image in 1-day-old girl shows exposedshows neural placode (arrow) flush with neural placode (arrow) that is flushskin surface. with skin surface, consistent with myelocele. There is no expansion of underlying subarachnoid space
Antenatal ultrasonogram shows a lumbar meningocele.
Chiari Malformations share common features, variable degree of reduction in size of the posterior fossa and (with the exception of the type IV) herniation of portions of the cerebellum into the foramen magnum, it is accepted that type I (resulting from a mesodermal hindbrain abnormality) should be separated from the other types that are related to neural tube closure defects
Chiari-I malformation Cerebellar tonsils >5 mm below basion-opisthion line or 3–5 mm and neurological signs or peg-like tonsils or syrinx 14–56% neurologically normal Significant incidence of hydrosyringomyelia and/or hydrocephalus Caudal ectopia of the cerebellar tonsils into the foramen magnum is the hallmark of the Chiari-I malformation
Axial T1-weighed image shows crowding of the foramen magnum due to the presence oftheSagittal T1-weighted image shows caudal tonsils (T) behind the medulla oblongatatonsillar ectopia (arrow).The posterior fossa is small Multiple haustrations are a typical fi nding with Chiari-I- associated hydromelia Sagittal T1-weighted image
Chiari-II malformation Small posterior fossa Downward displacement of vermis, brainstem and fourth ventricle 90% has OSD Associated brain malformations Antenatal ultrasonogram shows a lemon sign and a banana sign
Sagittal images very small posterior cranialfossa and the typical cascade of herniationsconstitutin the hallmark of the Chiari-IImalformation.
Diagrammatic representation of the spectrum of cervicomedullary deformitiesin the Chiari II malformation
Chiari II malformation as result of diversion of ventricular CSF to the amnion with “collapse” of the developing ventricular system The fluid-filled space of the developing brain and spinal cord is called the neurocele. The medial walls of the thoracic neural tube normally appose and occlude the neurocele transiently during central nervous system distal myelomeningocele fail to occlude the neurocele, even at sites remote from the myelomeningocele. This failure to appose the walls appears to result from the same biosynthetic defect in cell surface glycosaminoglycans that prevents the neural tube from closing. the mechanism that causes failure of neurulation also causes failure of apposition of the medial walls of the neurocele.
theory proceeds as follows neurocele is not occluded, CSF passes freely down the central canal and out the myelomeningocele to the amnionic cavity This abnormal shunt collapses the developing primitive ventricular system. Therefore, the volume of the ventricular system and surrounding neural tissue is less than normal. The mesenchyme condenses in relation to an abnormally small volume of developing CNS. This establishes a smaller-than normal posterior fossa with low tentorium. The developing CNS must then grow within an envelope of membrane, cartilage, and bone that is too small for it. This leads to failure to form the pontine flexure, downward growth of the cervicomedullary junction, medulla, and cerebellum through the foramen magnum, and upward growth of the cerebellum through the incisura.
11. Reduced size of the third ventricle means closer approximation of the thalami with larger massa intermedia. Collapse of the cerebral ventricles leads to disorganization of the developing hemispheres with gray matter heterotopias,disorganization of cerebral gyri, and dysgenesis of the corpus callosum The collapse of the ventricular system leads to disordered development of the membranous bone of the vault .Normally, the skull develops from centers in each cranial plate. As the brain expands, the collagen bundles are drawn out from those centers in an orderly radial fashion, much like the uniform expansion of the surface of an inflating balloon. As radial expansion proceeds, the collagen bundles become calcifiable and membranous bone forms. Lack of distension of the brain mass by increasing volumes of CSF produces disordered arrays of collagen bundles. Thus, instead of radial lines of collagen, whorls and coils of collagen form with varying density between them. Ossification of this disorganized collagen mat then leads to lükenshädel
Chiari malformationChiari-III malformation Chiari-IV malformation Chiari II + cephalocele Severe cerebellar hypoplasia + myelomeningocele
Closed Spinal Dysraphisms With aSubcutaneous MassLipomas with a dural defect Meningocele Lipomas with a dural defect include both Herniation of a CSF-filled sac lined by lipomyeloceles and lipomyelomeningoceles. dura and arachnoid mater is referred to as a meningocele. The spinal cord is These abnormalities result from a defect in not located within a meningocele but primary neurulation whereby mesenchymal may be tethered to the neck of the tissue enters the neural tube and forms CSF-filled sac. lipomatous tissue 2 types… characterized clinically by the presence of a Posterior meningoceles herniate subcutaneous fatty mass above the through a posterior spina bifida intergluteal crease. (osseous defect of posterior spinal The main differentiating feature between a elements) and are usually lumbar or lipomyelocele and lipomyelomeningocele is sacral in location but also can occur in the position of the placode–lipoma interface the occipital and cervical regions With a lipomyelocele, the placode–lipoma Anterior meningoceles are usually presacral in location but also can interface lies within the spinal canal occur elsewhere With a lipomyelomeningocele, the placode– lipoma interface lies outside of the spinal canal due to expansion of the subarachnoid space
Lipomyelocele. Axial T2-weighted MR image shows placode–lipoma interface Lipomyelocele. Sagittal T1-Lipomyelocele. Axial schematic of weighted MR image (arrow) within spinal canal,lipomyelocele shows placode– characteristic for lipomyelocele lipomyelocele showslipoma interface (arrow) lies subcutaneous fatty masswithin spinal canal (black arrow) and placode– lipoma interface (white arrow) within spinal canal.
Lipomyelomeningocele. Axialschematic oflipomyelomeningocele showsplacode–lipoma interface(arrow) lies outside of spinalcanal due to expansion ofsubarachnoid space Lipomyelomeningocele. Axial T1-weighted MR image in 18-month-old boy shows lipomyelomeningocele (arrow) that is differentiated from lipomyelocele by location of placode–lipoma interface outside of spinal canal due to expansion of subarachnoid space.
,. B,. C. , Sagittal T2-weightedSagittal T1-weighted MR Sagittal T2-weighted MR MR image in 30-image shows posterior image shows large month-old girl showsherniation of CSF-filled sac posterior meningocele small posterior(arrow) in occipital region, (arrow) in cervical region meningocele (arrow) inconsistent with posterior lumbar regionmeningocele 6—Posterior meningocele Sagittal (A) and axial (B) T2-weighted MR images in 6-month-old boy show small anterior meningocele (arrows
Terminal myelocystocele Myelocystocele— Herniation of large terminal A nonterminal syrinx (syringocele) into a myelocystocele occurs posterior meningocele through a posterior spinal defect is when a dilated central referred to as a terminal . canal herniates through a The terminal syrinx component posterior spina bifida communicates with the central defect Myelocystoceles are canal, and the meningocele component communicates with covered with skin and can the subarachnoid space. occur anywhere but are The terminal syrinx and most commonly seen in meningocele components do not usually communicate with each the cervical or other cervicothoracic regions
SchematicTerminal myelocystocele. of nonterminalA, Sagittal schematic of terminal myelocystocele shows terminal myelocystocele showssyrinx (star) herniating into large posterior meningocele herniation of dilated(arrows). central canal throughB and C, Sagittal (B) and axial (C) T2-weighted MR images show posterior spinal defectterminal syrinx (white arrows) protruding through largeposterior spina bifida defect and herniating into posteriormeningocele component (black arrows).
Closed Spinal DysraphismsWithout a Subcutaneous MassSimple dysraphic states Complex dysraphic states Complex dysraphic states be intradural lipoma, divided into two categories: filar lipoma, A) disorders of midline tight filum terminale, notochordal integration, persistent terminal ventricle dorsal enteric fistula, neurenteric cyst, and dermal sinus. diastematomyelia, B)disorders of notochordal formation, caudal agenesis and segmental spinal dysgenesis.
lipoma An intradural lipoma refers to a lipoma located along the dorsal midline that is contained within the dural sac No open spinal dysraphism is present commonly lumbosacral in location usually present with tethered-cord syndrome Fibrolipomatous thickening of the filum terminale is referred to as a filar lipoma. On imaging, a filar lipoma appears as a hyperintense strip of signal on T1-weighted MR images within a thickened filum terminale Filar lipomas can be considered a normal variant if there is no clinical evidence of tethered-cord syndrome tethered-cord syndrome a clinical syndrome of progressive neurologic abnormalities in the setting of traction on a low-lying conus medullaris
Spinal lipomafocal premature disjunction of epidermalfrom neural ectoderm.curved arrows are also used toindicate the course of mesenchymemigrating through the focal disjunction tothe dorsal surface of the closing neural folds
Diagrammatic representations of spinal lipomas. A: Intradural lipoma. The laminae(L) are bifid. The dura (dark line) is intact. The pia-arachnoid (dashed line) enclosesthe spinal cord and the lipoma. The lipoma lies predominantly within a midline cleft inthe dorsal spinal cord but fungates beneath the pia to bulge into the dorsalsubarachnoid spaceD, dorsal root; V, ventral root; G, dorsal root ganglion. B: Lipomyelocele. There isposterior spina bifida with everted C: lipomyelomeningocele
Intradural lipoma Filar lipoma , Sagittal (A) and axial (B) T1-weighted MR images I with filar lipoma (arrows), which has characteristic T1 hyperintensity and marked thickening of filum terminale.Sagittal T1-weighted (A) and sagittal T2-weighted fat-saturated (B) MR images show largeintradural lipoma (arrows), which ishyperintense on T1-weighted image and hypointenseon T2-weighted fat-saturated image. Lipoma isattached to conus medullaris, which is low lying.
Intraspinal lipomas may produce posterior scalloping of vertebral bodies and flattening of the pedicles D/D intraspinal tumors; neurofibromatosis; acromegaly; achondroplasia; communicatingPlain radiographs show posterior scalloping. hydrocephalus; syringomyelia; and a number of congenital syndromes, including Ehlers- Danlos, Marfan, Hurler, Morquio, and osteogenesis imperfecta syndromes.
Simple dysraphic states TIGHT FILUM TERMINALE Tight filum terminale is characterized by hypertrophy and shortening of the filum terminale . This condition causes tethering of the spinal cord and impaired ascent of the conus medullaris. The conus medullaris is low lying relative to its normal position, which is usually above the L2–L3 disk level fila thicker than 2 mm were abnormal. Sagittal T2-weighted MR image in 12-month-old boy shows tight filum terminale, characterized by thickening and shortening of filum terminale (black arrow) with low-lying conus medullaris. Incidental cross-fused renal ectopia (white arrow) is also present.
Left, plain radiograph of the lumbar spine Left, anteroposterior (AP) plain radiograph of the lumbar spine shows shows bony defects in the laminae of L2 to a defect within the laminae of S1 and S1. Right, myelogram shows a split cord.Left plain anteroposterior (AP) radiograph of S2. Right, myelograms in the samethe lumbar spine shows spina bifida occulta. patient show a markedly thickened,Right, myelogram of the same patient shows a low tethered cordthick tethered cord
Simple dysraphic states TERMINAL VENTRICLE Persistence of a small, ependymal lined cavity within the conus medullaris is referred to as a persistent terminal ventricle . It appears to represent the point of union between the portion of the central canal made by neurulation and the portion made by canalization of the caudal cell mass Key imaging features include location immediately above the filum terminale and lack of contrast enhancement, which differentiate this entity from other cystic lesions Persistent terminal ventricle. of theconus medullaris A and B, Sagittal T2-weighted (A) and sagittal T1-weighted contrast-enhanced (B) MR images in 12-month-old boy show persistent terminal ventricle as cystic structure (arrows) at inferior aspect of conus medullaris, which does not enhanc
Simple dysraphic states Dermal sinus A dermal sinus is an epithelial lined fistula that connects neural tissue or meninges to the skin surface. If the superficial ectoderm fails to separate from the neural ectoderm at one point, lumbosacral region and is often associated with a spinal dermoid at the level of the cauda equina or conus medullaris Clinically, patients present with a midline dimple and may also have an associated hairy nevus, hyperpigmented patch, or capillary hemangioma Surgical repair is of great importance because , Sagittal schematic (A) and sagittal T2-weighted MR image (B) in the fistulous connection between neural tissue and the skin surface can result in infectious 9-year-old girl show intradural dermoid (stars) with tract complications such as meningitis and abscess extending from central canal to skin surface (black arrows). Note tenting of dural sac at origin of dermal sinus (white arrows). C, Axial T2-weighted MR image from same patient as in B shows posterior location of hyperintense dermoid (arrow)
.Proposed embryogenesis of dorsal dermalsinus by incomplete disjunction Dorsal dermal sinus. Diagrammatic representation
Disorders of midline notochordalintegration Dorsal enteric fistula and neurenteric cystA dorsal enteric fistula occurs when there is an abnormal connection between the skin surface and bowel.Persistence of a patent neurenteric canal (canal of KovalevskyNeurenteric cysts represent a more localized form of dorsal enteric fistula .These cysts are lined with mucin-secreting epithelium similar to the gastrointestinal tract and are typically located in the cervicothoracic spine anterior to the spinal cord
Split notochord syndrome. Diagrammaticrepresentation of developmental posteriorenteric remnants.
5—Neurenteric cyst in 3-year-old girlA and B, Sagittal T2-weighted (A) and axial T1-weighted (B)MR images show bilobed neurenteric cyst (arrows) extendingfrom central canal into posterior mediastinum.C, Three-dimensional CT reconstruction image shows osseousopening (arrow) through which neurenteric cyst passes. Thisopening is called the Kovalevsky canal
Disorders of midline notochordalintegration Diastematomyelia Separation of the spinal cord into two hemicords is referred to as diastematomyelia. The two hemicords are usually symmetric, although the length of separation is variable. There are two types of diastematomyelia. In type 1Dual Dural-Arachnoid Tubes (Pang Type I), the two hemicords are located within individual dural tubes separated by an osseous or cartilaginous septum In type 2, Single Dural-Arachnoid Tube (Pang Type II) there is a single dural tube containing two hemicords, sometimes with an intervening fibrous septum Diastematomyelia can present clinically with scoliosis and tethered-cord syndrome. A hairy tuft on the patients back can be a distinctive finding on physical examination
Embryogenesis of split notochord syndrome Posterior view of the patient reveals the large patch of long, silky hairs overlying stematomyelia and a small sacral dimple (arrow
Type 1 diastematomyelia Sagittal T2-weighted MR (A), axial T2-weighted MR (B), and axial CT with bone algorithm (C) images in 6-year-old boy show two dural tubes separated by osseous bridge (arrows), which is characteristic for type 1 diastematomyelia. Axial CT scans through the upper lumbar spine show a split cordlumbosacral region; a long, tethered cord; anddiastematomyelia.
Type 2 diastematomyelia. , Sagittal T1-weighted (A), coronal T1- weighted (B), and axial T2-weighted (C) MR images show splitting of distal cord into two hemicords (white arrows, B and C) within single dural tube, which is characteristic for type 2 diastematomyelia. Incidental filum lipoma (black arrows, A and B) is present as well.
Disorders of notochordalformation: Caudal agenesis Caudal agenesis refers to total or partial agenesis of the spinal column and may be associated with the following: anal imperforation, genital anomalies, renal dysplasia or aplasia, pulmonary hypoplasia, or limb abnormalities.
Caudal agenesisCaudal agenesis can be categorizedinto two types. In type 1, there is a high positionand abrupt termination of theconus medullaris. In type 2, there is a low positionand tethering of the conusmedullaris , Sagittal T2-weighted (A) and sagittal T1- weighted (B) MR images in show agenesis of sacrum. Conus medullaris is high in position and wedge shaped (arrow) due to abrupt termination. These findings are characteristic of type 1 caudal agenesis. Distal cord syrinx (arrowhead) is present as well.
Syndrome of Caudal Regression constellation of anomalies of the hind end of the trunk, including partial agenesis of the thoracolumbosacral spine, imperforate anus, malformed genitalia, bilateral renal dysplasia or aplasia, pulmonary hypoplasia, and, in the most severe deformities, extreme external rotation and fusion of the lower extremities (sirenomelia) Sacral agenesis arises early in gestation, probably before the 10th week of gestation diabetes mellitus, OEIS complex, VATER syndrome (see later discussion), and congenital heart defects (24%); genitourinary complaints with hydronephrosis, unilateral renal agenesis, pelvic and horseshoe
Posterior view of the patient reveals theshort, shallow intergluteal cleftand poorlydeveloped gluteal musculature.
Classification of LumbosacralAgenesis I Total SA; some lumbar vertebrae also missing IWa Ilia articulate with sides of the lowest vertebra, maintaining relatively normal transverse pelvic diameter INa Ilia articulate or fused with each other below last vertebra, severely shortening transverse pelvic diameter II Total SA; lumbar vertebrae not involved IWa Ilia articulate with sides of L-5 vertebra maintaining relatively normal transverse pelvic diameter INa Ilia articulate or fuse with each other below L-5 vertebra, severely shortening transverse pelvic diameter III Subtotal SA; at least S-1 is present, sacrum lacks four, three, two, or one of its caudal segments, ilia articulate with sides of rudimentary sacrum, maintaining normal transverse pelvic diameter
IV Hemisacrum IVA Total hemisacrum; all sacral segments present on one side, but entire opposite side is missing IVB Subtotal hemisacrum, unilateral; all sacral segments present on one side, only part of opposite side is missing IVC Subtotal hemisacrum, bilateral; part of each side is missing but to different extents V Coccygeal agenesis VA Total VB Subtotal
Disorders of notochordal formation Segmental spinal dysgenesis The clinical–radiologic definition of segmental spinal dysgenesis includes several entities: segmental agenesis or dysgenesis of the thoracic or lumbar spine, segmental abnormality of the spinal cord or nerve roots, congenital paraparesis or paraplegia, and congenital lower limb deformities. Three-dimensional CT reconstruction image (A) in Three-dimensional CT 4-year-old girl and schematic illustration (B) show multiple reconstructions can be segmentation anomalies in lumbar spine (superior to helpful in showing various inferior beginning at level of arrow): partial sagittal partition, vertebral segmentation butterfly vertebra, hemivertebra, tripedicular vertebra, anomalies and widely separated butterfly vertebra
Congenital Spine and Spinal Cord Malformations—Pictorial Review
CONTENTS.. STAGES OF DEVELOPMENT OF VC formation of mesenchymal vc formation of cartilaginous vc ossification of vc
development begins during gastrulation when epiblastic cells migrate toward the cranial portion of the primitive streak, ingress through the primitive groove, and then migrate laterally as the prospective somitic mesoderm
stages Stage 1 formation of mesenchymal vertebral column : 4th week 1.Migration of sclerotomes. Differentiation ofsclerotomic segments Each segments differentiated into Cephalic part (less condensed) Caudal part (more condensed)
3. Development of intervertebraldiscs Densely packed cell move cranially to the middle part of each segments Form peripheral part annulus fibrosus Enclosed notochord expands and undergo mucoid degeneration Form central part – nucleus pulposus
4. Development of the body ofvertebrae Caudal remained part fuse with cephalic part adjacent to it to form mesenchymal centrum Notochord degenerates and disappears when surrounded by vertebral body
5. Development of neural arch Sclerotomic tissue migrate backward from both side of centrum and surround neural tube. Neural spine forms at meeting point of neural arch Sclerotomic tissue also extends laterally from both sides of centrum form 2 processes Costal (ventral) Transverse (dorsal)
Stage 2Stage of formation of cartilaginous vertebral column 6th week 2 centers of chondrification in each Centrum appear Fuse together at the end of embryonic period (8th week) form cartilaginous centrum – Centers of chondrification appear in neural arhes and fuse with each other and centrum – Chondrification spreads until a cartilaginous vertebral column formed
Stages of ossification Comprises of 2 stages: 1. primary ossification center 2. secondary ossification center Primary ossification center at the end of 8th week. 3 ossification centers are present by the end of embryonic period one in the centrum one in the neural arch
Process: bony halves of the vertebral arch fuse together during the first 3 to 5 years the arches articulate with the centrum at cartilaginous neurocentral joints these joints dissapear when vertebral arches fuses with the centrum during the 3rd to 6th years
Secondary ossification center Time of development: after pubertythe 5 secondary ossification center appears at, 1. tip of spinous process 2. tip of each transverse process 3. superior rim of the vertebral body 4. inferior rim of the vertebral body
Fate of notochord Cranial part: merged with basilar part of occipital bone & posterior part of body of sphenoid Notochord located in the vertebra undergo degeneration and disappear The ones located in between undergo mucoid degeneration to form nucleus pulposus
Fate of the costal process Costal process results from ventrolateral outgrowth of the caudal, denser half of a sclerotome. In the cervical region: form anterior and lateral boundary of the foramen transversum In the thoracic region: form the ribs In the lumbar region: fuse with the transverse process In the upper sacral region: they unite to form the anterior portion of the ala of sacrum
Spina bifidaCause: incomplete fusion ofhalves of the vertebral archesresulting in midline defectusually in lumbosacralregionFeature: It varies, butgenerally the small bones(vertebrae) that make up thespine don’t form fully andmay have gaps betweenthem.
Congenital Spinal Deformity caused by anomalous vertebral development in the embryo simple and benign, causing no spinal deformity, or they may be complex, producing severe spinal deformity or even cor pulmonale or paraplegia.
On basic developmental pathogenesis,divided into the following 3 categories: Malformation a failure of the embryologic differentiation and/or development of a specific anatomic structure, causing it to be absent or improperly formed before the fetal period commences formation of a hemivertebra. Disruption destruction of an anatomic feature that formed normally during the embryonic period. This phenomenon, resulting in a structural defect, limb…. Deformation an alteration in the shape or structure of an individual vertebra or of the entire spine during the fetal and/or postnatal periods, after the involved regions initial, normal differentiation
Defects of formation may beclassified as follows: Anterior formation failure - This results in kyphosis, which is sharply angulated. Posterior formation failure - This is rare but can produce a lordotic curve. Lateral formation failure - This occurs frequently and produces the classic hemivertebrae of congenital scoliosis
Schematic drawing depicting thedevelopment ofnormal and abnormal vertebral bodies
Vertebral Body ConfigurationsCongenital B. Hemivertebra Asomia (A genesis) Unilateral wedge vertebra is due to lack of ossification of one-half of the body apex of the wedge reaching the midplane Scoliosis is often present
Metametric hemivertebrae in the lowerDorsal hemivertebra involving Li lumbar spine with “mermaid” deformity of the lower extremities
Metametric hemivertebrae in the lowerDorsal hemivertebra involving Li lumbar spine with “mermaid” deformity of the lower extremities
“Butterfly” vertebra involving L4Vertebrae with coronal clefts.
(A) Block vertebra with congenital fusion ofC4 andCS Note the presence of a “waist” at the site offusion (arrow). (B) Acquired vertebral body fusionof CS and C6.
HemivertebraCause: failure of one of thechondrofication center to appearand subsequent failure of half ofvertebra to formFeature: defective vertebra producescoliosis ( lateral curvature)Most likely to cause neurologicproblems
Sacralization of 5th lumbar vertebra Cause: 5th lumbar is fused with the sacrum Feature: number of lumbar vertebra is 4 and the sacrum is formed of 6 vertebra
Lumbrization of first piece ofsacrum to form separate vertebra Cause: separation of first piece of sacrum to form separate vertebra Feature: number of lumbar vertebra is 6 and the sacrum is only formed of 4 sacral vertebra
Congenital Kyphosis Two types of congenital kyphosis exist: defects of segmentation defects of formation Defects of segmentation occur most often in midthoracic or thoracolumbar regions and may involve 2-8 levels . produce a round kyphosis
Congenital Scoliosis lateral curvature of the spine that is caused by congenital anomalies of vertebral development classified according to the types of anomalies. Failure of formation Partial failure of formation (wedge vertebra) Complete failure of formation (hemivertebra)
Failure of segmentation (see image below) Unilateral failure of segmentation (unilateral unsegmented bar) Bilateral failure of segmentation (block vertebra)Mixed (see image below)
Congenital Lordosis least common of the 3 major patterns of congenital spinal deformity caused by a failure of posterior segmentation in the presence of anterior active growth usually is progressive Treatment of congenital lordosis is purely surgical.
•We can summarize above notes as follows: 1.The vertebra is intersegmental structure made up from portions of two somites the position of the somite is represented by intervertebral disc. 2.The transverse processes and the ribs are intersegmental structures. They separate the muscles derived from two adjoining myotomes. 3.Spinal nerves are segmental structures. They emerge from between two adjacent vertebrae and lie between two adjacent ribs. 4.The blood vessels supplying the structures derived from the myotome are intersegmental like vertebrae. Therefore the intercostal and lumbar arteries lie opposite the vertebral bodies
Imaging of the bony spine requires methods different from those used to image the spinal canal and its contents. Age influence the choice of modality The best way to image skeletal anomalies : plain radiography combined with conventional tomography Spinal malformations :best performed by MRI Skeletal scintigraphy with technetium-99m diphosphonates has high sensitivity but low specificity In the evaluation of the spinal canal, ultrasonography is limited to the neonatal period, though a spinal defect covered with soft tissue may be imaged well into adult life Fetal ultrasonography is increasingly used as a primary screening tool for NTDs, usually at about 18 weeks gestational age
Limitations of techniques X ray : Radiation delivers a high dose : gonads, particularly in female patients. Ultrasonography remains operator dependent; depends on the skill and experience and on the quality of the equipment. Transaxial CT images may be difficult to interpret because of the complex anatomy of the vertebral bodies, the presence of segmentation anomalies, and the presence of spinal curvature abnormalities. , in as much as sagittal and coronal reconstruction now provide exquisite images of the spine. In parts of the developing world, MRI is not readily available In addition, use of MRI may not be possible in patients with claustrophobia, and it is contraindicated for some patients with implanted devices Children may require sedation.
Special concerns Neural tube defects (NTDs) exact emotional and economic toll on families and health care systems The tragedy is that NTDs are preventable simply by having women take a folic acid supplement during the 2 months before they become pregnant. 0.4 mg daily before conception and for the first 3 months of pregnancy, reduces the risk of having a baby with spina bifida. risk(4 mg) of folic acid.
SUMMARY Spinal dysraphism, or neural tube defect (NTD), is a broad term encompassing a heterogeneous group of congenital spinal anomalies, which result from defective closure of the neural tube early in fetal life and anomalous development of the caudal cell mass. can cause progressive neurologic deterioration. The anatomic features common to the entire group is an anomaly in the midline structures of the back, especially the absence of some of the neural arches, and defects of the skin, filum terminale, nerves, and spinal cord. classified as closed forms or open forms, open forms are often associated with hydrocephalus and Arnold-chiari malformation type II Spina bifida is described in the medieval literature, although the condition was recognized even earlier. Indeed, the association of foot deformities with lumbar or lumbosacral hypertrichosis may be the origin of the mythological figure of the satyr.
Spina bifida occulta is characterized by variable absence of several neural arches and various cutaneous abnormalities, such as lipoma, hemangioma, cutis aplasia, dermal sinus, or hairy patch, and it is often associated with a low-lying conus Whenever the conus lies below the L2-3 interspace in an infant, cord tethering should be considered. Patients with spina bifida occulta may present with scoliosis in later years. Approximately 95% of couples that have a fetus affected with ONTD have a negative family history.
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