Congenital Spine and Spinal Cord Malformations Pictorial Review

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1 JR Integrative Imaging LIFELONG LERNING FOR RDIOLOGY ongenital Spine and Spinal ord Malformations Pictorial Review Stephanie L. Rufener 1,2, Mohannad Ibrahim 2, harles. Raybaud 3, Hemant. Parmar 2 Downloaded from by on 01/20/18 from IP address opyright RRS. For personal use only; all rights reserved Objective ongenital abnormalities of the spine and spinal cord are referred to as spinal dysraphisms. This article reviews normal embryological development of the spine and spinal cord and the imaging findings of congenital abnormalities of the spine and spinal cord with particular focus on MRI. onclusion Knowledge of the normal development of the spine and spinal cord provides a framework for understanding these complex entities. Spinal ord Development Spinal development can be summarized in three basic embryologic stages [1, 2]. The first stage is gastrulation and occurs during the second or third week of embryonic development. Gastrulation involves conversion of the embryonic disk from a bilaminar disk to a trilaminar disk composed of ectoderm, mesoderm, and endoderm. The second stage in spinal development is primary neurulation (weeks 3 4) in which 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 bidirectionally in a zipperlike manner (Fig. 1). The final stage of spinal development is secondary neurulation (weeks 5 6). During this stage, a secondary neural tube is formed by the caudal cell mass. The secondary neural tube is initially solid and subsequently undergoes cavitation, eventually forming the tip of the conus medullaris and filum terminale by a process called retrogressive differentiation. bnormalities in any of these steps can lead to spine or spinal cord malformations. ategorization of Spinal Dysraphisms Spinal dysraphisms can be broadly categorized into open and closed types [1 3]. 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. losed spinal dysraphisms can be further subcategorized on the basis of the presence or absence of a subcutaneous mass [4]. ppendix 1 summarizes the key features of open and closed spinal dysraphisms. Open Spinal Dysraphisms Myelomeningocele and myelocele Myelomeningoceles and myeloceles are caused by defective closure of the primary neural tube and are characterized clinically by exposure of the neural placode through a midline skin defect on the back. Myelomeningoceles account for more than 98% of open spinal dysraphisms [1]. Myeloceles are rare. 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 [2]. The neural placode protrudes above the skin surface with a myelomeningocele (Fig. 2) and is flush with the skin surface with a myelocele (Fig. 3). Hemimyelomeningocele and hemimyelocele Hemimyelomeningoceles and hemimyeloceles can also occur but are extremely rare [5]. These conditions occur when a myelomeningocele or myelocele is associated with diastematomyelia (cord splitting) and one hemicord fails to neurulate. losed Spinal Dysraphisms With a Subcutaneous Mass Lipomas with a dural defect Lipomas with a dural defect include both lipomyeloceles and lipomyelomeningoceles. These abnormalities result from a defect in primary neurulation whereby mesenchymal tissue enters the neural tube and forms lipomatous tissue [6]. Lipomyeloceles and lipomyelomeningoceles are characterized clinically by the presence of a subcutaneous fatty mass above the intergluteal crease. The main differentiating feature between a lipomy Keywords: congenital spinal cord malformation, congenital spine malformation, spinal dysraphism, spine DOI: /JR Received November 20, 2008; accepted after revision March 14, Presented at the 2008 annual meeting of the merican Roentgen Ray Society, Washington, D. 1 Present address: Mount Scott Diagnostic Imaging enter, 9200 SE 91st ve., Ste. 330, Portland, OR ddress correspondence to S. L. Rufener (stephanie_rufener@yahoo.com). 2 Department of Radiology, University of Michigan Hospital, nn rbor, MI. 3 Department of Pediatric Neuroradiology, The Hospital for Sick hildren, Toronto, ON, anada. JR 2010;194:S26 S X/10/1943 S26 merican Roentgen Ray Society S26 JR:194, March 2010

2 ongenital Spine and Spinal ord Malformations Fig. 1 Illustrations of primary neurulation. D, Notochord (circle) interacts with overlying ectoderm to form neural plate (dark green), which then bends to form neural tube that ultimately closes in zipperlike fashion. Downloaded from by on 01/20/18 from IP address opyright RRS. For personal use only; all rights reserved elocele and lipomyelomeningocele is the position of the placode lipoma interface [4]. With a lipomyelocele, the placode lipoma interface lies within the spinal canal (Fig. 4). With a lipomyelomeningocele, the placode lipoma interface lies outside of the spinal canal due to expansion of the subarachnoid space (Fig. 5). Fig. 2 Myelomeningocele., xial schematic of myelomeningocele shows neural placode (star) protruding above skin surface due to expansion of underlying subarachnoid space (arrow)., xial T2-weighted MR image in 1-day-old boy shows neural placode (black arrow) extending above skin surface due to expansion of underlying subarachnoid space (white arrow), which is characteristic of myelomeningocele., Sagittal T2-weighted MR image from same patient as in with myelomeningocele shows neural placode (white arrow) protruding above skin surface due to expansion of underlying subarachnoid space (black arrow). D Meningocele Herniation of a SF-filled sac lined by dura and arachnoid mater is referred to as a meningocele. The spinal cord is not located within a meningocele but may be tethered to the neck of the SF-filled sac. Posterior meningoceles herniate through a posterior spina bifida (osseous defect of posterior spinal elements) and are usually JR:194, March 2010 S27

3 Rufener et al. Fig. 3 Myelocele., xial schematic of myelocele shows neural placode (arrow) flush with skin surface., xial T2-weighted MR image in 1-day-old girl shows exposed neural placode (arrow) that is flush with skin surface, consistent with myelocele. There is no expansion of underlying subarachnoid space. Downloaded from by on 01/20/18 from IP address opyright RRS. For personal use only; all rights reserved Fig. 4 Lipomyelocele., xial schematic of lipomyelocele shows placode lipoma interface (arrow) lies within spinal canal., xial T2-weighted MR image in 3-year-old girl shows placode lipoma interface (arrow) within spinal canal, characteristic for lipomyelocele., Sagittal T1-weighted MR image in 3-year-old girl with lipomyelocele shows subcutaneous fatty mass (black arrow) and placode lipoma interface (white arrow) within spinal canal. Fig. 5 Lipomyelomeningocele., xial schematic of lipomyelomeningocele shows placode lipoma interface (arrow) lies outside of spinal canal due to expansion of subarachnoid space., xial 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. S28 JR:194, March 2010

4 ongenital Spine and Spinal ord Malformations Downloaded from by on 01/20/18 from IP address opyright RRS. For personal use only; all rights reserved lumbar or sacral in location but also can occur in the occipital and cervical regions (Fig. 6). nterior meningoceles are usually presacral in location but also can occur elsewhere [7] (Fig. 7). Terminal myelocystocele Herniation of large terminal syrinx (syringocele) into a posterior meningocele through a Fig. 6 Posterior meningocele., Sagittal T1-weighted MR image in in 12-month-old girl shows posterior herniation of SF-filled sac (arrow) in occipital region, consistent with posterior meningocele., Sagittal T2-weighted MR image in 5-year-old boy shows large posterior meningocele (arrow) in cervical region., Sagittal T2-weighted MR image in 30-month-old girl shows small posterior meningocele (arrow) in lumbar region. Fig. 7 Meningocele. and, Sagittal () and axial () T2-weighted MR images in 6-month-old boy show small anterior meningocele (arrows). posterior spinal defect is referred to as a terminal myelocystocele [2] (Fig. 8). The terminal syrinx component communicates with the central canal, and the meningocele component communicates with the subarachnoid space. The terminal syrinx and meningocele components do not usually communicate with each other [8]. JR:194, March 2010 S29

5 Rufener et al. Downloaded from by on 01/20/18 from IP address opyright RRS. For personal use only; all rights reserved Myelocystocele nonterminal myelocystocele occurs when a dilated central canal herniates through a posterior spina bifida defect (Fig. 9). Myelocystoceles are covered with skin and can occur anywhere but are most commonly seen in the cervical or cervicothoracic regions [9]. Fig. 8 Terminal myelocystocele., Sagittal schematic of terminal myelocystocele shows terminal syrinx (star) herniating into large posterior meningocele (arrows). and, Sagittal () and axial () T2-weighted MR images in 1-month-old girl show terminal syrinx (white arrows) protruding through large posterior spina bifida defect and herniating into posterior meningocele component (black arrows). Sagittal image shows turbulent flow in more anterior meningocele component (star, ). losed Spinal Dysraphisms Without a Subcutaneous Mass losed spinal dysraphisms without a subcutaneous mass can be subcategorized into simple and complex dysraphic states. Simple dysraphic states Simple dysraphic states consist of intradural lipoma, filar lipoma, tight filum terminale, persistent terminal ventricle, and dermal sinus. n intradural lipoma refers to a lipoma located along the dorsal midline that is contained within the dural sac (Fig. 10). No open spinal dysraphism is present. Intradural lipomas are most commonly lumbosacral in location and usually present with tethered-cord syndrome, a clinical syndrome of progressive neurologic abnormalities in the setting of traction on a low-lying conus medullaris [2]. 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 (Fig. 11). Filar lipomas can be considered a normal variant if there is no clinical evidence of tethered-cord syndrome [10, 11]. Tight filum terminale is characterized by hypertrophy and shortening of the filum terminale (Fig. 12). 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 [2]. Persistence of a small, ependymal lined cavity within the conus medullaris is referred to as a persistent terminal ventricle (Fig. 13). Key imaging features include location immediately above the filum terminale and lack of contrast enhancement, which differentiate this entity from other cystic lesions of the conus medullaris [12]. Fig. 9 Schematic of nonterminal myelocystocele shows herniation of dilated central canal through posterior spinal defect. S30 JR:194, March 2010

6 ongenital Spine and Spinal ord Malformations Fig. 10 Intradural lipoma. and, Sagittal T1-weighted () and sagittal T2- weighted fat-saturated () MR images in 6-year-old girl show large intradural lipoma (arrows), which is hyperintense on T1-weighted image and hypointense on T2-weighted fat-saturated image. Lipoma is attached to conus medullaris, which is low lying. Downloaded from by on 01/20/18 from IP address opyright RRS. For personal use only; all rights reserved Fig. 11 Filar lipoma. and, Sagittal () and axial () T1-weighted MR images in 2-year-old boy with filar lipoma (arrows), which has characteristic T1 hyperintensity and marked thickening of filum terminale. JR:194, March 2010 S31

7 Rufener et al. Downloaded from by on 01/20/18 from IP address opyright RRS. For personal use only; all rights reserved dermal sinus is an epithelial lined fistula that connects neural tissue or meninges to the skin surface. It occurs most frequently in the lumbosacral region and is often associated with a spinal dermoid at the level of the cauda equina or conus medullaris (Fig. 14). linically, patients present with a midline dimple and may also have an associated hairy nevus, hyperpigmented patch, or capillary hemangioma [13]. Surgical repair is of great importance because the fistulous connection between neural tissue and the skin surface can result in infectious complications such as meningitis and abscess. omplex dysraphic states omplex dysraphic states can be divided into two categories: disorders of midline notochordal integration, which include dorsal enteric fistula, neurenteric cyst, and diastematomyelia, and disorders of notochordal formation, which include caudal agenesis and segmental spinal dysgenesis. Disorders of midline notochordal integration: Dorsal enteric fistula and neurenteric cyst dorsal enteric fistula occurs when there is an abnormal connection between the skin surface and bowel. Neurenteric cysts represent a more localized form of dorsal enteric fistula (Fig. 15). 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 [14]. 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 1, the two hemicords are located within individual dural tubes separated by an osseous or cartilaginous septum (Fig. 16). In type 2, there is a single dural tube containing two hemicords, sometimes with an intervening fibrous septum [15] (Fig. 17). Diastematomyelia can present clinically with scoliosis and Fig. 12 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. Fig. 13 Persistent terminal ventricle. and, Sagittal T2-weighted () and sagittal T1-weighted contrast-enhanced () MR images in 12-month-old boy show persistent terminal ventricle as cystic structure (arrows) at inferior aspect of conus medullaris, which does not enhance. S32 JR:194, March 2010

8 ongenital Spine and Spinal ord Malformations Downloaded from by on 01/20/18 from IP address opyright RRS. For personal use only; all rights reserved Fig. 14 Dermal sinus. and, Sagittal schematic () and sagittal T2-weighted MR image () in 9-year-old girl show intradural dermoid (stars) with tract extending from central canal to skin surface (black arrows). Note tenting of dural sac at origin of dermal sinus (white arrows)., xial T2-weighted MR image from same patient as in shows posterior location of hyperintense dermoid (arrow). Fig. 15 Neurenteric cyst in 3-year-old girl. and, Sagittal T2-weighted () and axial T1-weighted () MR images show bilobed neurenteric cyst (arrows) extending from central canal into posterior mediastinum., Three-dimensional T reconstruction image shows osseous opening (arrow) through which neurenteric cyst passes. This opening is called the Kovalevsky canal. JR:194, March 2010 S33

9 Rufener et al. Downloaded from by on 01/20/18 from IP address opyright RRS. For personal use only; all rights reserved Fig. 16 Type 1 diastematomyelia., Sagittal T2-weighted MR (), axial T2-weighted MR (), and axial T with bone algorithm () images in 6-year-old boy show two dural tubes separated by osseous bridge (arrows), which is characteristic for type 1 diastematomyelia. Fig. 17 Type 2 diastematomyelia., Sagittal T1-weighted (), coronal T1-weighted (), and axial T2-weighted () MR images in 9-year-old girl show splitting of distal cord into two hemicords (white arrows, and ) within single dural tube, which is characteristic for type 2 diastematomyelia. Incidental filum lipoma (black arrows, and ) is present as well. S34 JR:194, March 2010

10 ongenital Spine and Spinal ord Malformations Fig. 18 audal agenesis. and, Sagittal T2-weighted () and sagittal T1- weighted () MR images in 6-month-old girl show agenesis of sacrum. onus 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. Downloaded from by on 01/20/18 from IP address opyright RRS. For personal use only; all rights reserved Fig. 19 Vertebral segmentation anomalies. and, Three-dimensional T reconstruction image () in 4-year-old girl and schematic illustration () show multiple segmentation anomalies in lumbar spine (superior to inferior beginning at level of arrow): partial sagittal partition, butterfly vertebra, hemivertebra, tripedicular vertebra, and widely separated butterfly vertebra. JR:194, March 2010 S35

11 Rufener et al. Downloaded from by on 01/20/18 from IP address opyright RRS. For personal use only; all rights reserved tethered-cord syndrome. hairy tuft on the patient s back can be a distinctive finding on physical examination [16]. Disorders of notochordal formation: audal agenesis audal agenesis refers to total or partial agenesis of the spinal column (Fig. 18) and may be associated with the following: anal imperforation, genital anomalies, renal dysplasia or aplasia, pulmonary hypoplasia, or limb abnormalities. audal agenesis can be categorized into two types. In type 1, there is a high position and abrupt termination of the conus medullaris. In type 2, there is a low position and tethering of the conus medullaris [17]. 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 T reconstructions can be helpful in showing various vertebral segmentation anomalies [18] (Fig. 19). onclusion ongenital malformations of the spine and spinal cord can be complex and variable in imaging appearance. n organized approach to imaging findings with consideration of clinical and developmental factors allows greater ease in diagnosis. cknowledgment The authors thank nne Philips, former medical illustrator from the Department of Radiology at the University of Michigan, for providing various illustrations used in this article. References 1. Tortori-Donati P, Rossi, ama. Spinal dysraphism: a review of neuroradiological features with embryological correlations and proposal for a new classification. Neuroradiology 2000; 42: arkovich J. Pediatric neuroradiology, 4th ed. Philadelphia, P: Lippincott Williams & Wilkins, 2005: nderson FM. Occult spinal dysraphisms: diagnosis and management. J Pediatr 1968; 73: Rossi, iancheri R, ama, Piatelli G, Ravegnani M, Tortori-Donati P. Imaging in spine and spinal cord malformations. Eur J Radiol 2004; 50: Parmar H, Shah J, Patkar D, Maheshwari M. Diastematomyelia and terminal myelocystocele arising from one hemicord: case report. lin Imaging 2003; 27: Naidich TP, McLone DG, Mutleur S. new understanding of dorsal dysraphism with lipoma (lipomyeloschisis): radiological evaluation and surgical correction. JR 1983; 140: Lee KS, Gower DJ, McWhorter JM, lbertson D. The role of MR imaging in the diagnosis and treatment of anterior sacral meningocele: report of 2 cases. J Neurosurg 1988; 69: McLone DG, Niadich TP. Terminal myelocystocele. Neurosurgery 1985; 16: Peacock WJ, Murovic J. Magnetic resonance imaging in myelocystoceles: report of two cases. J Neurosurg 1989; 70: rown E, Matthes J, azan III, Jinkins JR. Prevalence of incidental intraspinal lipoma of the lumbosacral spine as determined by MRI. Spine 1994; 19: Guiffrè R. Intradural spinal lipomas: review of the literature (99 cases) and report of an additional case. cta Neurochir (Wien) 1966; 14: oleman LT, Zimmerman R, Rorke L. Ventriculus terminalis of the conus medullaris: MR findings in children. JNR 1995; 16: Scotti G, Harwood-Nash D, Hoffman HJ. ongenital thoracic dermal sinuses: diagnosis by computer-assisted metrizamide myelography. J omput ssist Tomogr 1980; 4: Harris P, Dias MS, rockmeyer DL, Townsend JJ, Willis K, pfelbaum RI. Neurenteric cysts of the posterior fossa: recognition, management and embryogenesis. Neurosurgery 1991; 29: Pang D, Dias MS, hab-armada M. Split cord malformation. Part I. unified theory of embryogenesis for double spinal cord malformations. Neurosurgery 1992; 31: Schijman E. Split spinal cord malformations: report of 22 cases and review of the literature. hilds Nerv Syst 2003; 19: Nievelstein RJ, Valk J, Smit LME, Vermeji-Keers. MR of the caudal regression syndrome: embryologic implications. JNR 1994; 15: Tortori-Donati P, Fondelli M, Rossi, Raybaud, ama, apra V. Segmental spinal dysgenesis: neuroradiologic findings with clinical and embryologic correlation. JNR 1999; 20: S36 JR:194, March 2010

12 PPENDIX 1: Summary of Spinal Dysraphisms ongenital Spine and Spinal ord Malformations Downloaded from by on 01/20/18 from IP address opyright RRS. For personal use only; all rights reserved Open Spinal Dysraphisms: not covered by intact skin Myelocele Neural placode flush with skin surface Myelomeningocele Neural placode protrudes above skin surface Hemimyelocele Myelocele associated with diastematomyelia Hemimyelomeningocele Myelomeningocele associated with diastematomyelia losed Spinal Dysraphisms: covered by intact skin With a subcutaneous mass Lipomyelocele Placode lipoma interface within the spinal canal Lipomyelomeningocele Placode lipoma interface outside of the spinal canal Meningocele Herniation of SF-filled sac lined by dura Terminal myelocystocele Terminal syrinx herniating into posterior meningocele Myelocystocele Dilated central canal herniating through posterior spina bifida Without a subcutaneous mass Simple dysraphic states Intradural lipoma Lipoma within the dural sac Filar lipoma Fibrolipomatous thickening of filum Tight filum terminale Hypertrophy and shortening of filum Persistent terminal ventricle Persistent cavity within conus medullaris Dermal sinus Epithelial lined fistula between neural tissue and skin surface omplex dysraphic states Dorsal enteric fistula onnection between bowel and skin surface Neurenteric cyst More localized form of dorsal enteric fistula Diastematomyelia Separation of cord into two hemicords audal agenesis Total or partial agenesis of spinal column Segmental spinal dysgenesis Various segmentation anomalies FOR YOUR INFORMTION The reader s attention is directed to the Self-ssessment Module for this article, which appears on the following pages. JR:194, March 2010 S37