Imaging in spinal dysraphism

Spinal dysraphism , classification , imaging and diagnosis

1. Dr.Pooja Junior Resident Department of Radiodiagnosis Azeezia Medical College Imaging in spinal dysraphism

2. Congenital malformations of the spine and spinal cord are generally referred to as spinal dysraphisms * Neural tube defects * Spina bifida In the spine, the most common congenital lesions diverse forms of spinal dysraphism diverse forms of caudal spinal anomalies

3. IMAGING MODALITIES MRI :IOC PLAIN RADIOGRAPH : bony defects , widened spinal canal , scoliosis , segmentation anomalies like block vertebra , butterfly vertebrae , bony spur (diastematomyelia ) USG: antenatal Dx – open widened neural arch , meningomyelocele sac , hydrocephalus . CT : bony spur

4. Spinal Cord Development Summarized in three basic embryologic stages The first stage : Gastrulation (the 2 or 3 week)  a bilaminar embryonic disk to a trilaminar disk. The second stage : primary neurulation (weeks 3–4)  the notochord and overlying ectoderm interact  neural plate . bends and folds  neural tube , which then closes bidirectional in a zipperlike manner The final stage : secondary neurulation (weeks 5–6),  a secondary neural tube is formed by the caudal cell mass . cavitation ,  the tip of the conus medullaris and filum terminale retrogressive differentiation.

5. 1. GASTRULATION

6. 2. Primary neurulation. Formation of the Neural Plate Shaping of the Neural Plate Bending of the Neural Plate F u s ion

7. Anterior neuropore close by Day 25 Posterior neuropore close by Day 27 Anencephaly Spina Bifida

8. Disjunction. Upon completion of disjunction, the cutaneous ectoderm fuses in the midline, dorsal to the closed neural tube . Failure leads to Myelomeningocele .

9. Canalization and retrogressive differentiation (synonym: secondary neurulation). Diagrammatic representation of proposed embryogenesis. 3.SECONDARY NERULATION

10. OPEN SPINAL DYSRAPHISM (OSD) There is a defect in the overlying skin, and the neural tissue is exposed to the environment. MYELOCELE AND MYELOMENINGOCELE Embryological defect : Complete nondisjunction of cutaneous ectoderm from neural ectoderm. Neural folds do not fuse in the midline to form neural tube. Remain in continuity with the cutaneous ectoderm. This exposed part of the spinal cord is NEURAL PLACODE . MC location : Lumbosacral region > thoraco - lumbar region Imaging usually not done(clinically obvious)

11. 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 MYELOCELE

12. Myelomeningocele. Axial schematic of myelomeningocele shows neural placode ( star ) protruding above skin surface due to expansion of underlying subarachnoid space ( arrow ). Myelomeningocele. Axial T2- weighted MR image Myelomeningocele. Sagittal T2- weighted MR image).

13. Myelocele. Axial schematic of myelocele shows neural placode ( arrow ) flush with skin surface. Myelocele. Axial 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

14. HEMIMYELOMENINGOCELE AND HEMIMYELOCELE Hemimyelomeningoceles and hemimyeloceles can also occur but are extremely rare . These conditions occur when a myelomeningocele or myelocele is associated with diastematomyelia (cord splitting) and one hemicord fails to neurulate.

15. Placode ulceration and infection are leading causes of mortality in the untreated newborn, affected patients are operated on soon after birth. MRI investigation should be performed whenever possible to obtain: anatomic characterization of the various components of the malformation, especially regarding the relationships between the placode and nerve roots. presurgical evaluation of the entity and morphology of the malformation sequence ( hydromyelia , Chiari-II malformation, and associated hydrocephalus ) identification of rare cases with associated cord splitting ( hemimyelomeningoceles and hemimyeloceles )

16. All patients with OSDs also harbor a Chiari -II malformation, which is an element, rather than an associated feature, of the disease commonly called “ myelomeningocele ,” as well as of the other forms of OSDs

17. CLOSED SPINAL DYSRAPHISM

18. CLOSED SPINAL DYSRAPHISMS WITH A SUBCUTANEOUS MASS Lipoma with dorsal defects Myelocystocele(Ter m inal or cervical) Meningocele Cervical myelomeningocele

19. 1.Lipomas with a dural defect lipomyeloceles and lipomyelomeningoceles . defect in primary neurulation whereby mesenchymal tissue enters the neural tube and forms lipomatous tissue Characterized clinically by the presence of a subcutaneous fatty mass above the intergluteal crease . Diff both based on lipoma – placode interface Lipomyelocele : interface within spinal canal Lipomyelomenigocele : Outside the spinal canal due to sub- arachnoid space expansion.

20. Fig. 4—Lipomyelocele. A, Axial schematic of lipomyelocele shows placode –lipoma interface (arrow) lies within spinal canal. B, Axial T2-weighted MR image in 3-year-old girl shows placode –lipoma interface (arrow) within spinal canal, characteristic for lipomyelocele . C, 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.

21. Fig. 5—Lipomyelomeningocele. A, Axial schematic of lipomyelomeningocele shows placode –lipoma interface (arrow) lies outside of spinal canal due to expansion of subarachnoid space. B, 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.

22. the hairy tuft overlying subcutaneous lipomas

23. 2. MENINGOCELE : herniation of CSF filled sac lined by dura and arachnoid matter . Spinal cord not located within a meningocele but may be tethered to the neck of the sac Posterior meningocele : posterior spina bifida  Lumbar/sacral Anterior : Pre-sacral mostly

24. Fig. 6—Posterior meningocele . A, Sagittal T1-weighted MR image in in 12-month-old girl shows posterior herniation of CSF-filled sac (arrow) in occipital region, consistent with posterior meningocele . B, Sagittal T2-weighted MR image in 5-year-old boy shows large posterior meningocele (arrow) in cervical region. C, Sagittal T2-weighted MR image in 30-month-old girl shows small posterior meningocele (arrow) in lumbar region.

25. ANTERIOR MENINGOCELE

26. 3.Myelocystocele Myelocystoceles are rare malformations composed of a herniation of the spinal cord , containing a hydromyelic cavity, within a meningocele . Myelocystoceles are classified into terminal and nonterminal , depending on whether the malformation involves the apex of the conus medullaris or an intermediate segment of the spinal cord.

27. TERMINAL MYELOCYSTOCELE M Y E L OC Y S TOCELE ( N O N TERMINAL) Herniation of large terminal syrinx (syringocele) into a posterior meningocele through a posterior spinal defect is referred to as a terminal . The terminal syrinx and meningocele components do not usually communicate with each other Dilated central canal herniates through a posterior spina bifida defect. covered with skin MC -cervical or cervicothoracic regions

28. Fig. 8—Terminal myelocystocele . A, Sagittal schematic of terminal myelocystocele shows terminal syrinx (star) herniating into large posterior meningocele (arrows). B and C, Sagittal (B) and axial (C) 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, B).

29. NON TERMINAL MYE L OC Y S T OCELE —Schematic of nonterminal myelocystocele shows herniation of dilated central canal through posterior spinal defect.

30. Closed Spinal Dysraphisms Without a Subcutaneous Mass COMPLEX DYSRAPHIC STATES A)Disorders of midline notochordal integration Dorsal neurentericfistula, Neurenteric cyst Diastematomyelia, B)Disorders of notochordal formation, Caudal agenesis Segmental spinal dysgenesis. SIMPLE DYSRAPHIC STATES Intradural lipoma, Filar lipoma, Tight filum terminale Persistent terminal ventricle Dermal sinus.

31. 1. LIPOMA 2 Types : Intradural lipoma and Filar lipoma Embryological defect : focal premature disjunction of epidermal from neural ectoderm. 1. INTRADURAL LIPOMA Lipoma within the dural sac MC : Lumbosacral spine a/w tethered-cord syndrome 2. FILAR LIPOMA Fibrolipomatous thickening of the filum terminale is referred to as a filar lipoma. MR : T1 hyperintense signal + thickened filum terminale

32. 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 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.

33. 3. TIGHT FILUM TERMINALE hypertrophy and shortening of the filum terminale EMBRYOLOGY : incomplete involution of the distal spinal cord during embryogenesis. 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 dis c level 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.

34. Persistence of a small, ependymal lined cavity within the conus medullaris. It is the widest part of the central canal at the level of conus point of union between the portion of the central canal made by neurulation and the portion made by canalization of the caudal cell mass  Imaging : Location – above the filum terminale and lack of contrast enhancment Persistent terminal ventricle. A and B, Sagittal T2-weighted (A) and sagittal T1-weighted contrast-enhanced (B) MR images show persistent terminal ventricle as cystic structure (arrows) at inferior aspect of conus medullaris, which does not enhanc e 4. PERSISTENT TERMINAL VENTRICLE

35. 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. MC : Lumbo sacral region C/F : midline dimple , hairy naevus , hyperpigmented patch /capillary hemangioma Infectious complication if not surgically treated 5.DERMAL SINUS

36. Fig. 14—Dermal sinus. A and B, Sagittal schematic (A) and sagittal T2-weighted MR image (B) 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). C, Axial T2-weighted MR image from same patient as in B shows posterior location of hyperintense dermoid (arrow).

37. COMPLEX DYSRAPHIC STATES DISORDERS OF MIDLINE NOTOCHORDAL INTEGRATION Dorsal enteric fistula, Neurenteric cyst Diastematomyelia, DISORDERS OF NOTOCHORDAL FORMATION Caudal agenesis Segmental spinal dysgenesis . { Gastrulation is characterized by the development of the notochord, a potent inductor that is involved in the formation of not only the spine and spinal cord, but also of several other organs and structures in the human body; therefore, spinal dysraphisms originating during this period will characteristically show a complex picture in which not only the spinal cord, but also other organs are impaired. Hence disorders of gastrulation are also called complex dysraphic states}

38. DISORDERS OF MIDLINE NOTOCHORDAL INTEGRATION DORSAL ENTERIC FISTULA Abnormal connection between the skin surface and bowel. 2. NEURENTERIC CYSTS Localized form of dorsal enteric fistula ~ Mucin-secreting epithelium (~GI tract ) lined cyst MC : cervico-thoracic spine anterior to spinal cord

39. Fig. 15—Neurenteric cyst in 3-year-old girl. A and B, Sagittal T2-weighted (A) and axial T1-weighted (B) MR images show bilobed neurenteric cyst (arrows) extending from central canal into posterior mediastinum . C, Three-dimensional CT reconstruction image shows osseous opening (arrow) through which neurenteric cyst passes. This opening is called the Kovalevsky canal .

40. 3.DIASTEMATOMYELIA Separation of the spinal cord into two hemicords The two hemicords are usually symmetric, although the length of separation is variable. Type 1 : Dual Dural-Arachnoid Tubes (Pang Type I) : the two hemicords are located within individual dural sacs separated by an osseous or cartilaginous septum In Type 2 : Single Dural-Arachnoid Tube (Pang Type II) : Single dural tube containing two hemicords, sometimes with an intervening fibrous septum C/F : Hairy tuft , scoliosis , tethered cord syndrome.

41. Fig. 16—Type 1 diastematomyelia . A–C, 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 .

42. Fig. 17—Type 2 diastematomyelia . A–C, Sagittal T1-weighted (A), coronal T1-weighted (B), and axial T2-weighted (C) MR images in 9-year-old girl 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.

43. II. DISORDERS OF NOTOCHORDAL FORMATION 1 . CAUDAL AGENESIS Total or partial agenesis of the spinal column A/w anal imperforation, genital anomalies, renal dysplasia or aplasia, pulmonary hypoplasia, or limb abnormalities. 2 Types Type 1 : high position of conus + abrupt termination of conus medullaris(D11/12)+ sig neuro deficit Type II : low position(L1) + tethering of conus medullaris

44. CAUDAL AGENESIS , Fig. 18A   — Caudal agenesis. Sagittal T2-weighted ( A ) and sagittal T1-weighted ( B ) MR images in 6-month-old girl 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.

45. CAUDAL REGRESSION SYNDROME Partial agenesis of the thoracolumbosacral spine Imperforate anus Malformed genitalia Bilateral renal dysplasia or aplasia Pulmonary hypoplasia Extreme external rotation and fusion of the lower extremities (sirenomelia) Sacral agenesis arises early in gestation, probably before the 10th week of gestation a/w diabetes mellitus,

46. CLASSIFICATION OF LUMBOSACRAL AGENESIS Type I : Total sacral agenesis + some lumbar vertebrae missing Type II: Total SA + lumbar vertebrae not involved, severely shortening transverse pelvic diameter Type III : Subtotal SA + a t least S-1 is present. Type 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 Type V: Coccygeal agenesis VA Total VB Subtotal

47. 2.SEGMENTAL SPINAL DYSGENESIS Segmental agenesis or dysgenesis of the thoracic or lumbar spine + segmental abnormality of the spinal cord / nerve roots + congenital paraparesis / paraplegia, + congenital lower limb deformities. Three-dimensional CT reconstruction image ( A) in 4-year-old girl and schematic illustration (B) show multiple segmentation anomalies in lumbar spine (superior to inferior beginning at level of arrow ): partial sagittal partition , butterfly vertebra , hemivertebra , tripedicular vertebra widely separated butterfly vertebra