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ECR 2019 / C-1766
Diagnostic Dilemma in MR Imaging of Spinal Dysraphism
Congress: ECR 2019
Poster No.: C-1766
Type: Educational Exhibit
Keywords: Musculoskeletal spine, Paediatric, MR, Diagnostic procedure, Congenital
Authors: S. Nagarajan, G. Kathirvelu, D. Jaganathan, C. Paraman; Chennai/IN
DOI:10.26044/ecr2019/C-1766

Findings and procedure details

In MR imaging of spine, different techniques are used depending upon the clinical situation. For spinal dysraphisms , we acquire both T1W and T2W axial and sagittal images. T1WI demonstrate spinal cord without  associated artifacts from circulating CSF. T2-weighted images show cauda equina,filum terminale, adhesions and any bony or fibrous spurs. These sequences can be performed with and without fat saturation, as in selected cases fat suppression is helpful for assessment of intra-spinal fatty lesions. Important concept to remember is that a single patient may have multiple spinal anomalies. Therefore, it is important to image entire spine if cutaneous anomaly or vertebral anomaly suggests the presence of  malformation. Because of its multiplanar imaging and tissue characterization capabilities, MRI has greatly improved the diagnosis of spinal dysraphisms and has enhanced the possibility of earlier and case-tailored treatment. MRI is the initial imaging modality of choice because it is noninvasive and does not use ionizing radiation.

 

Classifications of spinal dysraphisms rely on correlation of radiological features with a specific derangement in normal developmental cascade. Spinal dysraphisms can be broadly categorized into open and closed types depending on integrity of skin overlying the defect.

Fig. 7: Clinico-radiological classification of Spinal dysraphisms
References: Govt Kilpauk Medical College Hospital, Govt Kilpauk Medical College Hospital , Kilpauk , Chennai - 10 , Tamilnadu. - Chennai/IN

In our review, we will compare some closely resembling entities and deal with the diagnostic dilemma in their diagnosis followed by some commonly encountered spinal dysraphisms.

Fig. 8: Review of spinal dysraphism
References: Govt Kilpauk Medical College Hospital, Govt Kilpauk Medical College Hospital , Kilpauk , Chennai - 10 , Tamilnadu. - Chennai/IN

DORSAL DERMAL SINUS

Background: Midline or paramedian sinus tract extending from skin surface. Midline dimple is most common presentation.

Embryological correlation: Focal nondisjunction of cutaneous ectoderm and neural ectoderm

Associated abnormalities: Epidermoid tumor and Epidural or Subdural abscess 

Protocol advice: Sagittal and Axial T1WI and T2WI

Imaging findings: Sinus tract appears hypointense to subcutaneous fat on both T1WI and T2WI. Tenting of dorsal dura indicates penetration. Intradural sinus tract is indistinguishable from cauda equina/filum.

Fig. 9: Dorsal dermal sinus: Sagittal T1WI and T2WI shows hypointense dermal sinus tract (red arrow) entering beginning at L4 level and coursing anteroinferior to become adherent to spinal cord. Serial axial T2 sections show clear subcutaneous hypointense tract (green arrow) but the intradural course of the sinus tract not clearly delineated.
References: Govt Kilpauk Medical College Hospital, Govt Kilpauk Medical College Hospital , Kilpauk , Chennai - 10 , Tamilnadu. - Chennai/IN
Fig. 10: Dorsal dermal sinus with extramedullary abscess: Diffusion restricting (*) T1 hypointense (#) and T2 hyperintense (~) extramedullary collection noted at lumbo sacral level pushing the spinal cord (^) anteriorly and diffuse cord edema (red arrow). Axial T1WI and T2WI shows a hypointense tract (yellow arrow) extending from the skin surface with invisible intra dural tract portion.Clinical image showing pin point appearence on the skin surface.
References: Govt Kilpauk Medical College Hospital, Govt Kilpauk Medical College Hospital , Kilpauk , Chennai - 10 , Tamilnadu. - Chennai/IN

DIAGNOSTIC CLUE: Hypointense sinus tract superimposed on hyperintense subcutaneous fat.

 

LIMITED DORSAL MYELOSCHISIS

Background: Distinct form of spinal dysraphism characterized by focal closed midline skin defect and fibro-neural tract connecting skin lesion to underlying spinal cord.

Embryological correlation: Interposition of mesodermal cells between the neural tube and cutaneous ectoderm after separation of these 2 layers, consequently forming a solid tract composed of mesenchymal tissue with or without neural tissue.

Associated abnormalities: Low-lying conus medullaris, Tethered cord syndrome, Intradural lipoma.

Protocol advice: Sagittal and Axial T1WI and T2WI

Types:  Saccular LDM consisting of a skin based cerebrospinal fluid sac topped with squamous epithelial dome or a thin membranous sac. Non-saccular LDM with a flat or sunken squamous epithelial crater or pit. 

Imaging findings: Intradural sinus tract is entirely or partially visible. Sinus tract appears hypointense to subcutaneous fat on both T1WI and T2WI.

Fig. 11: Saccular Limited dorsal myeloschisis: Axial images demonstrate a CSF signal intensity (yellow arrow) thin membranous sac. Serial Sagittal T2-weighted MR images show that the hypointense tract (red arrow) displaying a distinct hypointense round structure separate from the filum terminale or nerve roots is completely traceable in its entire course. The attachment site of the tract is the spinal cord just above the conus medullaris. A low-lying conus medullaris and dorsal tenting of the spinal cord at the tract-cord union are seen.
References: Govt Kilpauk Medical College Hospital, Govt Kilpauk Medical College Hospital , Kilpauk , Chennai - 10 , Tamilnadu. - Chennai/IN
Fig. 12: Non-saccular Limited dorsal myeloschisis : Sequential axial T2WI show tract with low signal intensity attached to the dorsal aspect of spinal cord. Sagittal T2WI demonstrates the dorsal tenting of the cord by the tract. Clinical image showing the typical cigarette burn appearence of limited dorsal myeloschisis.
References: Govt Kilpauk Medical College Hospital, Govt Kilpauk Medical College Hospital , Kilpauk , Chennai - 10 , Tamilnadu. - Chennai/IN

DIAGNOSTIC CLUE: Distinct intrathecal tract that attaches to the spinal cord above the conus medullaris and shows characteristic dorsal tenting of cord at tract-cord union.

 

Fig. 13: Diagnostic dilemma - Dorsal dermal sinus vs Limited dorsal myeloschisis
References: Govt Kilpauk Medical College Hospital, Govt Kilpauk Medical College Hospital , Kilpauk , Chennai - 10 , Tamilnadu. - Chennai/IN

 

CAUDAL REGRESSION SYNDROME

Background: Constellation of caudal developmental growth abnormalities with associated regional soft tissue anomalies.

Embryological correlation: Developmental abnormality involving caudal cell mass.

Associated abnormalities: Tethered cord syndrome, Diastematomyelia, Genitourinary anomalies.

Protocol advice: Sagittal and Axial T1WI and T2WI

Fig. 14: Types of Caudal Regression Syndrome
References: Govt Kilpauk Medical College Hospital, Govt Kilpauk Medical College Hospital , Kilpauk , Chennai - 10 , Tamilnadu. - Chennai/IN

Imaging findings:

     Group 1- Distal cord hypoplasia with severe sacral osseous agenesis

Fig. 15: Group 1 Caudal regression syndrome: Sagittal T1WI and T2WI depicts high truncated bulbous ending of cord (red arrow) with mild prominence of central canal of the cord in the lower dorsal level. Sagittal T2WI shows sacral agenesis involving the lower sacrum and coccyx vertebra (curved yellow arrow). Coronal T1WI demonstrates multiple vertebral segmentation fusion anomalies in the cervical and upper dorsal vertebra (yellow arrows) with scoliosis and convexity to right (yellow arrowhead).
References: Govt Kilpauk Medical College Hospital, Govt Kilpauk Medical College Hospital , Kilpauk , Chennai - 10 , Tamilnadu. - Chennai/IN

Group 2- Tapered low-lying distal cord with tethering and less severe sacral anomalies

Fig. 16: Group 2 Caudal regression syndrome: Sagittal T1WI and T2WI shows agenesis of sacrum (red arrow) involving the lower sacrum (from S3) and coccyx. Cord seen up to S2 level with a T1/T2 hyperintense lesion (lipoma – green arrow) in the inferior spinal canal. Neurogenic bladder with left hydroureteronephrosis (red arrowhead) changes.
References: Govt Kilpauk Medical College Hospital, Govt Kilpauk Medical College Hospital , Kilpauk , Chennai - 10 , Tamilnadu. - Chennai/IN

DIAGNOSTIC CLUE: Lumbosacral dysgenesis with abnormal distal spinal cord

 

 

SEGMENTAL SPINAL DYSGENESIS

Background: Localized agenesis or dysgenesis of lumbar or thoraco-lumbar spine, severe congenital kyphosis or kypho-scoliosis, and focal abnormalities of underlying spinal cord and nerve roots.

Embryological correlation:  Chordo-mesodermal derangement during gastrulation with incorrect axial specification.

Associated abnormalities: Diastematomyelia, Thickened filum terminale and tethered cord.

Protocol advice: Sagittal and Axial T1WI and T2WI

Imaging findings: Segmental agenesis or dysgenesis of thoracic or lumbar spine with segmental abnormality of spinal cord.

Fig. 17: Segmental spinal dysgenesis: Sagittal T2WI and coronal T1WI shows high bulbous ending of spinal cord at D11 vertebral level (yellow arrow) and lower cord seen separately in the lower spinal canal L5- S1 to S1 – S2 (green arrow). Sagittal T2WI demonstrates congenital cartilaginous fusion of posterior part of L3, L4 vertebral body (red arrow) and fusion of posterior elements of L3 and L4 (red arrowhead). Absence of lower segment of sacrum and entire coccyx (blue arrow).
References: Govt Kilpauk Medical College Hospital, Govt Kilpauk Medical College Hospital , Kilpauk , Chennai - 10 , Tamilnadu. - Chennai/IN

 

Diagnostic clue: Normal upper spinal cord that abruptly changes in caliber forming markedly thinned out or indiscernible middle cord segment devoid of nerve roots and a bulky, low-lying cord caudally.

 

Fig. 18: Diagnostic dilemma : Caudal regression syndrome vs Segmental spinal dysgenesis
References: Govt Kilpauk Medical College Hospital, Govt Kilpauk Medical College Hospital , Kilpauk , Chennai - 10 , Tamilnadu. - Chennai/IN

 

LIPOMYELOCELE & LIPOMYELOMENINGOCELE

Background: Lipomyelocele – Neural placode – lipoma complex contiguous with subcutaneous fat through dysraphic defect. Lipomyelomeningocele is lipomyelocele with associated meningocele causing displacement of neural placode outside spinal canal.

Embryological correlation: Premature disjunction of neural ectoderm from cutaneous ectoderm. 

Associated abnormalities: Vertebral segmentation anomalies, Terminal diastematomyelia, Anorectal and Genitourinary anomalies.

Protocol advice: Sagittal and axial T1WI and T2WI including entire sacrum. STIR or Chemical fat saturated sequences confirm fat components.

Imaging findings: LMMC-T1/T2 hyperintense lipoma contiguous with subcutaneous fat. Herniation of placode-lipoma complex immediately inferior to last intact lamina above dorsal defect. In STIR sequences fat appears hypointense. LMC- Placode lipoma complex is within spinal canal.

Fig. 19: Lipomyelomeningocele: Posterior spinal defect at D12-L1 with herniation of spinal cord & CSF(red arrow)and subcutaneous fat extends into spinal canal. Neural placode -lipoma interface (yellow arrow) lies outside the spinal canal.Anterior subarchnoid space appears expanded (blue arrow).
References: Govt Kilpauk Medical College Hospital, Govt Kilpauk Medical College Hospital , Kilpauk , Chennai - 10 , Tamilnadu. - Chennai/IN
Fig. 20: Lipomyelocele: Posterior lipoma (blue arrow) noted at lumbar cord level with low lying conus (L5 level) causing tethering of cord. Fatty component (orange arrow) inferior to posterior lipoma herniates along with nerve roots (green arrow) in to the subcutaneous plane with lipoma-placode interface (red arrow) within the spinal canal.
References: Govt Kilpauk Medical College Hospital, Govt Kilpauk Medical College Hospital , Kilpauk , Chennai - 10 , Tamilnadu. - Chennai/IN

DIAGNOSTIC CLUE: Position of neural placode-lipoma interface and appearance of subarachnoid space gives  diagnosis.

 

MENINGOCELE

Background: Herniation of dura, arachnoid and CSF into spinal subcutaneous tissue.

Embryological correlation:  Failure of disjunction

Associated abnormalities: Hydromyelia, Tethered cord syndrome, Diastematomyelia, Dermal sinus

Protocol advice: Sagittal and axial T1WI and T2WI. Sagittal images to evaluate the cord. Axial T2WI for detecting nervous tissue within the sac. Axial T1WI to evaluate the size of dysraphic defect.

Imaging findings: T1WI shows skin covered hypointense dural sac which appears hyperintense on T2WI.

Fig. 21: Meningocele: Small posterior meningocele (red arrow) at D12 – L1 vertebrae level extending to the spinal canal through the posterior spinal defect at L2 vertebrae level (yellow arrow). Syringomyelia (green arrowhead) noted at D12, L1 vertebrae level. Diastematomyelia (green arrow) of the cord from upper part of lumbar vertebrae level with thick T1/ T2 hypointense septae (blue arrow) separating the two hemi cords at L3 vertebrae level.
References: Govt Kilpauk Medical College Hospital, Govt Kilpauk Medical College Hospital , Kilpauk , Chennai - 10 , Tamilnadu. - Chennai/IN

DIAGNOSTIC CLUE: Skin covered dorsal dural sac protruding through posterior osseous defect.

 

Fig. 22: Diagnostic dilemma: Lipomyelomeningocele vs Lipomyelocele vs Meningocele
References: Govt Kilpauk Medical College Hospital, Govt Kilpauk Medical College Hospital , Kilpauk , Chennai - 10 , Tamilnadu. - Chennai/IN

 

DIASTEMATOMYELIA

Background: Sagittal division of spinal cord into two hemicords, each one with one central canal, dorsal horn and ventral horn.
Embryological correlation:  Abnormal notochord development and clefting of spinal canal.

Associated abnormalities: Vertebral segmentation anomalies, Tethered cord syndrome, Syringohydromelia etc.

Protocol advice: Coronal and axial T1WI and T2WI best demonstrate the hemicords. Bone CT may be supplement in defining the spur anatomy for surgical planning.

Fig. 23: Pangs classification of diastemetamyelia
References: Govt Kilpauk Medical College Hospital, Govt Kilpauk Medical College Hospital , Kilpauk , Chennai - 10 , Tamilnadu. - Chennai/IN

Imaging findings: Two hemicords with isointense(fibrous) or hyperintense(osseous) spur on T1WI and hypointense (fibrous / osseous) spur on T2WI best demonstrated in axial and coronal plane.

Fig. 24: Diastematomyelia Type 1: Serial axial sections of T1WI shows splitting of spinal cord (yellow arrow) from L1-L2 level to L3 level by a fibrous spur (green arrow) seen at L2 level with each cord having a separate dural sac (green arrowhead). Intraspinal dorsal lipoma (red arrow) along the posterior and lateral aspect of cord D12-L1.
References: Govt Kilpauk Medical College Hospital, Govt Kilpauk Medical College Hospital , Kilpauk , Chennai - 10 , Tamilnadu. - Chennai/IN
Fig. 25: Diastematomyelia Type 2: Serial axial sections of T2WI shows splitting of spinal cord (yellow arrow) from L1 level to L3 level by a fibrous spur with both cords sharing a single dural sac (red circle).
References: Govt Kilpauk Medical College Hospital, Govt Kilpauk Medical College Hospital , Kilpauk , Chennai - 10 , Tamilnadu. - Chennai/IN

DIAGNOSTIC CLUE: Fibrous or osseous spur splits spinal cord into two hemicords.

 

MYELOMENINGOCELE

Background: Posterior spinal defect through which neural tissue, CSF and meninges are exposed without skin covering.

Embryological correlation:  Failure of disjunction

Associated abnormalities: Vertebral segmentation anomalies, Diastematomyelia, Tethered cord syndrome.

Protocol advice: Sagittal and axial T1WI and T2WI including entire spine.

Imaging findings: Sagittal images shows loss of normal posterior epidural fat segmentation at anomaly level. Wide osseous spinal dysraphism with nerve roots originating from ventral placode surface on T2.

Fig. 26: Myelomeningocele: Sagittal T1 and T2 weighted image shows a wide posterior osseous spinal defect (red arrow) at S1 vertebral level through which meninges and neural elements herniates forming a sac (yellow arrow) uncovered by skin. Axial T1 and T2 hyperintense lesion consistent with lipoma (red arrowhead) is noted with in the meningocele sac.
References: Govt Kilpauk Medical College Hospital, Govt Kilpauk Medical College Hospital , Kilpauk , Chennai - 10 , Tamilnadu. - Chennai/IN

DIAGNOSTIC CLUE: Wide osseous defect with low lying cords/roots and neural tissue / meninges exposed to air without skin covering.

 

HEMIMYELOMENINGOCELE

Background: Diastematomyelia associated with myelomeningocele of one hemicord at the same vertebral level.

Embryological correlation:  Splitting of notochord associated with failure of disjunction.

Associated abnormalities: Low-lying conus medullaris and thickened filum terminale

Protocol advice: Sagittal and axial T1WI and T2WI including entire spine.

Imaging findings: Two hemicords can be enclosed in single or separate dural sheaths and separated by a fibrous or osteocartilaginous septum. Herniation of one hemicord, along with meninges and cerebrospinal fluid through defect in posterior element of the vertebra forming a large subcutaneous mass uncovered by skin.

Fig. 27: Hemimyelomeningocele: Complex formation and segmentation anomaly involving the D4 to D8 vertebrae (green arrow). (Yellow arrows) Diastematomyelia from D2 to upper border of D8 vertebra with two hemicords unit inferiorly at D8 vertebrae level. There is a myelomeningocele (red arrow) through the posterior spinal defect on the right side D7 vertebrae.
References: Govt Kilpauk Medical College Hospital, Govt Kilpauk Medical College Hospital , Kilpauk , Chennai - 10 , Tamilnadu. - Chennai/IN

 

DIAGNOSTIC CLUE: Diatematomyelia with herniation neural tissue / meninges of one hemicords without skin covering.

Fig. 28: Diagnostic dilemma: Myelomeningocele vs Hemimyelomeningocele
References: Govt Kilpauk Medical College Hospital, Govt Kilpauk Medical College Hospital , Kilpauk , Chennai - 10 , Tamilnadu. - Chennai/IN

SPINAL LIPOMA

Background: Spinal lipoma is intimately associated with spinal cord (intradural)or filum insertion(terminal).

Embryological correlation:  Premature separation of cutaneous ectoderm from neuroectoderm during neurulation.         

Associated abnormalities: Intradural lipoma is associated with localized spinal dysraphism. Terminal lipoma is associated with Diastematomyelia, Sacral hypogenesis and Dermal sinus.

Protocol advice: Sagittal and axial T1WI to define the extent of lipoma and its relation to neural placode.

Imaging findings: Intradural lipoma – Lobulated or ovoid T1/T2 hyperintense intradural mass intimately associated with spinal cord with or without canal narrowing. Terminal lipoma – T1/T2 hyperintense mass attached to distal cord or filum with or without cord compression. Chemical fat saturation or inversion recovery MR sequence may be used to confirm the fat content.

Fig. 29: Intradural spinal lipoma: Sagittal and axial images demonstrate a T1/T2 hyperintense lesion at L3-L4 level.
References: Govt Kilpauk Medical College Hospital, Govt Kilpauk Medical College Hospital , Kilpauk , Chennai - 10 , Tamilnadu. - Chennai/IN
Fig. 30: Terminal spinal lipoma: Sagittal and axial T1WI demonstrate hyperintense lesion (red arrow) at S2-lower sacral level. Sagittal and axial T2WI demonstrate hyperintense lesion (blue arrow) at S2-lower sacral level.
References: Govt Kilpauk Medical College Hospital, Govt Kilpauk Medical College Hospital , Kilpauk , Chennai - 10 , Tamilnadu. - Chennai/IN

DIAGNOSTIC CLUE: T1 hyperintense intradural mass lesion.

 

TETHERED CORD SYNDROME

Background: Low lying conus medullaris tethered by thick and short filum terminale.

Embryological correlation:  Incomplete involution of the distal spinal cord during secondary neurulation.

Associated abnormalities: Lumbosacral hypogenesis, Diastematomyelia, Spinal lipoma, Meningocele etc.

Protocol advice: Sagittal and Axial T1WI and T2WI. Phase contrast MRI adds value by demonstrating decreased spinal cord motion.

Imaging findings: Dorsal positioning of conus medullaris even in prone position. Thickening of filum. Low lying conus may be difficult to distinguish from thickened filum.

Fig. 31: Tethered cord syndrome Patient 1: 2 years old male child postoperative case of limited dorsal myeloschisis. Sagittal T2WI show the spinal cord ending at L4 level (green arrow) and conus extending below S1 vertebra (red arrow). Sagittal T1WI and T2WI demonstrate hyperintense lesion consistent with lipoma(yellow arrow) at sacral level causing tethering of cord leading to low lying conus. Patient 2: Axial T2 weighted images demonstrates measurement of filum terminale thickness at L5-S1 level which is 2.95mm (Normal thickness is less than 2mm).
References: Govt Kilpauk Medical College Hospital, Govt Kilpauk Medical College Hospital , Kilpauk , Chennai - 10 , Tamilnadu. - Chennai/IN

DIAGNOSTIC CLUE: Conus ends below L2 vertebra inferior end plate tethered by thickened filum measuring >2mm at L5-S1 level in axial MRI.

 

KLIPPEL FEIL SYNDROME

Background: Congenital Spinal malformation characterized by segmentation failure of two or more cervical vertebra.

Embryological correlation:  Failure of normal segmentation of cervical somites

Associated abnormalities:Hemivertebrae, butterfly vertebra, spina bifida, Diastematomyelia etc.

Protocol advice: T1WI and T2WI in multiple planes to evaluate cervical fusion, canal compromise and cord compression.

Imaging findings: Both T1WI and T2WI shows cervical fusion with or without degenerative changes. T2WI shows marrow signal changes and cord compression.

Fig. 32: Klippel Feil syndrome with Type II diastematomyelia - Coronal T2WI shows two hemi cords in the upper cervical region (red arrow) up to the level of C4 without bony / thick fibrous septum. Sagittal T2WI shows multiple segmentation anomaly of the cervical and upper dorsal vertebra (yellow arrow).
References: Govt Kilpauk Medical College Hospital, Govt Kilpauk Medical College Hospital , Kilpauk , Chennai - 10 , Tamilnadu. - Chennai/IN

DIAGNOSTIC CLUE: Single or multiple level congenital cervical segmentation and fusion anomalies.

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