A Practical Imaging Approach to Spinal Dysraphism

A practical radiology review of A Practical Imaging Approach to Spinal Dysraphism, focused on imaging findings, differential diagnosis, reporting points, and high-yield teaching pearls.

Embryology Essentials

• Gastrulation (2–3 wks): Trilaminar disc → endoderm + mesoderm + ectoderm; notochord forms
• Primary neurulation (3–4 wks): Neural plate → neural folds → neural tube; failure = OPEN SD
• Secondary neurulation (5–6 wks): Tail bud cavitation → conus + filum; failure = LOWER SD

Classification Overview

Open SD: Skin defect + exposed placode (neurosurgical emergency)

Closed SD w/ mass: Lipomas, meningoceles, myelocystoceles

Closed SD w/o mass: Intradural lipoma, filar lipoma, DST, diastematomyelia, CRS, LDM, SSD

OPEN Spinal Dysraphisms

Myelomeningocele

• Placode + expanded CSF sac herniate through spina bifida
• Always ⇢ Chiari II (small PF, tonsillar herniation, tectal beaking, ventriculomegaly)
• MRI: Skin defect + exposed placode elevated by meningocele

Myelocele / Myeloschisis

• Same as above but no CSF expansion
• Placode flat (myelocele) or sunken (myeloschisis)
• Hemimyelomeningocele / Hemimyelocele
• One hemicord fails to neurulate → split cord + one open side

CLOSED SD with Subcutaneous Mass

Lipomas with Dural Defect (LDD)

• Subtypes = Lipomyelomeningocele, Lipomyelocele, Lipomyeloschisis
• Early ectoderm–neuroectoderm separation → mesenchyme → fat infiltration
• Key = location of cord–lipoma interface
• LMMC: Interface outside canal + meningocele
• LMCe: Interface at arches
• LMSch: Interface in canal

Meningocele

• Pure CSF sac, no neural tissue
• Mild symptoms; late embryologic meningeal defect

Myelocystocele

• Herniating syrinx cavity + meningocele
• Terminal type = secondary neurulation failure
• Nonterminal = primary neurulation failure

CLOSED SD without Subcutaneous Mass

Intradural Lipoma

• Subpial fat within dural sac; may tether cord
• Often cervical/dorsal

Filar Lipoma

• Fatty filum; secondary neurulation issue
• Important only if thickened + tethering

Persistent Terminal Ventricle

• CSF cavity in conus; usually incidental

Dermal Sinus Tract (DST)

• Epithelium-lined tract → skin → spinal canal
• Can cause meningitis/abscess
• MRI: Thin T1/T2 tract, look for dermoid/epidermoid (DWI!)

Diastematomyelia (Split Cord)

• Type I: 2 hemicords, 2 dural sacs + bony/cartilaginous septum
• Type II: 2 hemicords, 1 dural sac, no bony spur
• Often with scoliosis, foot deformities

Caudal Regression Syndrome

• Tail-bud failure → sacral agenesis spectrum
• Type I: High abrupt conus, severe vertebral defects
• Type II: Tethered cord + intraspinal mass (lipoma, myelocystocele)

Limited Dorsal Myeloschisis (LDM)

• Midline closed skin defect + fibroneural stalk
• MRI: Tethering stalk, “trapezoid” cord shape
• Segmental Spinal Dysgenesis (SSD)
• Localized segmental cord + vertebral absence
• Severe deformity; “Buddha-like” limb posture

MRI Protocol Tips

• Whole-spine sagittal T1/T2
• Axial T1/T2 at lesion
• Heavily T2 (CISS/FIESTA) for DST / cord–root detail
• Look for tethering
• Evaluate bone anatomy (split, hemivertebra, bifid pedicles)

Key Differentiators

• 》Open vs closed: Skin defect = OPEN
• 》Placode elevated vs flat: Meningocele vs myelocele
• 》Cord-lipoma interface level classifies LDDs》Septum present? → Diastematomyelia Type I
• 》Tethered + intraspinal mass → CRS Type II
• 》DST vs LDM: DST = skin-to-cord tract; LDM = fibroneural stalk + closed skin defect