Ref; G & A 6th edition

1. SPINAL MALFORMATIONS
Dr. Soe Moe Aung
Radiology PG Student

2. Embryology

4. Normal Spinal Cord Development
• Spinal cord forms during three embryological stages
• Gastrulation (at 2–3 weeks)
• Primary neurulation (3–4 weeks)
• Secondary neurulation (5–6 wks)

9. Gastrulation
• The embryonic bilaminar disc consists of epiblast (future ectoderm)
and hypoblast (primitive endoderm)
• It is converted to a trilaminar disc by migration of cells from the
epiblast through Hensen’s node, a focal region of thickening occurring
at the cranial end of the midline ‘primitive streak’ of the disc.
• This results in the midline notochord and a layer that will form the
future mesoderm.

10. Primary neurulation
• Notochord induces the overlying ectoderm to become
neurectoderm and form the neural plate.
• Subsequent folding and bending occurs until the margins unite to
form the neural tube.
• Cranial end closes at day 25, while the caudal end closes a couple of
days later.

11. Secondary neurulation
• Finally the caudal cell mass arises from the primitive streak and
undergoes retrogressive differentiation with cavitation.
• This is the origin of the foetal neural tissue and vertebrae distal to
S2, and will become the conus medullaris.

12. Terminal ventricle
• focal expansion of the fetal canal as a result of incomplete
retrogressive differentiation.
• may be seen as a normal asymptomatic finding in young children and
may persist in a small minority into adulthood.
• seen on all post-mortem studies but is bigger in those detectable on
MRI.

13. Spinal dysraphisms
• can result from abnormalities occurring during any of above three
periods.

14. Spinal Dysraphisms
• also known as a neural tube defect (NTD)
• comprises a group of congenital spine abnormalities that may cause
progressive neurological damage
• may be open, in which case nervous tissue is exposed, or closed, in
which case the defect is covered by skin, although a cutaneous lesion
such as a dimple, sinus, hairy naevus or haemangioma may be seen
as a marker of an underlying defect in 50% of these cases.

15. Spina bifida
• refers to the failure of fusion of the posterior spinal bony elements.
Neural placode
• is a flat segment of un-neurulated nervous tissue that may be seen at
the end of the spinal cord or at an intermediate position along its
course

16. Tethered cord syndrome
• low-lying conus medullaris tethered by a short thick filum terminale,
seen at or below the level of L3
• majority of normal cord lie between T11/12 and L1/2.
• is a clinical diagnosis of progressive neurological deterioration (usually
leg weakness, deformities such as scoliosis or foot abnormalities, loss
of bladder and bowel function), presumed to be due to traction
damage on the tethered cord.

17. Open Spinal Dysraphism
• most are myelomeningoceles
• virtually always associated with Chiari II malformation
• neural placode protrudes beyond the level of the skin and there is an
expanded CSF-containing sac lined by meninges.
• small proportion of OSDs are myeloceles where the placode is flush
with the surface and there is no meningocele component.
• these disorders usually at the lumbosacral level at the spinal cord
termination.

18. • nerve roots (from the everted ventral placode) cross the widely
dilated meningocele subarachnoid spaces to enter the neural exit
foraminae.
• posterior elements of the vertebral column and the other
mesenchymal derivatives (e.g. paravertebral muscles) remain everted.
• Myelomeningoceles are operated on soon after birth; if untreated,
the exposed neural tissue is prone to ulceration and infection.

19. Closed Spinal Dysraphism
• often associated with midline cutaneous stigmata or a mass.
• This may be a subcutaneous lipomatous mass overlying the spinal
defect, as in lipomyeloceles and lipomyelomeningoceles.
• In these conditions there is an intraspinal lipoma.
• In a lipomyelocele the junction between the placode and the lipoma
lies within the spinal canal, while in lipomyelomeningoceles it lies
outside.

20. Closed spinal dysraphism.
The spinal cord is too low and the neural placode terminates at the lumbosacral junction in a
lipomyelocele (black arrows).
There is an associated spinal cord syringomyelic cavity (white arrows).
The posterior elements are deficient and everted.

21. • Typically the placode is rotated to one side while the lipoma rotates
on the other.
• These lipomas may be dorsal, with a normal conus below, or
transitional where the lipoma extends caudally along the conus.
• In both these situations the lipoma–placode junction is dorsal and
well-defined.

22. ‘Chaotic’
• 3rd form of closed Spinal Dysraphism
• where the lipoma extends ventrally around the neural placode and
the lipoma is much more difficult to resect.
• these are less common conditions but are more commonly seen with
sacral agenesis.

23. Dorsal Dermal Sinus
• is an epithelial-lined opening on the skin with variable fistulous
extension to the dural surface.
• typically seen in the lumbosacral region
• often associated with cutaneous stigmata, such as hairy naevus and
capillary haemangioma.
• Dermal openings seen at the sacrococcygeal level are directed
inferiorly below the thecal sac and are known as sacrococcygeal pits.
• US may provide useful information about the intradural extension of
the dermal sinus tract and the mobility of the conus.
• MRI is more sensitive for additional intraspinal findings such as spinal
cord syrinx and intraspinal dermoid.

24. Dorsal dermal sinus.
(A) The termination of the spinal cord is very low and there is a syringomyelic cavity with internal
septations.
In addition there is a more focal cyst within the conus confirmed at surgical untethering to be a
dermoid cyst (arrow).
(B, C) There is an associated dermal sinus track (arrows).

25. Diastematomyelia
• split notochord syndromes are disorders of notochord midline
integration.
• spinal cord is split in two, with each hemicord having one anterior and
one posterior grey matter horn.
• There has two types.
• Type I
• Type II

26. In type I diastematomyelia
• there are two complete dural sacs.
• scoliosis or hemivertebrae or bifid/fused vertebrae at the level of the
bony spur.
• bony spur is completely extradural and usually midline.

27. In diastematomyelia type II
• There is a single dural sac in which the two hemicords lie, and a
fibrous septum may be seen passing intradurally between the two
hemicords.
• There may be no septum or there may only be partial clefting of the
cord.
• Conus is often low and there may be a tight or fatty filum.
• Both forms of diastematomyelia may be associated with hydromyelia
within the spinal cord.

28. (A) Sagittal T2-WI MRI
appears to show signal
abnormality and thinning
of the spinal cord, and is
the clue to the
diastematomyelia seen
on the axial images.
(B, C) Axial T2-WI MRI
shows that the cord
has split into two
hemicords. The
apparent signal
abnormality is in fact
normal cerebrospinal
fluid interspersed
between the two
hemicords.
These reunite
inferiorly. The
meningocele is seen
herniating through a
bony defect in the
vertebral posterior
elements.
Diastematomyelia type II with associated
craniocervical meningocele.

29. Neurenteric Cysts
• severest and rarest form of notochordal midline integration anomaly
occurs with dorsal enteric fistulas and neurenteric cysts.
• cysts are usually seen intradurally anterior to the spinal cord and
• are derived from endodermal remnants trapped between a split
notochord.
• They have signal characteristics of CSF or of proteinaceous fluid with
T shortening.

30. Neurenteric cyst
Ventral to the medulla and upper cervical spinal cord, displacing them posteriorly, and with the
vertebral arteries displaced around it.
The cyst is hyperintense on the T2-weighted images and there is also some mild T1 shortening
(arrow)

31. Disorders of the Caudal Cell Mass/ Caudal Regression Syndrome
• affects development of the caudal cell mass.
• caudal agenesis and the rarer condition of segmental spinal
dysgenesis are considered to occur as a result of apoptosis of
notochordal cells which have not formed in their correct craniocaudal
position.

32. In caudal agenesis
• there is a severe abnormality which results in absence of the
vertebral column at the affected level, as well as a truncated spinal
cord, imperforate anus and genital anomalies.
• may be seen with
• OEIS (omphalocele, exstrophy, imperforate anus, spinal defects),
• VACTERL and
• Currarino triad
• Anorectal malformation
• Presacral mass which may be a teratoma or anterior
meningocele

33. There is a presacral cystic lesion in continuity with the thecal sac at the level of the sacrum.
A small solid component is seen in keeping with a benign teratoma with associated
meningocele.
The conus is seen at the L2/3 level and the spinal cord was untethered at surgery.
The left side of the sacrum has a scimitar configuration, with the meningocele seen on the
right. These are the features of the Currarino triad.

34. Segmental Spinal Dysgenesis
• Segmental abnormality affecting the spinal cord, segmental nerve
roots and vertebrae
• Associated with a congenital paraparesis and lower limb
deformities.
• Short segment of the spinal column is deficient and the spinal canal
may be obliterated.
• On imaging, there may be an acute angle kyphus.
• These anomalies may be a result of a postneurulation insult.

35. THANK YOU!