hemivertebra and tethered cord syndrome

1. Congenital Hemivertebra and
tethered cord syndrome
Dr.Sairamakrishnan

2. Embryology
1. Formation of Neural Tube

3. • Neural Folds
• Neural Crest
• Neural Groove
• Somites

5. Anterior
neural
pore
Posterior
neural
pore
failure to close =
anencephaly
failure to close =
spina bifida

6. • Neural crest becomes
peripheral nervous
system (PNS)
• Neural tube becomes
central nervous system
(CNS)
• Somites become spinal
vertebrae.
Somites

7. • At the end of 3 weeks there are 42 to 44
consecutive segments of somites.
• In weeks 4 and 5 the mesenchmal cells in the
somites devide into 3 parts.
– The one surrounding the notocord becomes the
precursor for vertebral bodies and the anulus
fibrosus of the disc
– The one surrounding the neural tube becomes the
precursor for the posterior elements.
– The third part forms the extra spinal soft tissue.

8. • Then the resegmentation of the somites into
cranial and caudal halves occur.
• The caudal half of the superior somite and the
cranial half of the inferior somite unite to form
the centrum, the precursor for the vertebral
body

9. • During the 6th week chondrification centers
develop producing type 2 collagen in the
extracellular matrix.
• Nucleus pulposus are the remanants of the
embryologic notocord.

10. • During the 8th week ossification centers for
the vertebra develop.
• A typical vertebra has 3 primary ossification
centers.
– One in the centrum
– One for each half of the vertebral arch
• Ossification initially starts at lower thoracic
vertebra and progress cranially and caudally.

11. • At puberty secondary ossification centers
develop.
– One at the tip of the spinous process
– One each at the tip of transverse process
– One ring epiphysis each at the superior and
inferior endplates of the vertebra.

12. • By 5th week the neural tube becomes diamond
shaped and forms the sulcus limitans leading
to anterior and posteior halves.
• Anterior half becomes the motor and
posterior becomes the sensory tracts.
• During the 6th week the anterior and posterior
halves unite.
• In 7th to 8th week white matter develops
within the spinal cord

13. • During fetal development the spinal cord is
found along the entire length of the vertebral
column
• In adults the spinal cord terminates at L1-2.

14. Hemivertebra
• Hemivertebrae, or wedge-shaped vertebrae,
are caused by failure of formation
or segmentation of somites
• One probable cause of this failure is a lack of
blood supply to the vertebrae.

15. • Hemivertebrae cause an angling of the spine
and are most commonly manifested in defects
such as kyphosis (posterior
curvature), scoliosis (lateral curvature),
and lordosis (anterior curvature).
• The most common location for hemivertebrae
is the midthoracic region (especially T8), and
they are the most likely vertebral defect to
cause neurological problems.

16. • There are four distinct types:
– Incarcerated hemivertebrae are those in which
the vertebral bodies above and below the
abnormal segment accommodate the
hemivertebrae
– Nonincarcerated hemivertebrae refers to the
failure of accommodation, usually resulting in
spinal curvature.

17. – Segmented hemivertebrae have a normal disk above
and below the defective body and are more likely to
lead to progressive curvature
– Unsegmented hemivertebrae are fused with the
vertebral body above and below.

18. • Neurological problems may result if the
hemivertebrae cause severe angulations of
the spine, narrowing of the spinal canal,
instability of the spine, or fractured vertebrae.
• Signs of neurological problems associated with
hemivertebrae include rear-limb weakness,
paralysis, urinary/fecal incontinence, and
spinal pain.

19. • Fortunately, most cases of hemivertebrae
cause few or mild symptoms and usually do
not require treatment.

20. Tether cord syndrome
• Tether = attached
• So tether cord is a cord which is attached to
surrounding structures
• M/C at the caudal end.
• In adults if the spinal cord is found at L3 or
lower tether cord needs to be ruled out.
• It most commonly occurs due to defective
degeneration of the caudal cell mass.

21. • Some conditions leading to anatomical
tethering of the cord are;
– Lipomyelomeningcele
– Diastematomyelia and Diplomyelia
– Anterior sacral meningocele
– Myelocystocele
– Dural dermal sinus

22. • Tethering of the cord may result in significant
disabilities and prolonged morbidities
• The leading problems are pain, motor
weakness, urologic issues, dermatologic
manifestations, orthopedic problems and
psychologic sequelae
• These problems occasionally present in
infancy while a majority is diagnosed in late
childhood to early adulthood

23. • All conditions need surgical intervention to
release the cord
• The primary aim of neurosurgical intervention
is to stop further progression and help in good
physical and neuro-rehabilitation
• A multidisciplinary approach and high degree
of clinical vigilance is necessary for diagnosis
• Signs and symptoms are non-specific to any
particular tethering cause

24. Fauns hairy tail

25. Lipomyelomeningocele
• Derives from the secondary remnant cells of the
notochords’ caudal end
• Mature adipose tissue fused to the dorsal dura
and protruding through the spinal defect
• Eventually causes tethering
• Two main types;
– adherent to the dorsal surface of the cord itself
– Adherent to the lower part of conus and filum
• Treatment is laminectomy and untethering of the
cord

28. Diastematomyelia / Diplomyelia
• Also called Split Cord Malformations
• Caused by duplication of the cord either by an
intervening bony spur or dural septum
• Causes cord tethering and neurological
problems
• Incontinence, gait abnormalities, lower limbs
pain and sensory loss in feet
• Associated with midline dermal stigmata, i.e.,
faun’s tail (but not specific)
• May be associated with scoliosis

30. • Two types;
– Split cord with an intervening bony spur
– without bony spur
• Female preponderance
• MRI is the confirming investigation
• Treatment is laminectomy, followed by excision
of the bony spur and repair of dura
• There is small risk of neurologic deterioration
post-operatively which should be communicated
to the patients / parents

31. Anterior Sacral Meningocele
• Evagination of meningeal sac anteriorly into the
pelvic cavity through a defect in the sacrum
• Rare cause of cord tethering
• Usually found accidentally on investigations for
pelvic pathology/ rarely during a laparotomy
• Any breach of the meningeal wall may increase
the risk of meningitis

32. • Pelvic ultrasound, CT myelography or MRI are
useful investigations
• Treatment is surgical reduction of the meningeal
sac and closure of the defect some times with a
fascial patch
• A posterior sacral laminectomy is the preferred
approach
• Division of filum terminale is essential step for
untethering

33. Congenital Dermal Sinus
• A tubular connection between the skin surface
where the channel may end subcutaneously,
interspinous area, inside the spinal canal,
intradurally or intramedullary cystic extension
• This type of sinus may easily be mistaken with a
pilonidal sinus
• Differentiation is done by the dimple created by
the tethered overlying skin which is not the case
in pilonidal sinus

34. • Treatment is by complete dissection of the sinus
tract and its excision in toto followed by water
tight closure of the dura and releasing the
tethering elements
• Extensive laminectomy is required in some
cases
• Filum terminale is usually divided in the wake of
untethering of the cord