the presence of a longitudinal cleft within the spinal cord across one or more vertebral segments Type I malformations formerly diastematomyelia are characterized by a bony septum that cleaves the spinal canal in the sagittal plane and a duplicated thecal sac ID: 935952
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Slide1
Split Spinal Cord
Slide2Definition
the presence of a longitudinal cleft within the spinal cord
across one or more vertebral segments.
Type I malformations (formerly diastematomyelia) are characterized by a bony septum that cleaves the spinal canal in the sagittal plane and a duplicated thecal sac.
Type II
malformations (formerly diplomyelia) are characterized by a cleft
cord within a single dural sac, often tethered by a fibrous midline
septum to the adjacent dura
.
Slide3Slide4Slide5S
ingle error
in embryogenesi
s
adhesion between the ectoderm and endoderm
leading to a persistent neurenteric canal.
SCMs are accompanied by nonfunctional
paramedian nerve roots traveling within a fibrovascular bundle
to or beyond the dura.
fibrous tract extending from the epidural
space to a small overlying plaque of atretic skin may also be
present.
Slide6SCM is often
heralded by characteristic cutaneous and orthopedic findings.
Slide7EPIDEMIOLOGY
Incidence
3.8% to 5% of all congenital spinal
anomalies
.
The prevalence of SCM is estimated to be 1 in 5000(0.02%) live births.
S
light female preponderance, approximately 1.3 : 1
.
peak age at initial medical evaluation is 4 to 7 years, although there is a second peak between 12 and 16years of age.
T
ype I SCMs occur more frequently
than type II lesions.
Slide8The most common associations (in descending order) are tethered/low
lying cord (>50%), kyphoscoliosis (44% to 60%),syringomyelia (27.5% to 44%), and other forms of spinal dysra-phism such as thickened or fatty filum, dermoid cyst, dermal sinustract, neurenteric cyst, and spinal lipoma (11% to 26%)
.
Slide9When SCM in association with myelomeningocele
three to four
times more likely to be a type I malformation and tends to occur
at or just rostral to
level
o
f
the
myelomeningocele
defec
t
.
Diastematomyelia is most commonly encountered in the
lumbar region, followed by thoracolumbar, thoracic, and cervical
regions, and occurs over an average of six vertebral levels
.
Slide10EMBRYOGENESIS
SCMs are thought to occur during the third week of embryogenesis, concurrent with gastrulation, as a result of failure of fusion
of the notochord in the midline and subsequent persistence of an
accessory neurenteric canal.
P
ersistent adhesion of the
ectoderm and endoderm, which called an accessory neurenteric canal.
A
cleft notochord, with subsequent
induction of a cleft spinal cord.
Slide11Slide12SIGNS AND SYMPTOMS
Slide13Slide14Slide15IMAGING
The cardinal feature on MRI
is the presence of two hemicords, which are best visualized on
T1-weighted sequences
.
The cleft begins
below T11, and the hemicords most often reunite after two tothree vertebral segments.
A
ssociated fatty filum
Associated tethering anomalies
.
Slide16IMAGING
proper categorization of the
malformation as type I (with an associated “owl sign” on MRI
or
type
2 on T2 MRI.
T2-weighted axial and coronal images
may also demonstrate a hypointense fibrous band in type II SCM.
In type I malformations, computed tomography (CT) best
delineates the configuration of the osseous spur.
The more common bony segmentation defects include
bifid vertebrae, bifid laminae, Klippel-Feil malformation, butterfly vertebrae, and hemivertebrae.
Slide17IMAGING
Hypertrophic
arches are often fused to the lamina of an adjacent segment, a
condition referred to as intersegmental laminar fusion. When associated with bony spina bifida (60% of cases), this finding is virtually pathognomonic for type I SCM
.
Slide18Slide19Slide20Slide21Slide22SURGICAL MANAGEMENT
The presence of a type I SCM is often taken as indication
for operative intervention.
By contrast,many surgeons elect to serially obser
v
e
ne
urologically and urologically asymptomatic patients in whom type II SCM is discovered incidentally or as a result of the presence of a cutaneousmarker only.
G
oal is to untether
the spinal cord by operative management of both the SCM and
any associated tethering anomalies.
Slide23Surgical repair of SCM performed in conjunction with intraoperative electrophysiology, including continuous somatosensory evoked potential
monitoring of the extremities at and below the malformation,motor evoked potential monitoring, or electromyography and
anal sphincter monitoring
.
The patient is positioned prone after a Foley catheter is
placed.
SURGICAL MANAGEMENT
Slide24Care
must be taken during midline exposure to avoid durotomy and neural injury given the high incidence of concomit
a
nt
neural arch defects.
The operation begins
with bilateral paraspinous muscle exposure generally extending
one to two levels above and below the SCM to allow dissection
to extend from normal to abnormal anatomy.
SURGICAL MANAGEMENT
Slide25Rongeurs or a high-speed drill (or both) should then
be used to perform bilateral paramedian laminectomies, while
preserving the midline lamina and spinous process and thus preventing any torque or lateral force from disrupting the bony spur
prematurely
.
Once the spur is isolated and exposed, blunt subperiosteal dissection may be performed to separate the dural sleeves
from the spur bilaterally.
Once freed, the spur may be resected carefully with a small
rongeur or high-speed drill.
SURGICAL MANAGEMENT
Slide26Under magnification, the dura is opened sharply in the midline
above and below the lesion and on either side of the split at the
level of the duplicated dural sleeves
.
Sharp dissection can be used
to free the hemicords from their medial attachments to the dural
sleeves.
Once freed, the central dura can be sharply resected
to the level of the posterior longitudinal ligament ventrally to
restore the normal configuration of a single thecal sac
.
SURGICAL MANAGEMENT
Slide27Any associated tethering lesion (sinus tract, fatty filum, or
terminal lipoma) should also be addressed.
Any additional tethering bands should also be transected so that both hemicords and the conus can move freely within the spinal canal.
Dorsally, the dura is
closed in watertight fashion, if
necessary, with a dural patch.
The patient should be kept flat postoperatively for 1 to 2 days
to allow a preliminary seal to form along the dural suture line.
SURGICAL MANAGEMENT
Slide28OUTCOMES
Slide29Slide30