Neonatal spine ultrasound...normal and abnormal findings
Riyadh Military Hospital
Why US spines ?
Spinal ultrasound (SUS) is becoming
increasingly accepted as a first line
screening test in neonates suspected of
spinal dysraphism .
The advantages of SUS are not only a diagnostic sensitivity
equal to MRI but that, unlike MRI, SUS can be
performed portably, without the need for sedation or
In addition, MRI is highly dependent on factors affecting
resolution, including patient movement, physiological
motion from cerebral spinal fluid (CSF) pulsation and
vascular flow, factors that do not affect SUS .
New generation high frequency ultrasound machines
with extended field of view capability now permit
imaging of high diagnostic quality in young
When to perform ?
SUS is possible in the neonate owing to a lack
of ossification of the predominantly cartilaginous
posterior arch of the spine . The quality of
ultrasound assessment decreases after the first
3–4 months of life as posterior spinous elements
ossify, and in most children SUS is not possible
beyond 6 months of age. However, the persisting
acoustic window in children with posterior spinal
defects of SD enables ultrasound to be performed
at any age
When to request US spines ?
Current RCR guidelines are that
all neonates with a hairy patch or sacral
dimple should undergo SUS . However,
while more than 90% of patients with occult
SD have a cutaneous abnormality over the
lower spine , a cutaneous marker may have
a low yield in predicting the presence of a
clinically significant abnormality. In a recent
review of 200 SUS examinations performed
over an 11-year period, SD was found in
less than 1% of cases when a cutaneous
marker was the only clinically detected
Retrogressive differentiation and
relative cord ascent
Formation of the
ventriculus terminalis, the
caudal portion of the
conus medullaris, and the
filum terminale through the
processes of canalization
Sonographic examination of the neonatal spine
is performed with the infant in a warm room lying
in a prone, lateral decubitus, or semi-erect
Feeding the infant before examination helps him
or her to relax.
Placing a towel under the infant’s pelvis will flex
the spine enough to separate the midline
posterior arches .
A high frequency (7- to 15-MHz) lineararray transducer should be used .. higher
frequency transducers are beneficial for
optimization of superficial structures such
as skin lesions and sinus tracts.
Extended field-of-view (EFOV) imaging is
an additional feature that can demonstrate
the whole neonatal spine from T12 to the
• Mark T 12 in
• Then count
end of cord.
Locating the last lumbar vertebra, L5, by
evaluating the lumbosacral junction. Then
count cephalad to the conus medullaris.
Locating the last ossified vertebral body,
the first coccygeal segment. Then count the
five sacral segments cephalad into the
The spinal cord lies in the spinal canal within anechoic
CSF of the subarachnoid space. Surrounding
the canal is the dura mater, which is shown by
anechogenic line dorsal and ventral to the canal. The
cord is lined with the arachnoid sheet, which exhibits an
echogenic line parallel to the cord’s surface.
Caudally, the lumbar enlargement tapers, forming the
conus medullaris, which extends and becomes the filum
The filum terminale images as an echogenic
cordlike structure that is surrounded by
echogenic nerve roots of the cauda
equina. For that reason, separation of the two is
However, the filum terminale is commonly more
echogenic than the surrounding cauda equina.
The filum terminale normally measure less than
or equal to 2 mm.
On a sagittal image, the spinal cord appears as
a hypoechoic cylindrical structure with two echogenic
complexes centrally. These represent the
central echo complex. The normal cord lies one
third to one half of the way between the dorsal and
ventral walls of the spinal canal
On a transverse image, the cervical spinal cord
appears as an oval shape, whereas the thoracic and
lumbar portions are more circular.
The level of the conus usually ends between
T12 and L1 or L2 .If it ends at the L2-L3 disk space or
lower, it is abnormal, and one should explore for any
tethering masses. However, it must be noted that a
normal cord may lie around L3, mainly in preterm infants.
The normal position of the cord should be central
in the spinal canal. The spinal cord is held in place
by echogenic dentate ligaments passing laterally
from each side of the cord.
The normal spinal cord produces a rhythmic movement
Three processes can lead to
First, premature separation of the skin
ectoderm from the neural tube
can lead to entrapment of
mesodermal elements, such as
Second, failed neurulation leads to
such as myelomeningocele(overt
or closed )
Last ,anomalies of the
filum terminale, such as
fibrolipomas and caudal
disembryogenesis of the
caudal cell mass
Congenital spinal dysraphisms can be classified on the
basis of the presence or absence
of a soft-tissue mass and skin covering .
Those without a mass include tethered cord,
diastematomyelia, anterior sacral meningocele,
and spinal lipoma.
Those with a skin covered soft-tissue mass include
lipomyelomeningocele and myelocystocele.
And those with a back mass but without skin covering
include myelomeningocele and myelocele
Search for cause
Sonographically, tethered cord is diagnosed
in neonates by the presence of a low-lying
conus (below the L2–L3 disk space) and
lack of normal nerve root motion during realtime
• Spinal ultrasound (SUS) is becoming
accepted as a first line screening test in
neonates with high sensitivity and
• Recognizing normal anatomy ,variants
and congenital anomalies early in life help
in futur planning of management .