Diagnostic ultrasound ( PDFDrive )

CHAPTER 49 The Pediatric Spinal Canal 1679
A
B
FIG. 49.11 Determining Level of Conus Medullaris. When it is
dificult to determine the level of the conus medullaris by ultrasound
alone, plain radiographs are often helpful. (A) Panoramic view shows
round ossiication center at S5; margins of other sacral vertebral bodies
are square. BB is placed on the skin of the infant at L2, at the position
of the tip of conus medullaris during sonography. (B) Lateral radiograph
of the lower thoracic, lumbar, and sacral spine shows the marker at L2,
conirming the counting done by ultrasound. Notice the inferior ribs at
T12, the normal lumbosacral junction, and the round ossiication at S5.
(C) Frontal radiography in another patient. A BB was placed on the skin
of an infant corresponding to the position of the tip of the conus medullaris
during sonography, to help determine the associated vertebral body
level.
musculoskeletal, urologic, or gastrointestinal abnormalities (Fig.
49.13). he clinical signs and symptoms are age dependent and
develop as a complication of open neural tube repair or as the
presentation of a closed spinal dysraphism. Spinal cord injury
is theorized to result from cord ischemia caused by excessive
tension or stretching of nerve ibers. he signs and symptoms
C
have also been described in patients that have a conus medullaris
in a normal position, although they usually have cutaneous
stigmata, vertebral anomalies, or intradural lipomas. 9
he treatment of a tethered cord in symptomatic patients is
surgical release with total or near-total resection of the tethering
mass and depending on the lesion repair of the dura. In asymptomatic
patients with imaging abnormalities or in symptomatic
patients with normal imaging, there is controversy with regard
to treatment. 37-41
Because newborns may have no neurologic deicits on presentation,
the role of ultrasound is to identify the tethering lesion or
condition and evaluate the position of the conus medullaris in
patients with high- or intermediate-risk cutaneous markers.
High-risk cutaneous markers include focal hypertrichosis,
infantile hemangioma, atretic meningocele, dermal sinus tract,
subcutaneous lipoma, caudal appendage, and segmental
hemangiomas in association with LUMBAR syndrome (lower
body hemangiomas, urogenital abnormalities, ulcerations,
myelopathy, bony defects, anorectal malformations, arterial
anomalies, and renal anomalies). Intermediate-risk cutaneous
markers include capillary malformations (salmon patches or
port-wine stains). Low-risk cutaneous markers do not require
routine neuroimaging or follow-up and include coccygeal dimples,
light hair, isolated café au lait spots, mongolian spots, hypomelanotic
and hypermelanotic macules or papules, and deviated or
forked gluteal clets. 42
Coccygeal dimples are present in 2% to 4% of newborns and
are deined as a sot tissue depression located up to 2.5 cm above
the anus, in proximity with the coccyx. hey can be classiied
as shallow if the bottom is visible or deep if the bottom is not
visible. A study of 84 infants with deep and shallow coccygeal
dimples who underwent MRI at a mean age of 1 year identiied
ibrolipomas of the terminal ilum in 16.7% of patients. he
ibrolipomas were more common in patients with deep dimples.
In addition, these researchers found a 7% incidence of a low
conus, deined as conus below the L3 vertebral body. 43 A study
of 50 neonates who underwent ultrasound examination and MRI
showed no pathologic indings in infants with simple coccygeal
dimples and deviated gluteal folds. In a group of 109 infants
with simple dimples, ultrasound revealed no pathologic indings
that needed surgery, but did show 20 cases of low dermal tracts,
which had no continuity with intraspinal structures and no cord
tethering. 44 hese likely ibrous tracts track anteriorly and
inferiorly from the dimple to the coccyx tip (see Fig. 49.12A). 12
In the group of 42 infants with deviated or split gluteal folds
that were not caused by an underlying sot or bony mass,
ultrasound revealed no pathologic indings. 44 herefore in low-risk
patients, if the need for imaging is questionable but imaging is
desired, ultrasound provides a reliable screening tool. 44,45
SPINAL DYSRAPHISM
he term “spinal dysraphism” stems from the Greek roots meaning
bad (“dys”) seam or suture (“raphe”) and was irst used in the
literature by Tulpuis in 1641. 46 Currently, the dysraphic lesions
describe a broad group of abnormalities that might be explained
by an error in the embryologic processes of gastrulation, primary