Diagnostic ultrasound ( PDFDrive )

CHAPTER 49 The Pediatric Spinal Canal 1689
transverse views. A ibrous septum can be seen on axial highresolution
magnetic resonance images. Hydromyelia may be
present and the conus is typically low, strongly associated with
ilar lipomas and tight ilum terminale. Vertebral anomalies are
usually milder than in type I. 10,79,80
he diagnosis of diastematomyelia can be made with ultrasound
in the newborn period. 62,64,81,82 About one-half of patients
with diastematomyelia have some surface stigmata of an underlying
malformation, such as a cranial hairy tut, nevi, lipomas,
dimples, or vascular lesions. 61,79,80 Despite this, it is not unusual
for the diagnosis to be delayed until older childhood because
scoliosis or other characteristic neurologic or orthopedic symptoms
develop. MRI is necessary beyond the neonatal period to
establish the diagnosis. Deinition of any dividing cartilaginous
or bony septum is an important part of surgical planning and
can be diicult to visualize with ultrasound, 45 sometimes necessitating
the additional step of spinal computed tomography (CT).
Diastematomyelia may occur in isolation or in conjunction
with other anomalies, such as myelomeningocele, lipoma, dermal
sinus, and dermoid or teratoma. 61,83
Disorders of Midline Notochordal Formation. he
notochord induces the development of the spinal cord, spinal
vertebrae, and other organs. If there are abnormal notochordal
segments, vertebral malformations and segmental abnormalities
of neurulation can exist. Most commonly the caudal segment is
involved and caudal agenesis develops. If an intermediate segment
is involved, this results in segmental spinal dysgenesis.
Caudal agenesis refers to a heterogeneous group of caudal
anomalies that include total or partial agenesis of the spinal
column (the majority involve the sacrum and coccyx), imperforate
anus, genital anomalies, renal dysplasia, pulmonary
hypoplasia, and lower limb anomalies. 84 Agenesis of the sacrum
and coccyx may be part of syndromic associations including
Currarino triad 85-88 (partial sacral agenesis, anorectal malformation,
presacral teratoma or anterior meningocele), OEIS 89
(omphalocele, exstrophy of the cloaca, imperforate anus, spinal
defects) and VACTERL (vertebral anomalies, imperforate anus,
cardiac malformations, tracheoesophageal istula, renal and limb
abnormalities). Lipomyelomeningocele and terminal myelocystocele
can be seen in up to 20%. Caudal agenesis is associated
with maternal diabetes. It is seen in about 1% of babies born to
mothers with uncontrolled type I diabetes mellitus; 16% of cases
are associated with maternal diabetes.
Depending on the location and shape of the conus medullaris,
caudal agenesis has been classiied into two types. 3,90,91-95 Type
1 or high-position caudal agenesis (T12 or L1) involves a
wedge-shaped or blunted contour of the conus owing to loss of
anterior horn cells and small sacral nerve roots. 45,96 he degree
of vertebral aplasia varies from absence of the coccyx to the
lower thoracic vertebra, but most commonly the last vertebra is
from L5 to S2. he dural sac ends at a high level. Clinically,
neurologic deicits are stable. If the sacral vertebrae are absent,
the iliac wings become closely opposed. here is oten associated
dislocation of the hips (Fig. 49.23).
Type II is caudal agenesis with low and tethered conus
medullaris with mild vertebral dysgenesis (last vertebra up to
S4). he partial agenesis of the conus may not be recognized
owing to stretched conus and tethering to a tight ilum, lipoma,
or anterior meningocele. hese patients clinically have tethered
cord syndrome. 97
Segmental spinal dysgenesis refers to a clinical and radiologic
syndrome that includes segmental agenesis or dysgenesis of the
lumbar or thoracolumbar spine, segmental abnormality of the
underlying spinal cord and nerve roots, congenital paraplegia
or paraparesis, and congenital lower limb deformities. he spine
and cord can form an acute-angle kyphosis and the canal can
be narrow or interrupted. he lower spinal cord is low lying
and bulky and can be hypoplastic or interrupted (Fig. 49.24,
Video 49.8, Video 49.9). Typically a horseshoe kidney and
equinovarus feet are present. 10,98
Several anomalies are associated with high incidence of
dysraphism. 99 About one-third of infants with high imperforate
anus, one-half with the cloacal malformation, and essentially
all with cloacal exstrophy have associated spinal cord anomalies.
One could argue that the cloacal exstrophy group should forgo
the ultrasound step and go straight to MRI. A large percentage
of the other groups can avoid sedated MRI if they are shown on
ultrasound to have a normal-appearing spine in the newborn
period. Because patients with spinal dysraphism oten have
associated renal anomalies, the kidneys should be examined as
well as the spine.
Anomalies at Risk for Spinal Dysraphism
Cloacal exstrophy (100%)
Cloacal malformation (50%)
High imperforate anus (30%)
Ectopic or low imperforate anus
Hemivertebrae result from a disruption of the primary
ossiication center and pairing defects of the involved sclerotomes.
Disorders of vertebral segmentation include block vertebrae
and unilateral unsegmented bars (Figs. 49.25 and 49.26). Fusion
can occur at myriad sites, including the anterior and posterior
spinal column, or at facet joints. 100 Ultrasound can characterize
many of the formational vertebral anomalies and is probably an
underused tool. 101-104 he suspicion of a subtle vertebral anomaly
seen on radiographs in the newborn period when ossiication
is incomplete can oten be proved or refuted with spine
sonography.
TUMORS
Tumors positioned in and around the vertebral canal are rare.
In the neonatal period, intraspinal neuroblastoma is the most
likely diagnosis when such a mass is discovered. 105 hese lesions
tend to calcify and extend into the vertebral canal from the
retroperitoneum. Both the calcium and the course of extension
can be observed with sonography (Fig. 49.27). hese infants may
have a palpable abdominal mass or signs of spinal cord compression.
Other diferential possibilities in the situation of intraspinal
tumor extension include hemangioma and rhabdoid tumor. 106