Diagnostic ultrasound ( PDFDrive )

CHAPTER 35 The Fetal Spine 1235
C
C
S
C
S
E
F
G
W
W
M
S
W
C
CC
H
E
M
FIG. 35.17, cont’d (E) Lateral view of the posterior cystic thoracic mass (C). (F) Sagittal magnetic resonance scan demonstrates the cystic
mass along the upper thoracic area, with the small sinus tract (arrows) extending from the posterior aspect of the spinal cord (S) toward the cystic
mass (C). (G) Gross pathologic specimen demonstrates the collapsed cyst (C) in contiguity with the cervical portion of the spinal cord (S). (H)
Histologic section shows abnormal channel (arrows) communicating with the posterior aspect of the spinal cord (S), as well as defect in the posterior
spinal cord (arrowheads) communicating with the central canal (CC) of the spinal cord. C, Central cystic component of posterior mass (M); E,
ependymal lining of central cyst, which communicates with central canal of spinal cord; W, outer wall of cystic mass.
cord. 100,101 his may be associated with a spina biida defect and
hydromyelia (dilation of central canal of spinal cord) but may
occur in the absence of overt spina biida. 102 Diastematomyelia
may also be associated with segmental anomalies of the vertebral
bodies or visceral malformations such as horseshoe or ectopic
kidney, utero-ovarian malformation, and anorectal malformation.
If the spinal canal is traversed by a bony septum or spur, the
septum will appear as an abnormal hyperechoic focus, 103-105 which
is best demonstrated in the posterior transaxial and lateral
longitudinal scan planes (Fig. 35.18). When diastematomyelia
is not associated with other spinal anomalies, the prognosis is
favorable. In seven of eight cases reported by Has et al., 106 the
defects had normal amniotic AFP and AChE levels and were
considered isolated. heir review of the literature showed 26
cases diagnosed prenatally, 12 of which had no associated
abnormality and had a favorable prognosis.
SCOLIOSIS AND KYPHOSIS
Kyphosis is exaggerated curvature of the spine in the sagittal
plane. Scoliosis is lateral curvature of the spine in the coronal
plane. Kyphosis and scoliosis may be positional and nonpathologic
or permanent based on an underlying structural abnormality,
such as hemivertebrae, butterly vertebrae, and block vertebrae.
Pathologic kyphosis and scoliosis are oten associated with spina
biida or ventral abdominal wall defects. 107 Less common
associations include limb–body wall complex, amniotic band
syndrome, arthrogryposis, skeletal dysplasias, VACTERL association
(vertebral abnormalities, anal atresia, cardiac abnormalities,
tracheoesophageal istula, renal agenesis, and limb defects), 108,109
and caudal regression syndrome. Mild scoliosis may be caused
by a hemivertebra (Fig. 35.19). 106,109
he posterior longitudinal scan is the best view to assess for
kyphosis; the lateral longitudinal plane is the best to assess for
scoliosis (Fig. 35.19). Because oligohydramnios can cause
positional curvature in the fetal spine, a conident diagnosis of
pathologic kyphosis or scoliosis should be made only if
the curvature is severe. Possible associated anomalies must then
be sought because prognosis depends on the coexistent
anomalies.
A hemivertebra represents underdevelopment or nondevelopment
of one-half of a vertebral body; that is, one of the two early