Diagnostic ultrasound ( PDFDrive )

1680 PART V Pediatric Sonography
B
A
D
C
F
E
FIG. 49.12 Variation in Normal Development of Coccyx in Six Infants. (A) Dorsal curve of the distal coccyx. Notice coccygeal skin dimple
(black arrow) and hypoechoic tract in the subcutaneous tissue (white arrow) that extends to the tip of the coccyx. See also Video 49.3. (B) The
coccygeal curve is less severe. (C) Smooth, classic curve of the cartilaginous coccyx (C). (D) A tiny ossiication nucleus is seen in the C1 segment
(arrow). (E) Larger focus of ossiication (arrow) and (F) ossiication nuclei are visible within all coccygeal segments.
neurulation, disjunction, canalization, and/or retrogressive
diferentiation of the caudal cell mass. hey can be grouped
based on clinical characteristics: nonskin-covered open neural
tube defects or skin-covered closed spinal lesions with or without
a subcutaneous mass or other cutaneous stigmata.
he terminology used to describe this spectrum of anomalies
can be confusing because there is a tendency to use the terms
imprecisely and there are several proposed classiications. his
can lead to confusion in interpreting the literature, inaccurate
assumptions about prognosis, inappropriate management, and
confusion in analyzing results of treatment. 39,47 Posterior spina
biida refers to incomplete closure of the posterior neural arch
of a vertebra. It may be isolated, incidental, and of no clinical
signiicance. he normal laminae at L5 remain unfused until 5
to 6 years. In the past, “spina biida aperta” was used to refer to
open spinal dysraphism and “spina biida occulta” to refer to
closed spinal dysraphism, but these terms are no longer favored.
A placode is a segment of lattened embryonic neural tissue
that did not undergo normal neurulation. A placode can be
terminal, if it is at the caudal end of the spinal cord, or segmental,
lying at any level of the spinal cord. A terminal placode can be
apical, involving the apex of the cord, or parietal if it involves a
longer segment.
he irst step of a clinical-neuroradiologic classiication of
spinal dysraphisms proposed by Tortori-Donati and Rossi, 5,10 is
to determine whether the malformation is exposed to air (open