Diagnostic ultrasound ( PDFDrive )

1678 PART V Pediatric Sonography
A
B
C
D
E
FIG. 49.9 Filar Cysts. (A) Small round cyst (arrow) distal to the conus medullaris is a normal variant. The rest of the ilum terminale is seen
distal to the cyst, has slightly echogenic borders and central hypoechogenicity, and can be distinguished from the nerve roots of the cauda equina.
(B) Another patient with an oval ilar cyst (arrow); in another patient, (C) and (D) sagittal and axial views of the spine and (E) T2-weighted sagittal
magnetic resonance image show a large ilar cyst (arrow).
FIG. 49.10 Normal Epidural Fat. Epidural fatty layer can sometimes
be prominent (arrow). Note the distal cord (C) and the cauda equina
(CE).
he normal conus is typically located in the ventral thecal
sac on prone position, between L1 and L2 and occasionally
extending to the superior endplate of L3. However, the range of
normal varies in children from T10-T11 to the superior end
plate of L3. 24 On MRI, the position of the conus ascends from
20 to 38 weeks. he mean conus position is L4 from 21 to 25
weeks, L3-4 from 26 to 30 weeks, L2-3 from 31 to 35 weeks, and
L2 ater 36 weeks. 25 A conus position at the third lumbar vertebra
(L3) or above by the beginning of the third trimester should be
considered normal. 26-28 A conus tip at the L3-L4 disc space level
is too low. 24,29-35 herefore a conus position of L3 proper in the
late preterm infant is equivocal, requiring follow-up. 8,32 Factors
other than conus position alone need to be considered when
determining the need, if any, for further evaluation with MRI.
When an experienced spine sonographer inds that the tip of
the conus medullaris is positioned over the upper third of the
L3 vertebral body with normal nerve root pulsation, and if no
other abnormalities are noted and the physical examination
indings are not suspicious, we do not generally recommend
further imaging.
If subsequent MRI is deemed prudent ater an equivocal
ultrasound examination, many pediatric neuroradiologists support
waiting until the infant is at least 3 months old because there is
poor tissue contrast (low signal to noise) in the newborn spine. 36
Greater anatomic detail can be displayed with MRI in the larger
infant using standard techniques.
As vertebral ossiication progresses and the infant becomes
more active, fewer details are visible with ultrasound.
SPINAL ANOMALIES
Tethered Spinal Cord
Tethered cord syndrome is a clinical condition that can be seen
with a spectrum of pathologic causes that tether the spinal cord
in a lower-than-normal position and may lead to neurologic,