Diagnostic ultrasound ( PDFDrive )

1686 PART V Pediatric Sonography
Intradural lipomas (Fig. 49.20) can be found anywhere in
the spinal canal but are more frequently lumbosacral. heir
embryology and pathology is similar to lipomas with dural defects,
but they are contained within an intact dural sac. hey are located
in the midline along the dorsal surface of the placode. hey are
generally subpial and may bulge posteriorly in the subarachnoid
space. If large they can displace the cord laterally. 10 heir size
can vary and they can be multifocal. Intramedullary lipoma
refers to fatty iniltration within the cord; the lipoma does not
extend beyond the pia.
Dorsal dermal sinuses (Fig. 49.21) are epithelium-lined istulas
that connect the skin to the central nervous system and meninges
and are thought to result from focal incomplete disjunction of
cutaneous ectoderm from neuroectoderm. hey should be
suspected on physical examination if there is a midline dimple
or ostium above the gluteal clet and more than 2.5 cm above
the anus, which can be associated with a hairy nevus, capillary
FIG. 49.18 Terminal Myelocystocele in a Fetus at 31 Weeks’
Gestation. Oblique coronal view shows the well-deined, echogenic
skin covering characteristic of these lesions (arrows).
hemangioma, or hyperpigmented patch. he sinus is seen as a
hypoechoic band that extends across the subcutaneous tissues,
through an osseous defect, and into the spinal canal to the dural
sac and may end in the subarachnoid space, the conus medullaris,
the ilum terminale, a nerve root, a dermoid, or an epidermoid
cyst. he cord is usually low and tethered. 12 Sinuses can cause
leakage of CSF if they are open to the subarachnoid space. In
this situation, sterile gel and a probe cover should be used. he
dermal sinus can originate from the skin overlying a lipomyelocele.
Dermoids are common (11%). 5,10 hey can be infected and are
usually in the cauda equina or conus medullaris. he lumbosacral
region is the most common site of such sinuses, and if present,
the skin opening tends to be positioned cephalad to the point
of contact with the dura. he sinus is easier to recognize in the
midline sagittal plane than on transverse images. On sagittal
views, the sinus is seen as a hypoechoic stipe in the subcutaneous
fat. Occipital, cervical, and thoracic sinuses can all occur but are
less common. he chief risks of undiagnosed dorsal dermal
sinuses are infection, chemical meningitis from rupture into the
subarachnoid space, and compression injury from any associated
intradural mass. 71-76
Complex Dysraphic States (Disorders
of Gastrulation)
Disorders of Midline Notochordal Integration. Abnormal
development of the notochord results in complex malformations
that involve the spinal cord and other organs. hese disorders
are present without a subcutaneous mass, except for the rare
hemimyelocele and hemimyelomeningocele. he disorders of
midline notochordal integration cause failure of fusion in the
midline to form a single notochordal process and result in
longitudinal notochordal splitting. 77
he rarest and most severe entity is dorsal enteric istula, in
which an abnormal neurenteric canal connects the skin with
the bowel and crosses a space between a duplicated spine and
cord. 4 Neurenteric cysts are in the spinal canal, can remain
trapped between a split notochord, and are lined by alimentary
tract epithelium; their internal contents, although variable, are
usually similar to CSF. hey are typically intradural, in the
A
B
FIG. 49.19 Fibrolipoma of Filum Terminale. (A) Sagittal ultrasound and (B) transverse T1-weighted magnetic resonance image show that
the ilum terminale is abnormally thickened and echogenic (arrow), with high T1 signal in the ilum (arrow) on magnetic resonance imaging.