Diagnostic ultrasound ( PDFDrive )

CHAPTER 45 Neonatal and Infant Brain Imaging 1557
A
B
FIG. 45.54 Hyperechoic Caudate Nucleus (Bilateral). (A) and (B) Coronal and sagittal sonograms show echogenic caudate nuclei that did
not appear abnormal until the premature infant was about 1 month of age (postulated to be remote ischemic damage).
with congenital CMV, half had lenticulostriate vasculopathy on
an initial head ultrasound, and this was a marker for sensorineural
hearing loss. 187 In a study by Chamnanvanakij and colleagues,
of 10 preterm infants who ultimately developed linear hyperechogenicity
in the basal ganglia and thalamus, the mean age of
diagnosis was 1 month and it was a marker for more difuse
brain injury and for poor neurologic outcome. 188
Hyperechoic Caudate Nuclei
Bilateral hyperechoic foci in the caudate nuclei develop in the
characteristic location of GMH but are atypical in that they are
sharply marginated, teardrop shaped, bilateral, and symmetrical
(Fig. 45.54). Schlesinger and colleagues 189 reported that ive of
nine infants had ischemia and two were normal in this area,
based on MRI and histopathologic review. Hyperechoic caudate
nuclei seem to occur late, usually ater the irst week of life, when
most GMH occurs.
POSTTRAUMATIC INJURY
Subdural and Epidural Hematomas
Subdural and epidural hemorrhage can be a diicult diagnosis
on sonography compared with CT or MRI. 7 On sonographic
examination, these hematomas appear as unilateral or bilateral
hypoechoic luid collections surrounding the brain parenchyma
(Fig. 45.55). Subdural hematomas are uncommon in newborns
and not necessarily indicative of birth trauma—13 of 26 afected
infants diagnosed on CT had a history of trauma. 190 Fortunately,
surgery is rarely required. Small amounts of luid may be diicult
to detect secondary to the near-ield artifact inherent in every
transducer. However, this is less of a problem if a high-frequency
transducer (10-12 MHz) is used. With a lower-frequency transducer,
interposing an acoustic gel pad between the transducer
and the fontanelle can assist in eliminating the near-ield artifact.
Magniied coronal sections with high-frequency linear transducers
(at least 10-12 MHz) are best for appreciating the epidural and
subdural collections in the supratentorial space. Imaging through
the foramen magnum or posterior fontanelle can assist in diagnosing
infratentorial extraaxial luid collections.
Color Doppler sonography has been shown to distinguish
subarachnoid and subdural luid and hemorrhage based on
displacement of vessels on the brain surface (see Fig. 45.55; see
Chapter 46). Doppler ultrasound may be useful in determining
which patients may be simply observed and which require MRI
for a more speciic diagnosis of hemorrhage.
Ater the neonatal period, when birth trauma may cause
hemorrhage, the presence of new subdural luid collections should
suggest preexisting meningitis (most oten from Haemophilus
inluenzae) or nonaccidental trauma. If an infant’s head circumference
increases abnormally quickly ater the irst 2 weeks of life,
a CT examination is usually performed to search for extraaxial
luid, because the most common cause is subdural hemorrhage,
not hydrocephalus. If a sonographic examination is performed,
the clinician should carefully search the near ield with magniied
views for extracerebral luid and cerebral tears, as well as membranes
seen in chronic subdural luid collections.
INFECTION
Congenital Infections
Congenital infections can have serious consequences for the
developing fetus. Death of the fetus, congenital malformations,