Diagnostic ultrasound ( PDFDrive )

CHAPTER 45 Neonatal and Infant Brain Imaging 1555
3
B
O
A
B
FIG. 45.52 Brainstem and Cerebellar Hemorrhage. (A) and (B) Sagittal and axial sonograms show highly echogenic hemorrhage in the
brainstem (B), cerebellar vermis, and hemispheres, and posteriorly in the occipital cortex (O), after acute, near-total intrauterine asphyxia. Clot is
also seen in the third ventricle (3) just below the cavum septi pellucidi.
and focal abnormal echogenicity in cerebral cortex and deeper
structures. Doppler ultrasound to look for low luctuations in
resistive indices and low in the dural sinuses is valuable.
In term infants treated with hypothermia for hypoxic ischemic
encephalopathy, there have been rare reports of IVH. 166,172,173
However, outcomes ater hypothermia for HIE from the NICHD
Neonatal Research Network studies show that there is a decrease
in deaths and that hypothermia does not increase rates of severe
disability among survivors.
Neonatal HIE is best evaluated with ultrasound in the irst
few days of life. MRI is the most sensitive and speciic imaging
technique, and is useful in stable term infants. Some authors
suggest that MRI late in the irst week of life may be useful but
term-equivalent age is best for prognosis. However, the brain
may appear normal or near normal at 5 to 7 days ater the event.
For severe hypotensive episodes, thalami, brainstem, and cerebellum
are most sensitive owing to their high metabolic activity.
In premature infants, HIE injury appears as increased echogenicity
on ultrasound, hypoattenuation on CT (may be missed because
of high neonatal brain water content), and hyperintensity from
restricted difusion on difusion-weighted imaging. In term infants,
the lateral thalami, posterior putamen, hippocampus, brainstem,
corticospinal tracts, and sensorimotor cortex are most
afected. 88,89,174
Focal Infarction
Cerebral infarction in the neonate, aside from PVL or periventricular
hemorrhagic venous infarction, is uncommon. Risk
factors are prematurity, severe birth asphyxia, congenital heart
disease (resulting in a let-to-right shunt), meningitis, emboli
(from the placenta or systemic circulation), polycythemia,
hypernatremia, and trauma. 120,175,176 Symptoms vary, ranging from
asymptomatic to seizures with lethargy and coma. he MCA
distribution is the most frequent site, although the anterior and
posterior circulations have also been afected. 46 Single areas of
infarction are more frequently seen in full-term infants, whereas
premature infants oten demonstrate multiple sites of injury.
Cerebral blood low evaluation with color and or power Doppler
sonography are used in unstable neonates, and difusion-weighted
MRI is used in stable infants to identify the earliest signs of
stroke. 177-182
Cerebellar infarction is much less common than cerebral
infarction. However, six cases were reported in 3 years at Hammersmith
Hospital in London, diagnosed by MRI in patients at
several years of age who were born prematurely. 183 All these
patients also had IVH, and thus cerebellar damage was likely a
result of difuse ischemic injury. Only one of the six patients
was diagnosed on sonography as having cerebellar damage.
Because the vermis is so echogenic, edema or hemorrhage can
be a diicult diagnosis in this region. Cerebellar infarction was
also diagnosed with MRI in 13 patients with severe cerebral
palsy who had cerebellar hemispheric and vermian damage. 184
Now that we are routinely evaluating the posterior fossa in detail,
we are more aware of cerebellar infarction at the time of the
injury in premature infants. 185
On sonography, the infarcted brain parenchyma demonstrates
speciic indings within the irst 2 weeks (see Fig. 45.52; Fig.
45.53). hese include echogenic parenchyma, lack of arterial
pulsation, lack of blood low appreciated by pulsed or color
Doppler sonography, mass efect from edema, arterial territorial
distribution of injury, and decreased sulcal deinition. Ater 2
weeks, the echogenic lesions begin to show cystic changes, and