Diagnostic ultrasound ( PDFDrive )

CHAPTER 46 Duplex Sonography of the Neonatal and Infant Brain 1581
A
B
C
D
FIG. 46.7 Severe Perinatal Hypoxic Ischemic Injury in a Full-Term Infant With Additional Respiratory Distress Due to Meconium Aspiration.
(A) and (B) Initial ultrasound study shows diffuse brain edema with increased echogenicity of the cerebral white matter, accentuated corticomedullary
differentiation, partially interrupted cortex along the midline (arrows), and slitlike ventricles. Anterior cerebral artery Doppler shows
elevated low during diastole and a reduced resistive index (RI) value (0.31). (C) and (D) Follow-up imaging shows a progressive severe tissue injury
with global gray and white matter echogenicity (loss of corticomedullary differentiation) and ventriculomegaly with pseudonormalization of the RI
value (0.60).
pattern of vasodilation is thought to be caused by the uncoupling
of CBF from local metabolic demands and is known as luxury
perfusion. 50,51
HYDROCEPHALUS
As ICP rises, arterial low tends to be more afected during diastole
than during systole, resulting in an elevated pulsatility of low
and increased RI. Seibert and colleagues showed that increasing
RI correlates well with ICP elevation in an experimental canine
model of hydrocephalus. 52 Also, signiicant decreases in pulsatility
and RI values have been shown to occur ater ventricular tapping
and shunting in infants with hydrocephalus. 53,54 However, elevated
ICP may not always be present in infants with ventricular dilation,
and the RI values may be well within the normal range. Furthermore,
the RI values vary with gestational and postnatal age,
cardiac function, heart rate, patency of the ductus arteriosus,
and executed treatment. Consequently, care should be taken to
not use the RI value as a sole indicator of raised ICP. 54
Several additional variations of the duplex Doppler technique
can be applied to enhance the diagnostic sensitivity and speciicity
of the imaging. Doppler sonography of the anterior cerebral
artery or MCA during fontanelle compression may be useful in
the early identiication of infants with abnormal intracranial
compliance before development of increased ICP, as shown by
elevated baseline RI. 21 Taylor and Madsen directly measured
changes in ICP and intracranial RI before and ater ventricular
drainage procedures. 55,56 hese studies showed that the change