Diagnostic ultrasound ( PDFDrive )

CHAPTER 47 Doppler Sonography of the Brain in Children 1613
A
B
C
D
FIG. 47.19 Shunt Dysfunction in 8-Year-Old. (A) CT scan shows mildly dilated ventricles. (B) TCD image through the temporal window
shows an increased RI of 0.82 in the MCA. (C) CT scan after shunt revision shows decrease in ventricular size. (D) TCD image of the MCA
demonstrates a decrease in RI to 0.47, now in the normal range (after age 2 years with fontanelle closure, normal RI is 0.5). (With permission from
Seibert JJ, Glasier CM, Leithiser JRE, et al. Transcranial Doppler using standard duplex equipment in children. Ultrasound Q. 1990;8:167-176. 14 )
Goh et al. 128 used an RI of greater than 0.8 as a sign of increased
ICP in the neonate and an RI of greater than 0.65 in children.
Because of varying normal values and overlapping normal and
abnormal values, RI is most useful on an individual basis following
a patient’s course to determine whether clinical changes and
ventricular dilation are secondary to increased pressure (such
as with shunt malfunction) or atrophy (Fig. 47.19). Any increase
in RI should be considered as potentially important in terms of
shunt malfunction. False-normal values may be the result of
cerebral spinal luid tracking along the shunt. Excessive thickness
of the skull may prevent TCD ultrasound from being obtained
successfully in some of these patients. 132,133
Pediatric patients with tuberculous meningitis oten have
raised ICP and cerebral vasculopathies, and attempts to obtain
a noninvasive technique to replace invasive ICP monitoring have
been studied. 134 Some researchers have suggested that TCDI can
help monitor pressure changes over time in these patients. 135
However, a study performed in children with tuberculous
meningitis with communicating hydrocephalus demonstrated
that PI obtained by TCD was not accurate in the assessment of
ICP and might not change even in cases in which a change in
ICP has been documented. 134
he use of TCD has been studied in adult patients with
idiopathic normal pressure hydrocephalus as a way of evaluating
positive results of the cerebrospinal luid tap and predict usefulness
of a shunt. In a small study performed by Sedighi et al., 136 patients
with idiopathic normal pressure hydrocephalus underwent TCD
evaluation before and ater a cerebrospinal luid tap test. In patients