Diagnostic ultrasound ( PDFDrive )

CHAPTER 47 Doppler Sonography of the Brain in Children 1611
A
B
C
FIG. 47.17 Reversed ACA Flow in 12-Year-Old After
Motor Vehicle Accident With Left ICA Dissection and
Subarachnoid Hemorrhage. (A) Axial MR angiogram
demonstrates no low in the left ICA. Additional MRI
sequences (not shown) conirmed the presence of a left
ICA dissection. (B) TCD image of the left ACA demonstrates
low toward the transducer similar to the ipsilateral MCA
which is abnormally reversed. (C) TCD image of the right
ACA demonstrates appropriate low away from the
transducer. Note the elevated PSV of 249 cm/sec consistent
with vasospasm from subarachnoid blood.
diferential diagnosis of headaches of unknown causes and could
prove useful in therapeutic interventions.
Sleep Apnea
Several studies have demonstrated changes in MCA velocities
in children with sleep-disordered breathing, a spectrum of upper
airway obstruction ranging from primary snoring to obstructive
sleep apnea. Increases in MCA low velocity have been documented
in children with mild sleep-disordered breathing. 122 In
a group of children with sleep-disordered breathing followed
ater adenotonsillectomy, MCA velocities decreased (suggesting
a normalization of MCA velocities) with a resultant increase in
mean overnight oxyhemoglobin saturation postoperatively. hese
children demonstrated an improvement in processing speed and
visual attention postoperatively as well. 123
In patients with SCD, sleep-disordered breathing and snoring
have a high prevalence, with 37% snoring and 24% positive
polysomnography indings. 124 In a study evaluating overnight
pulse oximetry, TCD, and central nervous system events in
patients with SCD, an association between nocturnal oxyhemoglobin
desaturation and central nervous system event risk was
seen. Evidence of obstructive sleep apnea, seen as dips in overnight
pulse oximetry, was not useful to predict central nervous system
events. 125 Another study evaluating the prevalence of sleepdisordered
breathing and the association with high-risk TCD
velocities in patients with SCD showed no signiicant diference
in the TCD velocities and percentage of patients with high-risk
velocities when comparing the snorers with the nonsnorers.
Overall, there was no association between sleep-disordered
breathing or snoring and cerebrovascular risk. 124
Hydrocephalus
he ability to diferentiate between ventriculomegaly and
hydrocephalus (increasing ventriculomegaly and increasing ICP)
can be diicult. When hydrocephalus develops, ICP increases,
resulting in a decrease in diastolic low. Stable ventriculomegaly