Diagnostic ultrasound ( PDFDrive )

CHAPTER 47 Doppler Sonography of the Brain in Children 1605
Left MCA
Left PCA
A
B
Basilar
D
C
FIG. 47.12 Low Middle Cerebral Artery (MCA) Velocity in
8-Year-Old Child With Sickle Cell Disease. Occluded distal
internal carotid artery (DICA) with collateralization from the PCA
and basilar artery. (A) TCD sonogram demonstrates abnormally
low velocities in the left MCA (TAMM velocity, 70.7 cm/sec)
with decreased pulsatility (RI, 0.43). No low was documented
in the left DICA. (B) and (C) Velocities in PCA and basilar artery
are higher than in left MCA. (D) Coronal reformatted MR angiogram
demonstrates occlusion of the left DICA (arrow).
TABLE 47.2 STOP Stroke
Risk Categories
Category
Low
Conditional
Abnormal
Deinition
<170 cm/sec TAMM velocity
170-199 cm/sec TAMM velocity
≥200 cm/sec TAMM velocity
or >250 cm/sec PSV
PSV, Peak systolic velocity; STOP, Stroke Prevention Trial in Sickle
Cell Anemia; TAMM, time-averaged maximum mean.
With permission from Adams RJ, McKie VC, Hsu L, et al. Prevention
of a irst stroke by transfusions in children with sickle cell anemia and
abnormal results on transcranial Doppler ultrasonography. N Engl J
Med. 1998;339(1):5-11. 73
ICA increase the risk of developing stenosis. hey also report
that increased extracranial ICA velocities (>160 cm/sec), even
in the absence of abnormal intracranial velocities, should be a
considered risk factor for cerebrovascular complications.
TCD is recommended as a screening test for all 2- through
16-year-old children with SCD. 79,80 Optimal timing and frequency
vary depending on the presence of velocities used as thresholds
(TAMM velocity range cutof of 155-170 cm/sec) and age. 56,81 It
has been suggested that SCD patients with a normal TCD can
be followed every 12 months, but closer follow-up should be
performed in patients with results at or near the threshold
(“conditional” velocities, at 3-6 months). 56 Patients with a TAMM
velocity of greater than 200 cm/sec or a PSV greater than 250 cm/
sec in the MCA on two examinations are at high risk of stroke
and are recommended for transfusion therapy. 77