Diagnostic ultrasound ( PDFDrive )

CHAPTER 47 Doppler Sonography of the Brain in Children 1609
A
B
C
FIG. 47.16 Vasospasm With Aneurysm. Ten-year-old boy with acute headache. (A) MR angiogram demonstrates narrow supraclinoid carotid,
narrow A1 segment, and small left bifurcation aneurysm (arrow). (B) After clipping of aneurysm, susceptibility metal artifact limits MRA evaluation
of the left proximal M1 segment. (C) On day 15, TCD sonogram demonstrates high PSV of 199 cm/sec, consistent with moderate vasospasm.
Patient did well after medical management.
to severe head trauma, vasospasm peaked at day 2 or 3 and
lasted for 2 to 4 days. 108
In the presence of vasospasm, blood low velocity increases
because of a decrease in the luminal cross-sectional area of the
afected vessel. hus TCD can be used to optimize timing of
therapy and is useful in following the efects of therapy (Fig.
47.16). When a hemodynamically signiicant vasospasm is
suggested, emergency cerebral angiography with balloon dilation
angioplasty or intraarterial infusion of vasodilating agents
may be helpful. 109 Serial TCD studies showing reduction in
velocities indicate the appropriate time to withdraw therapy,
minimizing complications and shortening intensive care unit
stays. TCD is most accurate in detecting vasospasm of the MCA.
TCD cannot be used to assess the ACA beyond its A1 segment
and is limited in the evaluation of the peripheral branches of
the MCA.
It is important to remember that studies evaluating vasospasm
assess the PSV. Depending on the mean velocities measured,
vasospasm can be considered mild, moderate, or severe as
demonstrated by angiography (Table 47.3). 29 Philip et al. 110
described increased arterial low velocities as those elevated by
more than 2 SD above normal for age and sex. TCD values
should always be combined with clinical and laboratory data. 111,112
A steep increase (>25 cm/sec/day) in velocity in the irst few
days ater subarachnoid hemorrhage is associated with a worse
prognosis. Sources of error in the detection of vasospasm by
TCD sonography (vs. arteriography) include missing peripheral
vasospasm, copresence of increased intracranial pressure (ICP),
and low volume low. 7 he Lindegaard ratio (ratio of velocities
of the MCA/ipsilateral ICA) can be used to diferentiate increased
velocities due to vasospasm versus other causes. A Lindegaard
ratio of 3 to 6 is suggestive of mild to moderate cerebral vasospasm