Diagnostic ultrasound ( PDFDrive )

1610 PART V Pediatric Sonography
TABLE 47.3 Severity of Vasospasm With Typical Velocities 29
Mild (cm/sec) Moderate (cm/sec) Severe (cm/sec)
Terminal ICA 120-130 >130
MCA 120-130 130-200 >200
Basilar 60-80 80-115 >115
Vertebral 60-80 >80 >80
ACA >50% increase in 24 h >50% increase in 24 h
PCA >110 >110
ACA, Anterior cerebral artery; ICA, internal carotid artery; MCA, middle cerebral artery; PCA, posterior cerebral artery.
With permission from Kalanuria A, Nyquist P, Armonda R, Razumovsky A. Use of transcranial Doppler (TCD) ultrasound in the neurocritical care
unit. Neurosurg Clin N Am. 2013;24:441-456. 29
and a ratio greater than 6 is suggestive of severe vasospasm. A
ratio less than 3 in patients with elevated low velocities is seen
as a result of physiologic processes such as hyperemia or autoregulation.
29,113 In a similar way, a ratio between the basilar artery
and the extracranial vertebral artery can also be obtained. 33 A
basilar artery to vertebral artery ratio of 2.0 to 3.0 is associated
with mild to moderate vasospasm and a ratio greater than 3 is
suggestive of severe vasospasm. 113
Evaluation of Collateral Flow
When stenosis or occlusive disease is present, collateral low via
the circle of Willis can be identiied with TCD evaluation.
Angiographic examinations provide a better evaluation and
diagnosis, but TCD can help with screening and reduce the
number of negative invasive procedures. 38
Collateral low can be seen in the anterior communicating
artery with a high sensitivity (95%) and speciicity (100%) (Fig.
47.17). It is diicult to distinguish from adjacent ACA low but
indirect signs can be identiied. 38 It is slightly more diicult to
evaluate the posterior communicating artery for collateral low,
with a sensitivity of 87% and speciicity of 95%. Reversed OA
low with low pulsatility with or without delayed systolic low
acceleration helps in the diagnosis of occlusion or critical stenosis
with high speciicity (100%) and good sensitivity (75%); normal
low direction does not exclude proximal occlusion/stenosis of
ICA or a stenosis of less than 80%. 38
Leptomeningeal collaterals more commonly originate from
the ACA and can be seen in patients with proximal MCA occlusion.
Leptomeningeal collateral presence has a sensitivity of
81% and speciicity of 77% for MCA occlusion. In the presence
of leptomeningeal collaterals secondary to MCA occlusion, high
velocity and low resistance low in the ipsilateral ACA or PCA
can be seen; a 30% velocity diference can be noted between the
right and let ACA or PCA. 38 In the setting of basilar artery
occlusion, reversal of basilar artery low can be seen characterized
by low resistance low toward the probe via suboccipital window
and decreased velocity and high resistance low in vertebral
arteries. Reversal of vertebral artery low can also be seen as a
collateral pathway.
Moyamoya angiopathy is a progressive stenosis of the terminal
ICA and proximal MCA and ACA with development of a network
of abnormal collateral vessels. It can be idiopathic (moyamoya
disease) or associated with another disease (moyamoya syndrome)
such as SCD, neuroibromatosis I, Down syndrome, or Turner
syndrome (see Fig. 47.15). In patients with moyamoya angiopathy,
TCD might be useful in monitoring, but more studies are needed
to validate its use. 114
Headaches
Prevalence of headache in children varies depending on the
population studied and has been reported to range between 8%
and 60%. Prevalence increases with age and the most common
causes are tension and migraine. No statistical diference has
been identiied in the overall prevalence in SCD when compared
to control population.
TCD has been used in the evaluation of adults with vascular
headaches. 7 hie et al. 115 found a signiicant increase in mean
velocity in migraine patients compared to controls during
headache-free periods. hey then continued to evaluate the
patients during headache episodes and demonstrated that those
with common migraines had decreased intracranial velocities
and increased pulsatility, whereas symptomatic patients with
classic migraines demonstrated opposite indings with an increase
in velocities and a decrease in pulsatility 116 (Fig. 47.18). Diferent
studies have shown migraine headaches to be associated with
mild to moderate vascular narrowing and/or decreased blood
low 117 as well as a decrease in RI and PI. 118
In pediatric patients, Wang et al. 119 evaluated the utility of
TCD sonography in the assessment of isolated headaches and
demonstrated a sensitivity and speciicity in detecting intracranial
lesions of 75% and 99.7%, respectively. Another study evaluated
children between 5 and 17 years of age and suggested the possibility
of cerebral vasospasm in the headache-free periods. 120
In a study of 1176 pediatric patients with SCD, 36% had
recurrent headaches, with migraine in 15%. In this study, no
association was seen between headaches and silent stroke. On
the other hand, recurrent headaches and migraines were associated
with lower hemoglobin concentration and higher pain event
rates. 121 Lower hemoglobin levels are associated with increased
cerebral blood low velocities in children with SCD with normal
neurologic examinations and vascular headaches when compared
to those without headaches. Similar indings have been described
in adults with SCD and severe/frequent headaches versus mild
or absent headaches. 121 TCD sonography may assist in the