Fetal middle cerebral arterial Doppler assessment
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Fetal middle cerebral arterial (MCA) Doppler assessment is an important part of assessing fetal cardiovascular distress, fetal anaemia or fetal hypoxia. In the appropriate situation it is a very useful adjunct to umbilical artery Doppler assessment. It is also used in the additional work up of
- intra-uterine growth restriction (IUGR)
- twin to twin transfusion syndrome (TTTS) 5
- twin anaemia polycythaemia sequence (TAPS)
Radiographic assessment
Doppler ultrasound
For an accurate measurement, the fetal head should be in the transverse plane. The MCA vessels are often found with colour or power Doppler ultrasound overlying the anterior wing of the sphenoid bone near the base of the skull. An angle of insonation of < 15o should be used; typically, an angle that approximates zero degrees can be achieved by moving the transducer on the maternal abdomen.
ParamatersParameters used include
- fetal MCA time averaged mean velocity (TAMV)
- fetal MCA
pulsalitypulsatility index (PI) -
fetal MCA peak systolic velocity (PSV)
- the: the highest velocity should be recorded -
fetal MCA systolic/diastolic (S/D) ratio
-: a normal fetal MCA S:D ratio should always be higher than the umbilical arterial S:D ratio. - cerebroplacental ratio (CPR)
-: ratio of pulsatility index of MCA and umbilical artery
Interpretation
- in the normal situation the fetal MCA has a high resistance flow which means there is minimal antegrade flow in fetal diastole.
- in pathological states this can turn into a low resistance flow mainly as a result of the fetal head sparing theory.
- paradoxically in some situations such as with severe cerebral oedema, the flow can revert back to a high resistance pattern when the pathology hasn't yet resolved.
- cerebroplacental ratio > 1:1 is normal , <1:1 is abnormal
See also
-</ul><h4>Radiographic assessment</h4><h5>Doppler ultrasound</h5><p>For an accurate measurement, the fetal head should be in the transverse plane. The MCA vessels are often found with colour or power Doppler ultrasound overlying the anterior wing of the sphenoid bone near the base of the skull. An angle of insonation of < 15<sup>o </sup>should be used; typically, an angle that approximates zero degrees can be achieved by moving the transducer on the maternal abdomen. </p><p>Paramaters used include</p><ul>- +</ul><h4>Radiographic assessment</h4><h5>Doppler ultrasound</h5><p>For an accurate measurement, the fetal head should be in the transverse plane. The MCA vessels are often found with colour or power Doppler ultrasound overlying the anterior wing of the sphenoid bone near the base of the skull. An angle of insonation of < 15<sup>o </sup>should be used; typically, an angle that approximates zero degrees can be achieved by moving the transducer on the maternal abdomen. </p><p>Parameters used include</p><ul>
-<li><a href="/articles/fetal-mca-pulsality-index-pi">fetal MCA pulsality index (PI)</a></li>- +<li><a href="/articles/fetal-mca-pulsality-index-pi">fetal MCA pulsatility index (PI)</a></li>
-<a href="/articles/fetal-mca-peak-systolic-velocity-psv">fetal MCA peak systolic velocity (PSV)</a> - the highest velocity should be recorded</li>- +<a href="/articles/fetal-mca-peak-systolic-velocity-psv">fetal MCA peak systolic velocity (PSV)</a>: the highest velocity should be recorded</li>
-<a href="/articles/fetal-mca-systolicdiastolic-ratio">fetal MCA systolic/diastolic (S/D) ratio</a> - a normal fetal MCA S:D ratio should always be <strong>higher</strong> than the umbilical arterial S:D ratio.</li>-<li>cerebroplacental ratio (CPR) - ratio of pulsatility index of MCA and umbilical artery</li>- +<a href="/articles/fetal-mca-systolicdiastolic-ratio">fetal MCA systolic/diastolic (S/D) ratio</a>: a normal fetal MCA S:D ratio should always be <strong>higher</strong> than the umbilical arterial S:D ratio.</li>
- +<li>cerebroplacental ratio (CPR): ratio of pulsatility index of MCA and umbilical artery</li>
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