At what age can a patient undergo a Middle Cerebral Artery (MCA) doppler test?

MCA Doppler Age Guidelines

For fetal assessment, MCA Doppler should be performed starting at 18-20 weeks of gestation when technically feasible, with routine surveillance beginning at 32 weeks for fetal growth restriction and at 2 years of age for sickle cell disease screening in children. 1

Fetal MCA Doppler Timing

For Fetal Anemia Screening

• MCA peak systolic velocity (MCA-PSV) measurements can begin at 18 weeks of gestation, which is when fetal blood sampling or intrauterine transfusion becomes technically feasible 1
• Surveillance should be reserved until the pregnancy is advanced enough (typically 18-20 weeks) for intervention to be possible 1
• After 24 weeks of gestation, routine testing is performed weekly, but may be done more frequently with higher MoM levels or other abnormal findings 1

For Fetal Growth Restriction (FGR)

• MCA Doppler assessment is primarily indicated after 32 weeks of gestation for late-onset FGR, as this is when cerebral blood flow redistribution becomes most clinically relevant 2, 1
• Before 32 weeks, umbilical artery Doppler is the primary monitoring tool for early-onset FGR 2
• Multiple guidelines recommend MCA Doppler at >32 weeks or after 34 weeks when FGR is diagnosed 1, 2

Surveillance Frequency in FGR

• For FGR with estimated fetal weight ≥3rd-9th percentile: MCA Doppler every 2 weeks after 32 weeks 2
• For severe FGR with estimated fetal weight <3rd percentile: weekly umbilical artery Doppler, with MCA Doppler added after 32 weeks 2
• New Zealand guidelines specifically recommend MCA Doppler and cerebroplacental ratio every 2 weeks after 34 weeks 2

Pediatric MCA Doppler Timing

For Sickle Cell Disease Screening

• The National Heart Lung and Blood Institute recommends transcranial Doppler ultrasound screening for children with sickle cell disease between 2 and 16 years of age, performed every 6 months 1
• Velocity measurements from the distal internal carotid artery or proximal middle cerebral artery assess stroke risk 1
• Time-averaged means of maximum velocity <170 cm/sec indicate low stroke risk, 170-199 cm/sec indicate intermediate risk, and >200 cm/sec indicate high risk (40% in next 3 years) 1

For Acute Stroke Evaluation

• MRA of the head (which includes MCA assessment) is appropriate for initial imaging in children >6 months of age with acute stroke presentation 1
• MRA is the study of choice to screen for vessel stenosis in children with sickle cell disease who have elevated transcranial Doppler velocities 1

Common Pitfalls to Avoid

• Do not perform MCA Doppler before 32 weeks for routine FGR surveillance, as umbilical artery Doppler is the primary tool in early-onset FGR and MCA findings are less clinically relevant before this gestational age 2
• Do not delay transcranial Doppler screening in children with sickle cell disease beyond 2 years of age, as early detection of elevated velocities allows for preventive transfusion therapy to reduce stroke risk 1
• Do not rely on MCA Doppler alone for fetal anemia assessment—the proper technique requires specific measurements at the origin of the MCA from the internal carotid artery, with at least 3 measurements taken and the highest value used 1
• Avoid performing fetal MCA-PSV measurements during fetal movement or breathing, as changes in fetal heart rate can impact the MCA-PSV values 1