Middle Cerebral Artery

MIDDLE CEREBRAL ARTERY

Mari and co-workers suggest a plane more caudal to the cerebral peduncles in the section containing the pons, medulla oblongata and the greater wings of the sphenoid.
It can also be visualized at the level of the cerebral peduncles at its anterolateral border, running anterolaterally towards the lateral edge of the orbit.
Results of a recent study (1). indicate that any segment of the MCA, with the exception of the area close to its division into terminal branches, can be sampled with good results (the distal area of the MCA does not have good reproducibility is due to a technical factor: any minimal movement of the fetal head can displace the sample volume in one of the terminal branches). There are usually two or three terminal branches but in my experience there can be as many as five. The MCA-PSV should be sampled at its proximal point, soon after its origin from the internal carotid artery, avoiding the need for angle correction, because measurement at this point is associated with the lowest intra- and interobserver variabilities (1).

at the level of the sphenoid bones;
color Doppler identifies the circle of Willis;
the image of the circle of Willis is enlarged;
the color box is placed around the MCA;
the MCA is zoomed;
the sample volume should be placed at the center of the vessel ;
the MCA flow velocity waveforms are displayed and the highest point of the waveform (PSV) is measured.
the waveforms should be all similar.
the above sequence is repeated at least three times in each fetus (1).

Normal Waveform

Effect of breathing on the waveform

Runs laterally to the lateral sulcus of Sylvius, to reach the lateral surface of the hemisphere.
Has 4 segments.

Supplies the corpus striatum, internal capsule and lenticulostriate artery
It continues over the insula and inferior frontal gyrus, carrying about 80% of the blood flow to the hemisphere.

Systolic component with absent end diastolic velocities from 8th to 11th gestational week.
End diastolic component seen inconsistently from 11th to 13th gestational week.
End diastolic flow seen consistently from 13th gestational week.
A significant drop in PI was observed 2 weeks earlier in the MCA than in other parts of the fetal circulation.
PI increases until the late second trimester of pregnancy (Graph), followed by a decline in the third trimester. Gunnarsson and Marsal attribute this phenomenon to an evolutionary pattern in the blood supply of the developing brain, where the blood supply changes from a centrifugal to centripetal pattern as the cerebral hemispheres develop and the germinal matrix decreases.

Mari G, Abuhamad A, Cosmi E, Segata M, Altaye M, Akiyama M. Middle cerebral peak systolic velocity: Technique and variability. J Ultrasound Med 2005; 24: 425-430
Gunnarsson GO, Marsal K. Blood flow velocity waveforms in the middle cerebral, renal and femoral arteries of human fetuses. Acta Obstet Gynecol Scand 1994;