Article Figures & Data
Figures
- fig 1.
Case 1: Hypoplasia of the left ICA.
A, Source image from a 3D time-of-flight MR angiogram shows diminished flow-related signal intensity within the petrous portions of the left ICA (arrow).
B, Compressed image from the MR angiogram shows a tortuous, enlarged PCOM (arrow) extending forward to supply the left MCA. The left ACA is supplied via a patent ACOM (arrowhead). There is no perceivable flow-related signal intensity within the supraclinoid left ICA on the compressed image.
C, Axial image from a CT angiogram at the level of the petrous ICA shows hypoplasia of the left carotid canal (arrowhead).
- fig 2.
Case 2: Agenesis of the left ICA.
A, Source image from a 3D time-of-flight MR angiogram reveals absence of flow-related signal within the left petrous ICA (arrow).
B, Compressed view from the MR angiogram displays absence of flow-related signal intensity within the left ICA with collateral supply to the left hemisphere through a patent ACOM. Normal flow is present within the right ICA (arrowhead). Focal loss of flow-related signal intensity within the A1 segment of the right ACA (arrow) represents a clinically insignificant stenosis.
C, Axial CT scan of the skull base shows absence of the left carotid canal and a normally developed right carotid canal (arrow).
D, Collateral supply to the left cerebral hemisphere is provided through a patent ACOM, as demonstrated on the frontal view from the right carotid arteriogram. Stenosis of the A1 segment of the right ACA is revealed again (arrow).
- fig 3.
Case 3: Absence of the right ICA.
A and B, Frontal (A) and lateral (B) projections from a left CCA arteriogram show an anomalous communication between the cavernous portions of the ICAs (arrow). This anomalous communication courses through the sella turcica. The right ACA is supplied via a patent ACOM, with the right A1 segment either being aplastic or extremely hypoplastic. The right MCA is a continuation of the right supraclinoid ICA.
- fig 4.
Case 4: Aplasia of the left ICA.
A, Frontal view from a right CCA arteriogram shows collateral flow to the left ACA across a patent ACOM (arrow).
B, Frontal view from a left vertebral arteriogram displays collateral flow to the left MCA (arrow) via forward flow through a patent PCOM (arrowhead).
C, Axial CT scan through the skull base reveals a diminutive left carotid canal (arrow).
- fig 5.
A and B, Illustrations of the developing embryo at 6 mm (A) and 11 mm (B). After Congdon, as reproduced in (5); see text
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