Abstract-Intimal cushions that project into the lumen of arteries are precursors of atherosclerotic plaque formation. The "carotid siphon," although frequently affected by atherosclerosis, was never analyzed for the occurrence of neonatal intimal hyperplasia. This study provides a topographic and morphometric analysis of intimal cushions in the parasellar internal carotid artery (pICA) of the human infant. A total of 35 specimens were studied in detail, using both standard histological techniques and a new method of computer-aided 3D reconstruction. Intimal hyperplasia occurred at 3 characteristic locations of the pICA: (1) the convex side of the posterior knee (C5 cushion), (2) the bottom of the horizontal segment (C4 cushion), and (3) the concave side of the anterior knee (C3 cushion). The extension of the cushions and the degrees to which they occluded the vessel lumens were measured. The complex shape of the pICA required 3D computer models for exact topographical descriptions and precise measurements. Our results suggest that the occurrence and degree of intimal hyperplasia are related to shape changes of the pICA during postnatal development. We predict that individuals who retain the relatively straight course of the fetal pICA throughout their lives are less prone to develop atherosclerotic lesions at this portion of the carotid artery. Key Words: intimal cushion Ⅲ hemodynamics Ⅲ 3D reconstruction Ⅲ internal carotid artery Ⅲ child I n the carotid artery system, the parasellar internal carotid artery (pICA) has a high propensity toward atherosclerosis, and lesions at this location frequently cause stroke. 1-7 Sites of intimal hyperplasia, which appear as intimal cushions that project into the lumen of arteries, represent precursors of atherosclerosis. 8,9 Such intimal cushions occur after vascular injury 10 -12 and vascular surgery, 13-17 but they are also physiologically present near the branchings and divisions of intracranial arteries in neonates 18 -21 and infants. [22][23][24] The extracranial carotid system and its intracranial branches have been studied extensively in regard to intimal hyperplasia and atherosclerosis. [25][26][27][28] In contrast, information about the occurrence, position, and size of intimal hyperplasia in the pICA is scant, and information about atherosclerotic plaques is contradictory. 29 -35 This lack of information is caused by the hidden position of the pICA, which prevents the use of modern in vivo techniques such as ultrasound. In addition, the strongly curved course of the blood vessel impedes exact positional and morphometric analyses based on individual histological sections.In 84% of adults, the pICA has the characteristic doublebent shape that gave rise to the term "carotid siphon," 36 but in all neonates, the pICA takes a much straighter course. This indicates that the shape of the pICA is strongly transformed during early childhood. 37 This period of life also coincides with the occurrence of sudden infant death syndrome (SIDS).One of the established factors in the...
