Fig 4.

Examples of segmental and pleurisegmental ICA dysgenesis. Lesions of the ICA, especially dysgenesis, narrowing, and nonvisualization, often involve the entire length of the artery (red arrows, A) or relatively long portions of the artery corresponding to developmental segments (red arrow, B). The right proximal MCA shows diminished flow-related enhancement as well (red asterisk, A). There is segmental dysgenesis of the petrous left ICA with irregular enlargement of the artery (B). Note also a markedly enlarged left ECA, which supplies a large hemangioma, and an absent right A1 segment.