Nomura et al. reported a case of extracranial common carotid artery pseudoaneurysm (pseudo-ECAA) with a rare clinical course and pathological features. A 58-year-old man presented with swelling and purpura on the left side of his neck after sneezing. Radiological examinations suggested a ruptured left common carotid artery aneurysm. The operative findings were consistent with a pseudoaneurysm. Pathological examination revealed disarrangement and degeneration of smooth muscle fibers in the media, in addition to scattered foci of mucoid accumulation and irregular-shaped cavitation in the medial extracellular matrix, raising the possibility of an intrinsic dysfunction of the vascular wall in the pathological process of pseudoaneurysm formation ¹⁾.