The Ambiguous "Internal Carotid Artery" - Ultrasound Diagnosis of One Case of Congenital Absence of the Internal Carotid Artery

Background: Congenital absence of the internal carotid artery (ICA) is a very rare congenital anomaly of the ICA. Most reports in the literature are of individual cases, and most were diagnosed by computed tomographic angiography (CTA) or digital subtraction angiography (DSA). There are few reports on the diagnosis of congenital absence of the ICA by carotid Doppler ultrasound (CDUS). Case presentation: A 61-year-old male patient who was admitted to the hospital because of dizziness and showed no abnormality on CDUS conducted at another hospital. CDUS conducted at our hospital found maldevelopment of the right common carotid artery (RCCA) with normal a blood flow velocity and spectrum. A high-resistance frequency spectrum could be detected in the “ICA” that continued directly from the RCCA, and two adjacent small blood vessel branches were also observed. Superficial temporal artery tap and tracing of the courses of the small blood vessels confirmed that the RCCA directly continued to the external carotid artery (ECA). The final diagnosis was congenital absence of the ICA, which was confirmed during the clipping of an anterior communicating artery (ACoA) aneurysm. Conclusion: CDUS, as a noninvasive and rapid screening tool for cervical vascular diseases, offers a new approach for the diagnosis of congenital absence of the ICA.