Abstract
Purpose: To report a rare case of internal carotid artery (ICA) agenesis combined with Lie’s types D and A, diagnosed by magnetic resonance angiography (MRA).
Methods: A 60-year-old woman with dizziness underwent cranial magnetic resonance imaging (MRI) and MRA of the intracranial region for the evaluation of brain and vascular lesions. The magnetic resonance machine was a 3.0-T scanner.
Results: MRI showed no abnormalities, except for multiple small white matter lesions. MRA showed that the left ICA was absent, except for the supraclinoid segment, and an anastomotic vessel was present between the paraclinoid segments of the bilateral ICAs, suggesting Lie's type D ICA agenesis. The left posterior communicating artery (PCoA) was also present. Thus, there were also features of type A ICA agenesis. The anastomotic vessels between the bilateral ICAs and ipsilateral PCoA were relatively small in caliber.
Conclusion: Lie’s type D ICA agenesis usually does not communicate with the anterior and posterior circulations. We encountered a case of combined type D and type A ICA agenesis. To our knowledge, no similar case has been reported in the English literature. This is the second case of type D ICA agenesis with patent ipsilateral PCoA. In these two cases of patent ipsilateral PCoA, the anastomotic vessels between the bilateral ICAs were relatively small in caliber. ICA agenesis is an extremely rare abnormality, and most patients are asymptomatic. However, it can be associated with an increased risk of stroke and aneurysm formation.