Flow-mediated pseudolesion mimicking an intracranial aneurysm secondary to cervical internal carotid artery dissection: illustrative case.

backgroundHemodynamic alterations caused by internal carotid artery (ICA) dissection (ICAD) may obscure the identification of intracranial aneurysms. These flow disturbances can compromise angiographic assessment and influence therapeutic decision-making. OBSERVATIONS: A 51-year-old female patient underwent digital subtraction angiography (DSA), which initially suggested the presence of a supraclinoid ICA aneurysm, prompting a referral for surgical intervention. However, anomalous collateral circulation patterns raised suspicion of proximal ICA pathology. Subsequent focused angiography identified a cervical ICA origin dissection. After endovascular stent placement, repeat imaging demonstrated that the previously observed "aneurysm" was in fact a hemodynamically distorted posterior communicating artery infundibulum. Thus, the scheduled craniotomy was deemed unnecessary and canceled. LESSONS: This report represents the first documented instance of a flow-mediated pseudolesion mimicking an intracranial aneurysm secondary to proximal ICAD. Although DSA remains the diagnostic criterion standard, this case underscores the potential for hemodynamic artifacts to yield misinterpretations. Comprehensive evaluation of cerebrovascular flow dynamics is essential to mitigate diagnostic errors and prevent unwarranted invasive procedures. https://thejns.org/doi/10.3171/CASE25652.