Junctional dilatation of the basilar tip: A Normal anatomical variant with a benign natural history

Purpose: The intracranial arterial vasculature has numerous anatomical variants, which vary from largely benign to having remarkable clinical implications. The significance of a lesser known variant described as a junctional dilatation of the basilar artery tip has not yet been described in the literature. Methods: Retrospective query of radiology imaging reports was performed for vascular specific imaging of the head, which included descriptions related to the basilar junctional dilatation variant from 2005 to 2019 at a single institution. Imaging studies were individually scrutinized for true presence of the variant, and were assessed for any change in appearance over time. Primary data-points collected included length of time between imaging studies with stable appearance, intracranial aneurysm incidence, and frequency of hemorrhage associated with aneurysm rupture. Results: Fifty patients with multiple vascular exams were found to have the typical appearance of the basilar junctional dilatation variant. The variant was found to be stable over time in all patients, without interval expansion or basilar tip aneurysm development. Interval follow-up ranged from 1 to 156 months, with a mean follow-up length of 3.83 years, and total patient-years of follow-up of 192. No adverse neurological events were found which could be attributed to the basilar junctional dilatation variant. Conclusion: Junctional dilatation of the basilar artery tip is a benign, normal variant of the posterior intracranial arterial circulation. It is important for both radiologists and clinicians to recognize its characteristic appearance and benign nature, as misdiagnosis may lead to unnecessary work-up, imaging, and/or treatment.