Posterior trifurcation of the internal carotid artery — normal or pathological? (a case report)

INTRODUCTION: Currently, there is no unified classification of variant anatomy of cerebral vessels, which underlies the contradictory character of data on the prevalence and clinical picture of such developmental variants as the posterior trifurcation of the internal carotid artery (ICA). AIM: To present a clinical case of diagnosis and confirm the anatomical norm of the posterior trifurcation of the ICA. The article describes diagnostic search in a 51-year-old female patient with a chronic tension headache. On examination, a fusiform aneurysm of the left ICA was suspected, but it was not confirmed by computed angiography, which detected posterior trifurcation of the ICA. CONCLUSION: The posterior trifurcation of the ICA in the analyzed clinical case is a finding not being a pathological condition. Anatomical differentiation of a complete posterior trifurcation and fusiform aneurysm of the ICA in chronic tension headache postulates the posterior trifurcation of the ICA being a variant of normal structure of the circle of Willis, which is of a principal clinical significance. For the first time the trifurcation of the ICA is presented as ontogenetic resource of the arterial system of the human brain, an ontogenetically determined variant of structure, and not ‘an embryonic type of structure’ of the circle of Willis, preserved due to delayed reduction of the posterior communicating arteries.