Persistent trigeminal artery variant associated with ipsilateral hypoplasia of the internal carotid artery

A persistent trigeminal artery is the most common persistent carotid-vertebrobasilar anastomosis, while persistent trigeminal artery variants involve termination at the cerebellar artery without connecting to the basilar artery. Internal carotid artery hyperplasia is also a rare congenital anomaly. To the best of our knowledge, there are no reports of persistent trigeminal artery variant associated with ipsilateral hypoplasia of the internal carotid artery. Herein, we report a case of a 44 year-old woman who visited a neurosurgical clinic because of chronic headaches. Magnetic resonance angiography showed impaired delineation of the left internal carotid artery, and she was referred to our hospital for catheter angiography. Angiogram revealed left internal carotid artery hypoplasia and a left persistent trigeminal artery variant that terminated at the left anterior inferior cerebellar artery. Computed tomography bone images showed a narrow left carotid canal. We diagnosed congenital hypoplasia of the left internal carotid artery concomitant with ipsilateral persistent trigeminal artery variant. Careful imaging assessment is important for identifying persistent trigeminal artery variant when associated with ipsilateral internal carotid artery hypoplasia.