Reflux compensation of persistent proatlantal intersegmental artery: report of one case.

The proatlantal intersegmental artery (PIA) is a rare embryonic residual blood vessel of which there are two types: I and II. Type I originates from the internal carotid artery and type II originates from the external carotid artery. It passes into the skull via the occipital bone. We report a rare case of PIA reflux compensation. A 45-year-old-man was admitted with dysphasia and right hemiparesis for one day. We performed cerebral angiography. The right external carotid artery was blocked. There was no stenosis of the right vertebral artery. A right PIA was seen. In the lateral view of the right vertebral artery, contrast can be seen to flow backward into the external carotid artery and branches from the vertebral via the PIA.