Internal carotid and ipsilateral type II proatlantal artery stenoses causing simultaneous hemispheric and vertebrobasilar transient ischemia.

A case of persistent proatlantal artery (PA) is described in a 60-year-old woman who presented with cerebellar ataxia, homonymous hemianopia, and aphasia. Both Doppler scan and magnetic resonance angiography (MRA) showed agenesis of both vertebral arteries, 80% stenosis of the left internal carotid artery (ICA), and an anastomotic vessel between the left external carotid artery (ECA) and the left vertebral artery (LVA) with a tight stenosis at the origin. It was thought to be a type II PA. Both lesions were successfully treated by ICA endarterectomy and common carotid artery to PA bypass. This case demonstrates the clinical significance of persistent PA in the evolution of an ischemic cerebrovascular disease.