[A case of left subclavian artery occlusion with transient ischemic attacks probably in the internal carotid artery system].

The subclavian steal syndrome is known to steal blood flow from the vertebrobasilar system. However, we experienced a case of subclavian artery occlusion presenting transient ischemic attacks in left internal carotid system. A left handed 41-year-old man developed transient dysarthria and right hemiparesis including face several times when he physically used his arms. He had no symptoms of the vertebrobasilar system. A brain MRI revealed an old cerebral lacuna at the left putamen supplied by perforating arteries of the middle cerebral artery. The angiography demonstrated a complete occlusion of the proximal portion of the left subclavian artery without a reverse flow from the vertebral artery. Instead, descending cervical branches and deep cervical branches of the ipsilateral external carotid artery supplied collateral pathways to the occluded subclavian artery. On the basis of above observations, we speculated that he developed symptoms of the internal carotid system due to the steal through the collateral network of the cervical arteries directed to the subclavian artery. We should consider not only the vertebrobasilar system but also the internal carotid system, especially its cervical artery network, when exploring collateral pathways for the subclavian steal syndrome.