To the Editor: Vernieri and colleagues1 concluded in their recent article that treatment options in internal carotid artery occlusion can be differentiated on the basis of cerebral hemodynamic status. Specifically, their results has demonstrated that the breath-holding index (BHI) in the middle cerebral artery detected by transcranial Doppler ultrasonography (TCD) is predictive of cerebrovascular ischemic symptoms ipsilateral to the internal carotid artery occlusion. Finally, the authors suggest the use of BHI in selecting patients for the classic or a new type of surgical extracranial/intracranial bypass study. I would like to raise the following comments. First, “carotid stump syndrome” is a well-known phenomenon: continual episodes of transient ischemic attack (TIA) and/or stroke ipsilateral to an occluded internal carotid artery; embolism has been implicated in the pathogenesis, and border-zone infarction is less common.2 3 The source of emboli includes the ipsilateral internal carotid artery stump, the ipsilateral external carotid artery, the contralateral internal and external carotid arteries, the vertebrobasilar system, and the heart. In the study by Vernieri and colleagues,1 patients with significant stenosis of the contralateral carotid artery system, significant vertebral artery disease, or cardiac source of emboli were excluded. These exclusions might have resulted in a lower rate of ischemic stroke, especially on the side contralateral to the carotid artery occlusion, and augmented the importance of hemodynamic mechanisms in producing cerebrovascular ischemia. In addition, I am interested in knowing whether there was any significant stenosis in the external carotid artery ipsilateral to the internal carotid artery occlusion. Second, CT or MRI of the brain was performed at baseline in all the patients with internal carotid artery occlusion, but the neuroimaging findings were not described in the article.1 This information may be important because some “asymptomatic” patients and some symptomatic patients with “TIA only” could have “silent” …