Effect of collateral flow patterns on outcome of carotid occlusion

The relationship between anatomical configuration of collateral flow and the outcome of the internal carotid artery (ICA) occlusion was analyzed. Sixty-one patients with occlusion of ICA were studied with transcranial Doppler ultrasonography. The authors monitored blood flow velocities in the middle cerebral artery (MCA) ipsilateral to the ICA occlusion during a series of carotid compressions. Blood flow through three major collateral arteries (anterior and posterior communicating arteries and ophthalmic artery) was determined as a residual flow in MCA after each compression. Twelve subjects had asymptomatic occlusion and 46 had stroke; patients with stroke were divided into mild, moderate, and severe stroke groups. Subjects with asymptomatic occlusion had a higher number of patent collateral vessels than severe stroke patients (p < or = 0.001). The same relationship was found between mild and severe stroke patients (p < or = 0.001) and between moderate and severe stroke (p < or = 0.01). Patients with watershed ischemia had a lower number of patent collateral arteries than patients with thromboembolic ischemia as revealed by CT examination (p < or = 0.02). This study demonstrates the crucial role of collateral flow in the stroke pathogenesis and stroke outcome in subjects with extracranial ICA occlusions.