Effect of internal carotid artery occlusion on intracranial hemodynamics. Transcranial Doppler evaluation and clinical correlation.

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Abstract
Neurologic deficits that occur simultaneously with or subsequent to internal carotid artery occlusion may be influenced by the adequacy of the intracerebral collateral circulation. Transcranial Doppler ultrasonography was used to evaluate mean middle cerebral artery blood velocity and blood flow in major collateral arteries in 78 patients, including 39 patients with 40 internal carotid artery occlusions and 39 control patients with less severe extracranial cerebrovascular disease, matched for age and sex distribution. Middle cerebral artery blood velocity was 38.9 .+-. 17.9 cm/sec ipsilateral to an occlusion, 50.9 .+-. 18.3 cm/sec contralateral to an occlusion (p < 0.01), and 56.8 .+-. 14.4 cm/sec in the controls (p < 0.01). Pulsatility index ipsilateral to an occlusion (0.86 .+-. 0.32) was reduced compared with contralateral and control pulsatility indexes (1.05 .+-. 0.33 and 1.03 .+-. 0.18, respectively; p < 0.05). Major intracerebral collateral arteries were detectable in 94.9% of occlusion patients and in 53.8% of controls (p < 0.01). A posterior communicating artery was demonstrated ipsilateral to an occlusion in 80.0% of the patients and contralateral to an occlusion in 39.5% (p < 0.01). An ipsilateral posterior communicating artery was identified in all 10 asymptomatic occlusions and in 75.8% of the symptomatic ones. Pulsatility index was 1.02 .+-. 0.34 for asymptomatic occlusions and 0.76 .+-. 0.30 for symptomatic occlusions (p < 0.01). Transcranial Doppler ultrasonography permits noninvasive quantification of the cerebral hemodynamic consequences of internal carotid artery occlusion and direct evaluation of the collateral blood supply, which can be correlated with symptomatology.