Carotid ultrasonographic findings in intracranial internal carotid artery occlusion.

Five cases of unilateral intracranial internal carotid artery (ICA) occlusion received both carotid angiographic and ultrasonographic studies. The Doppler examination showed that the resistive index (RI) of the common carotid artery (CCA) and ICA was higher but the peak systolic velocity was lower on the diseased side as compared with the normal side. Absence of the diastolic phase was found in the CCA flow in 2 cases and in the ICA flow in 3 cases on the diseased side. The mean CCA flow volume on the diseased side (271 +/- 82 mL/min) was half or less than that on the normal side (680 +/- 86 mL/min) (P < 0.01). The flow volume of the diseased ICA (49 +/- 20 mL/min) was markedly lower than that of the normal side (344 +/- 49 mL/min) (P < 0.01) and was also less than that of the ipsilateral external carotid artery (ECA) (129 +/- 43 mL/min). The Doppler ophthalmic artery flow all showed a forward direction. The authors propose that the following extracranial carotid ultrasonographic findings may be helpful in the prediction of intracranial carotid artery occlusion: (1) diminished frequencies, increased RI, and a more than 50% reduction of flow volume in the CCA as compared with the opposite side; (2) diminished frequencies to loss of the diastolic phase, a more than 50% reduction of the flow volume, and reversed ICA/ECA flow volume in the ICA as compared with the opposite side; and (3) a forward Doppler ophthalmic artery flow.