Transcranial Doppler Sonography: Collateral Pathways in Internal Carotid Artery Obstructions

Fifty-four patients with stenoses and occlusions of the extracranial internal carotid artery (ICA) demonstrated by intravenous digital subtraction angiogra phy (IVDSA) were studied by extracranial duplex and transcranial Doppler. Two hundred healthy volunteers served as control group. Intracranial collateralization was demonstrated in 32 patients with ICA stenoses >80% and occlusions. Twelve patients with unilateral and 8 patients with bilateral ICA obstructions >80% showed collateral supply via the anterior (ACA) and/or posterior cerebral artery (PCA). In 5 cases of unilateral ICA oc clusion and in 7 patients with bilateral ICA stenoses >80% and occlusions, the ophthalmic artery and ACA and/or PCA served as collateral vessels. Five pa tients with ICA occlusions showed leptomeningeal anastomoses in the region of the postocclusive middle cerebral artery (MCA). All 54 patients showed normal time-mean flow velocity in the postobstruc tive MCA. In unilateral ICA stenoses >80% and occlusions, the pulsatility in dex in the ipsilateral MCA was reduced in comparison with the contralateral side, indicating that this parameter is more sensitive to hemodynamic effects of ICA obstructions than time-mean velocity.