TRANSCRANIAL DOPPLER ULTRASOUND CRITERIA FOR HEMODYNAMICALLY SIGNIFICANT INTERNAL CAROTID-ARTERY STENOSIS BASED ON RESIDUAL LUMEN DIAMETER CALCULATED FROM EN-BLOC ENDARTERECTOMY SPECIMENS

Background and Purpose Transcranial Doppler (TCD) is often used in con junction with carotid duplex ultrasonography (CDUS) to evaluate the he modynamic significance of internal carotid artery (ICA) stenosis. We e xamined the sensitivity and specificity of TCD criteria for detection of a hemodynamically significant stenosis (residual lumen diameter <1. 5 mm) at the origin of the ICA. Methods We selected patients who under went carotid endarterectomy (CEA) and had preoperative TCD data availa ble. Eighty-one patients underwent transorbital evaluation, 49 of whom also had transtemporal TCD performed. The endarterectomy specimens we re removed en bloc and sectioned, and the minimal residual lumen diame ter calculated by computer analysis. Results For the transorbital appr oach, the strongest indicators of a residual lumen diameter <1.5 mm we re reversed flow in the ipsilateral ophthalmic artery and a >50% peak systolic velocity difference between the carotid siphons (distal ICAs) in patients with unilateral ICA origin stenosis. They were 100% speci fic and 31% and 26% sensitive, respectively. For the transtemporal app roach in patients with a unilateral stenosis, a >35% difference in ips ilateral middle cerebral artery (MCA) peak systolic velocity relative to the contralateral MCA or a >50% difference in contralateral anterio r cerebral artery (ACA) peak systolic velocity relative to the ipsilat eral ACA were 100% specific for identifying a residual lumen diameter of <1.5 mm. Sensitivities were 32% and 43%, respectively. Irrespective of contralateral stenosis, a >35% difference in ipsilateral MCA peak systolic velocity relative to the ipsilateral posterior cerebral arter y had a 100% specificity and a 23% sensitivity for detecting a <1.5 mm minimal residual lumen diameter. Conclusions Although the TCD sensiti vity for detecting a hemodynamically significant stenosis is relativel y low, it can be highly specific (up to 100%). We conclude that TCD en hances the specificity of highly sensitive CDUS criteria for detecting a hemodynamically significant ICE stenosis.