PREDICTION OF TOLERANCE TO CAROTID-ARTERY OCCLUSION USING TRANSCRANIAL DOPPLER ULTRASOUND

Surgical sacrifice of the carotid artery is a frequently anticipated e vent during the treatment of certain aneurysms and tumors. The ability to predict tolerance to carotid artery occlusion is therefore of bene fit when planning procedures in which the carotid artery is at risk. A trial of carotid artery occlusion using an angiographic balloon durin g concurrent neurological examination or blood flow studies is an acce pted method for testing tolerance, but it carries the risks of an angi ogram and cannot be performed at the bedside. Transcranial Doppler ult rasound (TCD) is a noninvasive modality that permits measurement of bl ood velocity in cerebral vessels. The immediate effects of carotid art ery occlusion on middle cerebral artery (MCA) perfusion can be obtaine d by insonating this artery during manual carotid artery compression. To compare the TCD response to carotid artery compression with the dat a obtained with more formal testing, the MCA of 22 patients was insona ted during manual carotid artery compression and the results compared with the clinical tolerance to balloon occlusion in all patients and t o blood now studied by single photon emission computerized tomography before or during balloon occlusion in 14 of the 22 patients. Surgery w as planned to treat giant unruptured aneurysms in 17 cases, intracrani al tumors in three, a carotid-cavernous fistula in one, and a carotid artery injury in one. Fifteen patients showed a reduction in TCD flow velocities by no more than 65%; of these, 14 (93%) clinically tolerate d the balloon occlusion test. Of the seven patients showing a TCD flow velocity decrease of more than 65%, six (86%) developed a transient f ocal deficit during the occlusion. It is concluded that the change in MCA velocity measured with TCD studies during manual carotid artery oc clusion is a useful predictor of the clinical and blood flow responses to a trial of carotid artery occlusion with an angiographic balloon.