Internal Carotid Artery Balloon Test Occlusion Does Require Quantitative Assessment of CBF

Abstract

At our institution intra-arterial balloon test occlusions (BTOs) in combination with Stable Xenon enhanced CT (Xe/CT) cerebral blood flow (CBF) studies prior to radiological or surgical treatment have been performed in more than 400 patients since 1985 in order to evaluate the risk of temporary or permanent internal carotid artery (ICA) occlusion. We reviewed studies of 156 patients who passed the clinical BTO and underwent a Xe/CT CBF study in combination with a second BTO. The quantitative CBF data were analyzed for absolute changes as well as changes in symmetry. Fourteen patients showed CBF values between 20 and 30 cc/100g/ min, an absolute CBF decrease, and a significant asymmetry in the middle cerebral artery (MCA) territory during BTO. These patients were considered at high risk for cerebral infarction following ICA occlusion. With one exception they belonged to a group of 61 patients at increased stroke risk who showed a bilateral or ipsilateral CBF decrease and a significant asymmetry with lower flow on the side of occlusion. The other 95 patients who showed a variety of CBF response patterns including ipsilateral or bilateral CBF increase, in our eyes, were at moderate or low stroke risk. In contrast to this, an exclusively qualitative CBF analysis lacks sensitivity and specificity to identify the patients at high risk. Thus, by an integration of a thorough analysis of quantitative CBF data before and during BTO we achieved a hemodynamic related overall stroke rate of 10% in 33 patients who underwent permanent clinical ICA occlusion.