Revaluation of collateral pathways as escape routes from hyperemia/hyperperfusion following surgical treatment for carotid stenosis.

Background: Although acetazolamide-challenged single-photon emission CT (SPECT) is recommended before carotid endarterectomy (CEA) and carotid artery stenting (CAS), given the relationship between preoperative decreased cerebrovascular reserve (CVR) and postoperative cerebral hyperperfusion syndrome (CHS), it is controversial whether all cases should be checked.

Methods: I-IMP-SPECT at rest was performed for 65 operative cases of carotid stenoses. At preoperative MR angiography we classified cases into two groups: G, featuring an anterior communicating artery with bilateral A1 with/without posterior communicating arteries; and P, a poor-escape-route group which did not match these criteria. Postoperative rCBF patterns were divided into two types: B, bilateral rCBF increase; and I, ipsilateral rCBF increase.

Results: Cases with high postoperative increase rate of rCBF were most frequently found in Group P and the Type I cases (p < 0.001). All four cases with hyperemia or hyperperfusion belonged to Group P. Only two out of 48 patients in Group G were Type I, both demonstrating a preoperative rCBF decrease rate more than 10 % as compared to the contralateral side.

Conclusions: From the present study, preliminary analysis of escape routes by preoperative MR angiography before surgical treatment of carotid stenosis is recommended and CVR investigation with acetazolamide-challenge SPECT should be considered for those relatively few cases with poor escape routes.