When to perform transcranial doppler to predict cerebral hyperperfusion after carotid endarterectomy?

Cerebral hyperperfusion syndrome (CHS) after carotid endarterectomy (CEA) is a potential life-threatening disease. Identification of patients at risk for CHS commonly takes place with use of intra-operative transcranial Doppler (TCD), but is associated with both false positive and false negative results. We aimed to determine the diagnostic value for predicting CHS, by adding a TCD measurement in the early post-operative phase after CEA. We retrospectively included 72 patients who underwent CEA between January 2004 and August 2010 and in whom both intra- and post-operative TCD of the ipsilateral middle cerebral artery monitoring were performed. Twelve patients (17%) had an intra-operative mean blood flow velocity (Vmean) increase ≥100% and 13 patients (18%) a post-operative Vmean increase of ≥100%. In 5 patients (7%) CHS was diagnosed; 2 of those had an intra-operative Vmean increase of ≥100% and all 5 a post-operative Vmean increase ≥100%. This results in a positive predictive value of 17% for the intra-operative and 38% for the post-operative measurement. In conclusion, a post-operative increase of the mean velocity in the ipsilateral middle cerebral artery of ≥100% as measured by TCD is superior to an intra-operative velocity increase, for the identification of patients at risk for the development of CHS after CEA.