Is transcranial Doppler a worthwhile examination for preoperative evaluation of the Circle of Willis? Evaluation of 137 carotid endarterectomies performed under regional anesthesia

Background. Transcranial Doppler is often proposed for evaluation of the Circle of Willis prior to carotid endarterectomy. The purpose of this study was to evaluate preoperative TCD before carotid surgery. Methods. This is a retrospective report of 137 carotid endarterectomies performed under regional anesthesia operated between January 1992 on June 1996. All patients have a thight stenosis between 70% on 99%, and 49% were symptomatic. Forty-three patients of the 132 had a controlateral hemodynamically significant carotid stenosis with none occlusion. The TCD examinations were all performed with ADMS Doppler Spectradop with 3-MHz and 2-MHz probes. Clinical evaluation during cross-clamping was compared to the preoperative TCD. In 14% of the patients, the TCD could not be performed because there are not temporal bone windows. Results. When the patients could be tested the positive predictive value of the TCD was 18% and the sensitivity was 33%. The negative predictive value was 94%. 8% of the patients were shunted. TCD had numerous difficulties. The most common is the lack of the temporal bone window (40% of the patients). The compression test is often difficult when the lesion is calcareous. Preoperative TCD is not according to our results, a reliable enough examination to modify operative strategy during carotid surgery. When coupled with arteriography it is a good way to study cerebral hemodynamics. Conclusions. Regional anesthesia with local supplication remains the method of choice to select those patients who require a shunt during carotid surgery. It can be used routinely and it is less complex than the various methods.