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 tight 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 hemoynamics.

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.