Objectives To investigate the methods of protecting external branch of the superior laryngeal nerve (EBSLN)in carotid endarterectomy and to observe the effect of using these methods in clinical surgery. Methods EBSLN (20 sides)of 10 heads of corpse were studied by using microanatomy from January 2013 to December 2013. The occurrence probability of EBSLN on the lower edge of posterior belly of digastric muscle,medial edge of external carotid artery and upper edge of superior thyroid artery in anatomy triangle was analyzed. The distances from the midpoint of the EBSLN to carotid bifurcation, mandibular angle and mastoid tip were measured. Sixty-five patients with carotid endarterectomy in Tianjin Huanhu Hospital from December 2013 to November 2014 were treated with the protective methods of the relevant EBSLN by using anatomy triangle as a mark. Whether the patients had injury symptoms of EBSLN were followed up after procedure. Results (1)The occurrence probability of 20-side EBSLN in anatomy triangle was 95%(19 sides). The midpoint of EBSLN in the anatomy triangle at the posterior mandibular angle was median 0. 34 (-1. 62 to 2. 43)cm,at the inferior mandibular angle was 1. 28 (-1. 33 to 3. 42) cm,at anterior mastoid tip was 2. 84 (0. 51 to 5. 14)cm,at inferior was 4. 51 (2. 82 to 6. 39)cm,and at anterior superior of the carotid bifurcation was 1. 64 (0. 57 to 3. 78)cm. (2)65 patients who underwent carotid endarterectomy used the protective methods of intraoperative EBSLN. There was no manifestation of EBSLN injury at 3 weeks to 9 months after procedure. Conclusion In carotid endarterectomy,taking an anatomic triangle as a symbol,it is no more than 2 cm of the anterior superior of carotid bifurcation during the separation process. As for the patients with higher or lower position of carotid bifurcation,in the range of crossing rear mandibular angle 0. 50 cm or below the mastoid tip 4. 50 cm for arterial separation should be avoided,and this can effectively protect EBSLN.

In recent years, through the measurement and analysis of size ratio(SR), inflow angle (IFA), volume-to-ostium ratio(VOR), flow angle(FA), parent-daughter angle(PDA), A1- A2 diameter ratio(A1/A2), a ratio of aneurysm volume to bounding sphere volume(AVSV), a ratio of aneurysm surface to bounding sphere surface (AASA), some international scholars assessed aneurysm rupture risk, and had made some preliminary progress. Research showed that the geometry parameters had the objective significance for the evaluation of the risk of aneurysm rupture, and the bigger the SR, IFA, VOR, FA, A1/A2, AVSV, AASA, the easier the rupture of aneurysms. The smaller the PDA, the easier the rupture of the aneurysms.