Objective To research the jugular foramen,internal auditory pore (IAP)and the turning point between its components by imageological methods and to provide theoretical basis for retrosigmoid approach in the operation of acoustic neurinoma.Methods The skulls of 100 volunteers were scanned to get the final result with thin-section computed tomographic image. High-resolution spiral CT multiplane reformation was used to reform images that were parallel to the Frankfort horizontal plane to measure the distance between the turning point of retrosigmoid (A),the edge of jugular foramen(B)and the lower edge of the internal auditory canal(C)(denoted AC,AB,BC) and the shortest distance from the jugular foramen to AC.The angles between AC,AB and sagittal axis(α,β) were measured.Results The distance of AC was (44.94 ± 3.84)mm,the distance of AB was (43.68 ± 4.56)mm.The distance of BC was (6.15 ±2.04)mm,and the shortest distance between jugular foramen and AC was (5.21±0.23)mm.The angleαwas measured as (39.50±4.74)°,and the angleβwas measured as (46.35± 5.51)°.Conclusion The research measure the distance and angle between entry points and landmarks of retrosigmoid approach and the safe distance.

Objective:To measure the safe range from the foramen rotundum to the siphon of internal carotid artery using three-dimensional reconstruction technique, and to provide guidance for operation through pterygopalatine fossa.Methods:The skulls of 121 volunteers were scanned to get the final results with thin-section computed tomographic images.The position of the siphon of internal carotid artery (point A)and foramen rotundum (pointB)were ascertained.Three-dimensional reconstruction technique was used to build a coordinate system paralleled to the frankfort horizontal plane and the nasal septum plane.The coordinate system took point A as the coordinate origin.Point C and point D were the projections of point A in two planes parallel with frankfort horizontal plane and nasal septum plane which included point B.The distances of AC,AB,and BC were measured. The angles of the line went through A and B to the three planes were also measured.Results:The distance of AC was measured as 13.22 (3.79)mm (range,8.33 - 105.67 mm;95%CI:8.55 - 21.39 mm).The angle to the sagittal plane was measured as 33.54 (9.23)° (range,5.38- 66.58°;95%CI:30.88 - 34.20°). The angle to the coronal plane was measured as 53.17 (10.48)°(range,5.60-75.02°;95%CI:51.29-55.06°).The angle to the horizontal plane was measured as 9.43 (12.91 ) mm (range,- 28.44 - 82.22;95% CI:7.11 - 11.76 ). Conclusion:The safety distance from foramen rotundum to the siphon of internal carotid artery in the operation through pterygopalatine fossa (PPF) under nasoendoscope is obtained by thin-section computed tomographic images.