Microsurgical Anatomy Of The Occipital Retrosigmoid Keyhole Approach

Part ?:Investigate the method of locating the keypoint in the craniotomy ofretrosigmoid keyhole approachObject: explore the precise location of the point of inferior margin of transverse sinus-posterior margin of sigmoid sinus junction in the craniotomy of retrosigmoid keyhole approach in order to provide the evidence for safe?accurate and rapid clinical craniotomy.Method: twenty-three cadaveric specimens(fifteen dry and eight wet)were used in the study,collected from Human Anatomy Center of Soochow University and the Second Affiliated Hospital of Soochow University.On the inner surface of dry skulls,mark the point of transverse-sigmoid sinus junction,then the correspondence point on the external surface is the keypoint.Measure the length between keypoint and end point of mastoid groove,the length between keypoint and mastoid apex and the length between keypoint and asterion.Imitate the retrosigmoid keyhole approach on the wet cadaveric specimens to verify the previous observations.Result: in the dry skulls: AD: 16.79 ± 3.50mm(left),14.82±2.96mm(right);BD: 33.98±3.87mm(left),32.78±3.29mm(right);CD: 19.53±3.84mm(left),22.59±4.08mm(right).The value of the left CD was smaller than the right side(P <0.05).In the wet cadaveric specimen,AD: 16.09±2.97mm(left),15.94±2.85mm(right);BD34.78±5.30 mm(left),33.92±4.97 mm(right);CD: 22.08±4.37mm(left),23.67±6.55mm(right).Conclusion: In order to precisely locate the point of inferior margin of transverse sinus-posterior margin of sigmoid sinus junction in the craniotomy of retrosigmoid keyhole approach,the keyhole point can be exact oriented according to 12 mm vertically above the end posterior point of mastoid groove.This method can insure safe?accurate and rapid craniotomy with a good vision and avoiding the injury of venous sinus.Part ?:Anatomic Study of Precise Drilling Posterior Wall of the InternalAuditory Canal by Using the Thin-section CT Scan Images of theTemporal BoneObject:To provide anatomical information for drilling posterior wall of the internal auditory canal through the retrosigmoid keyhole approach by using the thin-section CT scan images of temporal bone.Method:A retrospective analysis was performed on thin-section CT scan images of normal temporal bone of the 100 patients who visited to The Second Hospital Affiliated to Soochow University from June 2012 to March 2016.The length of AB,BC,BD,BG,CD,the degree of ?CBD and the area of ? BCD were measured.Result:BG in male was 17.05±2.39 mm on the left side and 16.08±2.81 mm on the right,while in female BG was 16.72±2.33 mm on the left side and 16.38±3.14 mm on the right.BD in male was 6.35±0.96 mm on the left side and 6.39±1.07 mm on the right,while in female BD was 5.95±0.95 mm on the left side and 6.17±1.23 mm on the right.The degree of ?CBD in the male was 48.41±9.22°on the left side and 44.80±7.96 °on the right,while in female the degree of ?CBD was 49.36±8.50°on the left side and 48.53±7.94°on the right.The area of ? BCD in male was 18.97±5.66mm2 on the left side and 18.58±6.83mm2 on the right,while in female BD was 16.31±5.52 mm2 on the left side and 16.99±7.11mm2 on the right.The lengths of BG,CD and the degree of ?CBD in male on the left side were more than those in right group with significant difference(P<0.05).There was no significant difference of the parameters between two sides in female(P>0.05).In comparison with male and female group on the same side,the degree of ?BCD on the right side in male was more than those in female with significant difference(P<0.05).The area of ? BCD in male on the two sides were more than those in female and there were significant differences between them(P<0.05).Conclusion:Application of the thin-section CT scan images of temporal bone can precisely orientate and quantify the drilling of the posterior wall of the internal auditory canal through the retrosigmoid keyhole approach.This method is simple,practical,easy to operate and helpful for intraoperatively guiding to full cut acoustic neuroma and protect the nerve function.