| Objective To supply microanatomic data for selection and reference of operation through the three routes (interforniceal,transforaminal and subchoroidal) via the corpus callosum to the third ventricle.Methods Ten adult cadaver heads were dissected by using microsurgical skill under microscope with 10-fold magnification,simulating the pro- cedures of the corpus callosum to the third ventricleapproach.Observation were performed on related anatomic structures,measurement and photog- raphs were taken,too.Counted the drainage-veins to the sagittal sinus in front of and behind the coronal suture;Image of CT or MRI of fifty nature people on septum pellucidum were observed;Seven cases of the third ven- tricle tumors were removed through corpus callosum approach, and the results were analysed.Results (1) The distance between the coronal suture and the root of nose was (139±1.92)mm.There were very few drainage-veins to the sagittal sinus anterior to the coronal suture,but much denser posterior to the coronal suture;Two points on the cortical surface were selected as ref- erences,the two points were located 5 and 7cm anterior to center sulcus respectively(P5,P7),mean values of relative measurements were obtained as follows:①the distance between P5 and the cingulated sulcus was 29.18mm, the distance between P7 and the cingulated sulcus was 31.02mm;②the distance between the lower margin of the corpus callosum and the fornix was7.49mm,9.86mm;③the thicknesses of the corpus callosum was 7.16mm,7.62mm;④the mean distance between the posterior border of the anterior commissure to the posterior border of the foramen of Monro was 10.1mm,range(9.6-10.4)mm ;The septum pellucidum was found midline in 9 cadaveric heads,it wasn,t midline in 1;The intercavity of septum pellucidum was found in 8 cadaveric heads and it was easily split,it couldn,t be split in 2; After incising the corpus callosum,it was found to access the intercavity of septum pellucidum directly in 5 cadaveric heads,to the right lateral ventricle in 4 and the left lateral ventricle in 1;The body of the fornix was very easily split to access the third ventricle in 9 cadaveric heads, it was difficultly split in 1;The sagittal and tra- nsverse diameters of the interventricular foreman were (5.6±1.3)mm,(2.7±1.0)mm,the distance between the angulus venosus and the foramen of Monro was 0-14.8mm,the mean distance (5.2±2.9 )mm, the distance between the angulus venosus and the foramen of Monro varied obviously.The choroidal fissure with the appearance of reversal shae of"C"was a natural cleft between the thalamus and the fornix. (2) In the image of CT or MRI of fifty nature people, The septum pellucidum was found midline in 41 cases (82%),it wasn,t midline in 4,and among 4,1 case was obvious to right side, the intercavity of septum pellucidum was found in 5;The whole third ventricle including pineal region was revealed through an interforniceal approach;The anterior structures of the third ventricle was revealed through a transforaminal approach;The middle structures of the third ventricle was revealed through a subchoroidal approach.(3) In 7-clinical cases of tumor of the third ventricle, 5 of which being male and 2 female, aging 11-46 years old, averaging 26 years old, and the course of disease being from 10 days ~ 2 years, averaging 5.3 month; they were incised through interforniceal approach in 5 cases, through transforaminal approach in 1,and through subchoroidal approach in 1;They were provided excellent exposure to all the tumors, and tumors were totally removed; Postoperative pathology: 1 case of glioma, 1 case of pituitary adenoma, 5 cases of craniopharyngioma; Complications: 1 case of memory impair- ment, which was disappeared after 3 days,1 case of electrolyte disturbance which was disappeared after management.Conclusion The region between the lines of P5-FM and P7-FM was best approach for entering the interhemispheric and incising the body of the corpus callosum. After the body of the corpus callosum was incised, there are three routes (interforniceal,transforaminal and subchoroidal) to access the third ventricle.The transcallosal–interforniceal approach permitted surgery directly,and the paired vital structures could be vie- wed unforcedly and they couldn,t be easily damaged,and The whole third ventricle could be adequately revealed.The approach is safe and direct. Transforaminal and subchoroidal approach were permitted while the int- ercavity of septum pellucidum were not split.The quantitative information obtained in this study permitted preservation of vital anatomic str- uctures in operation,such as the motor strip,genu of the corpus cal- losum,fornical commissure and anterior commissure. |
