| 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 between5-fold and25-fold magnification,simulating the procedures 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 fifty nature people on septum pellucidum were observed; twenty-four cases of the third ventricle 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 (126.75±0.19)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 references,the two points were located5and7cm anterior to center sulcus respectively(P5,P7),mean values of relative measurements were obtained as follows:①the distance between bregma and the cingulated sulcus was31.02mm;②the P5-point connection point and the foramen on the corpus callosum thickness7.18±0.22mm;③P7-point connection with ventricular septum between the hole intercept of17.40±1.19mm;④In combination with the microscope head angle (26±3)°range by raising, forward, back, etc., may expose the third ventricle;(2) In the image of fifty nature people, The septum pellucidum was found midline in41cases (82%),it wasn,t midline in4,and among4,1case was obvious to right side, the intercavity of septum pellucidum was found in5.(3) Twenty four patients with third ventricle tumors,10out of them being located in the anterior portion of the third ventricle,12in the middle portion and2in the posterior portion, underwent tumor resection via transcallosal interforniceal approach. Total resection of third ventricle tumors was achieved in20cases, subtotal resection in3and partial resection in1. The pathological examination revealed9craniopharyngiomas,7colloid cysts,4astrocytomas,2ependymocytomas,1glioblastoma and1teratoma. Postoperative short-term memory disturbance occurred and recovered within2months in6patients. Transient diabetes insipidus was seen in5patients and the symptoms disappeared after treatment for1-2weeks. Mutism appeared and recovered in one month in2patients. Four patients had hydrocephalus,3out of them underwent ventriculoperitoneal shunt with good recovery, and the treatment was given up in the other one because of no improvement of preoperative coma.Conclusion The region between the lines of P5-FM and P7-FM was best approach forentering 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-interfomiceal 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.
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