Microanatomy Of Transcallosal Transseptal Transinterforniceal Approach To The Third Ventricle

Objective: To acquaint with the relevant microanatomy of transcallosal transseptal transinterforniceal approach , such as Longitudinal fissure , corpus callosum, septum pllucidum, fornix and third ventricle by microdissection and the measurement of relevant data to wet adult cadaveric heads of our country . To quantify every data and provide the data of microanatomy for removing tu- mors of third ventricle via transcallosal transseptal transinterforniceal approa- ch , so as to protect vital anatomic tissue and structure in operation , increase operation's safety, elevate operation's achievement ratio , decrease postopera- tive complications.Methods: Six silicon-injected cadaveric heads were dissected imitately through transcallosal transseptal transinterforniceal approach under operating microscope . To observe and record in detail the step for reveal the microanat- omy of the third ventricle. Split the cadaveric heads along mid-sagitral plane after operation, observe and measure the distances as follows : the distance between glabellum and bregma ; the distance from bregma to central sulcus; the distance between the first draining vein before bregma and bregma(Right- Sidedness) ; the distance between the first draining vein after bregma and bre- gma(Right-sidedness);the distance between bregma and callosal on the line of bregma and foramen of monro ; the thickness of the corpus callosum on the line of bregma and foramen of monro ; the distance between bregma and the bottom of the third ventricle on the line of bregma and foramen of monro ; the distance between posterior border of anterior commissure and posterior border of foramen of monro; anteroposterior diameter of the intermediate mass; the distance between anterior commissure and Posterior commissure; the distance between the posterior border of foramen of monro and anterior border of aque- duct of midbrain. At last, proceed statistical analyze and obtain statistical con- clusion. The values are express by mean±standard deviation.Results: The distances between glabellum and bregma were relatively constant, the distance between glabellum and bregma in our experiment were 130.8±3.5( 126.0～135.0)mm ; the distance between bregma and central sulcus were 46.2±4.7( 40.0～52.0 )mm; the nearest distance between the first draining vein before bregma and bregma( Right-Sidedness ) was 17.0mm and the furthermost was 84.0mm , among which 83.0% (five example) were beyo- nd 50.0mm before bregma; the nearest distance between the first draining vein after bregma and bregma ( Right-Sidedness ) was 4.0mm and the furthermost was 22.0mm, among which 83.0% (five example) were beyond 50.0mm after bregma; the distance between bregma and callosal on the line of bregma and foramen of monro were 48.7±3.6(42.0～52.0)mm; the thickness of the corpus callosum on the line of bregma and foramen of monro were 5.9±0.8 (5.0～7.0) mm ; the distance between bregma and the bottom of the third ventricle on the line of bregma and foramen of monro were 90.0±3.2 ( 85.0～94.0)mm; the di- stance between posterior border of anterior commissure and posterior border of foramen of monro were 10.3±0.5(9.5～11.0)mm ; the anteroposterior diam- eter of the intermediate mass were 4.9±0.4(4.5～5.5)mm; the distance betw- een anterior commissure and Posterior commissure were 22.0±2.2(20.0～24.0 )mm; the distance between the posterior border of foramen of monro and ante- rior border of aqueduct of midbrain were 19.8±1.2 (18.0～21.0)mm.Conclusions: The transcallosal transseptal transinterforniceal approach is technically safe, enter along with clearance of embryogeny of brain , no cere- bral cortex and major deep vein must be manipulated , has nearest distance from cerebral cortex to the third ventricle,offers adequate exposure of the third ventricle without excessive split, and it is relatively simple to manipulate. We should attach much importance to the following key anatomic structures via this approach: thick draining veins drain to superior longitudinal sinus; perica- llosal artery; corpus callosum; psalterium;internal cerebral veins and their Su- bordinate branches; anterior commissure . The anterior-posterior operating sp- ace of the approach is relatively narrow and need adjust constantly the micros- copic angle to increase the exposure of the lesion . It has excellent exposure to the anterior and middle lesions of the third ventricle and the distance to the po- sterior of the third ventricle is relatively far. However, the transcallosal transs- eptal transinterforniceal approach should be take the priority when the lesions protrude from the posterior of the third ventricle and the area of pineal body to the anterior of the third ventricle. The third ventricle has complicated anatomic structure, therefore , the practice in the cadaveric laboratory are mandatory to elevate operative safety and prevent postoperative complications.