Comparative Study On Microsurgical Anatomy And Clinical Application Of Surgical Approaches To The Third Ventricle

Objective To discuss microanatomic features and clinical application value of the transcallosal-transchoroidal approach. To supply microanatornic knowledge for the clinical application of the transcallosal-transchoroidal approach, in order to help surgeons to identify and protect vital neural and vascular structures such as corpus callosum, choroidal fissure, internal cerebral veins and so on during operation.Methods Twelve adult cadaveric head specimens with arteries and veins perfused with colored latex were carefully dissected under microscope with magnification ranging from 4 times to 10 times, the anatomic feature of the choroidal fissure was successively explored. Six adult cadaveric fresh heads were studied, simulating the procedure of the transcallosal-transchoroidal approach. Observation were performed on relative anatomic structures, photographers were taken with a digital camera at the same time, too. Using the line between coronal suture on the cortical surface and foramen of Monro as references, measurement of distances between important brain structures that were encountered during the surgical approach were made, and all the results were analysed statistically.Results 1. In the body of the lateral ventricle, the choroid plexus is located in the medial part of the floor. The choroidal fissure is a C-shaped natural cleft between the thalamus and the fornix, being white translucent membranes and it is identified by following the choroid plexus in the lateral ventricle.2. After careful opening of the taenia fornicis, the contents of the velum interpositum are exposed. The cavity of the third vertricle is reached through opening the roof of the third vertricle between the two internal cerebral veins.3. Significant anatomic structures such as corpus callosum, septum pellucidum, lateral ventricle and choroidal fissure were encountered during this approach to the third ventricle after both cingulate gyrus were separated. 4. There was a slender artery coursing in a superficial groove located between bilateral medial longitudinal striaes in the middle of the corpus callosum.5. Mean values of measurements of relative anatomic structures were obtained:(1) the distance between posterior commissure and anterior commissure was 25.94±2.16mm. (2) the distance between foramen of Monro and mamillary body was 19.62±1.79mm. (3) the length of the body of choroidal fissure was 28.65±2.23mm. (4) the distance between coronal suture on the cortical surface and the cingulate sulcus was 30.27±1.85mm. (5) the distance between coronal suture on the cortical surface and sulcus of corpus callosum was 39.21±2.89mm. (6) the distance between cingulate sulcus and sulcus of corpus callosum on the line between coronal suture and foramen of Monro(the height of cingulate gyrus) was 8.93±0.97mm. (7) the height of the corpus callosum on the line between coronal suture and foramen of Monro was 6.88±0.83mm. (8) the distance between coronal suture and foramen of Monro was 61.53±4.02mm.Conclusion 1. Eligible bone window which posterior borderline located coronal suture should be adopted in the transcallosal-transchoroidal approach.2. Anterior and middle corpus callosum can be reached safely by dissecting longitudinal fission following the line between coronal suture and foramen of Monro in the transcallosal-transchoroidal apporoach.3. The slender artery coursing in a superficial groove located between bilateral medial longitudinal striaes should be used to landmark of incision into the corpus callosum.4. An understanding of the choroidal fissure is fundamental for use of the transchoroidal approach. Comparing with other approach to the third ventricle, the transcallosal-transchoroidal approach which follows a natural route is of advantages of less injury and wider exposure, we suggest therefore that the transchoroidal approach be extensively adopted in clinical neurosurgery.Objective To discuss microanatomic features and clinical application value of the trans-lamina terminalis approach. To supply microanatomic knowledge for the clinical application of the trans-lamina terminalis approach in order to help surgeons to identify and protect vital neural and vascular structures such as optic chiasm, anterior communicating artery complex and so on during operation.Methods Twelve adult cadaveric head specimens with arteries and veins perfused with colored latex were carefully dissected by using microsurgical anatomic skill under microscope with magnification ranging from 4 times to 10 times, the anatomic feature of lamina terminalis and adjacent structures were successively explored. Observation were performed on relative anatomic structures, photographers were taken with a digital camera at the same time, too. Measurements of distances between important brain structures in this region were made, and all the results were analysed statistically.Results The lamina terminalis was a thin sheet of gray matter that attached to the upper surface of the optic chiasm and stretched upward to fill the interval between mid-portion of the optic chiasm and the anterior commissure. The length and maximal width of the lamina terminalis were 14.4±2.8mm and 4.8±1.3mm respectively. The thickness of the lamina terminalis was about 0.27±0.16 mm. The optic recess was superior to the posterior half of the optic chiasm in the median line. The length of the recess was 5.6±1.5mm. Cisterna lamina terminalis which located anterior to lamina terminalis carried anterior cerebral artery A1 segment, anterior communicating artery, the proximal part of anterior cerebral artery A2 segment, Heubner recurrent artery and perforating branch to hypothalamus. The correlative structures of the lamina terminalis included anterior communicating artery complex and their perforating branches.Conclusion The trans-lamina terminalis approach is a surgical space obtained when the lamina terminalis has been opened, and the surgical space was made of dorsal rim of optic chiasm, medial rim of both optic tracts and dorsal rim of lamina terminalis. The median crest and the bulge of the central area are both important signs to incise the lamina terminalis safely.Objective To compare the application effect of several approaches to the third ventricle, and explore the optimal approach to resect the tumors located at the third ventricle.Methods Under the operative microscope thirty-five patients (prophase group) with the third ventricle tumors were operated via transcortical approach, trans-lamina terminalis approach or infratentorial supracerebellar approach. Twenty-one patients (anaphase group) via transcallosal transseptal interforniceal approach. Operative effect was observed and compared.Results Among the prophase group, the tumors were totally removed in 16 cases, subtotally in 6 cases and partially in 13 cases. Among the anaphase group, the total removals of tumor were obtained in 11 cases, the subtotal in 8 cases and the partial in 2 cases. Rate of total and subtotal tumor removal had significant difference between two groups. Rate of postoperative complications in anaphase group was lower than in prophase group.Conclusion Transcallosal transseptal interforniceal approach approach is one of the several surgical approaches to be considered for treatment of tumors in the third ventricle by providing a quite large operative field and direct corridor, resecting tumors easily, postoperative complications being rare.