Study On The Microsurgical Anatomic Features Of Trans-lamina Terminalis Approach And Its Clinical Utilization

Objective:The lamina terminalis (LT) is a very important structure in microneurosurgery, forming great part of the anterior wall of the third ventricle. More and more neurosurgeons have paid attention to the studies on trans-lamina terminalis approach of removing the lesions that occur within the anterior third ventricle or compress or invade the walls of the chamber and LT fenestration. So accuracy knowledge regarding the LT's normal anatomic features and variations is required. The purpose of this study, which was based on microanatomic dissection of adult human cadaveric specimens, was to get the microsurgical anatomic features of the LT and its neurovascular relationships. The microsurgical implications of the morphometric data were discussed, in order to design and improve operating techniques, helping to identity and protect the important vessels and nerves during operating and to decrease the operating complications. Methods:Use 10 adult human cadaveric heads, obtained from 8 formalin-fixed adult cadavers and 2 fresh adult cadavers. In cadaveric head specimens, the arterial and venous systems were injected with colored silicone rubber via the internal carotid arteries and internal jugularveins, under pressure, respectively, to maintain the diameters of vessels. Each head was rigidly fixed in a headholder and opened, to expose the the LT region and structure related. An operating microscope was used for all dissections and measurements. And all results were analysed statistically by SPSS 11.0 statistical software and were considered significant at a probability level less than 0.05.Results:The LT is composed of a thin sheet of gray matter covered by a pial layer, constitutes the biggest part of the third ventricle. The LT starts from upper edge of the chiasm and ends superiorly in the anterior commissure. We performed measurements of the distance(curve length) between the lower edge of the anterior commissure and the midportion of the upper edge of the chiasm, which averaged 14.2±2.5mm; The distance between the medial edges of the optic tracts (maximum width) averaged 11.5±2.4mm;The surface area of LT averaged 53.26±11.2mm2;The thickness averaged 0.25±0.17mm. The LT is intimately related to both A1 tracts of the ACA, the AComA complex, A2 segments of the ACA perforating branches, both recurrent Heubner arteries.Conclusion:1.The trans-lamina terminalis approach is to get a surgical access by opening the LT, and the access is limited by the lower edge of the anterior commissure, medial edges of the optic tracts, upper edge of the chiasm. The approach is intimately related to both Al tracts of the ACA, the AComA complex, A2 segments of the ACA, perforating branches, both recurrent Heubner arteries.2. Generally, there was minimally need to mobilize the anterior cerebral artery-anterior communicating artery complex to fully expose the LT3. Perforating branches to the optic apparatus and hypothalamus are laterally located and do not interfere with LT incision and fenestration.4. The allowable extent of LT opening is sufficient to provide wide access to remove the lesions that occur within the anterior third ventricle or compress or invade the walls of the chamber and LT fenestration.Objective:To explore the effect of fenestration of lamina terminalis during clipping of intracranil aneurysms to prevent chronic hydrocephalus after aneurysmal subarachnoid hemorrhage.Methods:The study Selected 64 patients with Preoperative Fisher 3 grade AComA aneurysmal subarachnoid hemorrhage, who were treated in our Neurosurgery Departmentbetween January 2001 and June 2005, were divided into 2 groups, one had fenestration of lamina terminalis during clipping of aneurysms, the other had clipped aneurysms only. CT or MRI scans,2 weeks after aSAH, were used to assess the occurrence of chronic hydrocephalus.Of all,32 patients had fenestration of lamina terminalis during clipping of aneurysms.Results:In all of the patients, the ratio of chronic hydrocephalus occurrence was 12.5% (8/64), the group of having fenestration of lamina terminalis was 3.13%(1/32), and the group without having fenestration of lamina terminalis was 21.88%(7/32)Conclusion:Fenestration of lamina terminalis during clipping of aneurysms had remarkable effect on prevention of chronic hydrocephalus. (p< 0.05)...