| Background and objective:1. Gerardus Blasius identified, described,and named the arachnoid membrane in1664. Key and Retzius provided the first detailed description of the arachnoid cisterns in1875. Yas.argil reported his intraoperative observations on the microsurgical anatomy of lamina terminalis cistern and lamina terminalis,and additional reports by neurosurgeons followed in1976.The research methods and results of microanatomy of lamina terminalis cistern and lamina terminalis are different. Moreover, the morphological features, borders and contents of LT cistern, the relationship between LT cistern and surrounding cerebral cistern, and the structure of LT are all in dispute. On the basis of microanatomy of human cadaveric heads, this study’s objective is to observe and measure the morphological features, borders and contents of LT; the relationship between LT cistern and surrounding cerebral cistern; the anatomic features of LT cistern; the relationship between surrounding anterior communicating artery and perforating branches; and to discuss the clinical application of morphological features and data of lamina terminalis cistern and lamina terminalis. 2. To summarize the clinical data of the anterior third ventricle tumor resection through LT space in our hospital, and to discuss how to use the LT space. To study the anatomy structures of the surrounding ACA-AComA complex, perforating branches, anterior commissure, optic chiasm, pituitary stalk, LT cistern and the anterior third ventricle in the lamina terminalis approach, providing the basis on dealing with the anterior third ventricle tumor.Method:1.20Chinese cadaver heads fixed by10%formalin were chosen in this study, while the arterial and venous system of10heads were filled with one-time molding filling agents. In craniotomy,10heads were opened through pterional approach, while the other10heads were opened through anterior interhemispheric approach. The pterional approach:Cadaver head was fixed on the operating table. Then partial frontal bone and temporal bone were opened, and the sphenoidal crest was ground to its medial. Subsequently, dura mater was incised and partial temporal lobe and frontal lobe were removed. Finally the lateral fissure was in exposure by pulling toward both sides. Using the operating microscope with6to40times magnification, we simulated the pterional approach to dissect lateral fissure layer by layer. Sylvian cistern was firstly separated and exposed the medial carotid, optic nerve, optic chiasma in turn then the lateral LT cistern in the end. Anterior interhemispheric approach:both sides of partial frontal bone were opened and the bone window was enlarged to the anterior cranial fossa. Then the eyeballs were removed, and the dura mater was incised when the frontal pole closed to the supraorbital horseshoe. Using the operating microscope with6--40times magnification, we simulated the anterior interhemispheric approach approach to dissect lateral fissure layer by layer. Frontal lobe was removed layer by layer. Then we entered into the saddle area along the diastematocrania direction to keep the LT cistern related vessels, pia mater and arachnoid purposefully. Subsquently, we dissected downward from knee corpus callosum to the top of LT cistern along A2segment of anterior cerebral artery. Eventually, dissection reached to the bottom of LT cistern and and surface of LT and optic chiasma. These two approaches can both observed morphological characteristics, borders, contents and membrane structures of LT cistern, and the relationship between LT cistern and related vessels and surrounding cerebral cistern. Moreover, they can confirm the structures of LT, optic recess, optic chiasma, anterior communicating artery, perforating branches, anterior commissure, massa intermedia and corpus albicans, and stimulate lamina terminalis approach to expose the anterior and bottom third ventricle. A digital camera was used to take photographs and shoot video and an electronic vernier caliper was used to measure the length of LT, optic chiasma, anterior communicating artery and related vessels. SPSS13statistical software was used to analyze the data.2. Clinical cases from78patients with the anterior third ventricle tumor received trans-LT resection in Guangzhou Nanfang Hospital from January2008to December2010, including craniopharyngioma60cases (27cases of teenagers≤16years old,33cases of adults>16years old), large pituitary adenomas6cases, hypothalamus glioma6cases, meningeoma2cases, germinoma2cases, non-Hodgkin’s lymphoma1case and nonspecific granuloma1case. The main clinical manifestations included increased intracranial pressure, visual impairment, visual field defect, hypopituitarism, polyphagia, polyuria, hypothalamic lesion and secondary sexual characteristics retardation. CT and MR scans results disclosed the information on tumor’s nature, size, texture, location involving. The observed index of MR scans on midsagittal images mainly included the relative position of the AComA complex and tumor, the height of tumor on sagittal image, shifting direction of corpus albicans, the degree of interpeduncal fossa involving, the relationship between interpeduncal fossa and basilar tip aneurysm and the vascular architecture of the AComA complex.38cases through frontotemporal-LT approach were chosen on the basis of tumor characteristic, size and involving parts, while40cases through the anterior interhemispheric-LT approach were chosen. These two surgeries needed to anatomize different cerebral cistern, and the approach of tumor exposure were different. However, it needed to expose and incise the LT completely. Tumor resection through LT approach included:(1) complete LT separation to remove tumor:mainly included craniopharyngioma burst into the third ventricle;(2) auxiliary application of LT approach:mainly included craniopharyngioma, pituitary adenomas, hypothalamus glioma, meningeoma which developed towards suprasellar cistern obviously. Then we discerned and protected the surrounding ACA-AComA complex, its perforating branches, anterior commissure, optic chiasma, pituitary stalk, corpus albicans, corpus albicans and hypothalamus in surgery. Finally, the tumor removal degree was evaluated by imaging after surgery, and cases follow-up were performed.Result:1. LT cistern was not an azygous cerebral cistern, which located on the top of optic chiasma and the upper front of LT. The superior wall consisted of medial LT membrane, extending upward to pericallosal cistern and connecting with arachnoid membrane forwardly. The interior wall comprised the upper surface of optic chiasma and LT, which was a free wall. The lateral wall was made of lateral LT membrane which both extended upward to medial LT membranes. The lateral LT membranes originated from posterolateral border of gyrus rectus, which extended downward to optic chiasma and the upper surface of optic nerve lateral border. It divided into sparse type, dense type and absent type. The medial LT membrane was azygous, consisting of both sides of gyrus rectus joint extending upward, which divided into convex type and flat sparse type. The contents of LT cistern included both of the A1 segments, the AComA, the proximal portions of the A2segments, partial Heubner artery, partial perforating branches of ACA-AComA complex, bilateral frontal orbitofrontal artery, bilateral the anterior cerebral veins and anterior communicating vein. The top of LT cistern was pericallosal cistern, and the medial LT membrane communicated between the rostrum of the corpus callosum and the inferior anterior of pericallosal cistern. Carotid membrane of LT cistern adhered to the inferior anterior of optic chiasma and the surface of optic nerve, connecting with the carotid membrane of optic chiasma. The lateral LT membrane extended downward to the lateral optic chiasma and the surface of optic nerve. The medial carotid cistern adhered to the inferior of the optic chiasma by the way of medial carotid membrane, extending downward to the lateral carotid membrane and covering the lateral saddle bed and posterior clinoid process. It was closed to the carotid cistern and bounded in lateral of optic chiasma and optic nerve, without communication. The anterior of lateral LT membrane and the inferior olfactory tract extended to gyrus rectus, communicating with the olfactory membrane.2. The morphology of thin LT was similar to the soft membrane. LT adhered to the central upper surface of optic chiasma, archedly ending in the inferior-anterior anterior commissure and the neighborhood of the rostrum of the corpus callosum, and taking up the space of the upper surface of optic chiasma and the rostrum of the corpus callosum. The inferior initial part of LT was the optic recess which was lower than optic chiasma. LT was the widest place in the third ventricle, which was mostly grey white, while the other was dark yellow and black blue. LT was divided into-protruded type and flat song type by morphology. Most central LT was transparent and protruded fenestra laminae terminalis. The positioning between optic chiasm and the tuberculum sellae was pre-type, normal type and post type. The length of optic recess was6.35mm±1.22mm, while the width was4.79mm±1.11mm. The distance between the anterior optic chiasma and the anterior optic recess was5.53mm±1.23mm, while the anteroposterior diameter was11.33mm±1.55mm. The length of LT was a curve distance, and the distance between the anterior LT (namely the central upper surface of optic chiasma) and the inferior anterior commissure was9.99mm±1.43mm, which was correspondent with LT length. The width of LT was the largest distance between both sides of medial optic tracts, which was11.23mm±2.23mm. Dissecting LT to the anterior and bottom of third ventricle,15massa intermedias and20corpus albicans could be observed clearly. The distance between the anterior optic chiasm and the inferior anterior massa intermedia was28.66mm±2.24mm, while the distance between the anterior optic chiasm and the anterior corpus albican was20.10mm±1.90mm.3.8cases of Heubner artery from the distal A1segments of ACA (the distance to AComA was within6mm) and30cases of Heubner artery from the proximal A1segments of ACA (the distance to AComA was within4mm) were observed. AComA was the vascular structure most closely connecting with LT. Its length was2.52mm±0.76mm. The height between the central inferior AComA and the central upper surface of optic chiasma was3.68mm±3.79mm, which was according with the distance between AComA and LT. The relative positioning between AComA and optic chiasm was pre-type, central type and post type. The perforating branches of AComA were mostly from superior wall, posterior wall and inferior wall, rarely from anterior wall, of which the total number ranged from several to dozens. The perforating branches were divided into posterior perforating branches, medial perforating branches and lateral perforating branches by the position of perforating branches and LT cistern. Hereinto, a relatively strong posterior perforating branch was from the posterior wall and inferior wall of AComA, via posterior LT cistern, and branched above the backward in the area subcallosa and hypothalamus. The average diameter was0.46mm.4. Tumor developed into the third ventricle behind optic chiasma. The relationship between craniopharyngioma with typical characteristics and the bottom of third ventricle could be confirmed by MR scans. On the basis of MR scans results, the frontotemporal-LT approach and the anterior interhemispheric-LT approach were chosen in surgery. Resection was performed in the cavity of third ventricle, however, the bottom of third ventricle could not discern clearly sometimes. The tumor removal degree was evaluated by intraoperative video and imaging.78cases were reviewed routinely by MR scans following surgery. Meanwhile,53cases were only reviewed by CT scans. Pathological diagnosis confirmed60patients with craniopharyngioma,6patients with large pituitary adenomas,6patients with hypothalamus glioma,2patients with meningeoma,2patients with germinoma,1patient with non-Hodgkin lymphoma, and1patient with nonspecific granuloma. Results of operating microscope observation and imaging review demonstrated that98.3%of craniopharyngioma (59/60) were removed entirely, while1.3%of those (1/60) were removed almost completely;4cases of large pituitary adenomas were removed entirely, while1case of those was removed almost completely, and1cases were removed in a great measure;2cases of hypothalamus glioma were removed entirely, while2cases of those were removed almost completely, and2cases were removed in a great measure;2cases of meningeoma were removed entirely;1case of germinoma was removed entirely, while1case of those was removed almost completely; both of non-Hodgkin lymphoma and nonspecific granuloma were removed entirely. In this group, most craniopharyngioma was removed safely through LT approach. the adhering positions of tumor in surgery mainly located in the superior pituitary stalk, the anterior and bottom of third ventricle. The partial infundibulum of pituitary stalk could be easily damaged. Therefore, the separation of tumor from pituitary stalk and the bottom of third ventricle was much difficult in surgery, and the continuity of pituitary stalk after tumor resection could not be preserved frequently. Among60cases of craniopharyngioma,43cases kept the pituitary stalk, while10cases separated the pituitary stalk for less recurrence, and the other cases all kept the pituitary stalk. However, some patients had partial lesion in the third ventricle in case review.90%of patients with craniopharyngioma had a function decline of pituitary gland;87%of patients with craniopharyngioma had a short-term diabetes insipidus following surgery, while56%of those had a long-term diabetes insipidus in case follow-up, which needed to used injection vasopressin tannate to control it;19patients with craniopharyngioma had vision disorder before surgery, while14patients improved their vision after surgery,3patients had no change, and2patients aggravated. There were3patients died in this group, but no complications of cerebrospinal fluid leakage and intracranial infection.Chief conclusion:1. The superior wall consisted of medial LT membrane; the interior wall comprised the upper surface of optic chiasma and LT; the posterior-interior wall was the central posterior LT; and the lateral wall was made of lateral LT membrane. The LT cistern, pericallosal cistern and carotid cistern had a strong connection. In first time,the lateral LT membrane was divided into sparse type, dense type and absent type, while the medial LT membrane was divided into convex type and flat sparse type. The anatomy features of LT cistern and the communication with adjacent cerebral cistern mignt affect the position of anterior communicating aneurysms hematocele after-broken.2. The color of LT was mostly grey white, which was divided into protruded type and flat song type by morphology. The length of LT was a curve distance, and the distance between the anterior LT (namely the central upper surface of optic chiasma) and the inferior anterior commissure was correspondent with LT length. LT was dissected in the central line distancing the posterior of anterior optic chiasma5.5mm--11mm.3. The relative positioning between AComA and optic chiasm was pre-type, central type and post type. The perforating branches were divided into posterior perforating branches, medial perforating branches and lateral perforating branches. In the frontotemporal approach or interhemispheric-LT approach, the method of opening LT cistern and exposing LT were different. It should treat with the lateral, medial and posterior perforating branches of AComA in turns, to expose the AComA and optic chiasm and enter the LT area in the end.4Diverse tumors involving anterior third ventrical chamber could be removed through Trans-lamina terminalis approach. It could be divided into two categories based on the application of LT space:(1) complete LT approach;(2) auxiliary extra-axial LT approach. Based on the pathological entities, size and ways of the third ventricle invasion of tumor, the frontotemporal-LT approach and the anterior interhemispheric-LT approach were chosen in surgery, which could meet the requirement of lesion resection involving the anterior third ventricle.5LT was a clear and discernable landmark of anatomic surgery. The separation of LT cistern, AComA, anterior commissure and its perforating branches could expose LT. Preoperative MR scans and the determination of LT, AComA, anterior commissure, pituitary stalk, corpus albicans, corpus albicans and other anatomic landmark had a important clinical significance on safe application of LT space. The important approach of treating with craniopharyngioma burst invaginated into the third ventricle from suprasella space was LT approach. It could completely remove the craniopharyngioma which was difficult to be exposed through typical extra-axial approach. |
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