| Backgroud and objection:Gerardus Blasius first discovered and named the arachnoid in1664. Key and Retzius first systematically described subarachnoid cisterns in1875. Liliequist named "Liliequist membrane" in the1850s,which was discovered by Key. In1976, Yasargil described the microanatomy of subarachnoid cisterns basing on intraoperative findings and micro concept was brought into neurosurgery The arachnoid membranes and the subarachnoid cisterns had been precised and excellently discribed by Rhoton. The arachnoid was classified into the inner layer and the outer layer.The former includes the membrane structures which comprises subarachnoid cisternal wall and arachnoid trabeculae inside cistern. Previous studies paid little attention to this irregular trabeculae. However,this trabecular distributed extensively in the cisterns,connecting nerves and vessels. Therefore, it is necessary to conduct further research on arachnoid membrane.Meningiomas are one of the most common intracranial tumors, accounting for about20%of intracranial tumors. Meningioma was divided into3grades and15subtypes in2007edition of the WHO central nervous system pathology classification. More than90%of the meningiomas are WHOI grade,5%-8%WHOII and3%-5%WHOIII grade. Now that meningioma origins from arachnoid cap-like cells, in theory, meningioma can occur wherever arachnoid existed. Meningiomas are epi-arachnoid tumors,so arachnoid membrane plays as a barrier between tumors and issues,especially in skull base meningiomas, such as tuberculum sellae and sphenoid ridge. Furthermore, the inner arachnoid with different shapes, may play a similar role as the outter arachnoid,what is more, the inner layer of the arachnoid can be attached between the outer arachnoid and nerves or blood vessels, nerves and nerves, vessels and vessels,nerves and vessels, which may become the media by which tumor involves the peripheral nerves and blood vessels..Therefore, further study on arachnoid and establishing the membrane concept in neurosurgery is of great significace. Materials and Methods1Morphology, classification, distribution of supratentorial arachnoid and its clinical significance6cases (12sides) of adult skull specimen was studied under the microscope.The morphology, classification, distribution of membrane structure in subarachnoid space was carefully observed. Videos of endoscopic eyebrow keyhole craniotomy and endoscopic pterion keyhole craniotomy were studied and the morphology, classification, distribution of membrane structure was confirmed.The significance of membrane structure was summarized according to the previous experience of our department.2Classification of suprasellar meningiomas and its clinical significanceBetween January2000and December2008,106patients with SM underwent surgical resection was analized. None of the patients had any prior treatment. A retrospective review of medical records of all patients was conducted. All the patients underwent a standard preoperative evaluation including history, neurological and ophthalmologic examination. The ophthalmologic examination consisted of testing visual acuity and visual field using the standard techniques. The hypothalamo-pituitary axis impairment was evaluated using the baseline endocrine panel of pituitary and target organ hormones. Based on the growth pattern of SM, we classified the cases into type A, B and C. Type A:tumor located at planum sphenoidale, rarely involves the optic pathway or pituitary stalk (PS); type B located at the tuberculum sellae, mainly involves the optic pathway but rarely involves PS; type C located at the diaphragma sellae, which can involves both the optic pathway and PS. Type C was then divided into C1and C2, C1-tumor pushes the chiasm in pre-fixed position, C2-optic chiasm is pushed in post-fixed position with expansion of pre-chiasmatic space. The parameters including clinical and neuro-ophthalmological examinations, operative reports, imaging studies, and surgical videotapes from these cases were reviewed. The factors that influence the outcome and recurrence including patient’s age and sex, duration of preoperative symptoms, tumor size, involvement of optic pathway, PS and ACA complex, surgical approach, postoperative complications and WHO grading were analyzed.3Classification of medial sphenoid ridge meningioma and its clinical significance33cases medial sphenoid ridge meningioma patients from2000to2008were retrospectively analized. Based on the growth pattern of tumor, we classified the cases into type A and type B.Type A tumor origined from the medial sphenoid ridge and growed outwards while type B was with the same origin growing inwards. The parameters including clinical and neuro-ophthalmological examinations, operative reports, imaging studies, and surgical videotapes from these cases were reviewed. The factors that influence the outcome and recurrence including patient’s age and sex, duration of preoperative symptoms, tumor size, involvement of optic pathway, PS,ICA and CS, postoperative complications and WHO grading were analyzed.Result 1Morphology, classification, distribution of supratentorial arachnoid and its clinical significanceIntracranial arachnoid in accordance with their location, can be divided into outer and inner arachnoid. Inner arachnoid can be sub-classified into inherent inner arachnoid(IIA) and adherent inner arachnoid(AIA).The morphology of supratentorial inner arachnoid include silk-like(SLIA),cord-like(CLIA),band-like(BLIA) and film-like(FLIA). The morphology of supratentorial inner arachnoid can be single or combined type mentioned above. Membranous structure plays a important role in tumor exposure,surgical disection, aneurysm separation and hydrocephalus treatment.Outter arachnoid layer form sleeve in the pituitary stalk and the internal carotid artery,which was of great siginifcance in tumor classification and resection in these areas,especially for meningiomas.2Classification of suprasellar meningiomas and its clinical significanceThere were32men and74women with mean age48.5±13.1years (range,20to78years). There were20.7%(22/106) cases of type A SM,25.4%(27/106) of type B,10.3%(11/106) of type C1and43.4%(46/106) of type C2. Visual impairment was found in77.4%(82/106) patients. The rate of visual symptoms for types A,B,C1and C2was13.6%(3/22),88.9%(24/27),90.9%(10/11) and97.8%(45/46) respectively. Headache was present in64.2%(68/106) patients; the rate for types A, B, C1and C2was63.6%(14/22),48.1%(13/27),54.5%(6/11) and76.1%(35/46) respectively (p=0.098). H-P axis impairment was present in55.7%(59/106) patients, and rate of h-p impairment for types A,B,C1and C2was9.1%(2/22),33.3%(9/27),100%(11/11) and80.4%(37/46)(p<0.001) respectively.Optic pathway involvement on neuroimaging was seen in77.4%(82/106) of all the cases. The most common types with optic pathway involvement was type C2 97.8%(45/46) followed by type C190.9%(10/11), type B88.9%(24/27) and type A SM13.6%(3/22)(P<0.001). The ACA complex involvement was present in53.8%(57/106) cases; type C2being the most common76.1%(35/46) followed by type B51.9%(14/27), C127.3%(3/11) and A22.7%(5/22)(P<0.001). PS was involved in43.4%(46/106) of all the cases. The most common types with PS involvement was type C190.9%(10/11) followed by C260.9%(28/46), B29.6%(8/27) and A (0/22)(P <0.001)Unilateral subfrontal approach was employed for17.9%(19/106) cases, fronto-temporal for48.1%(51/106) and anterior interhemispheric approach for34%(36/106). Most type A tumors94.7%(18/22) were resected through unilateral subfrontal approach. Type B70.4%(19/27) and C1100%(11/11) were operated on using fronto-temporal approach. Anterior interhemispheric approach was used in56.5%(26/46) of type C2tumors. The type of approach used for each tumor type was statistically different..(P<0.001,Chi-Square Tests). The optical canal involvement was identified intraoperatively in50%(53/106) cases. The most common type with optical canal involvement was67.4%(31/46) type C2SM followed by66.7%(18/27) type B,18.2%(2/11) typeC1and9.1%(2/22) type A(P<0.001,).Total resection (Simpson Ⅰ-Ⅲ) was achieved in79.2%(84/106) of cases. The rate of total resection was86.4%(19/22),85.2%(23/27),45.5%(5/11) and80.4%(37/46) for type A, B, C1and C2respectively (P=0.03,Chi-Square Tests).The tumor type, preoperative h-p axis impairment, preoperative visual impairment, PS involvement on MRI, tumor size, surgical approach employed, intraoperative ACA complex involvementand optical canal involvementwere all associated with subtotal resection. The tumor type was the only significant predictor of subtotal resection.The perioperative mortality rate was5.7%(6/106).Follow-up was conducted at3,6,12-month after surgery, and then follow up was conducted once every year. The mean follow-up time was70.4months (median86months, range64.5-76.3months). The postoperative visual impairment was seen in34%(34/100). The rate of postoperative visual impairment was significantly different among four tumor types (P=0.019). The univariate analysis displayed that tumor type, preoperative h-p impairment, preoperative visual impairment, age group, surgical approach used and degree of resection were all related to postoperative impairmentof visual outcome. The surgical approach employed was the only significant predictor of postoperative visual impairment.The postoperative h-p axis impairment was encountered in51.9%(55/106). The tumor type, tumor size group, headache,preoperative h-p impairment, preoperative visual impairment, PS involvement on MRI, surgical approach used, ACA complex involvement,optical canal involvement and degree of resection degreewere associated with postoperative h-p axis impairment. The tumor type and surgical approach employed were significant predictor of postoperative h-p function impairment. The rate of recurrence was14%(14/100). The recurrence was significantly associated with tumor type, tumor size, preoperative h-p impairment, preoperative visual impairment, PS involvement on MRI, WHO grade and degree of resection. The subtotal resection was the only significant predictor of recurrence. The mean PFS time was102.9±3.2months PFS rate was86%. The mean PFS duration was different among4groups.3Classification of medial sphenoid ridge meningioma and its clinical significanceThere were11men and22women with mean age48.7±12.5years (range,25to67years). There were39.4%(13/33) cases of type A and60.6%(20/33) of type B. Visual impairment was found in54.5%(18/33) of all patients. The rate of visual symptoms for types A and B was84.6%(11/13) and35.0%(7/20),respectively. Preoperative ophthalmoplegia was present in30.3%(10/33) patients; the rate for types A and B was53.8%(7/13) and15.0%(3/20),respectively.17cases (51.5%) had preoperative headache.38.5%type A tumors (5/13) and60.0%(12/20) type B tumor harbored headache respectively. There was no significant difference in headache between these two types. Preoperative endocrine disorders were rare, with an incidence of6.1%(2/33).2cases (15.4%) were seen in patients with type A.The relationship between tumor and ICA can be as follows:ICA without involvement by tumor;ICA involved by tumor with arachnoid and ICA involved by tumor without arachnoid.The relationship between type A tumors and ICA were:no involvement7.7%(1/13), involved by tumor with arachnoid38.5%(5/13) and ICA involved by tumor without arachnoid53.8%(7/13); The relationship between type B tumors and ICA were:no involvement20.0%(4/20), involved by tumor with arachnoid65.0%(13/20), and involved by tumor without arachnoid15.0%(3/20). No significant difference was found between types of tumors and ICA involvement. Further comparation between inter-group showed there are significant differences between the types and ICA involvement pattern. The relationship between type A tumors and CS were:no involvement of23.1%(3/13), only the lateral wall involvement23.1%(3/13), invasion into the later walls of the cavernous sinus53.8%(7/13); The relationship between type B tumors and CS were:no involvement of75.0%(15/20), only the lateral wall involvement15.0%(3/20), invasion into the later walls of the cavernous sinus10.0%(2/20). Statistically significant differences between the types of tumors and cavernous invovlement was found. Optic canal involvement was found in7cases of type A(53.8%) while6cases was found non-involvement (46.2%); optic canal involvement and none-involvement was30.0%(6cases) and70.0%(14cases) respectively of type B tumors. There was no statistically significant differences between types of tumors and optic canal invovlement. The relationship between type A tumors and visual pathway were:no involvement15.4%(2/13), involved by tumor with arachnoid69.2%(9/13) and visual pathway involved by tumor without arachnoid15.4%(2/13); The relationship between type B tumors and visual pathway were:no involvement65.0%(13/20), involved by tumor with arachnoid35.0%(7/20), and involved by tumor without arachnoid0(0/20). Differences in the relationship between the two types and the visual pathway involvementwas not statistically significant.Total resection rate of type A tumor was61.5%(8/13) and85.0%(17/20) of type B tumor. Total resection rate was statistically different between two types. Preoperative factors related to subtotal resection include:tumor type ophthalmoplegia. After Logistic regression analysis, tumor type and ophthalmoplegia are significant predictors subtotal resection, Intraoperative and postoperative factors associated with subtotal resection included the ICA involvement and CS involvement. After Logistic regression analysis, CS involvement is the only significant predictor.The postoperative visual impairment was seen in27.3%(9/33). In the preoperative factors, only ophthalmoplegia was related to postoperative impairmentof visual outcome. In intraoperative and postoperative factors, univariate results show the ICA involvement, CS involvement, extent of resection and decreased visual acuity was statistically related to postoperative impairment. Multivariate analysis showed the extent of resection is the only significant predictor of postoperative visual impairment.8cases (24.2%) patients preseneted more seriously ophthalmoplegia. In the preoperative factors, only preoperative ophthalmoplegia was statistically significant; while in intraoperative and postoperative factors, univariate results showed the ICA and involvement, CS involvement, extent of resection and tumor WHO grading were all related to postoperative ophthalmoplegia. Multivariate analysis showed the extent of resection was the only statistically significant predictor. Seven patients (21.2%) presented postoperative hypopituitarism. univariate results showed tumor type, preoperative headache, preoperative endocrine abnormalities, ophthalmoplegia were all related to postoperative hypopituitarism. Multivariate analysis showed ophthalmoplegia was the only statistically significant predictor.The mean follow-up time was62.4±23.5months (14-98months).12(36.4%) patients suffered recurrence. Tumor recurrence was related to tumor type and preoperative ophthalmoplegia. Multivariate analysis results showed preoperative ophthalmoplegia is the only statistically significant predictor. In the postoperative factors, CS involvement and extent of resection was related to recurrence. Multivariate analysis showed CS involvement was the only predictor of recurrence.The mean progression-free survival time was51.5±27.6months (8-89months), while progression-free survival rate was72.6%. PFS rate for type A and B was respectively60.7%and80.0%; and PFS time for type A and B was38.8±26.2months and59.8±25.9months. Difference between the two group was statistically significant.ConclusionThe knowledge of intracranial membranous structure and the establishment of membranous concept have great significane in modern neurosurgery. As everything has two sides, arachnoid acts as protection interface during operations;on the other hand it may become the media by which tumor involved neurovascular issues. As any meningioma, the classification of meningioma originating in the tuberculumsellae and medial sphenoid ridge has inherent limitations due to their inconsistent growth pattern, direction of growth and extent of dural attachment. However, the classification is useful to systematize the most appropriate surgical approaches, potential preoperative, perioperative and postoperative characteristics that might differ based on their growth pattern.Innovations of our study1,We discribed the arachnoid,especially the inner arachnoid,quantitatively and qualitatively for the first time.We also discussed the role of arachnoid played during neurosurgery clinical practice and summarized its significance.2, We propose a systematic characteristics of suprasellar meningiomas based on their origin and location. The proposed classification is useful to systematize the most appropriate surgical approach, and to elucidate the preoperative, perioperative and postoperative features that characterize each of this tumor types.3, We also propose a systematic characteristics of medial sphenoid ridge based meningiomas on their origin and location. The proposed classification is useful to systematize the most appropriate surgical approach, and to elucidate the preoperative, perioperative and postoperative features that characterize each of this tumor types. |
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