| Background and objection:Meningiomas are one of the most common brain tumor, accounting for about 20% of intracranial tumors. The incidence is 6/100000 people,and the tumor mainly occurs in middle-aged people, aged 42 to 56 years old.The ratio of male to female is about 1:2 to 1:3. Meningioma can be derived from arachnoid cap cells and (or) arachnoid trabeculae,and ususlly locates at the brain convexity, parasagittal, falx,sphenoid ridge, tuberculum sellae and tentorium.In 2007 edition of WHO pathological classification of central nervous system tumors, meningioma is divided into three grades and 15 subtypes.90%-95% of the meningiomas are WHOⅠgrade,5%-7% WHOⅡand 1%-2.8% WHOⅢgrade.Most meningiomas are WHOⅠgrade tumors, which can be cured by complete surgical excision. Nevertheless,3%-20% of WHOⅠmeningiomas recur,as to WHOⅡand WHOⅢgrade meningiomas, the overall recurrence rate is respectively as high as 30%-40% and 50%-80%. The pathological grade and extent of surgical resection of the tumor are the key factors which affect the recurrence rate. To achieve a permanent cure of meningiomas of different histological grades,the required surgical removal of the scope is different. Therefore, meningioma surgery, can not be generalized.Preoperative imaging of tumors and biological characteristics of meningiomas are of great significance in operations.MRI before surgery is the most important examination for meningiomas. The performance of subtypes is different in MRI, such as tumors in different signal sequences, dural tail sign, peritumoral edema. These features can be used for predicting the grade and subtype of meningiomas before surgery.As early as 1953, Simpson's grades provide the standards for resecting meningeomas.However, some benign tumors recur under Simpson's gradeⅠresection. Simpson's grades don't provide how much of the range of the tissues,especially the dura,around the tumors should be resected,which leads the tumor cells remaining in the adjacent dura to recur. So it will be of great significance that we can predict the invasive range of dura arounding the tumors before surgery.In this study, we reviewed imaging features of meningiomas in our department in recent years and proposed the MRI classification of,which is of great significance for reducing the recurrence rate of meningiomas.Methods:1,magnetic resonance imaging study of meningiomasThis retrospective study included 428 patients with histological proven intracranial meningiomas.We used the software to analyze the tumor location, T1, T2 sequence signal, the scope of edema and the form of dural tail sign. Multiple samples rank sum test and chi-square test by spss 16.0 was used for statistical analysis and a P value less than 0.05 was considered statistically different.2,Pathological study of meningiomas 2.1 Study on invasion of different types of meningeomas to the surrounding tissue124 patients with meningioma were analyzed, of which 122 cases were convex tumors (including convex, falx, parasagittal tumor, tentorial meningiomas) and 2 cases were sphenoid ridge meningioma (not Including full sphenoid ridge meningioma). After the tumor and surrounding tissue was resected,we put it into 10% formalin,then paraffin-embedded and HE stained. All patients in this study had been obtained pathological imformation. SPSS16.0 package was used for chi-square test and multiple samples rank sum test. A P value less than 0.05 was considered statistically different.2.2 A classification of dural tail signs of meningiomas in MRI179 patients with convex meningiomas resected under Simpson's gradeⅠand 89 patients with non-convex meningiomas resected under Simpson's gradeⅡwere reviewed.89 patients with non-convex meningiomas meningiomas were used to analyze the distribution of DTS. The cutoff range of the dura of 181 patients was 3cm from the basement of the tumor,which showed DTS in MRI. The dura mater,respectively 0.5cm,1.0cm,1.5cm,2.0cm,2.5cm and 3.0cm from the tumor basement,was examined with haematoxylin and eosin(H&E) after surgery.Results:1,magnetic resonance imaging study of meningiomasOf all the 428 cases of meningiomas,there were 362 in WHO gradeⅠ, including 84 cases of syncytial type,72 cases of mixed type,65 cases of fiber type,54 cases of sandbody type,33 cases of secretory type,25 cases of vascular tumor type,18 cases of microcapsules,11 cases of rich in lymphocytes-plasma cell type; 38 cases were WHO gradeⅡ,including 21 cases of atypical type,11 cases of clear cell type and 6 cases of chordoma-like type; 28 cases were WHOⅢ, including 13 cases of anaplastictype,12 cases papillary type and 3 cases of rhabdoid type.locations:150 cases of the convex,87 cases of parasagittal falx,44 cases of sphenoid ridge,38 cases of tuberculum sellae,32 cases of anterior cranial fossa,25 cases of petroclival,22 cases of tentorial,17 cases of posterior fossa,13 cases of ventricle in. Tumor size ranged from 0.3* 0.6* 0.8cm to 9.9* 10.2* 12.3cm.signal in MRI:The meningothelial shows slightly high or equal signal on T1 image and high signal on T2 image;the image of the transitional(mixed) on MRI has different types and the signal is hybrid;the signal of fibrous is slightly low or equal on both T1 and T2;and the signal is homogeneous;the signal of the psammomatous is low on both T1 and T2,sometimes cystic degeneration and necrosis exists in the tumor.The rest of benign meningioma is rare and usually shows low or equal signal on T1 image and slightly high signal on T2 image; the signal of the non-benign meningioma mostly shows low or equal on T1 image and slightly high on T2 image, cystic degeneration,necrosis and heterogeneous enhancement is common. T1 sequences of different pathological types were significantly different (P<0.001), while were no significant difference in subtypes(P=0.306); different histological subtypes and different sequences of WHO histological grade of T2 were statistically difference (P=0.002).Dural tail sign:326 of 428 (76.17%) cases of meningiomas can be seen dural tail sign in MRI.288 of 362(79.56%) benign meningiomas can be seen dural tail sign in MRI.,38 of 66 cases non-benign meningiomas (57.58%) can be seen dural tail sign in MRI.The incidence of DTS between benign meningiomas and non-benign meningiomas was statistically significant (P=0.017); 259 cases of convex tumors (including cerebral convexity, parasagittal falx, tentorial meningiomas), of which 208 cases can be seen dural tail sign (80.31%); 156 cases of skull base tumors (not including 13 cases of intraventricular meningioma), of which118 cases(75.64%)can be seen dural tail sign. The incidence of DTS between convex meningiomas and non-convex meningiomas was not statistically significant (P=0.518). In 208 convex tumors with dural tail sign,136 cases (65.38%)had more than one tail;while In 118 non-convex tumors with dural tail sign,32 cases (27.12%)had more than one tail.There was a significant statistical difference between them.(P=0.001).Peritumoral edema:211 of 428 cases (49.30%)of meningioma can be see peritumoral edema. In 155 cases WHOI grade tumors with peritumoral edema,Ⅰdegree of edema can be seen in 82 cases,Ⅱdegree edema in 39 cases,Ⅲdegree edema in 34 cases; In 33 cases WHOII grade tumors with peritumoral edema,Ⅰdegree of edema can be seen in 5 cases,Ⅱdegree edema in 9 cases,Ⅲdegree edema in 19 cases; In 23 cases WHOⅢgrade tumors with peritumoral edema,Ⅰdegree of edema can be seen in 1 cases,Ⅱdegree edema in 7 cases,Ⅲdegree edema in 15 cases.Meningiomas with higher WHO grade had higher degree of edema (P<0.001), the degree of edema of meningiomas in different parts was not statistically significant (P=0.113), but tumor location and the incidence of edema was statistically significant, convex tumors were more likely to be with edema than non-convex tumors (p< 0.05).2,Pathological study of meningiomas2.1 Study on invasion of different types of meningeomas to the surrounding tissueOf all the124 cases of meningioma,84 cases were WHOI grade; 29 cases were WHOⅡgrade; 11 cases were WHOⅢgrade. Invasion was rare in WHOⅠgrade tumor, the incidence of invasion was 38.1%,while 97.5% in non-benign tumors. The invasive range in 27 of 28 cases WHOⅠgrade tumors with dural invasion (96.4%) was within 2cm from the base; and the invasive range in 21 of 29 cases WHOⅡgrade tumors with dural invasion (72.4%) was over 2cm from the base and 93.10%(27/29) was within 2.5cm; invasion of all the WHOⅢgrade meningioma were over 2cm (100%), 8 of which (72.7%) were more than 2.5cm.2.2 A classification of dural tail signs of meningiomas in MRIDural tail sign in MRI can be divided into five types:smooth type, nodular type, mixed type, symmetric multipolar type and asymmetric multipolar type. Different types of dural tail sign in MRI were significantly different in the length, length from long to short were smooth type, symmetrical multipolar type, mixed type, nodular, asymmetric multipolar type; the dura mater corresponding to different types of dural tail sign were statistically different. Tumoral invasion range from from long to short were:nodular type, mixed type, asymmetric multipolar type, symmetric multipolar type and smooth type. The invasion of 96.13% dura corresponding to dura dural tail sign was within 2.5cm, The invasion of all the dura corresponding to smooth dural tail sign was within 1.5cm.conclusions:1 The location, MRI the signal characteristics, characteristics of peritumoral edema, and dura tail sign have certain relationships with the histological subtypes, and tumor WHOgrade,which is of great significance for operations.2 Meningiomas with different histological subtypes and WHO grade have different invasive characters,which should be carried out before surgeryor even by intraoperative frozen to determine the pathological type, to enable the individual tumor therapy.3 Dural tail sign is a special performance of meningiomas in MRI. For resecting the dura surrounding the of meningioma, we can refer to this classification in order to reduce the rate of distant recurrence of tumor. Innovations of our study:1 We summarize the MRI features of different subtypes of meningiomas and proposed various subtypes of peripheral invasion of meningiomas which is important for the concept of the individual of treatment for meningiomas.2 We propose a classification of dural tail signs of meningiomas in MRI and analyze invasive range of dura surrounding the tumor, which is important for reducing the rate of distant recurrence of tumor. |
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