| Purpose : Meningiomas are slow-glowing, well-circum-scribed tumors that arise from the arachnoid cap cells of the dura mater. They may invade or cause hyperostosis of subjacent bone. They usually indent and sometimes invade the brain. Gross-total resection of a meningioma is associated with an expectation of permanent cure and is frequently a source of satisfaction to neurosurgeons and their patients. Unfortunately, despite gross-total resection with removal of involved dura and bone, approximately 10% of patients experience tumor recurrence. This often leads to reoperations and much greater risk of morbidity and mortality for the patient. It is believed that recurrences represent the continues proliferation of tumor cells left behind after resection; however, anatomical location of the reservoir of these residual cells has not been conclusively established. Our objective in the present study was to determine whether the dura, bone and brain of peritumor could be invaded by meningiomas, as well as the invasive extent and mechanisms. Moreover, we examined the relationships between preoperative specific MR imaging features and invasive behaviors of meningiomas, which may be useful in the preoperative surgical evaluation of meningiomas.Methods: MR imaging studies, operative reports, clinical data, and histopathological findings were examined retrospectively in this series,which included 54 patients with intracranial meningiomas who underwentoperations in which microsurgical techniques were used. The total patientswhose histopathological findings belonged to WHO I did not undergoradiotherapy. The findings were assessed by a pathologist and a radiologistthrough double blind method.Part One: Comparative Studies Between Histopathology of InvasiveExtent of Meningioma and MR imaging1 , Dural group: A prospective surgical, histopathological, and MRI studywas performed in 46 patients. Contrast-enhanced MRI was obtained beforesurgery. Histopathological examination of the dural specimens wasperformed in all patients in which the studies of 20 patients were performedon invasive extent.2, Skull group: Preoperative radiographic evaluation using MR imaging wasperformed in 36 patients, and the conditions of abnormal bone wereidentified. During the resection of the tumor, biopsies from these abnormalskull regions were sent for histological evaluation regarding the presence orabsence of tumor invasion of the bone.3, Brain group: CSF-vessel circum-interspace, peritumoral brain edema onMR imaging, and brain-tumor interfaces in operative performance wereprospectively studied. Biopsies from abnormal brain regions were sent forhistological evaluation regarding the presence or absence of tumor invasionof brain.Part Two: Invasive Behavior in Meningiomas Is Associated WithIncreased Vascular Endothelial Growth Factor Expression and Featuresof MR imagingMeningioma tissue samples from 46(dural group), 36(skull group), and 30(brain group)patients who underwent surgery were examined retrospective for the extent of expression o immunoreactive VEGF. Additionally, features of MR imaging were assessed on a blinded basisradiographically from preoperative MR imaging scans. Results:Part One: Comparative Studies Between Histopathology of Invasive Extent of Meningioma and MR imaging1, Dural group: MRI disclosed that dura invaded by the tumor had a break in the continuity of enhancement, or that there was no discernible enhancement. Association between patterns of dural enhancement and tumor invasion of dura was statistically significant(p<0.05). There were not statistically significant (p>0.05) between invasive probability and pathological subtype in WHO I. So was the associations between dural enhancement and invasion of dura. Sites of meningiomas did not correlated with invasion of dura. In 15 patients, tumor cells invaded the dura mater and vessels, packing the latter. Probabilities of invasive extension of dura were individually observed over 100%, 35%, and 25% at the point of lcm, 1.5cm, and 2.0cm which were adjacent to the margin of meningiomas.2, Skull group: Preoperative neuroradiological assessment identified statistic significance with the invasion of bone(p<0.05). All of invaded bone tissue were found infiltration of Haversian canaliculus by tumor cells. However, there were not statistically significant (p>0.05) between invasive probability and pathological subtype in WHO I.3, Brain group: Ildan types, namely the degree of microsurgical dissection on the brain-tumor interfaces, the grade of peritumoral brain edema on T2WI, and CSF-vessel circum-interspace individually seemed to correlate very precisely with the invaded brain tissue by tumors(p<0.05), allowing the prediction of microsurgical effort required during surgery. Additionally, a positive correlation was found between the CSF-vessel circum-interspace and the types of cleavage(p<0.05).Part Two: Invasive Behavior in Meningiomas Is Associated With Increased Vascular Endothelial Growth Factor Expression and Featuresof MR imagingWhether meningiomas invaded dura, bone, and brain tissues or not seemed to correlate precisely with the extent of VEGF expression(p<0.05) which the most strong expression was at the point of the most predominant invasion. Additionally, there was statistic significance between the signal intensity on T2-weighted MR images and the extent of VEGF expression(p<0.05).Conclusions:Part One: Comparative Studies Between Histopathology of Invasive Extent of Meningioma and MR imaging1, A fairly uniform "enhanced dura" adjacent to a tumor correlates with a dural inflammatory reaction, whereas discontinuous enhancing dura indicated dural invasion.2, There were invasive probability on the range from the margin of meningioma to the 2cm point.3, The mechanism of "dural tail" on contrast-enhanced MRI may be caused by invasion of the dura mater and vessels, packing the latter. 4, Merely hyperostosis or non-change did not represent the invasion of tumors, and destroyed bone tissue represented the invasion. MR imaging-assessed was superior to CT as using evaluative and predictive meningiomas with preoperation.5, The extent of peritumoral brain edema and CSF-vessel circum-interspace may predict the types of cleavage and invasion of brain. Part Two: Invasive Behavior in Meningiomas Is Associated With Increased Vascular Endothelial Growth Factor Expression and Features of MR imagingMeningiomas-assocated invasion may be a result of the capacity of meningioma cells to produce VEGF locally. The signal intensity on T2-weighted MR images may be a predictable factor, leading to increased... |
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