上髓帆位置的改变在小脑中线髓母细胞瘤与星形细胞瘤鉴别诊断中的应用价值

The Position of the Superior Medullary Velum: A Sign for Diagnosis between Midline Medulloblastoma and Astrocytoma

目的探讨上髓帆位置的改变在小脑中线髓母细胞瘤和星形细胞瘤鉴别诊断中的应用价值。方法搜集经手术病理证实的29例小脑中线髓母细胞瘤和星形细胞瘤患儿的MRI资料,其中髓母细胞瘤21例,星形细胞瘤8例。观察不同肿瘤正中矢状位上髓帆的位置;测量不同肿瘤上髓帆与前颅底水平线的夹角,并绘制ROC曲线;预测小脑中线髓母细胞瘤与星形细胞瘤鉴别诊断的最佳角度。结果髓母细胞瘤组19例患儿上髓帆向上移位,1例向前移位,1例上髓帆位置无异常;星形细胞瘤组6例患儿上髓帆向前/向下移位,2例向上移位;髓母细胞瘤上髓帆与前颅底水平线的夹角平均值为(130.8±23.5)°,小脑中线星形细胞瘤上髓帆与前颅底水平线的夹角为(99.2±18.2)°,小脑中线髓母细胞瘤鉴别星形细胞瘤时上髓帆与前颅底水平线的最佳角度为115°。结论肿瘤正中矢状位上髓帆位置的改变可用于儿童小脑中线髓母细胞瘤和星形细胞瘤的鉴别诊断;上髓帆与前颅底水平线夹角>115°时,诊断为髓母细胞瘤的准确性较高。

Objective In this study,we aim to detect the role of the position of the superior medullary velum（ SMV）in midline posterior fossa tumours as a sign in helping to distinguish between midline medulloblastomas and midline astrocytomas. Methods Sagittal T1-weighted MRI images of 29 consecutive patients with histologically documented posterior fossa midline astrocytomas（ 8 cases） and medulloblastomas（ 21 cases） were reviewed,with respect to the position of the superior medullary velum. The angle of superior medullary velum and anterior skull baseline in medulloblastomas and astrocytomas were measured,and receiver operating characteristic（ ROC） curve were delineated. The optimum angle value for differential diagnosis of midline astrocytomas and medulloblastomas was analyzed and determined. Results In 19 medulloblastomas the SMV were superiorly dislocated,in 1 medulloblastomas the SMV presented upward dislocation,and 1 have no dislocated; in 6 astrocytomas it was anteriorly and / or inferiorly dislocated,in 2 astrocytomas the SMV presented upward dislocation. The mean angle of superior medullary velum and anterior skull baseline in medulloblastomas was（ 130. 8 ±23. 5） °,while that of astrocytomas was（ 99. 2 ± 18. 2） °. The optimum angle to distinguish midline astrocytomas and medulloblastomas was 115°（ 81% sensitivity and 87% specificity）. Conclusion In the differential diagnosis between midline medulloblastomas and midline astrocytomas,the position of the SMV is helpful. When the angle of superior medullary velum and anterior skull baseline is larger than 115°,it is strongly suggestive of medulloblastomas.