摘要：

目的: 探讨儿童后颅窝常见肿瘤的影像学诊断与鉴别诊断方法，并按照先定位诊断再定性诊断的思路，基于DWI是否弥散受限提出儿童后颅窝常见肿瘤的诊断流程图。方法: 共纳入2021年1月至2024年1月在复旦大学附属华山医院予以手术切除的118例儿童后颅窝肿瘤患者，均行头部CT和MRI检查，并据此进行术前定位和定性诊断，分别以术中所见和术后病理学检查为诊断“金标准”，判断术前定位诊断和定性诊断的准确性；再基于DWI是否弥散受限提出儿童后颅窝常见肿瘤的诊断流程图。结果: 共118例后颅窝肿瘤患儿定位和定性诊断为第四脑室肿瘤计41例，包括髓母细胞瘤27例、毛细胞型星形细胞瘤7例、室管膜瘤5例、脉络丛乳头状瘤1例、形成菊形团的胶质神经元肿瘤1例；脑干肿瘤38例，包括弥漫性中线胶质瘤，H3 K27变异型24例、毛细胞型星形细胞瘤5例、海绵状血管瘤3例、儿童型弥漫性高级别胶质瘤（倾向弥漫性中线胶质瘤，H3野生型）2例、节细胞胶质瘤2例、非典型性畸胎样/横纹肌样肿瘤1例、儿童型弥漫性低级别胶质瘤1例；脑桥小脑角肿瘤计9例，包括毛细胞型星形细胞瘤3例、胆脂瘤2例、髓母细胞瘤1例、弥漫性中线胶质瘤，H3 K27变异型1例、毛细胞黏液型星形细胞瘤1例、尤文肉瘤1例；小脑肿瘤计30例，包括毛细胞型星形细胞瘤15例、髓母细胞瘤7例、海绵状血管瘤2例、室管膜瘤1例、儿童型弥漫性低级别胶质瘤1例、儿童型弥漫性高级别胶质瘤（倾向弥漫性中线胶质瘤，H3野生型）1例、胚胎发育不良性神经上皮肿瘤1例、错构瘤1例和肾外横纹肌样瘤小脑转移瘤1例。定位诊断，术前CT的定位诊断准确率为93.22%（110/118），MRI的定位诊断准确率达100%（118/118）。定性诊断，74例（62.71%）患儿定性诊断准确，23例（19.49%）诊断笼统，21例（17.80%）诊断错误。儿童后颅窝肿瘤的影像学鉴别诊断集中于髓母细胞瘤、毛细胞型星形细胞瘤、室管膜瘤、弥漫性中线胶质瘤，H3 K27变异型。位于脑干外的髓母细胞瘤、毛细胞型星形细胞瘤和室管膜瘤的DWI弥散受限发生率分别为100%（35/35）、4%（1/25）和5/6，3种肿瘤之间差异有统计学意义（Z=-5.601，P=0.000）；位于脑干的弥漫性中线胶质瘤，H3 K27变异型和毛细胞型星形细胞瘤的DWI弥散受限发生率为79.17%（19/24）和1/5，两种肿瘤之间差异亦有统计学意义（Fisher确切概率法：P=0.038）。结论: 儿童后颅窝肿瘤早期诊断较为困难，DWI是鉴别诊断的重要依据，基于DWI是否弥散受限提出的儿童后颅窝常见肿瘤诊断流程图有望提高术前诊断的准确性。

关键词: 脑肿瘤, 颅窝，后, 磁共振成像, 诊断，鉴别, 儿童

Abstract:

Objective: To investigate the imaging diagnosis and differential diagnosis methods for common tumors in the posterior fossa of children, and to propose a flow chart for the diagnosis of common tumors in the posterior fossa of children based on the limited diffusion of DWI according to the idea of localization diagnosis followed by qualitative diagnosis. Methods: A total of 118 pediatric patients with posterior fossa tumors who underwent surgical resection in Huashan Hospital, Fudan University from January 2021 to January 2024 were enrolled, and all of them underwent head CT and MRI examinations, and preoperative localization diagnosis and qualitative diagnosis were carried out accordingly. Then, based on whether DWI was diffusion limited, a flow chart for the diagnosis of common tumors in the posterior fossa of children was proposed. Results: A total of 118 children with posterior fossa tumors were localization and qualitatively diagnosed, including 41 cases of fourth ventricular tumors, including medulloblastoma (27 cases), pilocytic astrocytoma (7 cases), ependymoma (5 cases), choroid plexus papilloma (one case), and rosette-forming glioneuronal tumor (RGNT, one case). There were 38 cases of brainstem tumors, including 24 cases of diffuse midline glioma, H3 K27-altered, 5 cases of pilocytic astrocytoma, 3 cases of cavernous hemangioma, 2 cases of pediatric-type diffuse high-grade glioma (prone to diffuse midline glioma, H3 wild type), 2 cases of ganglio glioma, one case of atypical teratoid/rhabdoid tumor (AT/RT), and one case of pediatric-type diffuse low-grade glioma. There were 9 cases of cerebellopontine angle (CPA) tumors, including 3 cases of pilocytic astrocytoma, 2 cases of cholesteatoma, one case of medulloblastoma, one case of diffuse midline glioma, H3 K27-altered, one case of pilomyxoid astrocytoma, and one case of Ewing sarcoma. There were 30 cases of cerebellar tumors, including 15 cases of pilocytic astrocytoma, 7 cases of medulloblastoma, 2 cases of cavernous hemangioma, one case of ependymoma, one case of pediatric-type diffuse low- grade glioma, one case of pediatric-type diffuse high- grade glioma (prone to diffuse midline glioma, H3 wild type), one case of dysembryoplastic neuroepithelial tumor (DNT), one case of hamartoma, and one case of extrarenal rhabdomyomatoid tumor cerebellar metastases. Localization diagnosis, the accuracy of preoperative CT was 93.22% (110/118), while the accuracy of preoperative MRI was 100% (118/118). Qualitative diagnosis, 74 cases (62.71%) had accurate qualitative diagnosis, 23 cases (19.49%) had general diagnosis, and 21 cases (17.80%) had wrong diagnosis. The imaging differential diagnosis of posterior fossa tumors in children focuses on medulloblastoma, pilocytic astrocytoma, ependymoma, and diffuse midline glioma, H3 K27-altered. The incidence of limited diffusion of DWI in medulloblastoma, pilocytic astrocytoma and ependymoma outside the brainstem was 100% (35/35), 4% (1/25) and 5/6, and the difference among the three tumors was statistically significant (Z =-5.601, P = 0.000). The incidence of limited diffusion of DWI in diffuse midline glioma, H3 K27-altered and pilocytic astrocytoma in the brainstem was 79.17% (19/24) and 1/5, and the difference between the two tumors was also statistically significant (Fisher's exact possibility: P = 0.038). Conclusions: The early diagnosis of posterior fossa tumors in children is difficult, and DWI is an important basis for differential diagnosis.

Key words: Brain neoplasms, Cranial fossa, posterior, Magnetic resonance imaging, Diagnosis, differential, Child