Study on diagnosis and differential diagnosis of common tumors in the posterior fossa of children based on diffusion⁃weighted imaging

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.

DOI: 10.3969/j.issn.1672⁃6731.2024.09.006