Key points
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Medulloblastoma is a common brain tumor; therefore, understanding its variations is crucial.
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Neuroimaging is helpful in the preoperative neuroaxis evaluation and postoperative assessment of medulloblastoma.
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Identifying and categorizing metastatic disease during diagnosis is paramount for effective therapy.
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Deciphering this challenging diagnosis can reflect positively on a patient’s prognosis.
Background
Search strategy
No | Authors | Origin | Age/sex | CT characteristics | MR characteristics | Management | Follow-up |
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1 | Kumar et al. [2] | CPA | 9 years/M | Hyperdense mass on plain scans, with heterogeneous enhancement | T1: hypointense; T2: heterogenous; CEMR: mass enhancement | Tumor excision; chemotherapy and radiotherapy | Died |
CPA | 8 years/M | Iso-to hypodense mass with heterogeneous enhancement | – | Tumor excision; radiotherapy | Died | ||
CPA | 20 years/F | – | T1 and T2: heterogeneous signal; CEMR: heterogeneous enhancement | Tumor excision; radiotherapy | Improved | ||
CPA | 24 years/M | Heterogenous mass | – | Subtotal resection; chemotherapy | Died | ||
2 | Spina et al. [5] | CPA (2 cases) | 22 years/M 26 years/F | – | T2/FLAIR: hyperintense; CEMR: heterogeneous enhancement | Total excision; radiotherapy | Improved |
3 | Fallah et al. [9] | CPA | 47 years/M | Homogenously enhancing mass with well-defined borders | – | Total excision; radiotherapy | – |
4 | Furtado et al. [10] | CPA | 32 years/M | Hyperdense mass on plain scan | T1: hypointense; T2: mixed intensity; CEMR: heterogenous enhancement + dural tail sign; MRS: choline and taurine peak increase and creatine peak decrease | Total excision; radiotherapy | Improved |
5 | Bhaskar et al. [12] | CPA | Infant/M | Hyperdense mass on plain scans | T1: hypointense; T2: isointense; CEMR: intense homogenous enhancement | Total excision | Died, postoperative day 20 |
6 | Yamada et al. [16] | CPA | 19 years/F | Hypoattenuated mass with homogenous enhancement | T1: hypointense; CEMR: mass enhancement | Subtotal resection; immunotherapy and radiotherapy | Improved, with no recurrence |
7 | Akay et al. [17] | CPA | 21 years/M | Heterogenous high attenuation | T1: hypointense; T2: hyperintense; CEMR: heterogeneous | Subtotal resection; chemotherapy and radiotherapy | Improved |
8 | Jaiswal et al. [18] | CPA (14 cases) | 3–53 years/seven M and six F | Heterogeneous attenuation with necrosis | T1: hypointense; T2: hyperintense; CEMR: heterogenous | Seven patients: Total excision; seven patients: subtotal resection; total eight patients received chemotherapy | Follow-up: nine cases Recurrence: two cases Symptom-free: seven cases |
9 | Becker et al. [22] | CPA (two cases) and tentorial (three cases) | 28–52 years/one M and four F | – | Heterogenous signal intensity and enhancement | – | – |
10 | Meshkini et al. [23] | Lateral cerebellar | 19 years/F | – | CEMR: heterogenous intense enhancement with cystic changes | Tumor resection | – |
CPA | 7 years/F | – | CEMR: heterogenous intense enhancement with cystic changes | Tumor resection | – | ||
11 | Doan et al. [24] | Tentorial | 29 years/M | – | CEMR: homogenous enhancement + dural tail sign | Subtotal resection; chemotherapy and radiotherapy | – |
12 | Presutto et al. [25] | Lateral cerebellar | 33 m/M | Mildly hyperattenuating on plain scans, with homogenous enhancement | T2/FLAIR: hyperintense; DWI: restricted diffusion | Total resection | Improved |
13 | Chung EJ, et al. [26] | Lateral cerebellar | 5 years/M | – | T1: isointense; T2: isointense; CEMR: homogeneous enhancement | Tumor excision; radiotherapy | Improved |
14 | Pant I et al. [45] | CPA | 15 years/M | T2: heterogeneous signal intensity with necrotic areas/cystic degeneration; CEMR: heterogeneous enhancement; DWI: restricted diffusion | Tumor resection | – | |
15 | Gil-Salu et al. [49] | CPA | 40 years/M | Homogeneously enhancing mass | Homogenous enhancement | Total excision; adjuvant therapy | – |
16 | Singh et al. [50] | CPA | 21 years/M | Heterogeneously non-enhancing mass | Heterogenous signal intensity and enhancement | Total excision | Recurrence and metastasis at 15 months |
17 | Bahrami et al. [51] | CPA | 23 years/M | – | T1: hypointense; T2: hyperintense; CEMR: heterogenous | Total excision; radiotherapy | Improved |
18 | Mehta et al. [52] | CPA | 40 years/M | – | Heterogenous enhancement | Subtotal resection; radiotherapy | Improved |
19 | Ahn et al. [53] | CPA | 9 m/F | – | T1: hypointense; T2: hypointense; CEMR: heterogenous | Subtotal resection; possible chemotherapy and Radiotherapy | Died after 2 months |
20 | Naim-ur-Rahman et al. [54] | CPA | 3 years/F | Heterogeneously enhancing mass | – | Tumor excision | Improved |
21 | Izycka-Swieszewska et al. [55] | CPA | 26 years/F | Homogenous enhancement | T1: hypointense; T2: hyperintense; CEMR: homogenous enhancement | Tumor excision | – |
22 | Park et al. [56] | CPA | 15 years/M | Hyperdense mass causing internal auditory canal dilation | T1: hypointense; T2: hypointense; CEMR: heterogenous | Subtotal resection; chemotherapy and radiotherapy | Improved |
23 | Santagata et al. [57] | CPA | 17 years/F | Hyperdense mass forming a flat surface against the posterior aspect of the left petrous bone and tentorium | CEMR: heterogeneous enhancement | Tumor excision; chemotherapy and radiotherapy | – |
24 | Nyanaveelan et al. [58] | CPA | 5 years/F | Mass eroding the petrous bone | – | Tumor excision; chemotherapy and radiotherapy | – |
25 | Yoshimura et al. [59] | CPA | 29 years/F | – | T1: isointense; T2/FLAIR: Hyperintense; CEMR: No enhancement; DWI: restricted diffusion; MRS: high ratio of choline‐to‐N‐acetyl aspartate | Subtotal resection; chemotherapy and radiotherapy | Improved |
26 | Cugati et al. [60] | CPA | 4 years/F | Contrast-enhancing extra-axial mass in the CPA, centered around the internal acoustic meatus | T1: hypointense; T2: hyperintense; CEMR: intense enhancement | Tumor excision | – |
27 | Kumar et al. [61] | CPA | 9 years/F | Isodense to hypodense mass in the right CPA Homogenous enhancement | T1: hypointense; T2: hyperintense; CEMR: brilliant enhancement | Tumor excision; radiotherapy | Improved |
Discussion of clinical review results
Cerebellopontine angle (CPA) location
Diagnosis | Common features |
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Meningioma | Short duration of symptoms, lack of cranial nerve involvement, and bony hyperostosis A well-demarcated lesion Follow the gray matter signal intensity |
Cholesteatoma | A destructive lesion with bony erosion Restricted diffusion on diffusion-weighted images |
Nerve sheath tumor | Destruction of the internal auditory canal Follow the signal intensity of the white matter Cystic degeneration and hemorrhagic components are common |
Epidermoid inclusion cyst | Follow the signal intensity of CSF with incomplete FLAIR suppression Restricted diffusion and no enhancement on post-contrast images |
Metastasis | History of a primary malignant lesion Metastatic work-up to look for other masses |
Primary bone tumor | Bony origin with erosion and a calcification or ossification pattern |
Choroid plexus papilloma | Well-defined lesion located in the foramen of Luschka Feathery appearance with restricted diffusion and intense postcontrast enhancement |
Hemangioblastoma | Young and middle-aged adults High intrinsic vascularity, as evidenced by high rCBV values on perfusion MRI If multiple, strong association with VHL syndrome |
Atypical teratoid rhabdoid tumor | Heterogenous solid-cystic mass occurring off-midline in children < 3 years of age |
Pilocytic astrocytoma | Cystic lesion with a pathognomonic mural nodule Hypodense on CT images |
Tentorial location
Lateral cerebellar location
Foramen magnum location
Advanced medical imaging for intra-axial and extra-axial medulloblastoma
Updates in radionuclide imaging
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Although at present, radionuclide imaging is not the primary diagnostic modality for intracranial tumors, primarily limited by its low specificity and low spatial resolution. In 1998, Müller et al. [31] evaluated potential applications of radionuclide-based imaging techniques for children with medulloblastoma. Radionuclide imaging is useful in detecting various intracranial tumors, including meningioma, pituitary adenoma, hemangioblastomas, gliomas, and medulloblastomas [32, 33]. Furthermore, the continued growth of tumor-specific radiotracers makes it very functional. For instance, a new radiotracer, 3-deoxy-3-[18F] fluorothymidine (FLT), is a molecule that is preceded by thymidine kinase-1 during phase S of mitosis. This tracer is distinct in that there is an uptake in setting a disrupted blood–brain barrier, which makes it very helpful and specific in detecting and determining the grade of brain tumors since higher-grade cancers are associated with greater disruption of the blood–brain barrier [34, 35].
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Radionuclide imaging has a limited potential in identifying medulloblastoma from differentiated diagnoses. However, the fusion of CT or MRI images with PET images can improve PET’s ability to diagnose and distinguish post-radiotherapy changes from tumor recurrence [36]. This is employed by the increase in cellular activity and glucose uptake in neoplasms relative to normal cells [37]. For instance, medulloblastomas have a limited potential for uptake in thallium-201 single-photon emission computed tomography and fluorodeoxyglucose PET (tumor-to-normal uptake ratio) [36, 38].
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Radionuclide imaging shows a limited potential capability in diagnoses and identification of medulloblastomas compared with differential diagnoses, and medulloblastomas have a limited potential for uptake in thallium-201 single-photon emission CT and fluorodeoxyglucose PET (tumor-to-normal uptake ratio) [39].
Updates in advanced MR imaging
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Dynamic susceptibility contrast imaging of medulloblastomas has revealed increased permeability, with the cerebral blood volume ratios close to 1 [40], particularly in desmoplastic cases. The findings significantly contradict those obtained from other differential diagnoses of enhancing the posterior fossa tumors [40].
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Finally, it is noteworthy that the characteristic arterial spin-labeling perfusion patterns have been studied among diverse pathologic types of brain tumors in children. These studies have revealed that the maximum relative tumor blood flow of high-grade tumors (grades III and IV) is significantly higher than that of low-grade tumors (grades I and II) [27, 41].
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Quantitative Apparent Diffusion Coefficient (ADC) value analysis can facilitate preoperative identification of medulloblastoma from its differentials, as well as grading of pediatric medulloblastoma [42, 43]. Further, it can facilitate optimal surgical treatment planning, with reduction of surgery-induced morbidity [43, 44].
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The ADC ratio—the proportion between the mean ADC observed in the tumor and the mean ADC observed in the contralateral white matter—is a simple tool used to distinguish juvenile pilocytic astrocytomas, ependymomas, and medulloblastomas [45]. In particular, the ADC ratio cut-off value was set below 1, as 1 was characteristic for medulloblastoma with 100% sensitivity and 90% specificity [44, 46].
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MRS based on the metabolic pattern can be used to identify medulloblastomas (Figs. 6C, 7C). A recent observational study of 111 medulloblastoma patients revealed a predictive accuracy of 95% for the SHH-activated group, 78% for group 4, 56% for group 3, and 41% for the WNT-activated group. Reflecting on specific preoperative features of MRI/MRS enabled the prediction of a molecular subgroup of medulloblastoma using a five-metabolite subgroup classifier (creatine, myoinositol, taurine, aspartate, and lipid) [46].
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MR perfusion is a distinguishing modality for posterior fossa diagnosis. In 2014, Yeom et al. [39] clarified the effect of maximal relative tumor blood flow (rTBF) on tumor grade (low vs. high grade) and found a difference in the range of rTBF between medulloblastomas (0.98 and 4.97) and pilocytic tumors (1.05 ± 0.18). In addition, medulloblastomas showed higher rTBF values compared to ependymomas, with an overlap between these two tumors because of the perfusion variability of the former [39]. Koob et al. [47] quantified the perfusion map parameters, i.e., the tumor-to-parenchyma ratios for relative enhancement, maximum enhancement, maximum relative enhancement, time to peak, and AUC values for medulloblastoma, which was significantly higher than ependymoma parameters (p < 0.05). A maximum cut-off enhancement value of 100.25 was used to distinguish between medulloblastoma and ependymoma (sensitivity 90.9%, specificity 100%) [47]. In 2020, Gaudino et al. [48] examined the data of 246 brain tumor patients by calculating the relative cerebral blood volume (rCBV) and the mean percentage of signal recovery (PSR). The optimum rCBV value threshold was 1.77 (sensitivity, 100%; specificity, 85%; PPV, 84%; NPV, 100%) [48].