Medulloblastoma in the first year of life: A report of five cases

Congenital medulloblastoma: Fetal and postnatal longitudinal observation with quantitative MRI

Congenital medulloblastoma is extremely rare. MRI appearance of this tumor in the fetal brain has not been described. A case of congenital medulloblastoma initially observed by antenatal MRI with postnatal follow-up and treatment is presented. A pregnant female underwent fetal MRI on the 31st gestational week for routine indications. Midline cerebellar lesion of ≤2 cm in size with minor T₂ hypointensity and T₁ hyperintensity was identified. Additionally, quantitative MRI including apparent diffusion coefficient (ADC) and fast macromolecular proton fraction (MPF) mapping was performed. The lesion showed a marked ADC decrease and MPF increase. MPF maps depicted the lesion most conspicuously. After term delivery, a male neonate presented with symptoms of increased intracranial pressure. Postnatal MRI identified obstructive hydrocephalus caused by a large posterior fossa mass. The child was treated by cerebrospinal fluid shunt placement. Follow-up quantitative MRI on the fifth month revealed tumor growth and vivid changes of its tissue contrast associated with brain maturation. The tumor appeared nearly isointense on T₁- and T₂-weighted images and slightly hypointense on the ADC map. MPF contrast showed the most remarkable change from hyper- to hypointensity due to brain myelination with stable MPF in the tumor. Subsequently, the child underwent partial tumor resection, and currently continues treatment with chemotherapy. The pathological diagnosis was desmoplastic/nodular medulloblastoma. The described case illustrates evolution of the tumor contrast in the course of fetal and postnatal brain development and highlights the added diagnostic value of MPF mapping in fetal and neonatal neuroimaging.

Congenital tumors of the central nervous system

Congenital tumors of the central nervous system (CNS) are often arbitrarily divided into "definitely congenital" (present or producing symptoms at birth), "probably congenital" (present or producing symptoms within the first week of life), and "possibly congenital" (present or producing symptoms within the first 6 months of life). They represent less than 2% of all childhood brain tumors. The clinical features of newborns include an enlarged head circumference, associated hydrocephalus, and asymmetric skull growth. At birth, a large head or a tense fontanel is the presenting sign in up to 85% of patients. Neurological symptoms as initial symptoms are comparatively rare. The prenatal diagnosis of congenital CNS tumors, while based on ultrasonography, has significantly benefited from the introduction of prenatal magnetic resonance imaging studies. Teratomas constitute about one third to one half of these tumors and are the most common neonatal brain tumor. They are often immature because of primitive neural elements and, rarely, a component of mixed malignant germ cell tumors. Other tumors include astrocytomas, choroid plexus papilloma, primitive neuroectodermal tumors, atypical teratoid/rhabdoid tumors, and medulloblastomas. Less common histologies include craniopharyngiomas and ependymomas. There is a strong predilection for supratentorial locations, different from tumors of infants and children. Differential diagnoses include spontaneous intracranial hemorrhage that can occur in the presence of coagulation factor deficiency or underlying vascular malformations, and congenital brain malformations, especially giant heterotopia. The prognosis for patients with congenital tumors is generally poor, usually because of the massive size of the tumor. However, tumors can be resected successfully if they are small and favorably located. The most favorable outcomes are achieved with choroid plexus tumors, where aggressive surgical treatment leads to disease-free survival.