The given CT scan shows which brain lesion

Ans. C. Medulloblastoma.The above picture is an unenhanced CT shows a high-density midline tumor in the posterior fossa with a small amount of surrounding vasogenic edema exerting mass effect on the fourth ventricle, with a moderate degree of hydrocephalus. One half of primary brain tumors in children originate in the posterior fossa. Medulloblastoma are highly malignant tumors; they are the most common malignant posterior fossa tumor in the pediatric population. They are characterized by their tendency to seed along the neuraxis, following cerebrospinal fluid (CSF) pathways, and they represent one of the few brain tumors, including ependymoma, pinealoblastoma, and lymphoma, to metastasize to extraneural tissues. Originally classified as a glioma, medulloblastoma is now referred to as a primitive neuroectodermal tumor (PNET).