This child is under chemotherapy treatment for acute lymphoid leukemia (LLA). CNS involvement is uncommon in the presentation of LLA and it is more likely to be seen in the relapse of the disease after initial treatment. 

In patients like this one, the differential diagnosis is made between infection vs. carcinomatosis (LLA leptomeningeal disease). 

CSF cytology and microbiology confirmed the diagnosis of leukemic meningitis (leptomeningeal disease), in keeping with the radiographic findings and clinical data.