The clinical presentation and the MRI features are most consistent with subacute sclerosing panencephalitis (in this case, the CSF analysis was positive for anti-measles antibodies).

Subacute sclerosing panencephalitis (SSPE), also known as Dawson disease, is a rare chronic, progressive and fatal encephalitis that affects primarily children and young adults, caused by a persistent infection of immune resistant measles virus.