Hi Acute means sudden onset within a time span of say 7 days or less. Encephalitis mean infection of brain. Sudden onset brain infection. A big list of the causes are there. Body can loose only sensation in very few conditions like spinal cord problems Anterior cord syndrome, central cord syndrome or brain problems like bleeding or ischemia. Numbness alone in 3 quarters is unheard but if its associated with muscle weakness too, then it is called as Paresis(quadriparesis or hemi paresis or para paresis). Health supplement which would contain B-12 and Omega fatty acids might help. Hope you are satisfied with the answer. Feel free to ask any more quarries. Thanking you Dr Samir