What Are The Symptoms Of Brain Fever?

Plz doctor .. My brother's son is 5 months and 2 weeks old . Yesterday he's hving fever and he getting the Big of the his back head. then we admitted the hospital and doctor said it may be he have brain fever they want to test the his backborn cartilage .. Plz tel me doctor for his having brain fever or not ?

If he is having brain fever what we have to do ?