is usually given as a prophylactic drug or in simpler words as a coverage therapy for seizures,a patient is more prone to have after a head injury
.and its slowly tapered down and then stopped after an year or more if no seizures.here may be you are just co-relating the two things.that is by chance.you should first look for another cause of fever
what are other symptoms?
is there sore throat?
is he having body aches?
does he have chills?
is thee burning urination?
so better rule out these causes first.
any queries you can revert back
all the best