slurring of speech

My husband was getting infusions and all of a sudden they switched him to a different med and in a few days he was slurring and then having problems swallowing he went to hospital for nine days . they did some kind of plasma thing where they were washing out his blood and putting it back in .. it worked for five days now today he is slurring again .they have him on 20 mg of prednisone until they get an ok from insurance for a new infusion hoping he wont develope swallowing issues again and end up back in the hospital