can infection cause disorientation?

my dad has been through it since they found a met to his c2..had c1 to c3 fused and had radiation to tumor..all good but 2 weeks later pain increased...then redness...then yellow drainage...funny thing is that every dr. said dont think its an infection...mmmm...k fst forward to today...easter sunday delerious out of it...went to hosptial that week..still in..and guess what..had a 7cm fluid infection in neck...hes feeling better now...cant remember much of the last 2 weeks from meds and infection...question i have is can he get strong enough to have chemo again????? he really responded well to past treatments and still wants to be treated...and also could onc stop treatment if we still want it???????