A straight answer?
This patient sounds like he had an extensive medical history. Not every diagnosis is one of the few in an EMT or Paramedic textbook. Often it is a combination of things the exacerbates something else. Not just one system may be affected. Often something else will have to be treated to fix another symptom. That is why UTI came to mind since it can cause some of the symptoms you mentioned. Of course without the results of the UA, that would be difficult to know. What did the follow up CT Scan or MRI show if one was done? Did the other hospital, whose lab may have more capability, do a repeat tox screen? Was that afebrile temp taken rectally (core)? Were any blood cultures done?
If you look at the physicians' notes, they will have make a long list of possibilites. They may not pinpoint the exact cause but will treat what they know from the test results and see what corrects.