Well I seem to have found my culprit. I had paid very close attention to the onset of the fog this week and discovered that it happened with hours of taking my post chemo steroid, dexamethasone (decadron). I take these pills the three days following my cisplatin doses which are on Mondays. I noticed this past week that my deepest fog was on the weekend. Saturday and Sunday was the worst. But by Monday, I was basically clear minded and able to function almost normally. And then all day Tuesday as well. I did not take my decadron until late in the evening last night. Lo and behold, within an hour or so of taking it... the brain fog started. My lucidity started to slip, all the symptoms I had described ramped up. So it seems that the decadron is what is doing it. Looks like I am affected for the three days I take it and then it takes another three days to get through my system and by the time Monday rolls around for chemo again, it wears off, only to start again when I take them on Tuesday.

So ... while I am not happy about these side effects, at least now I am fairly certain what is causing them and that they wear off after I stop taking the decadron.