I also find that Tramadol helps me with the "fog". In my case, I don't think the Tramadol is actually doing anything directly about the "fog", but through experimentation I have found that if I take both Tramadol and Gabapentin in the evening I wake up feeling very significantly better in the morning; more clear-headed and even a little less depressed than I am without taking those medications.
I think that the only explanation is that I am sleeping better, more deeply, with those drugs in my system than without them, and probably because my body is not in so much pain and so I am not uncomfortable, can rest. That is what makes sense to me, anyway.
Whatever you can do (not necessarily Tramadol) that will help you to sleep more deeply, and perhaps longer, will help you with the "fog", I am convinced. May not make it go away completely, but if you don't get enough truly deep and restful sleep it interferes with the brain's functioning, even in a completely healthy person.