Yep, brain overload as much as everything else, @rose, possibly even affected from the anaesthetic as well .... I didn't have chemo but did have rads - & also have memory/speech issues just as you've experienced.
I just apologise in advance now for forgetting everyone's names & all my friends know to email me with things I am supposed to follow up on later on, as I'll have forgotten about them by the time I get home! Mind you, my husband has been diagnosed with dementia, so maybe it has rubbed off onto me too?? I hope not!
take care x