What Causes Memory Loss And Delusions In A Cancer Survivor?

my mother is a cancer survivor. twice within a week, she has experienced stroke like symptoms and considerable changes in her mental state. the first time, her memory was gone and she was delusional for roughly 24 hours. the second time, she was drastically more disorientated and confused and that lasted over 3 days before she returned to normal. she still isn t herself, but she is much better than she was initially. she has been hospitalized and undergone an mri with and without contrast, but doctors still have no answers. I m not sure what to ask for, but I don t feel like the doctors here are concerned with her issue or taking necessary measures to diagnose and treat the condition.