Actually yes those were found in people with bipolar but I can't post links to case studies here. Just google "White matter sensitivies in bipolar" and you will come up with a variety of articles so that have found that to be true and are researching it. As I said you could ask the psychiatrist you will be seeing more though but they are just finding out more about that area of research.
I don't know. Although like everyone here I don't have medical knowledge I am involved in some clinical cases studies as regards new treatment modalities and know about clinical research. I had an MRI done of my brain relatively recently. I have schizoaffective. And they didn't find anything abnormal in that regard. However PET scans as regards schizophrenia and bipolar are different and I have a photo (in the public domain) of a PET scan of a person with schizophrenia on my personal page and it shows marked deficits. I believe there would be some differences for bipolar as well. But a PET scan shows how the brain functions. The MRI is a scan of what the brain itself looks like and I am not sure if there is a difference. You could ask the psychiatrist you will be seeing but if you want to know clinically up to date research you can look on PubMed and ClinicalTrials.gov out of interest but remember any clinical study or clinical finding is not conclusive until the study is over.