The MRI requires a thorough explanation by you neurologist Kris.
There is also a lot of information on line. I inform myself so I can ask good questions.
When I have MRIs to help explain any neurological changes the hippocampus is a major focus of any memory concerns I have.

I have not, but I know where to go to get the explanation about the Hippocampus. This will not give you the answer to "no defined hippocampus", but it will help you while waiting for your neurologist to explain it by giving you some insight into the Hippocampus from medical experts (with all of the knowledge that humans have about it through research to date). I have not been told by GOD what GOD knows about the hippocampus, but I did a very human (with public access) search for the explanation, and I can find additional information to help take away the "medical language" "doctors' speak" to give you the translation to "Plain English" of what this article from the US National Library of Medicine on the Hippocampus means.

Understanding medical terminology was something that I needed for my job from August 2000 - September 2014, but I have also been taught "Plain English" (just didn't know it as "Plain English" until 2014 and didn't remember approximately when I was taught it over my life until in the summer of 2014 a committee from Massachusetts General Hospital (which included the Director of Treadwell Library -- where I worked at MGH for those years and the Director was my boss' boss, since she was the Assistant Director). The committee created a video that explained "Plain English" to us (how confusing it is for most people to hear their doctors speak in doctors dialect of English to us).

NOTE: This is especially so in the United States where the average American has the scientific vocabulary of a 4th grader.

Here is the article I was talking about (in the doctors dialect of English):
Hippocampus in health and disease: An overview: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC35...

NOTE: GOD did not have me experience what I did and then put knowledge into my head while letting me know that He did -- only recently-- for my benefit. GOD did it for OUR benefit.