Thanks for using the forum. I am happy to address your questions, and my answer will be based on the information you provided here. Please make sure you recognize that this forum is for educational purposes only, and it does not substitute for a formal office visit with a doctor.
Without the ability to examine and obtain a history, I can not tell you what the exact cause of the symptoms is. However I will try to provide you with some useful information.
MRIs are subject to the strength of the magnet used to obtain. Also, MRIs obtain images at certain distances, for example 5mm. A small aneurysm may be missed if it is not included in the slice that is obtained on a repeat image. It would be important for you to have a follow up angiogram with either MR or CT.
Areas of gliosis on MRI can be from a prior infarct. Gliosis is an area of scar tissue.
If you have not done so, I suggest you follow up with a neurologist to understand why you had a stroke and what you need to do to prevent from a future stroke (such as blood pressure control, blood sugar control, taking an antiplatelet, determining the etiology of the stroke, etc).
Thank you for this opportunity to answer your questions, I hope you find the information I have provided useful, good luck.