Hello, My Sister Is 23 Years Old And Has Been

Hello, my sister is 23 years old and has been experiencing some frightening symptoms. She has been experiencing random bouts of left side body numbness and loss of vision in her left eye. The doctors have ruled out stroke, multiplesclerosis, and diabetes. I have a friend from the ER that suggests she get an ultrasound of the right corroded artery due to the fact that it may be FMA. What are possible diagnoses?