Differential diagnosis of stroke vs migraine aura without migraine pain

I have had two episodes, 4 years apart, in which I experience a visual distortion that lasts about 15 minutes and includes geometric lines in some portion of my field of vision.  In the second incident, my speech was also affected; I was speaking, but my sentence and words did not make any sense and I was aware that I was not making sense.  This lasted less than 10 minutes.  An MRI was performed after the first incident, and a CAT scan was performed after the second incident, and both were normal.  My retinas were normal, blood work normal, and check of my carotid arteries was also normal. The diagnosis I was given was ophthalmic migraine or migraine without headache.  I was told that because I did not have any pain associated with these events, if it happens again, I would have to check myself into an emergency room each time, since there is no way to tell if these symptoms are that of a stroke, TIA, or migraine.  Is this true or is there some way to differentiate between these things without having to check myself into the hospital to be evaluated?