Recently a close friend called me in panic to ask me whether I thought she might be having a stroke. At first, she described her symptoms as 10 minutes of partial blindness in the "left side of the world". This could indeed be a stroke, I thought to myself, and started to prepare her for an emergent trip to the nearest hospital. But as I started to ask more and more questions about the event, it became obvious that instead of a stroke, my friend was having a migranous aura. How could I tell? I simply asked her whether she had seen any flashing lights in her vision. And she had. In fact, she still could see them out of the corner of both eyes. They were white and flashing, and bothered her to the point that she needed to keep her eyes closed and stay still.
Her description of this event is classic for a migrainous aura, and not classic at all for a stroke. Strokes typically manifest themselves as “negative phenomena”, or as the unnoticeable absence of previously intact function. Typically people who suffer a stroke take some time to realize that they have lost a certain body function. This is in part why people who suffer a stroke while they are sleeping never notice it until after they wake up in the morning.
Thus, a stroke that affects a person’s vision is usually not noticed by that person for some time, until she begins to notice that she is constantly bumping into things, usually on one side of the body, over and over again. Migraines, on the other hand, lead to “positive phenomena” which is felt by that person as a bothersome, painful, or annoying symptoms such as the painful flashing lights that my friend described to me over the phone.
Having said the above, I must say that the symptoms of a stroke can present in the most unexpected of ways, depending on the part of the brain that is affected. Consequently, it may be virtually impossible to differentiate a stroke from a migraine in some people. I strongly recommend always erring on the side of caution and taking a trip to the nearest emergency room so that brain imaging (CT scan or MRI) can be performed. This way you and your doctors can rest assured that your symptoms are not being caused by a stroke