We don't much like to think about it but the fact is that people can have a stroke at any age. People between the ages of 40 and 60 years are candidates may be vulnerable to atypical causes for stroke.
Some atypical causes for stroke would be carotid dissection, drug use and migraine. Other possible causes for stroke are blood clotting abnormalities, congenital heart disease and patent foramen ovale.
Family history where other family members have experienced a stroke at a relatively early age should be noted.
The good news is, people between the ages of 40 and 60 years who experience a stroke also have a better chance of greater recovery afterward. They have greater brain plasticity which means their brains are better able to adapt to the changes that may have happened from a stroke.
According to Dr. Ana Felix, a neurologist at the University of North Carolina, people between the ages of 40 and 60 years are less likely to experience atrial fibrillation.
"Most importantly, surviving a stroke should be a wake-up call, said Felix, who noted that about a quarter of all strokes occur in people who have already had one."
http://www.kevinmd.com/blog/2010/06/stroke-young-adults.html#more-44372