An irregular heartbeat called atrial fibrillation is a big cause of stroke, especially for people who have recently had a stroke. But it's not something that most people can feel.
Doctors test for atrial fibrillation by hooking people up to an electrocardiogram machine at the office, or having them wear a Holter monitor for a day or a week. There are also implantable monitors to check for afib, but they aren't widely used.
Thousands of Syrian infants born to refugee parents are now stateless. Their births are unregistered and will pose many difficult challenges in this long-term conflict.
The exact numbers are far from certain. A recent report by the United Nations refugee agency, UNHCR, suggests that 75 percent of Syrians born in Lebanon since 2011 have not been properly registered. Many families don't have any identification documents, which were destroyed in the fighting, or left behind in a panicked escape.