My sister also had a clot to brain. She is a horse owner and does lots of rides in the beautiful places around the country. One day she noticed a red ring around a circular rash on the surface of her skin. It was the result of the dreaded Lyme Disease. The infection can spread to joints, the heart, and the nervous system. In the case of the heart, it can cause irregular contractions that create blood cavitations that promotes blood clots. Yikes!