Yankees right-hander Phil Hughes will be examined in St. Louis on Monday by Dr. Robert William Thompson, one of the country's leading experts on thoracic outlet syndrome. The team believes Hughes is suffering from the condition, which has led to his ineffectiveness this spring and a drop in velocity. The 24-year-old showed a "slight positive" on a circulatory test this week, according to general manager Brian Cashman, suggesting that TOS might be the root of Hughes' dead-arm problems. "You're trying to come up with some clinical diagnosis based on a lot of information - some of it testing, some of it conversations with the patient about what he's feeling," Cashman said Thursday. "You try to put it all together and try to make sense of it."