Hughes underwent a dye MRI exam, a CT scan, nerve tests and other tests in the last two days. The most recent theory is that Hughes has Thoracic Outlet Syndrome, a nerve and circulatory condition, and will be sent to a specialist in St. Louis, MLB.com's Bryan Hoch writes.
"We can't tell you if he has it or if he doesn't have it," manager Joe Girardi said. "But we're sending him to a specialist."
Earlier in the day, Cashman wasn't optimistic about a quick return for Hughes.
"They are trying very hard to find out what is going on," Cashman told the New York Post. "It's always concerning when you don't have somebody pitching active for you. He's not active, and it doesn't look like he will be for a while."
Hughes went on the disabled list April 15 with "dead arm" but had been showing a dead arm all season. He cut short a bullpen session on Monday, leading to this round of tests.
In three starts this season, Hughes was 0-1 with a 13.94 ERA, allowing 16 earned runs in 10 1/3 innings. Last season the 24-year-old right-hander was 18-8 with a 4.19 ERA.@cbssportsmlb on Twitter or subscribe to the RSS feed.