DETROIT — The good news for Yankees right-hander Phil Hughes is that he does not have a circulation or vascular problem in his pitching arm.

The puzzling news for the disabled hurler is, what’s IS wrong?

Hughes was examined by a specialist, Dr. Robert William Thompson, in St. Louis yesterday after tests in New York last week indicated Hughes was possibly suffering from thoracic outlet syndrome, which causes circulation trouble.

Surgery is a worst-case remedy for that condition.

But, as the Yankees announced here tonight during the team’s game against the Tigers, Thompson eliminated TOS yesterday as a reason for Hughes’ dead arm, which landed him on the disabled list.

However, Thompson did not give a reason for Hughes’ drop in velocity from 94 mph last year to 89 this season, when he was 0-1 with a 13.94 ERA in three starts before being placed on the DL.

The Yankees did not say what the next step is for Hughes — only that he is returning to New York and not rejoining the team on this road trip.