PITTSBURGH -- Pirates reliever Craig Hansen returned to PNC Park on Tuesday to undergo another nerve test, and while speaking to reporters, Hansen revealed a little more about the medical ailment that has kept him from throwing since April.

After about a month and a half of looking for an explanation for a "ghost injury," as Hansen called it, doctors identified Hansen's condition as Parsonage-Turner Syndrome, a rare disorder in which a nerve deteriorates and, as a result, the muscle in that area of the body weakens. For Hansen, the nerve affected was in the upper right side of his back and weakened the trapezius muscle, which is a critical muscle in his throwing motion.

The only cure for such an ailment is rest, though Hansen is undergoing nerve tests once a month to continue to look for signs of improvement. Hansen said that in his research he has read that recovery time can range from six months to five years. Medical research has shown that 75 percent of people affected with PTS recover fully in two years.

"It's frustrating," said Hansen, who still does not have a timetable for when he can pick up a baseball again. "It's [about being] mentally tough more than anything. Right now, I've just got to keep myself busy and stay in shape so that when the nerve does come back and fully regenerate, I'll be ready."

How and exactly when Hansen initially suffered this paralysis of the nerve is still unknown. The best guess is that it was caused by a viral infection -- something as seemingly innocuous as a common cold -- and happened over the offseason. Hansen said that it was during Spring Training when he first noticed that he had lost significant strength in his pitching arm.

"All of a sudden you just notice that the strength gets significantly weaker," Hansen said. "It's been very challenging. It's too hard for me to sit back and watch and not be given an opportunity to play right now."

He has ruled out any attempt at trying to come back this season and is at this point looking to a return in 2010.

The 25-year-old Hansen has continued to earn his $825,000 salary this season despite spending all but the first month on the disabled list. His service time will fall just under that, which would make him arbitration-eligible this offseason, meaning the Pirates won't have to make a decision this winter about whether to non-tender the right-hander.