Outfielder Rene Tosoni was recalled from Triple-A Rochester and will join the Twins before Friday's game against the Rangers.
Span suffered the concussion last Friday during a home-plate collision with Royals catcher Brayan Pena, and has been dealing with head and neck issues ever since. He said he was feeling better on Thursday, but there were still some lingering effects.
"I feel better than I did [Wednesday], just taking one day at a time," Span said. "My neck's still a little bit sore, and I still get dizzy here and there."
After flying back from Cleveland to Minnesota on Tuesday night because of the headaches, dizziness and a stiff neck, Span saw a specialist at a balance and dizziness center.
Span spent four hours going through a number of tests on Thursday.
"All different types of tests, letting them spin me around in chairs and throwing on goggles and all this crazy stuff," Span said. "They wore me out today."
Span said the symptoms are similar to the vestibular neuritis he dealt with in 2009, and that those symptoms have never fully gone away. Doctors told Span that some of the symptoms he had in 2009 had flared up again after being triggered by the concussion last week.
Over the last couple days, Span said he would occasionally feel "spaced out," or like the "room was moving a little bit."
"It's not all the time, it just comes and goes," he said. "There have been times when I'm at home relaxing and it comes, and sometimes I'm relaxing and I don't feel it. I think little things, like maybe bright lights every now and then or if I've got a lot of people around me like now, I start to feel a little funny."
The seven-day DL was implemented this season to give teams more options when dealing with concussions.
With so many other players already injured already this season, it helps the Twins bring up an extra outfielder without having to sideline Span any longer than necessary.
"If I'm healthy in seven days I come off, if I'm healthy in eight days, I come off," Span said. "There's a lot more flexibility for the player to come back. With a concussion everybody heals different and you just never know. I could feel better tomorrow. You just never know."