Holmgren said Grossmann is seeing concussion specialists in Pittsburgh for what he said were "vestibular issues."
Grossmann, who was injured during a practice last month, has not played since March 18. He has four points in 30 games but leads the team with 82 blocked shots and is fourth with 81 hits.
Holmgren also said center Danny Briere, who also sustained a concussion during a practice last month, could return to the lineup Thursday against the Ottawa Senators. Briere, who has five goals and eight assists in 26 games, has been skating for about a week.
It's cool when you think about how many great American players have played the game and the two players that were at that 18-game point streak and what they've done in their careers. It's pretty cool right now, but it was kind of overshadowed by the loss.
— Blackhawks forward Patrick Kane after breaking the record for longest point streak by an American-born player with a goal and an assist in a 3-2 overtime loss against the Kings