Cameron missed last week's game against the Tampa Bay Buccaneers after sustaining a concussion the week before in the Browns' victory over the Oakland Raiders. It was his third concussion in the past two years.
Per the NFL's concussion protocol, Cameron has to be medically cleared before he can return to practices or games. He didn't practice at all this week in Cleveland's quick turnaround from Sunday to Thursday, and it's unknown how much longer he'll be out.
Cameron also injured his shoulder earlier this season and has said he expects to have to deal with the issue all season.
Cameron, 26, has 13 receptions for 250 yards and one touchdown this season. He made his first career Pro Bowl last year when he had 80 receptions for 917 yards and seven touchdowns.
The fourth-year pro is in the last season of his contract and isn't expected to agree to a new deal until after the season, if at all.
The Bengals are 5-2-1 and in first place in the AFC North, while the Browns are close behind at 5-3. Thursday's matchup marks the first time since 1988 that each enters the game with at least five wins and a winning record.
- Ben Estes