Juulsen, 22, suffered a facial fracture after taking two pucks to the face in a game against the Washington Capitals last November. He appeared in four games after that, then missed the rest of the season with the injury.
In January, a senior executive with the team told Sportsnet’s Eric Engels that Juulsen did not suffer a concussion.
On Saturday, Juulsen arrived at training camp with headaches and has been kept off the ice ever since.
Juulsen was Montreal’s first-round pick in 2015. In 44 career games over parts of two seasons, he has two goals and eight points.
The Canadiens also announced forward Michael McCarron, another former first-round pick by the team, was day-to-day with a groin injury.