According to the team, Patrick was diagnosed with migraine disorder after consulting with the Flyers' medical staff and a specialist from the University of Michigan.
The 21-year-old will not accompany the Flyers on their trip to Europe for a preseason game in Switzerland on Monday and then their regular-season opener against the Blackhawks in Czech Republic on Oct. 4. He is listed as week-to-week.
Patrick was the team's first-round pick in 2017. He recorded 13 goals and 18 assists in 72 games last season.