You are caring for a 16-year-old gymnast who is complaining of neck pain. Although she is very active, she denies significant trauma precipitating the pain. She has tried nonsteroidal anti-inflammatory agents, ice, rest, and physical therapy with no results. She denies radiculopathy, fever, chills, weight loss, or other significant symptoms. Her medical and social histories are unremarkable, other than the fact that she reports trying marijuana once at a friend’s house. In addition to the fact that she isn’t getting better with treatment, which item described in her history represents a “red flag” for a serious underlying condition or disease?