Also in the documentary, Dion shares an extremely vulnerable moment where she experiences a full-body spasm.

While laying on a massage table and going through some exercises with her physical therapy, Dion’s foot begins to cramp. Within minutes her entire body seizes and locks up to the point where she is unable to communicate with those in the room with her.

As the camera continues to roll, another member of her medical team comes into the room with benzodiazepine nasal spray and administers it to Dion, who, though motionless, is crying out in pain. The video is painful to watch.

Once the spasms have subsided – they typically last anywhere from 30 minutes to an hour – Dion is able to sit up and speak.

“Every time something like this happens, it makes me feel so embarrassed,” she says. “I don’t know how to express it, you know, to not have control over yourself.”

Her physical therapist speculates the attack was brought on by being “overstimulated” from an earlier singing session.

“If I can’t get stimulated by what I love, then I’m going to go on stage, and you’re going to put the pulse oximeter on me and turn me on my back?” she wonders.

Dion hopes that one day soon she’ll be able to return to the stage. You can watch the harrowing footage of her seizure here.