Céline Dion reveals raw footage of a seizure in her new documentary "I am: Céline Dion." Céline shares her journey living with the rare neurological disease, Stiff Person Syndrome. The disease causes muscle stiffness and painful spasms triggered by loud noises, stress, light contact, or cold. Muscles can become board-like, and spasms can be so severe they lead to falls and broken bones. Symptoms of classic SPS include frequent muscle spasms, a stiff gait, and persistent pain throughout the day.