Celine Dion has lost control over her muscles, says sister

According to the Stiff Person Syndrome Research Foundation, SPS is a neurological disease with autoimmune features. Symptoms include muscle spasms, hyper-rigidity, debilitating pain, and chronic anxiety. Muscle spasms can be so violent they can dislocate joints and even break bones. The foundation further states that most people suffering from SPS experience worsening of stiffness and muscle spasms over the long term. Moreover, the stiffness may affect limbs to a different extent.