Your questions answered about the rare neurological disorder in the wake of this week’s media coverage of Céline Dion
Céline Dion’s sister said this week that the singer’s future music career was uncertain after her diagnosis with an autoimmune disease called stiff person syndrome. The condition prompted Dion to cancel all future tour dates earlier this year and her sister, Claudette Dion, told the Canadian website 7 Jours that she “doesn’t have control over her muscles”. So how common is the condition and can it be treated?
By Hannah Devlin Science correspondent
What is stiff person syndrome?
Stiff person syndrome (SPS) is a rare autoimmune neurological disorder that can cause progressive muscle stiffness and painful spasms in the lower back, legs and torso. Stiffness often fluctuates, getting worse and then improving temporarily. People affected by SPS can suffer from chronic pain, falls, and loss of mobility over time.
Who does it affect?
It is a very rare condition, affecting an estimated one to two people in a million. It most commonly occurs in people aged 40-50, but in rare cases affects children. The disorder was originally known as stiff man syndrome, but like most autoimmune conditions it is more common in women.
What causes it?
Scientists are still figuring out the biology behind SPS, and the rarity of the condition makes it difficult to study. However, there is converging evidence that the condition is caused by an autoimmune reaction, where the body attacks healthy tissues. About 80% of people with SPS have autoantibodies in their blood that are thought to target specific nerve cells in the brain that produce a brain chemical called GABA. GABA, broadly speaking, helps dampen down brain activity and regulates motor neurons. One theory is that, with less GABA available in the brain, overactive neurons send signals to the muscles to tense up and continuously contract or become more prone to sudden spasms.
Many patients with SPS also have another autoimmune disease, such as type 1 diabetes, vitiligo or pernicious anaemia.
How is SPS diagnosed?
Since SPS is rare, it is often misdiagnosed as Parkinson’s disease and its symptoms overlap with other conditions, including multiple sclerosis, fibromyalgia, anxiety and phobias. Blood tests to identify autoantibodies can help diagnosis, although a proportion of patients don’t test positive. MRI and CT scans are sometimes used to examine the spine and muscles, although normally to rule out other conditions that could be confused with SPS.
There is no cure for SPS, but there are various treatments that can help keep symptoms under control. Sedatives, muscle relaxants and steroids can help with muscle stiffness and spasms. There is also some evidence that immunotherapy could help. One trial found that patients who were given intravenous immunoglobulin – antibodies that are designed to outcompete the problematic antibodies – had reduced stiffness, improved gait and balance.