Some patients require mobility aids due to the risk of falls. About 65 percent of SPS patients are unable to function independently. About ten percent of SPS patients require intensive care at some point; sudden death occurs in about the same number of patients. These deaths are usually caused by metabolic acidosis or an autonomic crisis. Epidemiology
SPS is estimated to have a prevalence of about one per million. Underdiagnosis and misdiagnosis hinder epidemiological information about the condition and may have led to its prevalence being underestimated. In the United Kingdom, 119 cases were identified between 2000 and 2005. It does not predominantly occur in any racial or ethnic group. The age of onset varies from about 30 to 60, and it most frequently occurs in people in their 40s. Five to ten percent of patients with SPS have the paraneoplastic variant of the condition. In one group of 127 patients, only 11 of them had paraneoplastic symptoms. About 35 percent of SPS patients have type I diabetes. History
SPS was first described by Moersch and Woltman in 1956. Their description of the disease was based on 14 cases that they had observed over 32 years. Using electromyography, they noted that motor-unit firing suggested that voluntary muscle contractions were occurring in their patients. Previously, cases of SPS had been dismissed as psychogenic problems. Moersch and Woltman initially called the condition "stiff-man syndrome", but the first female patient was confirmed in 1958 and a young boy was confirmed to have it in 1960.
The stiffness leads to a change in posture, and patients develop a rigid gait. Persistent lumbar hyperlordosis often occurs as it progresses. The muscle stiffness initially fluctuates, sometimes for days or weeks, but eventually begins to consistently impair mobility. As the disease progresses, patients sometimes become unable to walk or bend. Chronic pain is common and worsens over time but sometimes acute pain occurs as well. Stress, cold weather, and infections lead to an increase in symptoms, and sleep decreases them.SPS patients experience superimposed spasms and extreme sensitivity to touch and sound. These spasms primarily occur in the proximal limb and axial muscles. There are co-contractions of agonist and antagonist muscles. Spasms usually last for minutes and can recur over hours. Attacks of spasms are unpredictable and are often caused by fast movements, emotional distress, or sudden sounds or touches. In rare cases, facial muscles, hands, feet, and the chest can be affected and unusual eye movements and vertigo occur. There are brisk stretch reflexes and clonus occurs in patients. Late in the diseases progression, hypnagogic myoclonus can occur. Tachycardia and hypertension are sometimes also present.Because of the spasms, patients may become increasingly fearful, require assistance, and lose the ability to work, leading to depression, anxiety, and phobias, including agoraphobia and dromophobia. Most patients are psychologically normal and respond reasonably to their situations.Paraneoplastic SPS tends to affect the neck and arms more than other variations. It progresses very quickly, is more painful, and is more likely to include distal pain than classic SPS.