Clinical diagnostic criteria were developed by Gordon et al. in 1967. They observed "persistent tonic contraction reflected in constant firing, even at rest" after providing patients with muscle relaxants and examining them with electromyography. In 1989, criteria for an SPS diagnosis were adopted that included episodic axial stiffness, progression of stiffness, lordosis, and triggered spasms. The name of the disease was shifted from "stiff-man syndrome" to the gender-neutral "stiff-person syndrome" in 1991.In 1988, Solimena et al. discovered that autoantibodies against GAD played a key role in SPS. Two years later, Solimena found the antibodies in 20 out of 33 patients examined. In the late 1980s, it was also demonstrated that the serum of SPS patients would bind to GABAergic neurons. In 2006, the role of GABARAP in SPS was discovered. The first case of paraneoplastic SPS was found in 1975. In 1993, antiamphiphysin was shown to play a role in paraneoplastic SPS, and seven years later antigephyrin was also found to be involved in the condition.In 1963, it was determined that diazepam helped alleviate symptoms of SPS. Corticosteroids were first used to treat the condition in 1988, and plasma exchange was first applied the following year. The first use of intravenous immunoglobulin to treat the condition came in 1994. See also
Satoyoshi syndrome
Hyperekplexia

References
Bibliography
Alexopoulos, Harry; Dalakas, Marinos (2010). "A Critical Update on the Immunopathogenesis of Stiff Person Syndrome". European Journal of Clinical Investigation. 40 (11): 1018–25. doi:10.1111/j.1365-2362.2010.02340.x. PMID 20636380. S2CID 30688501. Ali, Fatima; Rowley, Merrill; Jayakrishnan, Bindu; Teuber, Suzanne; Gershwin, Eric; Mackay, Ian (2011).
Stiff-person syndrome (SPS), also known as stiff-man syndrome (SMS), is a rare neurologic disorder of unclear cause characterized by progressive rigidity and stiffness. The stiffness primarily affects the truncal muscles and is superimposed by spasms, resulting in postural deformities. Chronic pain, impaired mobility, and lumbar hyperlordosis are common symptoms. SPS occurs in about one in a million people and is most commonly found in middle-aged people. A small minority of patients have the paraneoplastic variety of the condition. Variants of the condition, such as stiff-limb syndrome which primarily affects a specific limb, are often seen. SPS was first described in 1956. Diagnostic criteria were proposed in the 1960s and refined two decades later. In the 1990s and 2000s the roles of antibodies in the condition became more clear. SPS patients generally have GAD antibodies, which seldom occur in the general population. In addition to blood tests for GAD, electromyography tests can help confirm the conditions presence. Benzodiazepine-class drugs are the most common treatment; they are used for symptom relief from stiffness. Other common treatments include baclofen, intravenous immunoglobin and rituximab. There is a limited but encouraging therapeutic experience of hematopoietic stem cell transplantation for SPS. Signs and symptoms
Patients with stiff-person syndrome (SPS) experience progressive stiffness in their truncal muscles (torso muscles), which become rigid and stiff because the lumbar and abdominal muscles engage in constant contractions. Initially, stiffness occurs in the thoracolumbar paraspinal and
abdominal muscles. It later affects the proximal leg and abdominal wall muscles.