Diagnoses & Conditions

Stiff Person Syndrome (SPS)

Understanding Stiff Person Syndrome (SPS)

SPS stands for stiff-person syndrome. SPS is believed to be an autoimmune disorder, which develops when the immune system malfunctions and creates antibodies that attack and cause damage to a part of the body. In most individuals with SPS, an enzyme in the brain called GAD, or glutamic acid decarboxylase, is attacked. This enzyme is important in the synthesis of a neurotransmitter in the brain that causes nerve signals to send a message to the muscles to relax. Less commonly antibodies to amphiphysin may be present. Amphiphysin is a protein involved in the transmission of signals between nerve cells.

Symptoms of Stiff Person Syndrome (SPS)

Symptoms of SPS include progressive muscle rigidity in the trunk and limbs that occurs with muscle spasms. Spasms frequently occurs in response to some stimulus, such as unexpected or loud noise, touch, cold environments, and other physical and emotional stressors. The rigidity, caused by contracted muscles, can interfere with posture, balance and walking. People with SPS become anxious by the increased rigidity, which also interferes with their ability to complete everyday tasks. Rigidity can be mild or so severe it causes pain and inability to walk.

Diagnosing Stiff Person Syndrome (SPS)

Diagnosing SPS is difficult because presenting symptoms can mimic other conditions such as Parkinson's, multiple sclerosis or anxiety. It may take years to definitively diagnose. There is also some thought that some forms of SPS may be so mild, they may simply be diagnosed as a back or leg strain.

Diagnostic testing may include:

  • Electromyography (EMG) to measure muscle activity.
  • Nerve conduction studies (NCS) to measure efficiency and speed of nerve signals.
  • Blood work to test for the anti-GAD or amphiphysin antibody that may be present in SPS.

Treating Stiff Person Syndrome (SPS)

Treatment of SPS may involve anti-seizure medications, muscle relaxants, anti-anxiety medications and/or immune globulin therapy. Immune globulin therapy is administered into the blood stream intravenously (IVIG). IVIG treatment should result in decreasing the attack on self and increasing the amount of GAD or amphiphysin, allowing muscles to relax. Muscle rigidity will subside and function will improve. The physician will assess response to therapy and determine the length of therapy needed.


  • American Autoimmune Related Diseases Association Inc., www.aarda.org, is the only national organization dedicated to addressing the problem of autoimmunity. 800-598-4668

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This content is not intended to substitute professional medical advice. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.

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At Nufactor, we are committed to providing our patients the education, support and resources necessary to complete your IVIG treatment successfully and with the desired outcomes. Please contact us with any further questions.