Stiff Person Syndrome
Stiff person syndrome is a rare autoimmune condition of the brain and spinal cord. It causes rigid muscles and sudden spasms, often set off by noise, touch or emotion. It’s often mistaken for something else for years.
Often misread as anxiety for years. Muscles locking up when startled is a neurology question, not a nerves one.
Symptoms
- Stiffness that comes and goes in the back, tummy and legs, often causing a stiff, hunched posture
- Painful spasms triggered by sudden noise, touch, cold or emotional stress (a car horn is a classic trigger)
- Falls, because protective reflexes don’t work normally. Falls can cause serious injuries
- Anxiety and fear of open spaces or crowds, often a result of unpredictable spasms
- Symptoms usually start in adulthood. It affects about twice as many women as men
Diagnosis
- A blood test for GAD antibodies (anti-GAD65) is usually strongly positive.
- Nerve and muscle tests (EMG) show muscles firing when they should be resting.
- It’s often misdiagnosed as Parkinson’s disease, multiple sclerosis, fibromyalgia or anxiety.
- It commonly occurs alongside other autoimmune conditions: type 1 diabetes, thyroid disease, vitiligo and pernicious anaemia.
Treatment
- Symptom control: diazepam (often in higher doses), baclofen, gabapentin and other muscle relaxants.
- Immune treatment: intravenous immunoglobulin (IVIG) reduced stiffness and sensitivity in a controlled trial. Plasma exchange is used in some people.
- Physiotherapy, falls prevention and psychological support help with daily life.
- Treatment controls symptoms for many people but isn’t a cure.
The new research
- In 2026, a phase 2 trial (KYSA-8) of a CAR-T cell therapy called miv-cel reported results in 26 people with hard-to-treat stiff person syndrome.
- Walking speed improved by a median of about 45% at 16 weeks, and all patients had stopped their immune treatments at last follow-up.
- Most had a mild to moderate immune reaction (cytokine release syndrome), and there are no long-term results yet. It isn’t available in Australia outside trials.
See your GP if
- You have unexplained stiffness, spasms set off by noise or touch, or frequent falls
- You’ve been told you have Parkinson’s, MS or anxiety but your symptoms don’t fit, especially if you have type 1 diabetes or thyroid disease
- Ask about a referral to a neurologist
Common questions
What is stiff person syndrome?
A rare autoimmune condition affecting the brain and spinal cord, causing rigid muscles and painful spasms that can be triggered by noise, touch, cold or stress.
How is stiff person syndrome diagnosed?
By a neurologist, using the symptoms, a blood test for GAD antibodies and nerve and muscle testing (EMG).
Is there a cure for stiff person syndrome?
Not yet. Medicines such as diazepam and baclofen, and immune treatments such as IVIG, control symptoms for many people. CAR-T cell therapy has shown promising early trial results.
Who gets stiff person syndrome?
Mostly adults, and about twice as many women as men. It’s more common in people with other autoimmune conditions such as type 1 diabetes and thyroid disease.
Helpful resources
- Brain FoundationInformation on neurological conditions. Free, Australia.
Evidence and more information
- NINDS via BrainFacts: Stiff-person syndrome
- EMJ: AAN 2026, CAR-T therapy shows promise in stiff person syndrome
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