What Is Stiff Person Syndrome (SPS)?
Stiff Person Syndrome (SPS) is a rare autoimmune neurological condition.
In autoimmune conditions, the immune system mistakenly attacks parts of the nervous system.
Classic SPS typically causes:
Persistent muscle stiffness (often in the trunk and legs)
Painful muscle spasms
Heightened startle response
Difficulty walking
Increased muscle tone
Symptoms often develop gradually.
Many people with classic SPS have antibodies such as anti-GAD antibodies, although not everyone does.
SPS can be serious, but in its classic form it usually progresses slowly.
What Is PERM?
Progressive Encephalomyelitis with Rigidity and Myoclonus
It is considered a more severe form within the SPS spectrum.
Breaking down the name:
Progressive – symptoms worsen over time
Encephalo- – brain involvement
Myelitis – spinal cord involvement
Rigidity – severe stiffness
Myoclonus – sudden muscle jerks
PERM can involve:
Severe whole-body stiffness
Repeated spasms
Brainstem symptoms
Swallowing or speech difficulty
Abnormal heart rate or breathing
Autonomic instability
Risk of life-threatening complications
PERM is often associated with anti-glycine receptor antibodies, although not always.
How Are SPS and PERM Different?
Classic SPS mainly affects muscle tone and stiffness.
PERM involves the brainstem and autonomic nervous system, which can affect:
Breathing
Heart rhythm
Blood pressure
Swallowing
Consciousness
PERM tends to progress more quickly and can become critical without treatment.