Question:

What is Stiff Person Syndrome?

Answer:

Stiff person syndrome (SPS) is a rare neurological disorder characterized by fluctuating muscle rigidity in the trunk and limbs and a heightened sensitivity to stimuli such as noise, touch, and emotional distress, which can set off muscle spasms (1).

This syndrome was first described as “stiff man syndrome” in 1956 by Moersch and Woltman at the Mayo clinic in the setting of being first identified in a 49 year old man with progressive stiffness in his neck, back and episodic painful muscle spasm and difficult walking. We now know that this syndrome affects both men and woman hence the terminology was changed to Stiff Person syndrome. This disease is rare and it is considered a one-in-a-million diagnosis with an estimate of it occurring in 1-2 per million people, although this is likely an underestimation based on the under-recognition of less severe or atypical presentations. Until recently in 2020, there was also limitation on the commercial availability of antibody testing with glycine receptor antibodies.

Diagnosis of SPS is made based on a combination of patient’s presenting symptoms, neurological examination, antibody testing, and electromyography (EMG). Antibodies that have been associated with SPS include GAD65, glycine receptor antibodies (2), amphiphysin, and DPPX.

What are the treatment options?

Treatment includes symptomatic treatment with antispasmodic agents and immunomodulatory therapy. Immunotherapy is often used given the presumed antibody-mediated disease mechanism, however large, randomized control trials are lacking. Intravenous immunoglobulin (IVIg) is most widely used as first-line therapy and there are small trials that have been shown to provide benefit with improved ambulation, decreased falls and increased ability to perform functions of daily living (3). Rituximab, while still used commonly as second-line therapy failed to demonstrate a statistically significant difference in only a small group of 24 patients (4).

References

(1.) Clinical and Immunologic Investigations in Patients With Stiff-Person Spectrum Disorder

(2) Novel clinical features of glycine receptor antibody syndrome

(3) High-dose intravenous immune globulin for stiff-person syndrome

(4)  A DOUBLE BLIND, PLACEBO-CONTROLLED STUDY OF RITUXIMAB IN PATIENTS WITH STIFF PERSON SYNDROME