Stiff Person Syndrome Health Article

Definition

Stiff person syndrome (SPS) is an extremely rare progressive neurological disorder characterized by persistent rigidity and spasms of certain voluntary muscles, especially those of legs and feet. In some cases, muscles of the neck, trunk, and shoulders may also be involved. SPS may begin as recurring (intermittent) episodes of stiffness and spasms, often precipitated by surprise or minor physical contact.

Description

SPS is a rare progressive neurological disorder characterized by constant painful contractions and spasms of voluntary muscles, particularly the muscles of the back and upper legs. In 1956, scientists at the Mayo Clinic also coined the term stiff man syndrome, and clearly described the stiff person syndrome as a neurological disorder. The rigidity, which is characterized by tightness and stiffness, begins slowly over several months at the axial muscles, especially the thoracic and lumbar spine, and spreads to the legs. The stiffness may worsen when the affected individual is anxious or exposed to sudden motion or noise. Affected muscles may become twisted and contracted, resulting in bone fractures in the most severe cases.

Another abnormality in SPS is called co-contraction: when the person attempts to contract a muscle to move in one direction, muscles that pull in the opposite direction are involuntarily activated. Individuals with SPS may have difficulty making sudden movements and may have a stiff-legged unsteady gait (manner of walking). The muscle contractions are usually reduced with extra rest.

Eventually, persons with stiff person syndrome may develop a hunched posture (kyphosis) or a swayback (lordosis).

Demographics

The frequency of SPS worldwide or in the United States is unknown, but the syndrome is rare. Unlike many autoimmune diseases, which have a higher incidence in women, SPS is found more frequently in men, occurring in men in approximately 70% of all cases. The syndrome also occurs in children younger than three years, most commonly in infants. Onset in adults is most frequent in the third to fifth decades of life.