Stiff Man Syndrome

Alternative names: Moersch-Woltmann Syndrome, Stiff Person Syndrome or SPS.

Stiff Man Syndrome is a neuromuscular condition in which a hyperactive startle reflex results in the contraction of the muscles, thus causing violent spasms.  These spasms are capable of slamming the victim into walls and furniture.  The disorder's cause is unknown, although evidence is pointing increasingly to the fact that it is an autoimmune disorder.

Stiff person syndrome is a rare progressive neurological disorder.  It is rather unique among neurologic diagnoses because of its lack of significant similarity to any other neurologic disease.  Although rare, once observed it is quite unforgettable.  Possibly the closest related disease is tetanus because both conditions affect peripheral inhibition via central mechanisms and both conditions inhibit central gamma-aminobutyric acid (GABA) systems.

Although they appear completely normal, those afflicted with Stiff Man Syndrome must avoid any situation where they might be exposed to sudden sounds or stimulation.  Often, they remain isolated in their home and excluded from normal living – orphaned from society by this rare and ruthless disorder.

One variation of the disease known as stiff limb syndrome is observed more frequently in patients with diabetes mellitus.  In this variation, the axial involvement is less marked, and one or (rarely) more extremities are affected.

Associated diseases:

• Diabetes mellitus: Although different epitopes for the GAD antibodies in diabetes have been identified, stiff person syndrome and type 2 diabetes have demonstrated comorbidity.  This comorbidity occurs in association with a finding of positive GAD antibodies.  Early distal involvement and involvement of a single limb is more frequent in patients with diabetes mellitus.  Stiff person syndrome has also been associated with diabetes mellitus and ICA 105 pancreatic autoantigen with and without the presence of anti-GAD antibodies.
• Thyroiditis: An association with thyroiditis has been described.  This may be due to comorbidity of multiple autoimmune entities or may be a more direct association.  At least one group has suggested a link due to neuromuscular hyperactivity.
• Breast cancer: A variant of stiff person syndrome occurs rarely in patients with breast cancer.  The antibodies involved are to a synaptic protein, amphiphysin.  Anti-GAD antibodies are absent.
• Epilepsy: Anti-GAD antibodies have been described in patients with resistant focal epilepsies.  In one series, 4 of 19 patients with anti-GAD-positive stiff person syndrome were also found to have localization-related epilepsy.
• Cerebellar ataxia: A number of case studies report the presence of cerebellar ataxia (with or without stiff person syndrome) associated with anti-GAD antibodies.

Causes and Development

Researchers theorize that stiff-person syndrome may be an autoimmune disorder.  Other autoimmune disorders such as diabetes, pernicious anemia (a chronic, progressive blood disorder), and thyroiditis (inflammation of the thyroid gland) may occur more frequently in patients with stiff-person syndrome.

Signs and Symptoms

SPS is characterized by constant painful contractions and spasms of voluntary muscles, particularly the muscles of the back and upper legs.

In general, increased muscle tension, which is more marked proximally than distally, is present.  Less frequently, lower extremities are most affected.  More rarely, upper and lower extremities are affected.  In people with diabetes, one limb may be affected, sparing other muscle groups.  In most if not all patients, opposing muscle groups are noted to be tense, and tonic contraction with long relaxation times may be noted following percussion of the muscle.  In most patients, the neurologic examination findings are otherwise normal.

Symptoms may occur gradually, spreading from the back and legs to involve the arms and neck.  Symptoms 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.

Individuals with stiff-person syndrome may have difficulty making sudden movements and may have a stiff-legged, unsteady gait.  Sleep usually suppresses frequency of contractions.  Stiffness may increase and patients may develop a hunched posture (kyphosis) or a swayback (lordosis).

Early stages:

• Stiff person syndrome begins insidiously in the axial muscles, and, if the patient is referred at an early stage, little objective findings may be found at the initial presentation.
• In the initial stage of the disease, the patient has an exaggerated upright posture (classic "tin-soldier" appearance) and may report back discomfort or stiffness or pain in the entire back and sometimes neck, which is worse with tension or stress.
• Patients may report disturbed sleep because, although the stiffness is relieved with sleep, when the patient transitions from rapid eye movement (REM) to stage 1 or 2 sleep they may lose the relief from the spasms, which may awaken them.
• In some patients in the early stages, brief episodes of rather dramatic severe worsening that resolve spontaneously within hours or days may occur.  Unfortunately, because of the subtle findings and apparent strong psychological components in the early stages, the patients are labeled as psychogenic, and effective treatment is often delayed.

Later stages:

• Later in the disease, proximal limb muscles also begin to be involved, particularly when the patient is stimulated, startled, surprised, angered, upset, or frightened.  This sort of stimulus may evoke painful, prolonged, severe spasms in the proximal arm and leg muscles that resolve slowly.  The patient begins to move very slowly because rapid movement induces severe spasms.  Even the distal extremities may become involved when moved rapidly.
• Not surprisingly, depression has been noted as a comorbidity at this stage.  The patient's quality of life is affected severely at this point, making it difficult or impossible to drive, work, or have a satisfying social life.

End stages:

• In the end stages of the disease, few muscles in the body are spared.  Trismus is absent.  However, facial and pharyngeal muscles may be affected markedly.
• Joint deformities may occur.  Skeletal fractures and muscle ruptures may occur during spasms.
• Postsurgically, abdominal incisions are at risk of spontaneous rupture.  Eating, simple movement, and other simple activities of daily living (ADLs) may be problematic.

Treatment and Prevention

Although there is no cure for stiff-person syndrome, the drug diazepam, which relaxes the muscles, provides improvement in most cases.  Baclofen, phenytoin, clonidine, or tizanidine may provide additional benefit.  Physical and rehabilitation therapy may also be needed.

Prognosis; Complications

The long-term prognosis for individuals with stiff-person syndrome is uncertain.  Management of the disorder with drug therapy may provide significant improvements and relief of symptoms.

Musculoskeletal complications are common, particularly in later stages of the disease.  Joint deformity, joint dislocation, joint contracture, skeletal fracture, and muscle rupture have been reported.