St. Vitus Dance is the historical name for the neurological disorder known medically as Sydenham Chorea (SC). This rare, usually temporary, movement disorder primarily affects children, typically between the ages of five and 15. SC is the most common form of acquired chorea in children globally. It is recognized as a major manifestation of Acute Rheumatic Fever (ARF), a complication following a streptococcal infection.
The Defining Physical Manifestations
The most noticeable characteristic of Sydenham Chorea is the presence of involuntary, rapid, and irregular movements, which are classified as chorea. These movements are often described as being “dance-like,” giving the disorder its historical name. The movements are unpredictable, sudden, and non-rhythmic, and they can affect the face, trunk, and all four limbs.
The involuntary jerking often begins in the hands and feet, and it can vary significantly in severity. In milder cases, the symptoms may appear as slight restlessness, fidgeting, or minor facial grimacing. More severe cases can become incapacitating, making walking, talking, or even eating extremely difficult.
The movements are aggravated by stress, fatigue, or voluntary actions, but they disappear completely during sleep. This loss of fine motor control results in clumsy gait, frequent stumbling, and difficulty with daily tasks like writing or dressing. A specific sign, “milkmaid’s grip,” involves the inability to maintain a steady hand grip, as muscle strength fluctuates when the child attempts to hold an object.
Associated Non-Motor and Behavioral Changes
Beyond the characteristic movements, Sydenham Chorea presents with a range of non-motor and neuropsychiatric symptoms that provide a more complete picture of the illness. Emotional lability is common, involving sudden and often inappropriate mood swings, such as bouts of unexplained crying or laughing. These behavioral changes can sometimes appear even before the involuntary movements start, causing significant distress for the child and family.
Muscle weakness, termed hypotonia, is another frequent finding, sometimes becoming the predominant symptom in severe cases. This weakness, combined with the chorea, can lead to difficulty maintaining posture or a halting, uncoordinated gait. Speech is frequently affected, resulting in slurred or explosive speech, a condition known as dysarthria.
Children may also exhibit motor impersistence, which is the inability to maintain a sustained posture, such as keeping the tongue stuck out. Obsessive-compulsive behaviors (OCD), anxiety, and difficulty with concentration are also associated with the disorder. These emotional and cognitive symptoms highlight the widespread impact of the disorder on the central nervous system.
Underlying Cause and Trigger
Sydenham Chorea is an autoimmune neurological disorder that develops as a delayed complication following infection with Group A beta-hemolytic Streptococcus (GAS) bacteria. This bacterium causes common strep throat and scarlet fever. SC is a neurological manifestation of Acute Rheumatic Fever (ARF), occurring in up to 40% of patients with the condition.
The underlying mechanism involves an abnormal immune response where the body mistakenly attacks its own tissues. The antibodies produced to fight the streptococcal antigens cross-react with specific proteins found in the basal ganglia of the brain. The basal ganglia are deep brain structures that regulate motor control, posture, and speech.
This phenomenon is known as molecular mimicry, where the body’s immune system cannot distinguish between the bacterial proteins and the components of its own brain cells. Symptoms of the chorea typically have a latency period, often appearing weeks or even months—sometimes up to six months—after the initial streptococcal infection has resolved. The resulting inflammation and damage to the basal ganglia cause the characteristic uncontrollable movements and neuropsychiatric symptoms.
Confirming the Diagnosis and Management
Diagnosing Sydenham Chorea is primarily a clinical process, relying on the observation of the characteristic chorea movements in a child who has no other identifiable cause for the movements. A medical history that includes a recent strep throat infection or a diagnosis of Acute Rheumatic Fever is highly supportive of the diagnosis. Diagnostic criteria, such as the revised Jones criteria for rheumatic fever, recognize chorea as a major sign.
Laboratory tests confirm the preceding streptococcal infection, even if the child currently lacks strep throat symptoms. Blood tests measure streptococcal antibody titers, such as Anti-streptolysin O (ASO) or Anti-DNAse B, to demonstrate recent Group A Streptococcus exposure. An echocardiogram is also performed to check for potential cardiac involvement, a common complication of rheumatic fever.
Management focuses on treating the underlying infection and controlling neurological symptoms. Long-term antibiotic prophylaxis, usually penicillin, is prescribed to prevent future streptococcal infections and recurrence, which could lead to heart damage. To manage the chorea, medications that stabilize nerve impulses or block dopamine activity, such as anticonvulsants or dopamine antagonists, are used to reduce involuntary movements. The condition is typically self-limiting, with most children recovering completely within a few months, though symptoms can persist for up to two years.