“Saint Vitus Dance” is a historical term describing a specific neurological disorder characterized by involuntary, dance-like movements. The condition, which is treatable and has a clear biological cause, primarily affects children and adolescents. It represents a delayed autoimmune complication following a common bacterial infection. Understanding the modern medical definition offers a clear contrast to its archaic, folkloric naming.
The Historical Origin of the Name
The name “Saint Vitus Dance” originated in the Middle Ages, associated with two distinct historical phenomena. One involved the “dancing plagues,” episodes of mass psychogenic illness where groups of people would dance uncontrollably until collapsing from exhaustion. These events were likely distinct from the neurological condition that later inherited the name, yet they established the linguistic link between involuntary movement and the patron saint.
Saint Vitus was the patron saint invoked against nervous disorders and epilepsy. People afflicted with involuntary movements would attend his chapels, seeking his curative powers. The term chorea is derived from the Greek word for “dance,” formally connecting the movement pattern to the symptoms.
Sydenham’s Chorea The Medical Definition
The condition historically known as Saint Vitus Dance is medically defined as Sydenham’s Chorea (SC), a post-infectious neurological disorder. It is characterized by chorea: rapid, irregular, non-rhythmic, and purposeless movements affecting the face, trunk, and limbs. These involuntary movements often worsen with anxiety and stress, but they completely disappear during sleep.
SC is classified as a major neurological manifestation of Acute Rheumatic Fever (ARF), typically appearing weeks to months after the initial infection. It predominantly affects children between the ages of 5 and 15 years and is slightly more common in girls. The underlying pathology involves a malfunctioning of the basal ganglia, deep brain structures responsible for motor control, posture, and speech.
The Autoimmune Mechanism of Movement
Sydenham’s Chorea is an autoimmune disorder triggered by infection with Group A beta-hemolytic Streptococcus (GABHS), the bacteria responsible for strep throat. The immune response to the bacteria is misdirected, causing the body to mistakenly attack its own brain tissue. This process occurs because the bacterial proteins share structural similarities with proteins found on nerve cells within the basal ganglia.
This phenomenon is known as molecular mimicry, where the antibodies created to fight the strep infection cross-react with the host’s antigens. The immune system cannot distinguish between the bacterial protein and the body’s own neural protein. Specifically, these autoantibodies target cells in the basal ganglia, particularly the caudate nucleus and putamen, leading to inflammation and damage.
The resulting neurological dysfunction is linked to the antibodies activating neuronal cell signaling pathways, which can lead to an excess release of dopamine. This misdirected immune attack disrupts the normal function of the basal ganglia, the brain’s control center for smooth, coordinated movement.
Clinical Picture and Modern Management
The clinical presentation of Sydenham’s Chorea extends beyond the characteristic “dancing” movements. Patients often exhibit a range of neuropsychiatric symptoms, including emotional lability, anxiety, and obsessive-compulsive behaviors. Muscular weakness, poor coordination, and difficulty with fine motor tasks such as writing or feeding oneself are also common observations.
Symptoms can range in severity from mild clumsiness to completely incapacitating involuntary movements, sometimes affecting only one side of the body. While the symptoms typically improve gradually and may last for a few weeks or months, the condition is not considered benign and can recur.
Modern management focuses on three main objectives: eliminating the initial infection, managing the symptoms, and preventing future episodes. The underlying streptococcal infection is treated with antibiotics to prevent further complications, such as rheumatic heart disease. Symptomatic management of the involuntary movements often involves medications like neuroleptics (e.g., haloperidol or pimozide) or anti-seizure medications like valproate. In severe cases, immunomodulatory treatments like corticosteroids or intravenous immunoglobulin may be used to suppress the autoimmune response.