Dystonia
Dystonia is a movement disorder characterized by constant or intermittent muscle contractions causing torsional, repetitive movements or abnormal posture of a body part. It always affects the same groups of muscles and it can be triggered or intensified precisely during the activity of those muscles.
The most common focal dystonia is cervical dystonia which causes involuntary muscle contractions that lead to abnormal movements and positions of the head and neck. The symptoms can be very mild and barely noticeable but also they can be more expressed and clearly visible: the patient may only have a slightly tilted head to the side but also an abnormal twisting position that prevents him from turning his head against the direction of the dystonia. The most common symptom is neck pain which occurs in 75% of cases of cervical dystonia followed by limited neck motion range and head tremors. Cervical dystonia most often occurs spontaneously with an unknown cause and appears as an independent symptom of focal distribution in adulthood. It can also be hereditary which often occurs in early-onset generalized dystonia associated with the DYT1 gene.
Contraction of the orbicularis oculi muscle causes the second most common focal dystonia; blepharospasm. In mild forms the patient has occasional involuntary blinking but in more pronounced dystonia there is a strong closing of the eyes with disturbance of visual function. Symptoms are usually bilateral but can be asymmetrical. Patients are often complaining about increased spasms during stress and bright light. Blepharospasm can be associated with dystonia of the lower part of the face and/or jaw which is called oromandibular dystonia. Involuntary, dystonia movements can also affect the muscles of the face, tongue, pharynx and vocal cords manifesting as abnormal jaw movements, tongue protrusion, speech and swallowing difficulties.
Extremity dystonia is a focal dystonia that leads to torsional repetitive movements or abnormal position of the upper or lower limb. In some cases, tremor-like spasms can be seen and dystonia movements may increase during activity of the affected limb. Generalized dystonia affects several parts of the body and most often occurs already in childhood.
