Dystonias

Overview

Dystonias are movement disorders in which sustained muscle contractions cause twisting and repetitive movements or abnormal postures. The movements are involuntary and sometimes painful and may affect a single muscle; a group of muscles or the entire body. People who have dystonia usually have normal intelligence and no associated psychiatric disorders.

Symptoms

Dystonia can affect many different parts of the body. Early symptoms may include:

  • deterioration in handwriting after writing several lines
  • foot cramps
  • a tendency of one foot to pull up or drag; this may occur "out of the blue" or may occur after running or walking some distance
  • the neck may turn or pull involuntarily especially when tired or stressed
  • sometimes both eyes will blink rapidly and uncontrollably rendering a person functionally blind
  • tremor and voice or speech difficulties

The initial symptoms can be very mild and may be noticeable only after prolonged exertion stress or fatigue. Over a period of time the symptoms may become more noticeable and widespread and be unrelenting. In other cases there is little or no progression from the initial symptoms.

Causes

It is believed that dystonias result from an abnormality in an area of the brain called the basal ganglia where some of the messages that initiate muscle contractions are processed. Scientists suspect a defect in the body's ability to process a group of chemicals called neurotransmitters that help cells in the brain communicate with each other.

Acquired dystonia also called secondary dystonia results from environmental or disease-related damage to the basal ganglia. Birth injury (particularly due to lack of oxygen) certain infections reactions to certain drugs heavy-metal or carbon monoxide poisoning trauma or stroke can cause dystonic symptoms. Dystonias can also be symptoms of other diseases some of which may be hereditary.

About half the cases of dystonia have no connection to disease or injury and are called primary or idiopathic dystonia. Of the primary dystonias many cases appear to be inherited in a dominant manner; i.e. only one carrier parent need contribute the dystonia gene for the disease to occur each child having a 50/50 chance of being a carrier. In dystonia however a carrier may or may not develop a dystonia and the symptoms may vary widely even among members of the same family. The product of one defective gene appears to be sufficient to cause the chemical imbalances that may lead to dystonia; but the possibility exists that another gene or genes and environmental factors may play a role.

Some cases of primary dystonia may have different types of hereditary patterns. Knowing the pattern of inheritance can help families understand the risk of passing dystonia along to future generations.

Diagnosis

Because there are so many different dystonias an effort is made to classify each according to the parts of the body they affect:

  • Generalized dystonia affects most or all of the body.
  • Focal dystonia is localized to a specific part of the body.
  • Multifocal dystonia involves two or more unrelated body parts.
  • Segmental dystonia affects two or more adjacent parts of the body.
  • Hemidystonia involves the arm and leg on the same side of the body.

Some patterns of dystonia are defined as specific syndromes:

Torsion dystonia is a rare generalized dystonia that may be inherited usually begins in childhood and becomes progressively worse. It can leave individuals seriously disabled and confined to a wheelchair.

Cervical dystonia also called spasmodic torticollis or torticollis is the most common of the focal dystonias. In torticollis the muscles in the neck that control the position of the head are affected causing the head to twist and turn to one side. In addition the head may be pulled forward or backward. Torticollis can occur at any age although most individuals first experience symptoms in middle age. It often begins slowly and usually reaches a plateau. About 10 to 20 percent of those with torticollis experience a spontaneous remission but unfortunately the remission may not be lasting.

Blepharospasm the second most common focal dystonia is the involuntary forcible closure of the eyelids. The first symptoms may be uncontrollable blinking. Only one eye may be affected initially but eventually both eyes are usually involved. The spasms may leave the eyelids completely closed causing functional blindness even though the eyes and vision are normal.

Cranial dystonia is a term used to describe dystonia that affects the muscles of the head face and neck.

Oromandibular dystonia affects the muscles of the jaw lips and tongue. The jaw may be pulled either open or shut and speech and swallowing can be difficult. Spasmodic dysphonia involves the muscles of the throat that control speech. Also called spastic dysphonia or laryngeal dystonia it causes strained and difficult speaking or breathy and effortful speech. Meige's syndrome is the combination of blepharospasm and oromandibular dystonia and sometimes spasmodic dysphonia. Spasmodic torticollis can be classified as a type of cranial dystonia.

Writer's cramp is a dystonia that affects the muscles of the hand and sometimes the forearm and only occurs during handwriting. Similar focal dystonias have also been called typist's cramp pianist's cramp and musician's cramp.

Dopa-responsive dystonia (DRD) of which Segawa's dystonia is an important variant is a condition successfully treated with drugs. Typically DRD begins in childhood or adolescence with progressive difficulty in walking and in some cases spasticity. In Segawa's dystonia the symptoms fluctuate during the day from relative mobility in the morning to increasingly worse disability in the afternoon and evening as well as after exercise. The diagnosis of DRD may be missed since it mimics many of the symptoms of cerebral palsy.

Treatment

No one treatment has been found universally effective. Instead doctors use a variety of therapies aimed at reducing or eliminating muscle spasms and pain.

  • Medication. Several classes of drugs that may help correct imbalances in neurotransmitters have been found useful. But response to drugs varies among patients and even in the same person over time. The most effective therapy is often individualized with physicians prescribing several types of drugs at different doses to treat symptoms and produce the fewest side effects.
  • Botulinum toxin. Minute amounts of this familiar toxin can be injected into affected muscles to provide temporary relief of focal dystonias. The toxin stops muscle spasms by blocking release of the excitatory neurotransmitter acetylcholine. The effect lasts for up to several months before the injections have to be repeated.
  • Surgery and other treatments. Surgery may be recommended for some patients when medication is unsuccessful or the side effects are too severe. In selected cases advanced generalized dystonias have been helped at least temporarily by surgical destruction of parts of the thalamus a structure deep in the brain that helps control movement. This surgery can be risky however since the thalamus lies near brain structures that help control speech. Surgically cutting or removing the nerves to the affected muscles has helped some focal dystonias. The benefits of these operations however can be short-lived. They also carry the risk of disfigurement can be unpredictable and are irreversible.

Some patients with spasmodic dysphonia may benefit from treatment by a speech-language pathologist. Physical therapy splinting stress management and biofeedback may also help individuals with certain forms of dystonia.