The Three Groups of Dystonia

The dystonias can be divided into three groups: idiopathic, genetic, and acquired.

Idiopathic dystonia refers to dystonia that does not have a clear cause. Many instances of dystonia are idiopathic.

There are several genetic causes of dystonia. Some forms appear to be inherited in a dominant manner, which means only one parent who carries the defective gene is needed to pass the disorder to their child. Each child of a parent having the abnormal gene will have a 50 percent chance of carrying the defective gene. It is important to note the symptoms may vary widely in type and severity even among members of the same family. In some instances, persons who inherit the defective gene may not develop dystonia. Having one mutated gene appears to be sufficient to cause the chemical imbalances that may lead to dystonia, but other genetic or even environmental factors may play a role. Knowing the pattern of inheritance can help families understand the risk of passing dystonia along to future generations.

Acquired dystonia, also called secondary dystonia, results from environmental or other damage to the brain, or from exposure to certain types of medications. Some causes of acquired dystonia include birth injury (including hypoxia, a lack of oxygen to the brain, and neonatal brain hemorrhage), certain infections, reactions to certain drugs, heavy metal or carbon monoxide poisoning, trauma, or stroke.

Dystonia can be a symptom of other diseases, some of which may be hereditary. Acquired dystonia often plateaus and does not spread to other parts of the body. Dystonia that occurs as a result of medications often ceases if the medications are stopped quickly.

Dystonia can be a symptom of other diseases, some of which may be hereditary. Acquired dystonia often plateaus and does not spread to other parts of the body. Dystonia that occurs as a result of medications often ceases if the medications are stopped quickly.

The Different Forms of Dystonia

There are several different forms of dystonia. Some of the more common focal forms are:

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

Blepharospasm, the second most common focal dystonia, is the involuntary, forcible contraction of the muscles controlling eye blinks. The first symptoms may be increased blinking, and usually both eyes are affected. Spasms may cause the eyelids to close completely, causing “functional blindness” even though the eyes are healthy and vision is normal.

Cranio-facial dystonia is a term used to describe dystonia that affects the muscles of the head, face, and neck (such as blepharospasm). The term Meige syndrome is sometimes applied to cranio-facial dystonia accompanied by blepharospasm. Oromandibular dystonia affects the muscles of the jaw, lips, and tongue. This dystonia may cause difficulties with opening and closing the jaw, and speech and swallowing can be affected. Spasmodic dysphonia, also called laryngeal dystonia, involves the muscles that control the vocal cords, resulting in strained or breathy speech.

Task-specific dystonias are focal dystonias that tend to occur only when undertaking a particular repetitive activity.

Examples include writer’s cramp 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. Musician’s dystonia is a term used to classify focal dystonias affecting musicians, specifically their ability to play an instrument or to perform. It can involve the hand in keyboard or string players, the mouth and lips in wind players, or the voice in singers.

Early-onset generalized dystonia (DYT1 and non-DYT1): Early-onset generalized dystonia is characterized by twisting of the limbs and torso. DYT1 dystonia is a rare form of dominantly inherited generalized dystonia that can be caused by a mutation in the DYT1 gene. This form of dystonia typically begins in childhood, affects the limbs first, and progresses, often causing significant disability. Because the gene’s effects are so variable, some people who carry a mutation in the DYT1 gene may not develop dystonia.

Dopa-responsive dystonia (DRD), also known as Segawa’s disease, is another form of dystonia that can have a genetic cause. Individuals with DRD typically experience onset during childhood and have progressive difficulty with walking. Symptoms characteristically fluctuate and are worse late in the day and after exercise. Some forms of DRD are due to mutations in the DYT5 gene. Patients with this disorder have dramatic improvements in symptoms after treatment with levodopa, a medication commonly used to treat Parkinson’s disease. Recently, researchers have identified another genetic cause of dystonia which is due to mutations in the DYT6 gene. Dystonia caused by DYT6 mutations often presents as cranio-facial dystonia, cervical dystonia, or arm dystonia. Rarely, a leg is affected at the onset.

Paroxysmal dystonias and dyskinesias: Episodic movement disorders in which abnormal movements occur only during attacks.

X-linked dystonia-parkinsonism: A hereditary form of dystonia that includes symptoms of Parkinsonism.

Rapid-onset dystonia-parkinsonism: A hereditary form of dystonia that includes symptoms of Parkinsonism.

Myoclonus dystonia: A hereditary form of dystonia that includes prominent myoclonus symptoms (brief, involuntary twitching of a muscle or a group of muscles).

Secondary dystonias: Dystonia that is triggered by factors such as trauma, medication exposure, toxins.

Trauma-induced: Dystonia may follow trauma to the head and/or to a specific body area.

Drug-induced (Tardive dystonia & dyskinesias): Specific drugs are capable of causing dystonia.

Toxin-induced: Several rare toxins are known to cause movement disorders.

Neurological and metabolic disorders: Dystonia can occur as a symptom of multiple disorders.

Psychogenic dystonia: Dystonia that is secondary to psychological causes.