How does dystonia work in the brain?

Authors Avatar

Dystonia

Primary dystonia is believed to be due to abnormal functioning of the basal ganglia which are deep brain structures involved with the control of movement. The basal ganglia assists in initiating and regulating movement. What goes wrong in the basal ganglia is still unknown. An imbalance of dopamine, a neurotransmitter in the basal ganglia, may underlie several different forms of dystonia, but much more research needs to be done for a better understanding of the brain mechanisms involved with dystonia.

Secondary forms of dystonia arise from and can be attributed to numerous causes, such as birth injury, trauma, toxins, or stroke. Secondary dystonia can be symptomatic and can also occur in association with other disorders such as Wilson's disease. When dystonia is secondary to certain injuries or small strokes, we often find lesions (areas of damage) in the putamen, one nucleus in the basal ganglia, as well as in certain nearby structures. Even though we can see no microscopic abnormalities of the brain in the great majority of cases of dystonia, including those with generalized dystonia, the evidence is so clear in the secondary dystonias that we believe the same part of the brain is involved in all types.

How does dystonia work in the brain? 

Dystonia is a disorder that has to do with the way we move. The control of our movements is very complicated and involves many areas in the brain. The area of the brain that is involved in dystonia is called the basal ganglia. The basal ganglia is a deep region of the brain that controls the speed of movement and prevents unwanted movements.

If there is a small change in the way the basal ganglia works, it can cause movements to occur even if you don't want them to. This small change is not found by medical tests or pictures of the brain on an MRI scan. Even if this deep area of the brain is not working the right way and dystonia occurs, the areas of the brain that have to do with thinking and learning work normally. Once researchers understand what the problem is in this part of the brain, they will be able to come up with ways to allow persons with dystonia to control these unwanted movements.


Can dystonia come about overnight? Are there any warning signs?

Dystonia generally develops gradually. Occasionally the dystonia may occur suddenly, as in the acute dystonic reactions related to the administration of antipsychotic drugs. These attacks most commonly affect the head and neck muscles and are usually transient and readily treatable.

Some clinical features may precede the full clinical presentation of dystonia. Eye irritation, excessive sensitivity to bright light, and increased blinking may precede blepharospasm. Subtle facial or jaw spasms, difficulty chewing, changes in the cadence or pitch of speech may suggest early face, jaw, or voice dystonia. Mild jerky head movements, stiff neck, or local neck discomfort may occur in early torticollis. Cramping or fatiguing of the hands during writing, other manual activities, or walking may suggest limb dystonia. Sometimes a local dystonia may seem to arise directly following injury to a local body region.

Can dystonia affect muscles such as the heart or diaphragm?

Dystonia can affect breathing in several ways. Severe neck dystonia can cause difficulty breathing when the upper airway is partially closed off. Dystonia involving the vocal cords can potentially cause shortness of breath when the vocal cords close tight, but in general the tightness is present primarily when speaking. The act of breathing involves muscles between the ribs and a large muscle called the diaphragm. Dystonia can cause stiffness in the muscles between the ribs and can cause a sensation or shortness of breath. Occasionally, the diaphragm can also be affected. Finally, when a person with dystonia has involvement of the spine, twisting of the torso can limit how much the lungs can expand when breathing, and this can potentially cause shortness of breath. The heart muscle is not affected by dystonia.


Is it possible to have focal dystonia of the back, abdomen, bladder or diaphragm? 

Dystonia can involve muscles in almost all parts of the body. Although pure back dystonia is uncommon, it certainly does occur. The same applies to abdominal musculature although this is probably seen even less frequently. These forms of dystonia tend to result in the body being pulled to one side, backwards (in the case of back involvement) or forward (in the case of abdominal muscle involvement). The bladder proper is made up of a different type of muscles (smooth muscle) which are not affected by dystonia. On the other hand, the muscles around the opening of the bladder (the external sphincter) can be rarely involved, resulting in difficulty of passing urine. This, too, is an extremely rare phenomenon and probably occurs most often in forms of dystonia complicating other brain diseases such as Parkinson's disease and its treatment than in people with "idiopathic" or isolated dystonia.


Can you die from dystonia? 

In the overwhelming majority of people with dystonia, it does not shorten life expectancy or result in death. In very severe, generalized dystonia, affecting all body areas, there can be problems that may arise secondary to the dystonia which can cause medical illnesses. However, these instances are quite rare and usually treatable.


What role, if any, do environmental factors play in dystonia? 

The role of environmental factors causing or contributing to dystonia remains uncertain. It is not clear why some individuals inheriting a specific gene develop a severe form of dystonia while many others who have inherited the same gene either never develop the problem or only demonstrate a very mild form (this is what is meant by "variable penetrance" in genetics parlance).

It is possible that unknown environmental factors could play a contributing role in determining whether or not a member of such a family might develop dystonia and, if so, whether it is a mild or severe form. On the other hand, numerous other unrecognized genetic factors may account for these differences. Where no genetic predisposition exists, it is also possible that environmental factors are an important cause of dystonia. However, at this time, the specific nature of such environmental factors is completely unknown.

Can exposure to toxins or specific chemicals cause dystonia? 

The answer to this question is clearly yes. This is distinctly different from widespread environmental exposures to which large numbers of dystonic patients could be exposed. A number of uncommon toxins are capable of causing brain damage centered in the motor control region known as the basal ganglia. Dystonia may be one prominent feature experienced by patients with these exposures, but it is extremely uncommon for "isolated dystonia" to be seen in such patients. In other words, the vast majority of patients exposed to toxins (for example, manganeses) have additional neurological problems associated with the dystonia. Possibly the most common feature in such patients is the presence of a Parkinson's disease-like state.

A large number of drugs are capable of causing dystonia. In most cases, the dystonia is transient but in some patients exposed to neuroleptics, such as Haldol, the dystonia may be persistent. This disorder, known as "tardive dystonia," in contrast to dystonia associated with other neurotoxins, commonly manifests isolated dystonia without additional neurological problems.


What is the chance of X-ray therapy generating dystonia? 

There are no reports of radio-therapy generating dystonia in any parts of the body.

Can childhood illnesses, such as measles, cause dystonia? 

Rarely is dystonia linked to the occurrence of a childhood illness. Dystonia can arise from birth injury, associated with a rare childhood metabolic disorder or following a brain infection such as encephalitis. Subacute sclerosing panencephalities is a rare complication of measles which has been associated with dystonia. In most instances, however, uncomplicated measles does not cause dystonia. The disorders mentioned above usually have other associated features, including cognitive problems, seizures, or other neurologic abnormalities, and do not typically cause only dystonic symptoms.

Join now!

Sometimes trauma to the head or neck area may cause slippage of the bony spine, particularly in a child. This is called atlantoaxial dislocation and may result in a picture which resembles spasmodic torticollis but is, in fact, not dystonia but an orthopedic problem.


Is there any correlation between general anesthetics and dystonia? 

There is not a causal link between general anesthetics and dystonia. Certain types of medication can cause dystonia. The medications most frequently implicated include antipsychotic agents and certain medications used to treat nausea and vomiting. These agents can cause acute and reversible symptoms of dystonia at ...

This is a preview of the whole essay