Oromandibular dystoni1

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Oromandibular dystonia is often misdiagnosed by GPs. Conditions that it is

commonly mistaken for include damage to the jaw, tic, bruxism (teeth grinding),

dental problem, orthopaedic problem or a psychological problem.

Indications for a GP that the problem may be oromandibular dystonia rather one ofthese other conditions include:

No damage shows up on x-rays

Does not clear up over time

Movement still present when patient unaware of being observed

Treatment

Although the symptoms of oromandibular dystonia may vary from person to person,

many people experience some reduction of spasm and improvement of chewing and

speech through regularbotulinum toxin injections. Injections into the muscles that

move the mouth can be difficult, as a very precise dose needs to be given to avoid

weakening the muscle too much and some muscles can be difficult to inject. Because

of these difficulties muscles are usually injected using electromyography (EMG).

A few differentdrugscan help reduce the severity of symptoms in people with

oromandibular dystonia. Although some people get great benefit from such drugs,

they are not effective in everyone, and some people experience side effects.

Oromandibular dystonia may respond to the use of sensory tricks to temporarily

reduce symptoms. For example, gently touching the lips or chin, chewing gum,

talking or placing a finger near an eye or underneath the chin may cause symptoms

to subside temporarily. Different sensory tricks work for different people.

Speech and language therapy

A number of dystonias can affect speech. Where speech difficulties occur referralshould be made to a speech and language therapist (SALT). Patients

withoromandibulardystonia with articulation difficulties can be given mouth and

swallowing exercises to help them reduce the risk of choking by chewing and

swallowing safely.

Wuthin the NHS there are very few SALT posts who have experience of dystonia, so

not everyone who may need to see one is referred. However, if a health professional

is concerned about a patients speech and swallowing issues they should always

seek the advice of a SALT.
http://www.dystonia.org.uk/index.php/about-dystonia/treatments/botulinum-toxin-injectionshttp://www.dystonia.org.uk/index.php/about-dystonia/treatments/drug-treatmentshttp://www.dystonia.org.uk/index.php/professional-research/types-of-dystonia/oromandibular-dystoniahttp://www.dystonia.org.uk/index.php/about-dystonia/treatments/botulinum-toxin-injectionshttp://www.dystonia.org.uk/index.php/about-dystonia/treatments/drug-treatmentshttp://www.dystonia.org.uk/index.php/professional-research/types-of-dystonia/oromandibular-dystonia


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Dietary support

A number of types of dystonia can affect nutrition. Dysphagia (difficulty swallowing)

can arise fromoromandibularwhen it can be difficult to chew or move food around the

mouth to prepare it for swallowing.

Dystonia can also lead to an inadequate diet:

Those who have excessive movements may also find it almost impossible to

keep still whilst eating, making hand to mouth feeding very difficult. As a

result, finger foods and feeding cups are often used but these may not

provide enough nutrition.

Texture modified diets (e.g. puree diets) may be recommended due to

dysphagia and can have negative impact on nutritional status due to their

poor nutritional content.

Nutrition can be monitored using a screening tool (e.g. MUST) during home/clinic

visits or inpatient admissions. A referral to the dietitian should be made if weight loss

has occurred or if malnutrition is a concern. A dietetic referral is also required when

dysphagia is present. The dietitian can suggest appropriate use of texture modified

diets, food fortification and nutritional supplement drinks (e.g. Build Up,

Complan, Ensure Plus and Fortisip) to supplement diet.

Last reviewed March 2012

Disclaimer

The Dystonia Society provides the information on this page as general information

only. It is not intended to provide instruction and you should not rely on this

information to determine diagnosis, prognosis or a course of treatment. It should not

be used in place of a professional consultation with a doctor.

The Dystonia Society is not responsible for the consequences of your decisions

resulting from the use of this information, including, but not limited to, your choosing

to seek or not to seek professional medical care, or from choosing or not choosing

specific treatment based on the information. You should not disregard the advice of

your physician or other qualified health care provider because of any information you

receive from us. If you have any health care questions, please consult the relevant

medical practitioner.
http://www.dystonia.org.uk/index.php/professional-research/types-of-dystonia/oromandibular-dystoniahttp://www.dystonia.org.uk/index.php/professional-research/types-of-dystonia/oromandibular-dystonia


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What happens in the brain to cause dystonia?

Update on the latest research

This article explores what may be going on in the brain when a person has dystonia.

There are a number of different theories about how dystonia arises. There are

persuasive arguments for each but, as explained below, also still some gaps and/or

contradictory evidence so none can yet provide a full explanation. How these theories

fit together and which will turn out to be most important remains to be seen.

1. INHIBITION THEORIES

The brain/nervous system is a complex network composed of neurons operating in a

system of highly specialised, distinct neural circuits. Every aspect of our behaviour,

from reflexes to movement, relies on the processes performed by these neural

circuits. For these to work effectively in harmony, they need to be switched on

(excitation) and switched off (inhibition) with exquisitely precise timing.

Excitatory/inhibitory systems are enabled by the passage of chemicals

(neurotransmitters) across the neurons. Some neurotransmitters inhibit neuronal

activity while others excite it. In dystonia, it appears that some inhibitory circuits are

defective causing a process calledco-contraction. Normally muscles work

harmoniously in pairs: one muscle (the agonist) is the prime mover while its partner

(the antagonist) must relax to allow the movement to happen. This enables a

smooth controlled movement. To achieve this the activity of the agonist must be

excited while that of the antagonist is inhibited. In co-contraction this harmony isdisrupted as the failure of inhibitory messages causes too much activity in the

antagonist resulting in the abnormal movements or postures seen in dystonia.

Evidence supporting inhibition theories

Researchers have shown that in healthy people, at the onset of a voluntary muscle

contraction, the neighboring muscles are less readily stimulated (so more inhibited).

In this way, the motor system can focus muscle activity and facilitate precise,

individual movements. So it appears inhibition is playing an important role in effecting
http://www.dystonia.org.uk/index.php/about-dystonia/what-happens-in-the-brain-to-cause-dystoniahttp://www.dystonia.org.uk/index.php/about-dystonia/what-happens-in-the-brain-to-cause-dystonia


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smooth movement.

Researchers have also compared the activity in the agonist and antagonist muscles

of people with dystonia to healthy controls. They have shown that in people with

dystonia the inhibition of the antagonist muscle is lower than in the controls while theexcitation of the agonist muscle appears normal. So it appears very likely that

inhibition failure is playing a causal role in co-contraction.

Further evidence is provided by the effectiveness of some medications such as

gabapentin and benzodiazepines in improving symptoms in some cases. These

medications stimulate the transmission of a neurotransmitter called GABA which

inhibits muscle activity so, if the medications can reduce symptoms, it suggests

inhibition was insufficient previously. In addition, it is this lack of inhibition that Deep

Brain Stimulation (DBS) treatment may address as DBS is thought to stimulate GABA

inhibitory neurons.

Evidence against inhibition theories

Abnormally reduced inhibition has been found in carriers of the DYT1 gene whether

or not they have dystonia symptoms (around 7 in 10 of those who inherit the DYT1

gene never develop dystonia). So reduced inhibition can be present without the

symptoms of dystonia appearing.Also reduced inhibition may be found in both the left and right sides of the brain in

some people even where the dystonia symptoms are only present on the one side.

Conclusion on inhibition theories

Inhibition has been shown to be abnormal in people with dystonia and seems a

plausible explanation of dystonic symptoms. However, as these abnormalities can be

present in clinically unaffected parts of the body and in non-manifesting DYT1 gene

carriers, reduced inhibition cannot be the whole explanation and additional factors

must be necessary to produce dystonia.

2. ABNORMAL NEUROPLASTICITY

Neuroplasticity is the ability of the brain to reorganise its structure/function and

change its connections and behaviour in response to new information, stimulation,

development, damage, or dysfunction. Neuroplasticity is a perfectly normal process


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and occurs when neurons in the brain sprout and form synapses. As the brain

processes information, frequently used junctions (synapses) are strengthened while

unused synapses weaken. Eventually, unused synapses are eliminated completely

leaving behind efficient networks of neural connections. It is thought that in the field ofneuroplasticity, if it fires, it wires, meaning that every time a person thinks about

something, or does something, a neural pathway is either being strengthened or

reinforced. This is how we learn and change.

In some types of dystonia, excessive neuroplasticity has been observed. This could

underlie the generation of dystonic movements. A simple analogy is to view

neuroplasticity like creating a path in freshly fallen snow(the snow representing the

plastic brain).At first, the result is a few footsteps in the snow but walk it again and

again and it becomes a track then a footpath. However, if this path is overused it can

become harder and harder to use any other path through the snow, as it requires too

much effort to start again.

This is fine if the path is useful but, in dystonia, plasticity may reinforce abnormal

movements. Each time the body repeats these movements, they claim more control

of the brains map of the body and prevent the relearning of normal movements. If the

brains of people with dystonia have a tendency to develop new tracks too quickly, the

tracks for abnormal movements may become hard wired too easily.

Evidence supporting abnormal plasticity theories

Abnormal plasticity has been measured in task specific focal dystonias such as

musicians dystonia, where repetitive activity is believed to be a trigger for the

development of dystonia.

Abnormal plasticity also appears to be present in DYT1 dystonia but importantly is

not present in DYT1 gene carriers who dont have dystonic symptoms. This may

explain why reduced inhibition doesnt always cause symptoms to appear - reduced

inhibition creates the potential for abnormal movements in all DYT1 carriers but these

movements only become hard-wired in the brain of those DYT1 carriers who also

have abnormal plasticity.


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When DBS is provided to people with dystonia initially their level of plasticity reduces

well below normal and then gradually increases toward normal levels. Despite this, it

can take several months for the symptoms to be improved. The slow improvement

suggests that, even with the plasticity reduced to normal levels or below, the brain stillneeds to unlearn the abnormal dystonic movements. This strongly suggests plasticity

has a role in dystonia.

Evidence against a role for abnormal plasticity in dystonia

Abnormalities of plasticity have been identified in patients with dystonia, but they

might not be sufficient to cause the development of dystonic movements and the

exact channels by which excess plasticity causes dystonia have not been identified.

In addition, if overtraining is a cause of some types of task-specific dystonia, this

does not explain why only some people develop dystonia after excessive training

whereas others are completely healthy.

Conclusion on neuroplasticity

The evidence strongly suggests that plasticity plays an important role but much work

needs to be done to explain how it influences dystonia and how it fits with other

causative factors.

3. INVOLVEMENT OF CEREBELLUM

Historically, dystonia was thought to be caused by abnormalities within a part of the

brain called the basal ganglia. However, unlike other movement disorders, there is no

evidence of degeneration within the brains neuronal circuitry. This suggests that the

problems causing dystonia result from abnormal connectivity that may occur in a

structurally normal appearing brain. Dystonia is therefore considered a system

disorder rather than a disease of a particular brain structure.

Recently there is evidence that the cerebellum may also be involved in causing by

dystonia suggesting that dystonia may result from disruption of motor networks

involving both the basal ganglia and cerebellum, rather than the isolated dysfunction

of only one part of the brain.


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The cerebellum is located at the base of the brain, just above the brain stem, where

the spinal cord meets the brain. The cerebellum receives information from the

sensory systems, the spinal cord, and other parts of the brain and then regulates

motor (muscle) movements. The cerebellum coordinates voluntary movements suchas posture, balance, coordination, and speech, resulting in smooth, balanced

muscular activity. It participates in fine tuning and co-ordination of movements

produced elsewhere in the brain, and it integrates all of these things to produce

movements so fluid and harmonious that people are not even aware of them

happening.

Evidence supporting cerebellar involvement

Scans have identified that people with musicians dystonia and focal hand dystonia

show abnormal cerebellar activation during different tapping tasks and abnormal

cerebellar activation was also observed during writing in people with writers dystonia,

in voice dystonia during voice production and in blepharospasm during eye blinking.

This abnormal cerebellar activity coupled with evidence of increased energy

metabolism within the cerebellum during these tasks provides evidence for its role in

dystonia.

Research suggests that the cerebellum and basal ganglia communicate to shared

regions of the cerebral cortex. The discovery of this shared connection between the

basal ganglia and cerebellum provides a possible structural basis to explain the role

of the cerebellum in dystonia.

Involvement of the cerebellum is also supported by the fact that that in many different

forms of dystonia, loss of harmony between excitation and inhibition is a problem.

These functions are regulated by the basal ganglia and cerebellum, with some

evidence that they may exert opposing influences. Therefore, the influences of the

basal ganglia and cerebellum seem to overlap on cortical excitability as a common

pathway for dystonic movement.

Evidence against a primary role for the cerebellar involvement

Although it is clear that in dystonia the cerebellum often shows abnormal activity, it is

as yet uncertain whether this activity plays a primary role or is just a compensation to

a problem created elsewhere. The types of symptom usually caused by problems in


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the cerebellum (such as uncoordinated movement, incorrectly timed movement,

dizziness) are different to the slow, writhing movements normally caused in dystonia.

Lack of these more common cerebellar symptoms may indicate that in most forms of

dystonia the cerebellum has abnormal, probably compensatory activity rather than aprimary role.

Conclusion on cerebellum

Cerebellar activity is often abnormal but it is unclear whether all manifestations of

dystonia involve both basal ganglia and cerebellar circuitry, or whether there is a

spectrum ranging from pure cerebellar dystonia, overlapping basal ganglia and

cerebellar dystonia, and pure basal ganglia dystonia. However, it is likely that the

cerebellum will have a key place within future models of dystonia.

CONCLUSION

This article illustrates that there has been considerable progress in understanding

what is happening in the brain to cause dystonia but there are still many questions to

resolve. The ideas emerging suggest that dystonia may have a combination of

causes - for instance abnormal inhibition together with plasticity. In addition, these

causes may result from abnormal activity in more than one part of the brain.

Causes of Dystonia

The cause of dystonia is not fully understood. There appears to be a problem with the

region of the brain called the basal ganglia. In most cases where dystonia appears in

adults and some case where it appears in children, there is no clear explanation for

why this problem arises.

However, in a minority of cases, the dystonia does have a clear cause. These are:

Another Medical condition

Where dystonias appear in children, in more than 80% of cases the dystonia will be

secondary to another condition. In the majority of cases, this will be cerebral palsy.
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Some dystonias appearing in adults may caused by stroke or tumour.

Drugs

Some dystonias, calledTardive, are caused by certain drugs (especially dopamine

blocking drugs used to treat psychiatric disorders).

Genetics

Some cases generalised primary dystonia may be inherited.Click here for more info.
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Oromandibular dystoni1