Dystonia

Written by Dr Helen Hanson, Movement Disorders Unit, King's College Hospital, London and Dr K Ray Chaudhuri, Movement Disorders Unit, King's College Hospital, London

What is dystonia?

Dystonia is a syndrome of spasms and sustained contractions of the muscles. These muscle movements are not under voluntary control and they result in repetitive abnormal movements of parts of the body or persistently abnormal postures.

Dystonia can affect virtually any single part of the body or several different areas at once.

What are the risks?

It is estimated that there are more than 38,000 people in the UK affected with dystonia. It can be very difficult to diagnose and many doctors will never have seen someone with it before. Therefore, the actual number of people with dystonia may be much higher than estimated.

Dystonia affects both men and women. It can affect all age groups but the most common age of onset is between 40 and 60.

It can also develop in childhood but then the pattern is generally different from adult-onset dystonia.

When dystonia starts in childhood it usually begins in the leg or foot and commonly spreads to involve the entire body. If dystonia begins in adult life it tends to be more localised, usually affecting one part of the body, such as the neck or hand.

What are the causes of dystonia?

Dystonia is a movement disorder. Although the causes of dystonia are not fully known it is currently thought that the condition results from a malfunction in a part of the brain called the basal ganglia.

The basal ganglia are structures situated deep in the brain. They help to regulate voluntary and involuntary movement by controlling muscle contractions in the body.

The problem may mainly lie in an area of the basal ganglia called the globus pallidus. If this area of the brain is not functioning correctly then the control of another structure in the brain called the thalamus is affected.

The thalamus controls the planning and execution of movement and sends nerves to muscles via the spinal cord. The end result is that muscle co-ordination is not regulated properly. The wrong muscles will contract on movement or all muscles will contract unnecessarily causing abnormal movement and posture.

Muscles positioned around joints usually work in pairs opposite each other, eg the biceps and triceps muscles of the upper arm bend or straighten the elbow respectively. Usually if one muscle of a pair is contracted the other is relaxed. However, in dystonia both muscles in the pair contract at the same time leading to the abnormal movement or posture.

It is thought that in some cases there may be a chemical imbalance or 'wiring fault' in the basal ganglia. Chemical transmitters, such as dopamine, convey messages from one nerve cell to another within the basal ganglia. If this balance is upset then incorrect signals will be sent out resulting in loss of regulation of co-ordinated movements.

Supporting this theory is the fact that people with dystonia do not show structural abnormalities of the brain. The 'wiring fault' theory is therefore more likely because it works at a much smaller scale.

The fault in the basal ganglia may be caused by an inherited factor or be secondary to another problem such as drugs or toxins, or a separate neurological disease. Recently scanning studies using positron emission tomography (PET) in patients with cervical (neck muscle) dystonia have revealed reduced basal ganglia density of an important dopamine receptor (the D2 receptor).

How is dystonia classified?

Dystonia can be classified according to the age of onset (childhood, adolescent or adult) by body distribution (focal, multifocal, segmental, generalised or hemidystonia) or by the cause (primary, secondary, 'dystonia plus' syndromes or combinations of hereditary and degenerative causes).

Focal dystonias affect one part of the body such as eyes, neck, arm or vocal cords and are the most common type.

Multifocal dystonias affect several different unrelated body parts, such as eyes, hands and vocal cords. Segmental dystonias involve two or more adjacent body parts, such as the arm and neck.

Hemidystonias affect only one side of the body, and commonly result from a stroke. Generalised dystonia is more severe and can affect the entire body.

Primary dystonia refers to the situation where dystonia is the only sign and there is no identifiable cause or structural abnormality in the central nervous system.

Secondary dystonia implies there is a clear cause, such as a change in the structure of the brain, an environmental cause, as part of an inherited or acquired neurological disease or due to drugs or toxins.

'Dystonia-plus' syndromes occur when dystonia is combined with other pathological changes. It includes dopa-responsive dystonia and myoclonic dystonia.

What are the different types of dystonia?

Primary dystonias

Generalised dystonia This is also known as primary torsion dystonia or dystonia musculorum deformans. The usual age of onset is between 5 and 16 years. Parents or teachers may notice an abnormal turning in of the foot, an awkward gait or contractions of many different muscle groups.

The involuntary dystonic movements may progress quickly to involve all the limbs and torso, but the rate of progression usually slows after adolescence.

A genetic basis for generalised dystonia has now been confirmed.

Focal dystonias

Spasmodic torticollis Torticollis, commonly called wry neck, is the condition of spasm affecting the muscles of the neck, causing the head to assume unnatural postures or turn uncontrollably.

Spasmodic torticollis, also known as cervical dystonia, is the most common of the focal dystonias. There are thought to be 10,000 people in the UK suffering from this condition.. The average age of onset is in the early 40s and more women are affected than men.

The head may tilt (laterocollis) or twist to one side (rotational torticollis), forward (anterocollis) or backward (retrocollis). The movements may be sustained or jerky (myoclonic torticollis). Muscle spasms or pinching nerves in the neck can be very painful. The neck may eventually be held permanently in one position.

Torticollis usually develops gradually. At first, the patient may notice that the head turns during everyday activities. In about a quarter of patients the hand may also develop some tremor, especially if trying to correct the involuntary movement. The tremor is common but not usually disabling and is referred to as an enhanced physiologic tremor.

The severity of torticollis can vary and may be worse if the patient is under stress. Occasionally drinking alcohol can improve the torticollis.

Some sufferers have a history of head or neck injury, but as yet there is no evidence to support the theory that torticollis is directly related to trauma.

Most patients find the condition deteriorates over the first five years, but their symptoms then stabilise. One third of patients progress to a segmental dystonia, usually involving the arm. The symptoms of about 10 per cent may stop spontaneously, but then later recur.

Patients with torticollis often find that their daily lives are affected. Head turning can prevent a proper view of the road when driving, it may become difficult to eat, brush teeth or apply makeup. Many sufferers find embarrassment and anxiety the major handicap.

Blepharospasm

Blepharospasm means the involuntary contraction of the eyelids, leading to uncontrollable blinking and closure of the eyelids.

It affects more women than men and in the UK and it is the second most common focal dystonia with approximately 4000 people affected. In very extreme cases, sufferers are unable to prevent their eyes from clamping shut so that despite normal vision they are functionally blind.

Muscles in the face can also become affected causing facial distortions and grimacing when the patient attempts to open her eyes.

Blepharospasm usually develops gradually. The first sign a sufferer may notice is eye irritation and discomfort, light sensitivity and increased blinking. They may find that the condition worsens when they are tired, under stress or reading. Bright flickering lights, smoke or wind can all irritate the condition making symptoms worse.

Go To Next Page>>



The documents contained in this web site are presented for information purposes only. The material is in no way intended to replace professional medical care or attention by a qualified practitioner. The materials in this web site cannot and should not be used as a basis for diagnosis or choice of treatment. Conditions for use



© Copyright 1998 - 2004 NetDoctor.co.uk - All rights reserved