Dystonia
Description
Dystonia is a neurological movement disorder that causes muscles in the body to contract or spasm involuntarily. The involuntary muscle contractions cause twisting, repetitive and patterned movements as well as abnormal postures.
Dystonia is not a single disease but a syndrome – a set of symptoms that cannot be attributed to a single cause but share common elements. Some forms of Dystonia may affect a specific body area, such as the neck, face, jaw, eyes, limbs or vocal cords.
Affects
Dystonia affects men, women and children of all ages and backgrounds. It can develop in childhood and is often particularly disabling for children. Dystonia may be genetic or caused by factors such as physical trauma, exposure to certain medications, or other neurological conditions.
Causes
The causes of Dystonia are not yet fully understood, but it is thought that it may be caused by a chemical imbalance in a particular area of the brain called the basal ganglia where the messages to initiate muscle contractions are believed to originate. The basal ganglia are structures deep in the brain that are in part responsible for controlling movement. They regulate the numerous muscle contractions that are necessary to move the body. If this part of the brain is damaged in some way, the wrong muscles contract when we try to move. Or the muscles contract unnecessarily even when we are immobile, causing uncontrollable twitching, tremors and contractions. These spasms are known as dystonic movements.
Some dystonia patients may have suffered from an illness or injury which has damaged the basal ganglia, but in the majority of cases the underlying cause of the condition is unknown. If no cause can be pinpointed, the dystonia is said to be idiopathic. Depending upon the type of dystonia, the specialist may decide to carry out blood tests or scans in an attempt to determine the cause.
Classification
Dystonia is best classified according to the parts of the body affected.
If only one part of the body is affected, such as the eyes, neck, a limb, or the voice, it is called Focal Dystonia. If a larger region such as the neck and arms is involved, it is called Segmental Dystonia. If the spasms affect the arm and leg on the same side it is known as Hemidystonia. If two or more unrelated parts of the body are affected it is named Multifocal Dystonia. Finally, if the Dystonia is more widespread, the term generalised Dystonia is used.
Why Haven’t I Heard of Dystonia Before?
It was only half-way through the last century that dystonia was recognised as a physical (organic) condition, and different forms were identified as manifestations of the same illness. In spite of this, dystonia often remains often misunderstood, misdiagnosed and therefore mismanaged. Research from the United States indicates that dystonia is as common as multiple sclerosis in certain areas of the world including parts of the Australia. However, there is little literature that provides adequate information about dystonia or explains its effects on those who live with the condition.
Common Forms of Dystonia
Cervical Dystonia
Cervical Dystonia, often referred to as spasmodic torticollis, is a particular type of focal dystonia that affects the muscles of the neck. The muscle spasms can be painful and cause the neck to twist to one side (torticollis), forward (anterocollis), or backward (retrocollis). The neck may pull, turn or jerk; it may be held persistently in one direction.
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Blepharospasm
This is a condition where the eyelid muscles spasm, causing the eyelids to close suddenly without warning. The individual has difficulty opening them again and, if severe, can lead to problems with sight although vision is not affected. Blepharospasm is often aggravated by sunlight.
Oromandibular Dystonia
Oromandibular Dystonia can affect the face, tongue, palate and jaw and presents with abnormal mouth or tongue movements, grimacing or forced opening or closing of the mouth.
Writer’s Cramp
Writer’s cramp, as the name suggests, affects the person’s ability to write. Writer’s cramp is usually task specific or related to the person’s occupation. The thumb and/or more fingers cramp and assume an abnormal posture while attempting to write or perform a repetitive task. A more correct term for this type of dystonia is Forearm Dystonia, as the muscles of the forearm are responsible for the cramping of the fingers as well as the hand muscles. Musicians using a range of instruments, are prone to this disorder, as are some people who perform complex repetitive tasks. This is a difficult dystonia to treat as there may be many small muscles in the hand and forearm involved. Individuals may choose to learn to use their non-dominant hand.
Spasmodic Dysphonia
Spasmodic Dysphonia, sometimes known as Laryngeal Dystonia, is a rare voice disorder. Overactive movement of the muscles of the larynx (excessive closure or opening of the vocal cords) occurs during specific vocal activities such as speaking but not during laughing or yawning. The voice may be strained and effortful with sudden interruptions causing momentary loss of voice. Dysphonia can be seen with other focal dystonias such as oromandibular dystonia and blepharospasm.
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Meiges’ Syndrome
Meiges’ Syndrome, also known as Breughel’s disease, from the 16th century Flemish painter who captured the syndrome on canvas. Meiges’ is a combination primarily of blepharospasm and oromandibular Dystonia but may be seen with dysphonia.
Hemidystonia
Hemidystonia: muscle groups of one side of the body are affected, causing loss of balance and difficulty moving around. There is a lot of strain put on the unaffected muscles.
Generalised Dystonia
Generalised Dystonia is a rare form of dystonia which is seen more often in children than in adults. It is generally a severe disability, affecting areas of the body. Generalised dystonia often starts in a lower limb then spreads to other areas such as the neck, limbs and trunk. People with generalised dystonia often have a genetic basis for their disease.
Other Forms of Primary Dystonia
Dopa-Responsive Dystonia (DRD)
Dopa-responsive Dystonia (DRD) is a broad term used to describe cases of Dystonia that respond dramatically to low doses of a medication called levodopa. Dopa-responsive Dystonia usually starts in childhood or adolescence with progressive difficulty in walking. It may be misdiagnosed as cerebral palsy or parkinsonism. Several genes have been associated with Dopa-responsive Dystonia.
Myoclonic Dystonia
Myoclonic Dystonia (hereditary essential myoclonus), often mistaken for essential tremor, is characterized by rapid jerking movements alone or in combination with the sustained muscular contractions and postures of dystonia. The symptom distribution of myoclonic dystonia is different from typical early-onset dystonia as it more often affects the upper body whereas typical early-onset dystonia usually affects the legs. A gene associated with myoclonus dystonia has been identified.
Rapid-onset Dystonia-Parkinsonism (RDP)
Rapid-onset dystonia-parkinsonism (RDP) is characterised by the abrupt onset of slowness of movement (parkinsonism) and dystonic symptoms. The classic features of RDP include involuntary dystonic spasms in the limbs, prominent involvement of the speech and swallowing muscles, slowness of movement and poor balance. Onset of the combined dystonic and parkinsonian symptoms can be sudden, occurring over hours to days. RDP usually occurs in adolescence or young adulthood (age range 15 to 45).
Paroxysmal Dystonia and Dyskinesias (PDD)
Paroxysmal Dystonia and Dyskinesias (PDD) are a group of disorders in which the patient experiences relatively brief episodes of abnormal movements and postures with a return to normal posture between episodes. Some forms of PDD are genetic.
X-linked Dystonia-Parkinsonism (lubag)
X-linked dystonia-parkinsonism (Lubag) is a form of dystonia found almost exclusively among men originally from the Philippine island of Panay. Female family members are carriers of the gene. X-linked dystonia-parkinsonism usually begins focally, generalises, and may be replaced by parkinsonian features.
Secondary (Symptomatic) Dystonia
In this type of Dystonia, the symptoms are due to small areas of brain damage. The dystonia is segmental, generalised or hemidystonia. The damage can be caused by reduced oxygen around the time of birth or in utero (cerebral palsy), by other injury to the brain, small strokes or tumours. Secondary dystonia usually results from apparent outside factors such as exposure to certain medications, trauma, toxins or infections. Dystonia can also be secondary to other illnesses that affect the nervous system such as Wilson’s disease, Huntington’s disease and multiple sclerosis.
Drug-Induced Dystonia
Acute Dystonic Reactions
Drugs frequently cause movement disorders. Often, those affected, experience an acute dystonic reaction after a single exposure to a drug. The symptoms are usually short-lived and may be treated successfully with medication. Dystonic reactions to (metoclopramide dydrochloride) Maxolon and (prochlorperazine maleate) Stemetil are particularly common in young people. Acute dystonic reactions can often be dramatic in presentation. Sometimes they can be so severe, they warrant life-saving measures. This usually occurs when the laryngeal muscles are involved and respiratory difficulties are experienced.
Tardive Dystonia and Tardive Dyskinesias
Tardive dystonia and tardive dyskinesias are neurologic syndromes caused by exposure to certain drugs called neuroleptics. Neuroleptic drugs are used to treat certain movement disorders, psychiatric disorders, and some gastric conditions. Tardive syndromes may also develop in some Parkinson’s patients as a result of exposure to levodopa. The word ‘Tardive’ means late or tardy, and in this case refers to the onset of the symptoms after the drug is taken. Dystonic postures and movements may present soon after the person has initiated neuroleptic therapy but may also be delayed by days or weeks. Movements can vary from brief jerks to prolonged muscle spasms often involving the eyes, mouth, throat and neck.
Dystonic symptoms typically occur between 2-24 hours after the first drug dose is administered. Signs may persist for hours or even days and the intensity of the symptoms vary. The way the drug affects a person is often age-related. Children may develop spasms involving the trunk and extremities, where as adults tend to develop dystonic spasms in the face, neck and upper extremities. These spasms and postures can come on abruptly, are often painful and may change in their distribution, affecting different body parts at different times. Tardive dystonias are often very difficult to treat and can persist long-term.
Trauma
The link between trauma and dystonia is not yet fully understood. It appears from published studies that persons who are carriers of a gene for dystonia may be more likely to have trauma as a triggering factor for the development of dystonia.
Toxins
A number of uncommon toxins are capable of causing brain damage centred in the motor control region known as the basal ganglia. Dystonia may be one prominent feature experienced by people with these exposures, but it is extremely uncommon for ‘isolated dystonia’ to be seen in such patients. In other words, the vast majority of people exposed to toxins (i.e. manganese) have additional neurological problems associated with the dystonia. Possibly the most common feature is such patients is the presence of a Parkinson’s Disease-like state.
Environmental Factors
The role of environmental factors causing or contributing to dystonia remains uncertain. It is not clear why some individuals inheriting a special gene develop and 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).
Related Disorders
Secondary dystonias can accompany other disorders resulting in dystonic symptoms. Wilson’s Disease and Hallervorden-Spatz Disease are examples of many disorders that can cause dystonia symptoms.
Wilson’s Disease
Wilson’s Disease (hepatenticular degeneration) is a rare hereditary disease resulting from excessive copper accumulation in the body. Normally, copper is excreted without any difficulties, but in Wilson’s disease, copper is deposited and accumulates in the liver, brain and around the eye. Dystonia is a prominent clinical feature in some people with Wilson’s disease. Wilson’s disease requires specific treatment.
Hallervordern-Spatz Disease
Hallervordern-Spatz disease is a very rare inherited progressive disease of the brain, typically involving the basal ganglia and often associated with severe dystonia and parkinsonism. A MRI scan of the brain is very helpful in making the diagnosis of Hallervordern-Spatz disease by demonstrating increased iron deposition in these deep brain regions.
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