Definition: "Involuntary muscle contractions causing a sustained, twisted or abnormal posture"
Features seen with Dystonia
Patients with dystonia may have
superimposed movements that are slow (athetosis), or rapid (myoclonic), or rhythmic (tremor). It is the sustained twisted postures that are the key to diagnosis. There is a tendency for the movements to
be absent at rest and be triggered by movement (action). The movements follow a similar pattern, and these repetitive postures support the diagnosis (unlike chorea which is random).
Dystonia is often is often better first
thing in the morning. Frequently patients often have "sensory tricks" (putting slight pressure close to the dystonic muscles inhibits the dystonia). Dystonia may be very task specific
(e.g. horn blowers lip dystonia). Several unusual properties (e.g.: leg dystonia improving when walking backwards) make this condition hard for family doctors to recognize as a real medical problem. It is not unusual to see several physicians prior to the diagnosis being made. Blepharospasm (eyelid spasms), and cervical dystonia (neck twisting) are the two most common types of focal dystonia.
Ways of Classifying Dystonia
1) By Anatomical Distribution (Body part or parts affected)
If only one body part is affected dystonia is called "focal".
The main examples are:
- eyes and face............. Miege syndrome
- jaw............................Oromandibular Dystonia (can be jaw opening or closing)
- neck..........................Cervical Dystonia
- vocal cords................ Spasmodic Dysphonia (can be adductor dysphonia or abductor dysphonia)
- trunk......................... Axial dystonia
- arm............................e.g. Writer's cramp
If only one segment of the body is
affected, dystonia is called "segmental". e.g. one arm and the neck, or both legs.
If only one side of the body is
affected, dystonia is called hemidystonia. This type is secondary to a brain problem on the opposite side from the dystonia and should be investigated with imaging the brain.
If one segment of the body and at least one other additional body part is affected, dystonia is called "Generalized".
2) By Cause
Primary vs Secondary
A primary condition is one that is not
due to any other cause. This may be of no known cause ("Idiopathic") or due to an inherited disorder (one that is passed on from generation to generation). A secondary form of dystonia
would be dystonia due to another disease (e.g. stroke or cerebral palsy)
Inherited Primary Dystonias and the inheritance pattern can be reviewed by this link
Secondary causes of dystonia include some of the following:
There are many medications (including
over the counter medications) that can either trigger an acute dystonic reaction, or if taken long enough can trigger a permanent problem with dystonia.
Some offending medications include:
antipsychotics (STEMETIL), metoclopramide (MAXERAN), Dilantin, Ca channel blockers, SSRI's (Prozac), Ergotamines, Antihistamines, etc.)
Inherited / Familial disorders that affect the nervous system
There are a variety of inherited
neurologic disorders that are associated with an increased risk of dystonia. These include; "Classic autosomal dominant dystonia" with an identified gene defect at DYT1 gene on
chromosome 9q34, Dopa responsive dystonia (Segawa variant), Myoclonic Dystonia, X-linked Dystonia-Parkinsonism (Lubag), Paroxysmal Dystonia, Wilson's Disease, Hallervorden-Spatz disease, Joseph's
Disease, Ataxia telangiectasia, and Neuroacanthocytosis.
Associated other with neurodegenerative disorders
There are a variety of non-inherited
neurologic disorders that are associated with an increased risk of dystonia. These include; Parkinson's Disease, P.S.P., multi-system atrophy, and multiple sclerosis
There are a variety of neurologic
disorders due to abnormalities of body metabolism that are associated with an increased risk of dystonia. These conditions usually present at childhood. These include;
disorders of amino acid and organic acid metabolism, disorders of lipid metabolism, disorders of mitochondria (a cellular organelle responsible for energy metabolism), and Lesch-Nyhan Syndrome.
Dystonia can occur after a variety of different types of trauma, including head injury, peripheral injury, and electrical injury.
Dystonia can occur after exposure to a
variety of different types of toxic substances, including; manganese, wasp stings, carbon monoxide, carbon disulfide, and methanol.
Post Anoxic (Lack of oxygen)
Dystonia can occur after brain damage
due to lack of oxygen. This is seen in children with cerebral palsy due to being deprived of oxygen at birth. It can occur in adults after stoke (a focal loss of oxygen supply to the brain due to a
blood vessel becoming blocked).
Dystonia can occur after exposure to a
variety of different types of infections that affect the brain including; viral encephalitis, toxoplasmosis, syphilis, AIDS, Jakob Creutzfeldt disease
Dystonia can occur as a result of a disturbance of brain functioning unassociated with any actual damage to the brain.
Hypnogenic Dystonia (Nocturnal)
Dystonia occasionally only occurs during the night while sleeping. One form Hypnogenic Dystonia is likely due to a seizure disorder.
There are some other conditions that
can result in abnormal or twisted postures that are not due to dystonia. One example would be a dislocation of the bones of the upper neck (Atlanto-Axial subluxation) resulting in a twisted
neck mimicking Cervical Dystonia.
3) By Age of onset
Childhood vs Adult onset
When dystonia starts in childhood it
is usually secondary, and unfortunately is commonly either generalized at onset, or becomes generalized over time. Usually when dystonia starts in adulthood it is primary and tends to remain focal.
Treatment of Dystonia
Levodopa (Sinemet, Prolopa) will work well in an inherited type of dystonia called the "Segawa variant". This condition usually starts in childhood, and can be mistaken for cerebral palsy. The children get worse during the day and usually is associated with some features of Parkinsonism. Even though the Segawa variant is rare doctors will often try levodopa just in case the patient responds. This condition can actually sometimes present as a focal dystonia in adults.
Anticholinergics (e.g. artane, cogentin, parsitan) have been the main group of drugs used to treat dystonia. They have been considered "the treatment of choice" meaning they are the most likely to work with the least side effects. They work up to 40% of the time in young adults. They are less well tolerated in older patients. The side effects are tolerated better in children, and higher doses can be reached, resulting in a higher rate of success in this age group.
Tetrabenazine (Nitoman), a more recently available medication acts to block the re-uptake of dopamine into nerve cells.
Carbamazepine (Tegretol) .
Benzodiazepines (Valium, Ativan, Lorazepam) can be helpful for some people with dystonia that is aggravated by anxiety. These have addicting potential, and therefore have to be used with caution.
Combinations of medications will
sometimes be necessary including one combination refereed to as "Triple Therapy" by Marsden: This "cocktail" includes a combination of an anticholinergic, diazepam
Botulnum toxin was first identified by
Dr. Allan Scott as a chemical who's action may help a variety of disorders due to overactivity of muscular activity. This toxin is purified from cultures of living bacteria, and is available in
a crystallized and liquid forms. BOTOX is a form that is kept frozen until
use. Xeomin is one that can be maintained at room temperature. Myobloc is one that comes in liquid form but is restricted to access in Canada. Dysport is a product available in Europe. Patients are treated by injecting the toxin directly into the dystonic muscles. The effect (weakness of the injected muscle is evident in 2 - 3 days, and the full effect is seen in 7 - 14 days. The effect typically lasts a duration of 3-4 months
Approximate Success Rate in different types of dystonia
Blepharospasm----------------------90 - 95 %
Cervical Dystonia (torticollis)-------- 90 % for pain, 70 % reduction of movement
Spasmodic dysphonia (vocal cord)--- 70 - 85 %
Jaw Closing dystonia-----------------60 - 80 %
Jaw opening dystonia----------------40 - 50 %
Writers cramp-----------------------15 - 20 %
1) Peripheral Denervation - by cutting the nerves to a dystonic muscle or group of muscles (Peripheral Denervation), the dystonic contractions may be reduced. This procedure is no longer frequently done.
2) Another surgical option is to cut or remove the dystonic muscles (Myectomy).This procedure is no longer frequently done.
3) Functional Steriotactic lesioning is a procedure that surgically destroys a very small area deep within the brain where dystonia may originate from, or be transmitted through. This, if successful, will stop or reduce the dystonia on the opposite side of the body. This type of procedure tends to help distal (forearm, hand, or foot) dystonia the most.
The two regions that
have been lesioned with some success in dystonia include the thalamus, and the globus pallidus. There are, as with any surgical procedure, possible side effects that need to be discussed and considered.
4) Another option is to implant a Deep Brain Stimulator (a small electrode implanted into the brain that is connected to a programmable transmitter under the chest wall, like a pacemaker). By electrically interfering with the natural firing pattern of the nerve cells in this area the dystonia is electrically suppressed. This procedure has been proven effective for inherited forms of generalized dystonia and more recently is proving successful for other refractory focal forms of dystonia. This, if successful, will stop or reduce the dystonia on the opposite side of the body. There are, as with any surgical procedure, possible side effects that need to be discussed and considered.
5) Another surgical option is to implant a pump that is able to continuously infuse baclofen (Intrathecal Baclofen Pump) into the fluid around the brain (cerebro-spinal-fluid). This is an technique for the treatment of generalized or severe dystonia refractory to other treatment options. Information so far suggests the main role is in cases combined with spasticity.