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...........................Blepharospasm
- eyes and face.............Miege syndrome
- jaw............................Oromandibular Dystonia
- neck..........................Cervical Dystonia
- vocal cords................Spasmodic Dysphonia
- trunk.........................Axial dystonia
- arm............................e.g. Writer's cramp
Segmental
If only one segment of the body is affected, dystonia is called "segmental". e.g. one arm and the neck, or both legs. Hemidystonia 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.
Generalized
If one segment of the body and at least one other additional body part is affected, dystonia is called "Generalized".
2) By Cause
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) Inherited Primary Dystonias and the inheritance pattern can be reviewed by this linkSecondary causes of dystonia include some of the following:Drug Induced
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: Levodopa, Bromocriptine, 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 Metabolic disorders 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. Post Traumatic Dystonia
can occur after a variety of different types of trauma, including head injury, peripheral injury, and electrical injury. Brain Tumors Toxic
Dystonia can occur after exposure to a variety of different types of toxic substances, including;maganese, 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). Infectious
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 Psychogenic Dystonia can occur as a result of emotional difficulties or due to a stress reaction. Hypnogenic Dystonia (Nocturnal) Dystonia occasionally only occurs during the night
while sleeping. One form Hypnogenic Dystonia is likely due to a seizure disorder. Pseudo-Dystonia
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
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
(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 levo-dopa just in case the patient responds.
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" as they are the most likely to work with the least side effects. They work up to 40% of the time. 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 reuptake of dopamine into nerve cells. This has recently been found to help dystonia up to 50% of the time.
Baclofen (Lioresol) may reduce dystonia up to 20% of the time. Clonazepam (Rivotril) may reduce dystonia up to 15% of the time. Carbamazepine
(Tegretol) may reduce dystonia up to 10% of time. 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 and tetrabenazine.
Botulinum Toxin Injections 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 form that is kept frozen until use. 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 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 % Surgical Options
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 fequently done.
2) Another surgical option is to cut or remove the dystonic muscles (Myectomy).This procedure is no longer fequently 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 experimental 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
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