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Dystonia (from Greek, meaning altered muscle tone) refers to a syndrome of involuntary sustained or spasmodic muscle contractions involving co-contraction of both the agonist and the antagonist. The movements are usually slow and sustained. They often occur in a repetitive and patterned manner, but they can be unpredictable and fluctuate. The frequent abnormal posturing and twisting can be painful and functionally disabling.
For excellent patient education resources, visit eMedicine's Back, Ribs, Neck, and Head Center. Also, see eMedicine's patient education article Torticollis.
Regardless of the causes, the dystonic contractions can have a chronic course and can lead to severe persistent pain and disability. Because each type of dystonia is treated in a different manner, the distinction between the various types is therapeutically important. Of note, pseudodystonia encompasses a group of movement disorders that may express dystonialike movements as one of the clinical features of syndromes. Sandifer syndrome, stiff man syndrome, and Isaac syndrome may fall into this category.
Dystonias can be classified according to age of onset, etiology, and anatomic distribution.
Infantile dystonia begins before age 2 years. Childhood dystonia begins at age 2-12 years. Juvenile dystonia begins at age 13-20 years. Adult dystonia begins after age 20 years.
Primary or idiopathic dystonia
This type can manifest in a sporadic, autosomal dominant, autosomal recessive, or X-linked recessive manner. Heritable childhood-onset dystonia is particularly common among Ashkenazi Jewish people.
Currently, at least 12 types of dystonia can be distinguished on a genetic basis. Identification of more dystonia genes may lead to better understanding and treatment of these largely nondegenerative disorders.
Classification of Primary Dystonia
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Type | Affected Chromosome Arm | Clinical Features | Mode of Inheritance |
---|---|---|---|
DYT1 | 9q34 | Early onset, generalized dystonia, starts in a limb | Autosomal dominant |
DYT2 | Not known | Early onset, generalized or segmental | Autosomal recessive |
DYT3 | Xq13.1 | Approximately 50% of patients with parkinsonism | X-linked recessive |
DYT4 | Not known | Whispering dysphonia | Autosomal dominant |
DYT5a | 14q22.1-22.2 | Onset in first decade of life; starts distally in leg and spreads to proximal limb, diurnal fluctuation; dopa-responsive mutations in genes for GTP* cyclohydrolase I and tyrosine hydroxylase | Autosomal dominant |
DYT5b | 11p15.5 | Dopa-responsive dystonia | Autosomal recessive |
DYT6 | 8p21-22 | Onset in adolescence, segmental | Autosomal dominant |
DYT7 | 18p | Adult onset, focal (writers' cramp, torticollis, dysphonia, blepharospasm) | Autosomal dominant |
DYT8 | DYT82q33-25 | Paroxysmal dystonia-choreoathetosis triggered by stress, fatigue, alcohol | Autosomal dominant |
DYT9 | 1p21-13.8 | Paroxysmal dystonia; paresthesias, diplopia; spastic paraplegia between attacks | Autosomal dominant |
DYT10 | Not known | Paroxysmal dystonia-choreoathetosis precipitated by sudden movements | Autosomal dominant |
DYT11 | 11q23 | Myoclonus and dystonia | Autosomal dominant |
DYT12 | 19q | Rapid-onset dystonia and parkinsonism | Not known |
Type | Affected Chromosome Arm | Clinical Features | Mode of Inheritance |
---|---|---|---|
DYT1 | 9q34 | Early onset, generalized dystonia, starts in a limb | Autosomal dominant |
DYT2 | Not known | Early onset, generalized or segmental | Autosomal recessive |
DYT3 | Xq13.1 | Approximately 50% of patients with parkinsonism | X-linked recessive |
DYT4 | Not known | Whispering dysphonia | Autosomal dominant |
DYT5a | 14q22.1-22.2 | Onset in first decade of life; starts distally in leg and spreads to proximal limb, diurnal fluctuation; dopa-responsive mutations in genes for GTP* cyclohydrolase I and tyrosine hydroxylase | Autosomal dominant |
DYT5b | 11p15.5 | Dopa-responsive dystonia | Autosomal recessive |
DYT6 | 8p21-22 | Onset in adolescence, segmental | Autosomal dominant |
DYT7 | 18p | Adult onset, focal (writers' cramp, torticollis, dysphonia, blepharospasm) | Autosomal dominant |
DYT8 | DYT82q33-25 | Paroxysmal dystonia-choreoathetosis triggered by stress, fatigue, alcohol | Autosomal dominant |
DYT9 | 1p21-13.8 | Paroxysmal dystonia; paresthesias, diplopia; spastic paraplegia between attacks | Autosomal dominant |
DYT10 | Not known | Paroxysmal dystonia-choreoathetosis precipitated by sudden movements | Autosomal dominant |
DYT11 | 11q23 | Myoclonus and dystonia | Autosomal dominant |
DYT12 | 19q | Rapid-onset dystonia and parkinsonism | Not known |
*GTP is guanosine triphosphate.
Secondary dystonia
This may result from a wide variety of neurologic diseases or inherited metabolic defects. Conditions or defects include the following:
On the basis of the clinical distribution, dystonia can be classified by its distribution as focal dystonia, segmental dystonia, multifocal dystonia, generalized dystonia, or hemidystonia.
Focal dystonia involves a single body part. Cervical dystonia or torticollis is the most common focal dystonia. Local limb dystonias often begin as action or task-specific dystonias such as writers' cramp dystonia or musicians' dystonia (repetitive wrist or finger movements). In 20-30% of patients, focal dystonias become segmental or multifocal.
Segmental dystonia affects 2 or more contiguous regions of the body. Examples of segmental dystonias of the head and neck include craniocervical dystonia, blepharospasm, oromandibular dystonia, and laryngeal dystonia.
Multifocal dystonia consists of abnormalities in noncontiguous body parts.
Unilateral dystonia, also known as hemidystonia, is usually associated with abnormalities in the contralateral basal ganglia.
Generalized dystonia involves segmental crural dystonia and at least one other body part. A generalized form of the disease called dystonia musculorum deformans, or torsion dystonia (TD), involves the trunk and limbs.
Cervical dystonia
Cervical dystonia or torticollis is the most common focal dystonia. It has an insidious onset in people aged 30-50 years, although it can begin earlier. Cervical dystonia commonly affects women.
Intermittent spasms of the neck muscles or abnormal head movement occurs because of contractions of the sternocleidomastoid, trapezius, and posterior cervical muscles. This effect results in a patterned, repetitive, and spasmodic movement that causes the head to twist (rotational torticollis), extend (retrocollis), flex (anterocollis), or tilt toward the shoulder (laterocollis). One or more of these head movements may occur simultaneously.
Patients may report psychiatric symptoms associated with depression or anxiety. These may be due to the chronic course of the illness rather than real psychopathology.
Upper limb dystonia
Upper limb dystonia causes cramping and posturing of the elbows, hands, and fingers that leads to the inability to perform certain occupational tasks. The literature describes at least 55 occupations in which individuals are affected by this condition. Men and women are affected with equal frequency. Onset is in persons aged 10-50 years.
A common upper limb dystonia is known as writers' cramp, occupational cramp, or graphospasm. This task-specific dystonia, manifesting as hyperextension or hyperflexion of the wrist and fingers, may be triggered by repetitive activities such as writing and playing the piano or other musical instruments. After cessation of the task, the spasm disappears. Although torticollis, tremor, and pain are accompanying symptoms, the spasm itself usually limits further activities.
The results of general physical and neuromusculoskeletal examinations are usually unremarkable. Some clinicians inadvertently label these conditions as occupational neuroses.
Lower limb dystonia
This may occur in stroke or dystonia-parkinsonism syndrome and can lead to painful positioning of the legs, impairing gait and altering bone development.
Oromandibular and lingual dystonia
Oromandibular, facial, and lingual dystonias are grouped together because of their possible coexistence. Cranial dystonia, commonly known as Meige syndrome, is the most common craniocervical dystonia. Women are more commonly affected, and onset is in the sixth decade of life.
Dystonia musculorum deformans or TD
Dystonia musculorum deformans, or TD, is the term used to describe a generalized form of the disease that involves the trunk and limbs. At least 2 types are described, and the onset may begin in childhood or adolescence, infrequently occurring as abnormal movement of a limb after an activity. The movements progress in severity and frequency until they become a continuous spasm, resulting in body contortion.
At first, rest relieves the spasms; however, as the disease progresses, the level of activity and positioning have no effect. The shoulder, trunk, and pelvic muscles undergo spasmodic twisting, as do the limbs. The hands are seldom involved. The orofacial muscles also may be affected, leading to dysarthria and dysphagia.
The pathology of dystonia musculorum deformans is yet to be described. In some cases, genetics appear to play a role. Autosomal dominant and recessive patterns of inheritance have been reported. A rare sex-linked form associated with parkinsonism has been described in the Philippines.
Tardive dyskinesia or dystonia
This is a common complication of long-term antipsychotic drug treatment due to dopamine receptor antagonism. The precise mechanism is unknown, but the risk appears to increase with advancing age. When medication is withdrawn relatively early during treatment, the dyskinesia may reverse, whereas after 6 months of exposure, the movement disorder may persist indefinitely. The clinical features of tardive dyskinesia include abnormal choreoathetoid movements, especially involving the face and mouth in adults (ie, blepharospasm, torticollis, oromandibular dystonia) and the limbs in children.
Impaired basal ganglia outflow is thought to play a role in the genesis of some dystonias. Lesions in the putamen have been linked to hemidystonia. Bilateral putaminal involvement may be responsible for generalized dystonia.
Torticollis and hand dystonia are thought to result from involvement of the head of the caudate nucleus and thalamus, respectively. Disease of the thalamus and subthalamus and derangement of hypothalamic function have also been suspected.
Because the basal ganglia play a role in maintaining normal head posture, the basal ganglia and the vestibulo-ocular reflex pathway have been implicated in the development of cervical dystonia. Disturbances of neurotransmitter systems have also been described in dystonias. Abnormalities in blink reflex recovery suggest involvement of the brainstem. Cervical and upper limb trauma has been implicated.
Drug-induced supersensitivity of striatal dopamine receptors or abnormality of GABAergic neurons are proposed mechanisms for some drug-induced dystonias. Although supersensitivity is an inevitable accompaniment of long-term antipsychotic drug treatment, tardive dyskinesia does not always occur.
Abnormalities of serotonin, dopamine, and norepinephrine in specific cerebral structures have also been associated with dystonia musculorum deformans.
History taking and physical examination are necessary, as in all cases of neuromuscular disorders. Family history is important; as many as 44% of patients have a family history of similar or other movement disorders.
Dystonia may be a clinical manifestation of many treatable neurologic conditions; therefore, a thorough screening should be performed to exclude Wilson disease (ie, hepatolenticular degeneration), hypoxic brain injury, traumatic brain injury, Huntington disease, Leigh disease, lipid storage disease, and Parkinson disease.
A number of medications can induce acute dystonic movements, and a careful investigation of the patient's medication list must be performed to rule out iatrogenic causes. Common drugs that can induce movement disorders and dystonias include dopamine antagonists, haloperidol, metoclopramide, antiepileptics, phenytoin, carbamazepine, valproic acid, felbamate, dopamine agonists, levodopa, monoamine oxidase inhibitors, adrenergic agents, amphetamines, methylphenidate, caffeine, beta-agonists, antihistamines, tricyclic antidepressants, buspirone, lithium, cimetidine, oral contraceptives, and cocaine, among others.
Various laboratory studies should be considered in the evaluation of dystonia. Blood chemistry testing, liver function tests, ceruloplasmin levels, and blood copper levels may be appropriate.
MRI and CT scanning of the brain are especially important in the pediatric population and may identify hypoxic, hemorrhagic, or tumorous lesions. Slit-lamp eye examination for Kayser-Fleischer rings and 24-hour urine copper analysis also may be useful.
Genetic screening for DYT gene abnormalities and genetic counseling is important for patients with an onset of primary dystonias at younger than 30 years or those who have an affected relative.
The functional impact of dystonia varies from barely noticeable to severely disabling. Dystonias can have a profound effect on the patient's personal, vocational, and emotional life and can impact his or her ability to live independently. Psychological counseling and participation in support groups are vital adjuncts to medical and physical approaches in the multidisciplinary management of this disorder.
The options to medically manage dystonic movements have traditionally been 4-fold, consisting of rehabilitative therapies, oral medications, neurochemolytic interventions, and surgery.
Rehabilitation and therapy
As with most movement disorders, dystonia may be influenced by fatigue, anxiety, relaxation, or sleep. Thus, attention to overall health, environment, and stressors can make dystonia more manageable.
Dystonic movements are often exacerbated or triggered by voluntary or intentional movements of the same or other body parts. Involuntary movements can be transiently suppressed by a contact stimulus, such as placing a hand on the ipsilateral or contralateral side of the face or neck in a patient with spasmodic torticollis.
Some dystonic movements may last seconds or minutes, but others may last hours or weeks. They can lead to permanent contractures, can cause boney deformity, or can significantly impair function. Appropriate use of upper and lower extremity splints and orthotics to support, guide, reduce, or stabilize movements can help prevent orthopedic deformities.
Physical therapy techniques (eg, massage), slow stretching, and physical modalities (eg, ultrasonography, biofeedback) are sometimes helpful in persons with focal or regional dystonias. Patients with generalized dystonia often benefit from gait and mobility training and instruction in the use of assistive devices.
Various physiatric therapies and modalities have been used with limited success for the treatment of dystonia symptoms. These include relaxation training, sensory stimulation, biofeedback, transcutaneous electrical nerve stimulation, and percutaneous dorsal column stimulation.
Occupational therapy is important for training for activities of daily living and for proper positioning and seating in patients who have impaired mobility. Adaptive equipment should be provided to enhance function.
Speech therapists can offer training and communication aids to patients with oromandibular or laryngeal dystonia, and they can help in preventing complications in patients with transient dysphagia resulting from botulinum toxin injections.
Vocational rehabilitation may aid individuals in job retraining or in adapting to the workplace, as appropriate.
Medications
Medications can be somewhat effective in controlling dystonic movements, but the lack of knowledge of the exact pathophysiology of dystonia makes specific pharmacologic therapies difficult. Systemic medications benefit approximately one third of patients and consist of a wide variety of options, including cholinergics, benzodiazepines, antiparkinsonism drugs, anticonvulsants, baclofen, carbamazepine, and lithium.
Successful drug therapy often requires combinations of several medications, with choices generally guided by empirical trials and adverse effect profiles. Doses should be slowly increased over the course of weeks or months until the therapeutic benefit is optimized or until adverse effects occur. In most patients, discontinuation of the drugs requires tapering to prevent withdrawal symptoms.
Baclofen, given intrathecally by an implanted pump, can be very effective for persons with certain types of dystonia, especially if they have coexisting spasticity. Advantages of this medication are the low prevalence of adverse effects when administered into the cerebrospinal fluid, the ability to deliver the medicine continuously, and the ability to test the therapeutic effect prior to proceeding with surgery; it may provide effective treatment to many patients.
Neurochemolytic procedures or muscle blocks
Neurochemolysis of dystonic muscles is another important therapeutic option. Botulinum toxins or phenol/alcohol injections have become powerful tools in improving the symptomatic treatment of focal dystonias. These injections temporarily reduce the ability of the muscles to contract and may be the treatment of choice for blepharospasm, cervical dystonia, and hemifacial spasm.
Botulinum toxins are produced by the gram-negative bacterium Clostridium botulinum and act by inhibiting the presynaptic release of acetylcholine at the neuromuscular junction. Of the 7 immunologically distinct serotypes, only types A and B are approved for clinical use. Onset of effect takes several days after injection.
The local injection of botulinum toxins into the offending muscles (often the sternocleidomastoid, trapezius, and splenius capitis) reduces muscle contraction for approximately 3 months. They are not associated with significant complications, although dysphagia and dry mouth can occur. The medications can be used for years effectively and, although expensive, are typically reimbursed by insurance. Most patients require repeated injections.
Phenol and alcohol nerve blocks also are temporary, but their effects last approximately 6 months and they are significantly less expensive. However, only selected nerves can be injected, and a skilled practitioner is needed in order to avoid adverse effects.
The selection of appropriate muscles should be based on careful clinical assessment of the maximally involved muscles and on a clear delineation of the goals (eg, improved function, hygiene, pain relief). Initial needle placement in the chosen muscle is based on anatomic landmarks, often with the aid of electromyelography localization. The number of injection sites and overall dose vary depending on the size of the muscle, the degree of dystonia present, and the functional change desired.
Surgery
Surgical options for intractable dystonias include transection of the spinal accessory nerve for cervical dystonia; stereotactic thalamotomy or pallidotomy for generalized dystonia; and muscle excision, lengthening, or transfer. Because of the risk of significant comorbidity, these approaches are reserved for patients with disabling dystonia in whom other treatment modalities have been exhausted.
Deep brain stimulation
Deep brain stimulation for severe dystonias is an investigational, compassionate-use therapy that is in the initial stages of development. Best results have been obtained with pallidal stimulation in patients with primary generalized DYT1 dystonia. The optimal target point in different patients is still uncertain, and its long-term efficacy and adverse effects are unknown. Stereotactic placement of the electrodes requires a skilled neurosurgeon, and programming of the stimulator requires an experienced physiatrist or neurologist. A thorough neurology, physiatric, neuropsychological, and physical therapy evaluation is important prior to considering surgery.
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