Clinical disorder manifested by sustained muscle contractions resulting in twisting and repetitive movements or abnormal postures.
Incurable movement disorders which vary with respect to age at onset, body distribution and genetics.
Caused by involuntary muscle contractions.
Results in abnormal postures of the trunk, face, arms or legs.
Dystonia
A neurological movement disorder syndrome in which sustained or repetitive muscle contractions result in twisting and repetitive movements or abnormal fixed postures.
May resemble a tremor.
The precise cause of primary dystonia is unknown.
Often intensified or exacerbated by physical activity, and symptoms may progress into adjacent muscles.
It may be hereditary or caused by physical trauma, infection, poisoning or reaction to pharmaceutical drugs, particularly neuroleptics.
Treatment may include oral medications, chemodenervation botulinum neurotoxin injections, physical therapy and/or other supportive therapies, and/or surgical procedures such as deep brain stimulation.
Dystonia is classified by age of onset, body distribution, nature of the symptoms, and associated features such as additional movement disorders or neurological symptoms, and cause.
Focal dystopias are the most common dystonias and tend to be classified as follows:
Anismus muscles of the rectum causing painful defecation, constipation, which may be complicated by encopresis.
Cervical dystonia, known as spasmodic torticollis, causing muscles of the neck rotate the head to one side, or to pull down towards the chest, or back, or a combination of these postures.
Blepharospasm affecting muscles around the eyes.
Oculogyric crisis with muscles of eyes and head undergoing extreme and sustained upward deviation of the eyes often with convergence causing diplopia.
Can be associated with backward and lateral flexion of the neck and either widely opened mouth or jaw clenching.
Can be a result of antiemetics such as the neuroleptic prochlorperazine or metoclopramide.
Can be caused by Chlorpromazine.
Oromandibular dystonia of the muscles of the jaw and muscles of tongue, causing distortions of the mouth and tongue.
Laryngeal dystonia of the muscles of larynx causing the voice to sound broken, hoarse, or sometimes reducing it to a whisper.
Focal hand dystonia, also ref2242ed to as musician’s or writer’s cramp with a single muscle or small group of muscles in the hand interfering with activities such as writing or playing a musical instrument by causing involuntary muscular contractions.
Focal hand dystonia is generally apparent during only certain activities.
Focal hand dystonia is neurological in origin?
Focal hand dystonia is not due to normal fatigue, and the loss of precise muscle control and unintentional movements result in painful cramping and abnormal positioning.
Segmental dystonias affect two adjoining parts of the body:
Hemidystonia affects an arm and foot on one side of the body.
Multifocal dystonia affects many different parts of the body.
Generalized dystonia affects most of the body, frequently involving the legs and back.
Associated with a variety of autosomal recessive and dominant gene abnormalities.
Autosomal dominant cranio-cervical dystonia can occur with prominent tremor.
Myoclonic dystonia cases are hereditary and have been associated with a missense mutation in the dopamine-D2 receptor.
In most cases it leads to abnormal posturing, in particular on movement.
Many have have pain, cramping, and relentless muscle spasms due to involuntary muscle movements.
Other motor symptoms may occur and are include lip smacking.
Early symptoms may include loss of precision muscle coordination, injuries to the hands, and dropped items, cramping pain with sustained use, and trembling.
Muscle pain and cramping may result from very minor exertions like holding a book and turning pages.
Individuals may notice trembling in the diaphragm while breathing.
Patients may need to place hands in pockets, under legs while sitting or under pillows while sleeping to keep them still and to reduce pain.
Trembling in the jaw may result in the grinding and wearing down of teeth, or symptoms similar to temporomandibular joint disorder.
The voice may crack frequently, and swallowing can become difficult.
Electromyelogram shows pulsating nerve signals being transmitted to the muscles even when they are at rest.
Muscles fatigue very quickly and some portions of the muscle groups do not respond manifesting as weakness, while other portions over-respond or become rigid.
The symptoms worsen significantly with use, and can affect other body parts.
Worsening symptoms may be due to anxiety, stress, disturbed sleep,sustained activity and exposure to cold.
Because of difficulties patients may become depressed as activities and livelihood ay be compromised.
Symptoms may plateau for years, or stop progressing entirely.
Differential diagnosis includes Parkinson’s disease, essential tremor, carpal tunnel syndrome, Tourette’s syndrome, conversion disorder or other neuromuscular movement disorders.
Prevalence is high in individuals with Huntington’s disease.
Primary dystonia is diagnosed when the dystonia is the only sign and there is no identifiable cause or structural abnormality in the central nervous system.
It is thought to be caused by pathology of the central nervous system, likely originating in those parts of the brain concerned with motor function, such as the basal ganglia, and the GABA producing Purkinje neurons.
Primary dystonia may involve some genetic predisposition combined with environmental conditions.
Secondary dystonia refers to dystonia brought on by some identified cause, such as head injury, drug side effect or neurological disease.
Meningitis and encephalitis caused by viral, bacterial, and fungal infections of the brain have been associated with dystonia.
Infection related inflammation causes restriction of blood flow to the basal ganglia, or direct nerve injury by the organism or a toxin, or autoimmune mechanisms.
Environmental and task-related factors are suspected to trigger the development of focal dystonias: they are disproportionate present in individuals who perform high precision hand movements such as musicians, engineers, architects, and artists.
Chlorpromazine, neuroleptic drugs can cause dystonia.
Dysfunction of the sodium-potassium pump may be a factor in some cases of dystonia.
Has been regarded as a basal ganglia dysfunction.
Recent evidence has emerged of cerebellar involvement in the pathophysiology of this process.
Reducing the types of movements that trigger or worsen dystonic symptoms provides some relief, as does reducing stress, and getting relaxation.
Other treatments include sedation, blocking nerve communications with the muscles via drugs, neuro-suppression, or denervation.
Physical therapy manage changes in balance, mobility and overall function.
Medications of benefit in some patients include: diphenhydramine, benzatropine and atropine. anti-Parkinsons agents, muscle relaxants, and anticholinergics.
A baclofen pump has been used to treat muscle spasticity along with dystonia.
Botulinum toxin injections into affected muscles provides some relief for around 3–6 months, depending on the kind of dystonia.
Muscle relaxants such as clonazepam, an anti-seizure medicine, is also sometimes employed.
Dopamine-responsive dystonia, can be treated with L-DOPA
Surgical denervation of muscles, may provide relief, and is considered only extreme cases.
Deep brain stimulation has proven successful in a number of cases of severe generalized, but may increase the risk of suicide in patients.
Such behavior includes head rotation, wristand finger flexion, arching of the back, ankle inversion, facial contractions, jaw contractions and laryngeal muscle contractions (Tarsy D, Simon DK).
Classified as focal and limited to one body part, segmental with involvement of adjacent body parts, multifocal, hemi-dystonia or generalized.
Classified additionally as primary or secondary.
Classification based on etiology includes primary, secondary, dystonia-plus syndromes and paroxysmal dystonia.
Primary dystonias are genetically determined and designated DYT1-DYT20.
Primary dystonias occur in the absence of other neurologic abnormalities except for tremor or myoclonus.
Primary dystonias are unassociated with known brain pathologic abnormalities, but reduced intracortical in addition and increased cortical excite ability are present (Defazio G et al).
Primary dystonias are a clinical diagnosis without imaging or laboratory findings, although diffusion tensor imaging has shown white matter abnormalities in some cases (Carbon M et al).
Secondary causes of dystonia include neurodegenerative diseases of the brain and metabolic causes.
Wilson’s disease is an important cause of dystonia and Parkinson’s symptoms.
An acute onset of dystonia may occur following in the administration of drugs such as phenothiazines with involuntary, sustained muscle contractions typically involving the cranial and cervical muscles.
Extent and severity of the muscle process ranges from intermittent contractions limited to a single area to generalized process with involvement of the limbs and axial muscles.
Focal involvement indicates that a single area is involved, a segmental involvement reflects 2 or more contiguous areas and if multifocal with 2 or more noncontiguous body regions and general involvement implies involvement of the legs and 1 other body region.
Confused with spasticity or rigidity.
Confused with cerebral palsy, blepharospasm, and cervical muscle strain.
Results from involuntary concomitant contractions of agonist and antagonist muscles.
Overflow of muscle contractions spreads to adjacent muscles.
Movements can be fast or slow and can change with different activities and positions and even become fixed in severe cases.
Can be associated with tremors.
By gentle touching of the affected body localized dystonias may respond.
Many dystonic movements are dependent upon specific actions.
Classification can be based on age at onset, cause or genetics.
The foot is frequently involved and assumes plantar flexion and plantar flexion with inversion.
The hand is flexed at the wrist and extended at the fingers.
The neck is forcefully turned to the side.
Typically begins with movement in the distal parts of the limb, but large twisting movements of the entire limb may develop.
With involvement of the trunk kyphoscoliosis, lordosis or bow-like arching of the back can occur.
Movements can vary in severity and location depending upon sleep, rest and voluntary actions.
When the disease begins in childhood or young adulthood it usually progresses from focal limb dystonia to a severe generalized form.
When the disease begins after the age of 25 years it usually involves craniocervical muscles and remains localized or segmental and is usually not progressive.
Treatment for focal or segmental dystonia is the injection of botulinum toxin to denervate affected muscles.
Botulinum toxin not successful for lesions with multiple muscle involvement, the presence of complex movement pattern or if neutralizing antibodies develop.
Drug therapy often unsatisfactory.
Bilateral pallidal deep brain stimulation for primary generalized and segmental dystonia reduces the severity of disease as reflected by a movement score improvement, a reduction in disability and improved physical aspects of the quality of life when compared to a sham stimulation group.