Merck Manual

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Alex Rajput

, MD, University of Saskatchewan;

Eric Noyes

, MD, University of Saskatchewan

Reviewed/Revised Feb 2024

Dystonias are involuntary muscle contractions, which may be sustained or intermittent. Dystonias may result in abnormal postures, movements, or both; movements may resemble tremor. Dystonias can be primary or secondary and can be generalized, focal, or segmental. Diagnosis is clinical. Botulinum toxin injections are used to treat focal or segmental dystonias. Treatment of severe generalized dystonia may require a combination of oral anticholinergic medications, muscle relaxants, and benzodiazepines. Severe dystonia that is refractory to pharmacotherapy may require surgery.

Dystonia may be

  • Primary (idiopathic)

  • Secondary to central nervous system (CNS) disorders or medications

CNS disorders that can cause dystonias include

Medications that most commonly cause dystonias include

  • Antipsychotics (eg, phenothiazines, thioxanthenes, butyrophenones)

  • Antiemetics (eg, metoclopramide, prochlorperazine)

Classification of Dystonias

Dystonias are classified based on

  • Etiology

  • Clinical features

Etiology is categorized as

  • Inherited: Has a proven genetic origin (previously known as primary) and includes disorders with autosomal dominant, autosomal recessive, mitochondrial or X-linked inheritance

  • Idiopathic: Can be sporadic

  • Acquired: Associated with neuroanatomic abnormalities due to other disorders or medications

Clinical features include the following:

  • Onset: Can occur at any age, from infancy to late adulthood

  • Body distribution: May be focal (limited to one body part), segmental (involving ≥ 2 more contiguous body parts, such as the upper and lower face or face and neck), multifocal (involving ≥ 2 noncontiguous body parts, such as the neck and leg), generalized (involving the trunk plus 2 different body parts), or hemicorporal (involving half the body; also called hemidystonia)

  • Temporal pattern: May be static, progressive, paroxysmal, or persistent and may have diurnal variability or be triggered by certain tasks (task-specific dystonia)

  • Isolated (no evidence of another movement disorder) or combined (accompanied by other involuntary movements [other than tremor], but predominantly dystonia)

Generalized dystonia may be inherited or secondary to another disorder or medication (eg, antipsychotics).

Pearls & Pitfalls

  • Consider antipsychotic and antiemetic medications as causes of sudden, unexplained dystonia.

Primary generalized dystonia (DYT1 dystonia)

This rare dystonia is progressive and characterized by sustained, often bizarre postures. It is often inherited as an autosomal dominant disorder with partial penetrance due to mutations in the DYT1 gene (TOR1A pathogenic variant); in some family members, the gene is minimally expressed. For example, some carriers have no symptoms (a forme fruste of the disorder) or only dystonic tremor.

Symptoms of primary generalized dystonia usually begin in childhood with inversion and plantar flexion of the foot while walking. At first, the dystonia may affect only the trunk or leg but often progresses to affect the whole body, usually moving cephalad. Patients with the most severe form may become twisted into nearly fixed postures and ultimately be confined to a wheelchair. Symptoms that begin during adulthood usually affect only the face or arms.

Mental function is usually preserved.

Dopa-responsive dystonia

This rare dystonia (also called Segawa disease) is inherited as an autosomal dominant (DYT5a, GTP cyclohydrolase 1 gene [GTPCH1]) disorder or an autosomal recessive (DYT5b) disorder (tyrosine hydroxylase deficiency).

Symptoms of dopa-responsive dystonia usually begin during childhood. Typically, one leg is affected first. As a result, children tend to walk on tiptoes. Symptoms are diurnal, worsening later in the day and improving after sleep. Walking becomes progressively more difficult, and arms and legs are affected. However, some children have only mild symptoms, such as muscle cramps after exercise. Sometimes symptoms appear later in life and resemble those of Parkinson disease Parkinson Disease Parkinson disease is a slowly progressive, degenerative disorder characterized by resting tremor, stiffness (rigidity), slow and decreased movement (bradykinesia), and eventually gait and/or... read more . Movements may be slow, balance may be difficult to maintain, and a tremor may occur in the hands during rest.

Symptoms lessen dramatically when low doses of levodopa are used. If levodopa relieves the symptoms, the diagnosis is confirmed.

Focal dystonias

Focal dystonias affect a single body part. They typically start during adulthood, after age 20 to 30 years.

Initially, the posturing may be intermittent or task-specific (and thus is sometimes described as spasms). The movements tend to be more prominent during action and less so at rest, but these differences lessen over time, often resulting in distortion of the affected body part and severe disability. However, pain is uncommon except in focal primary dystonia of the neck (cervical dystonia Cervical Dystonia Cervical dystonia is characterized by involuntary tonic contractions or intermittent spasms of neck muscles. The cause is usually unknown. Diagnosis is clinical. Treatment can include physical... read more ) and in the dystonias that occur when response to levodopa starts to wear off in Parkinson disease Parkinson Disease Parkinson disease is a slowly progressive, degenerative disorder characterized by resting tremor, stiffness (rigidity), slow and decreased movement (bradykinesia), and eventually gait and/or... read more (most often affecting the lower limb, eg, causing inversion of the foot).

Occupational dystonia consists of task-specific focal dystonic spasms triggered by performing skilled acts (eg, writer’s cramp, musician´s dystonia, the yips in golfers).

Spasmodic dysphonia consists of a strained, hoarse, or creaky voice due to focal dystonia of the laryngeal muscles.

Cervical dystonia manifests with involuntary tonic contractions or intermittent spasms of neck muscles. It has two forms:

  • Caput: When the most proximal cervical vertebrae (C1 or C2) are involved

  • Collis: When any of the lower cervical vertebrae (C3 to C7) are involved

The caput form (torticaput) involves muscles that move the skull or head joints; it is further described as anterocaput, laterocaput, or retrocaput. The collis form involves muscles that control the lower cervical vertebrae and is further described as anterocollis, laterocollis, retrocollis, or torticollis.

Segmental dystonias

These dystonias affect 2 contiguous body parts.

Meige syndrome (blepharospasm plus oromandibular dystonia) consists of involuntary blinking, jaw grinding, and grimacing, usually beginning during late adulthood. It must be distinguished from the buccal-lingual-facial chorea of tardive dyskinesia and tardive dystonia (a variant of tardive dyskinesia).

Diagnosis of Dystonias

  • Clinical evaluation

Diagnosis of dystonia is clinical.

Treatment of Dystonias

  • For generalized dystonia, anticholinergic medications, muscle relaxants, or both

  • For focal or segmental dystonia, botulinum toxin injections to paralyze muscles

  • Sometimes a neurosurgical procedure

Generalized dystonia that is severe or does not respond to medications may be treated with deep brain stimulation of the globus pallidus interna (GPi), a stereotactic neurosurgical procedure. In some cases, stereotactic unilateral ablative surgery of the GPi is indicated.

For focal or segmental dystonias or for generalized dystonia that affects mainly one body part, the treatment of choice is

  • Purified botulinum toxin type A or B injected into the affected muscles, done with or without electromyographic guidance and by an experienced practitioner

Botulinum toxin weakens excessive muscular contractions through chemodenervation, but it does not alter the abnormal brain circuitry that causes dystonia. Toxin injection is most effective for blepharospasm and torticollis but can be very effective for most other forms of focal dystonia. Dosage varies greatly. Treatments must be repeated every 3 to 4 months because the toxin's duration of activity is limited. Repeating injections before the 3 months have elapsed may cause antibodies against botulinum toxin to develop and thus lessen the toxin's benefit. In some patients, repeated injections, even with dosing intervals > 3 months, cause antibodies against the toxin to develop. However, not all of these antibodies neutralize botulinum toxin.

Treatment references

Key Points

  • Dystonias cause abnormal postures and/or movements that may resemble tremor, which may be sustained or intermittent.

  • Focal dystonias are common and usually begin during adulthood.

  • Generalized dystonia may be inherited or secondary to another disorder or a medication.

  • Diagnosis is clinical.

  • Treat generalized dystonias with anticholinergic medications and/or muscle relaxants; treat focal or segmental dystonias and generalized dystonias that affect mainly one body part with botulinum toxin injections.

Drugs Mentioned In This Article

Drug Name Select Trade
Gimoti, Metozolv, Reglan
Compazine, Compazine Rectal, Compazine Solution, Compazine Syrup, Compro
INBRIJA, Larodopa
ED Baclofen, FLEQSUVY, Gablofen, Lioresal, Lioresal Intrathecal, LYVISPAH, OZOBAX, OZOBAX DS
Ceberclon , Klonopin
NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
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