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Dystonias

by Hector A. Gonzalez-Usigli, MD, Alberto Espay, MD

Dystonias are sustained involuntary muscle contractions of antagonistic muscle groups in the same body part, leading to abnormal posturing or jerky, twisting, intermittent spasms that can resemble tremors, athetosis, or choreoathetosis. 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 drugs, muscle relaxants, and benzodiazepines. Severe segmental or generalized dystonia that is refractory to treatment may require surgery.

Dystonia may be primary (idiopathic) or secondary to degenerative or metabolic CNS disorders (eg, Wilson disease, pantothenate kinase‒associated neurodegeneration [PKAN] associated with PANK2 mutations [previously, Hallervorden-Spatz disease], various lipidoses, multiple sclerosis, cerebral palsy, stroke, brain hypoxia) or drugs—most often antipsychotics (eg, phenothiazines, thioxanthenes, butyrophenones) and antiemetics (eg, metoclopramide, prochlorpromazine). Disordered movement that appears to be athetosis or choreoathetosis may be caused by dystonia.

Pearls & Pitfalls

  • Consider antipsychotic and antiemetic drugs 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; in some family members, the gene is minimally expressed. Asymptomatic siblings of patients (carriers) may have a forme fruste of the disorder.

Symptoms 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 grotesque, 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 is hereditary. Symptoms usually begin during childhood. Typically, one leg is affected first. As a result, children tend to walk on tiptoes. Symptoms worsen at night. 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. 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

These dystonias affect a single body part. They typically start during adulthood, after age 20 to 30 yr. 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) and in the dystonias that occur when response to levodopa starts to wear off in Parkinson disease (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 is involuntary tonic contractions or intermittent spasms of neck muscles (see Cervical Dystonia).

Segmental dystonias

These focal 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

Diagnosis is clinical.

Treatment

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

  • For focal or segmental dystonia, botulinum toxin injections to paralyze motor nerves (chemodenervation)

For generalized dystonia, an anticholinergic drug (trihexyphenidyl 2 to 10 mg po tid, benztropine 3 to 15 mg po once/day) is most commonly used; the dose is slowly titrated to target. A muscle relaxant (usually baclofen), a benzodiazepine (eg, clonazepam), or both may provide adjunctive benefit. Generalized dystonia that is severe or does not respond to drugs may be treated with deep brain stimulation of the globus pallidus interna, a stereotactic neurosurgical procedure.

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, ideally done with 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 mo because the toxin's duration of activity is limited. However, in a few cases, when the toxin is repeatedly injected, this treatment becomes less effective because neutralizing antibodies against the toxin protein develop; not all antibodies that develop neutralize the toxin.

Key Points

  • Dystonias cause abnormal postures and/or twisting, jerky movements.

  • Focal dystonias are common and usually begin during adulthood.

  • Generalized dystonia is usually secondary to a disorder or drug and rarely a primary disorder.

  • Diagnosis is clinical.

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

Cervical Dystonia

(Spasmodic Torticollis)

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 therapy, drugs, and selective denervation of neck muscles with surgery or locally injected botulinum toxin.

In cervical dystonia, contraction of the neck muscles causes the neck to turn from its usual position. It is the most common dystonia.

Spasmodic (adult-onset) torticollis is the most common form of cervical dystonia. It is usually idiopathic. A few patients have a family history, and in some of them, a genetic cause (eg, DYT6, DYT7 ) has been identified. Some of these patients have other dystonias (eg, of the eyelids, face, jaw, or hand).

Cervical dystonia can be congenital or secondary to other conditions such as lesions of the brain stem or basal ganglia or use of dopamine -blocking drugs (eg, haloperidol).

Rarely, dystonia has a psychogenic cause. In this type of dystonia, pathophysiology is not well understood; however, changes in brain function have been detected by functional neuroimaging. In many cases, an emotional stressor or an abnormal core of beliefs is identified as a trigger. In such cases, a multidisciplinary team, including a neurologist, psychiatrist, and psychologist, is necessary.

Symptoms and Signs

Symptoms may begin at any age but usually begin between ages 20 and 60, with a peak between ages 30 and 50.

Symptoms usually begin gradually but may begin suddenly. Sometimes symptoms begin with a tremor that rotates the neck (in a no-no gesture). The cardinal symptoms and signs are painful tonic contractions or intermittent spasms of the sternocleidomastoid, trapezius, and other neck muscles, usually unilaterally, that result in an abnormal head position. Sternocleidomastoid muscle contraction causes the head to rotate to the opposite side and the neck to flex laterally to the same side. Rotation may involve any plane but almost always has a horizontal component. Besides rotational tilting (torticollis), the head can tilt laterally (laterocollis), forward (anterocollis), or backward (retrocollis, common when dopamine -blocking drugs are the cause). Patients may discover sensory or tactile tricks that lessen the dystonic posturing or tremor (eg, touching the face on the side contralateral to the deviation). During sleep, muscle spasms disappear.

Spasmodic torticollis ranges from mild to severe. Usually, it progresses slowly for 1 to 5 yr, then plateaus. About 10 to 20% of patients recover spontaneously within 5 yr of onset (usually in milder cases with onset at a younger age). However, it may persist for life and can result in restricted movement and postural deformity.

Diagnosis

  • Clinical evaluation

The diagnosis is based on characteristic symptoms and signs and exclusion of alternative diagnoses, as in the following:

  • Tardive dyskinesia can cause torticollis but can usually be distinguished by a history of chronic antipsychotic use and involuntary movements in muscles outside of the neck.

  • Basal ganglia disorders and occasionally CNS infections can cause movement disorders but usually also involve other muscles; CNS infections are usually acute and cause other symptoms.

  • Neck infections or tumors are usually differentiated by features of the primary process.

  • Antipsychotics and other drugs can cause acute torticollis, but the symptoms usually develop in hours and resolve within days.

Treatment

  • Physical measures

  • Sometimes botulinum toxin or oral drugs

Spasms can sometimes be temporarily inhibited by physical therapy and massage, including sensory biofeedback techniques (eg, slight tactile pressure to the jaw on the same side as head rotation) and any light touch.

Injections of botulinum toxin type A or B into the dystonic muscles can reduce painful spasms for 1 to 4 mo in about 70% of patients, restoring a more neutral position of the head. However, in a few cases, when the toxin is repeatedly injected, it becomes less effective because neutralizing antibodies against the toxin develop.

Oral drugs can usually relieve pain, but they suppress dystonic movements in only about 25 to 33% of patients. Anticholinergic drugs, such as trihexyphenidyl 10 to 25 mg po once/day or bid, may help, but adverse effects may limit their use; benzodiazepines (particularly clonazepam 0.5 mg po bid), baclofen, and carbamazepine may help. All drugs should be started in low doses (eg, trihexiphenidyl 2 mg po tid). Doses should be increased until symptoms are controlled or intolerable adverse effects (particularly likely in the elderly) develop.

Surgery is controversial. The most successful surgical approach selectively severs nerves to affected neck muscles, permanently weakening or paralyzing them. Results are favorable when the procedure is done at centers with extensive experience.

Key Points

  • Spasmodic torticollis is a common adult-onset cervical dystonia and is usually idiopathic.

  • Diagnosis is clinical and involves exclusion of tardive dyskinesia, basal ganglia disorders, CNS infections, neck infections and tumors, and drugs.

  • Treatment is most often physical measures, botulinum toxin injection, and/or oral drugs.

Resources In This Article

Drugs Mentioned In This Article

  • Drug Name
    Select Trade
  • REGLAN
  • LIORESAL
  • No US brand name
  • COGENTIN
  • KLONOPIN
  • HALDOL
  • TEGRETOL

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