Limb dystonia …

Movement Disorders

Updated 01.12.2026
Released 08.31.1995
Expires For CME 01.12.2029

Limb dystonia

Authors: Aparna M Prabhu MD MRCP, Shikhar Khurana MD

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Editor: Robert Fekete MD

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Limb dystonia

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Introduction

Overview

Limb dystonia is a type of dystonia consisting of involuntary contractions of the arms or legs associated with abnormal posturing, repetitive movements, and functional impairment. In this article, the authors review current knowledge on limb dystonias as well as updates on the classification, genetics, and pathophysiology of limb dystonia. The main clinical features of limb dystonia, together with advances in the etiology, pathogenesis, and treatment, are also reviewed, including the rapidly expanding genetic landscape and the emergence of novel therapeutic modalities like MR-guided focused ultrasound.

Key points

	• Dystonia is classified based on both clinical characteristics (age of onset, body distribution, temporal pattern, and associated clinical features) and etiology (underlying nervous system pathology: inherited, acquired, or idiopathic).
	• Early-onset dystonia is rare, usually affects one or both lower limbs, and often generalizes, whereas adult-onset dystonia is relatively common, typically starts in the upper limbs, and remains focal. Up to 20% of all dystonias have an identifiable genetic cause.
	• Writer’s cramp is the most common task-specific upper limb dystonia.
	• Suspected secondary limb dystonias should prompt a search for structural brain lesions and heredo-metabolic causes (eg, Wilson disease or neurodegeneration with brain iron accumulation).
	• Limb dystonia may be the initial presenting sign in neurodegenerative disorders like Parkinson disease, progressive supranuclear palsy, and corticobasal ganglionic degeneration.
	• Current models suggest that dystonia results from dysfunction within a distributed sensorimotor network involving abnormal plasticity, impaired cortical and spinal inhibition, and aberrant cerebellar–basal ganglia–cortical connectivity. Repetitive motor activity and peripheral injury may act as environmental triggers in genetically susceptible individuals.
	• Botulinum toxin injections remain first-line for focal limb dystonias, whereas deep brain stimulation is considered for refractory or generalized cases.

Historical note and terminology

The term dystonia is defined as a sustained, involuntary contraction of muscle that produces an abnormal posture and frequently causes twisting and turning. The task specificity and presence of sensory tricks make dystonia unique among other neurologic symptoms. In 1830, Charles Bell described hand dystonia in professional writers followed by Gowers’ description of dystonia in musicians. Oppenheimer described generalized dystonia in the early 20th century, naming it dystonia musculorum deformans (23). As dystonia is not a disease of muscle, the term primary torsion dystonia is now preferred (76). Over the last century, the classification of this disorder has evolved from a clinical characterization, such as focal, segmental, or generalized dystonia, to encompass a parallel molecular biological dimension with acknowledgement of affected chromosomal loci, mutated proteins, and biochemical dysfunctions. Currently, dystonia is classified along two axes: Axis I describes the clinical characteristics (age of onset, body distribution, temporal pattern), and Axis II describes the etiology (eg, structural, inherited, acquired, or idiopathic), a framework that continues to be refined with new genetic and pathophysiologic insights (02). Until recently, inherited dystonias have been named using DYT acronym followed by a number (eg, DYT1). However, a new nomenclature was introduced so that only isolated genetic dystonias are designated “DYT” followed by the affected gene (eg, DYT-TOR1A, instead of DYT1). The combined dystonias will be named using a double prefix, including both dystonia and the associated phenotype (eg, DYT/PARK-TAF1, instead of DYT3).

Focal dystonia is defined as dystonia with only one body region affected. Typical examples of focal forms are blepharospasm, oromandibular dystonia, cervical dystonia, laryngeal dystonia, and writer’s cramp.

Writer's cramp, a task-specific and common dystonia of the hand, underscores many difficulties in the diagnosis of this disorder. Historically, patients may initially notice tightness or stiffness with writing prior to diminished writing speed and cramping with prolonged writing. The cramping of the hand will be present only with writing and will disappear almost immediately after stopping this activity. Physical examination of affected patients frequently reveals normal findings, except when performing certain tasks or adopting a certain posture. As a result of this, the condition was once thought to be of psychogenic origin (70). Fortunately, increasing electrophysiological studies and documentation of abnormal findings in patients with limb dystonia have improved the acceptance of this disorder as one resulting from neurologic mechanisms (28; 08). Traditional views regarded dystonia primarily as a basal ganglia disorder, with dysfunction localized to these deep brain nuclei. Research has expanded this perspective, describing dystonia as a network disorder involving the basal ganglia, cerebellum, and cerebral cortex. The motor network model proposed by Jinnah and colleagues highlight dystonia as arising from abnormal interactions within this distributed sensorimotor network rather than from a single anatomical lesion (31). This conceptual shift informs current approaches to diagnosis and treatment, including deep brain stimulation, which targets multiple nodes within these networks.

Clinical manifestations

Presentation and course

	• Early-onset limb dystonia typically begins in the lower extremities and commonly generalizes, whereas adult-onset limb dystonia usually remains focal.
	• Writer’s cramp, the most common task-specific limb dystonia, is characterized by abnormal flexion or extension of the fingers, wrist, or elbow triggered by writing.
	• Occupational and sports-related dystonias result from repetitive stereotyped movements in skilled professional or recreational activities.
	• Limb dystonia appearing in patients older than 30 years may signal underlying neurodegenerative disorders, particularly idiopathic Parkinson disease.

Limb dystonia consists of sustained, repetitive, and patterned contractions of muscles producing an abnormal posture of the upper or lower limb that may be present at rest, when changing position, or when performing a specific motor activity.

$Dystonia (limb) triggered by ulnar fracture and casting$

Dystonia (limb) triggered by ulnar fracture and casting

This woman was well until she sustained an ulnar fracture playing racquetball, requiring a cast. After the cast was removed, she noted a dystonic deformity of her right hand. This peripherally induced dystonia subsequently progres...

Focal, segmental, and generalized dystonic disorders may produce limb dystonia, and are increasingly related to genetic abnormalities. Involvement of the upper extremity is most often associated with "writer’s cramp," a task-specific, focal dystonia, and may evolve from a dystonia triggered by a single activity to one triggered by multiple other activities to one also present at rest. In adult-onset limb dystonia, the dystonia usually remains confined to the originally affected location; however, an initial presentation below 18 years of age or with bilateral lower extremity onset is usually associated with progression to generalized dystonia.

Writer’s cramp postures may produce any combination of finger flexion or extension, wrist flexion or extension, and elbow flexion.

Myoclonus-dystonia syndrome, alcohol responsive (2)

Three members of a family with alcohol-responsive, myoclonus-dystonia (DYT11) with a mutation in the epsilon-sarcoglycan (SGCE) gene on chromosome 7q (Cazurro-Gutiérrez A, Marcé-Grau A, Correa-Vela M, et al. ε-Sarcogly...

Although symptoms of dystonia disappear with sleep, patients with limb contractures will not have diminished limb tone at this time. In addition to dystonic muscle contraction from sustained agonist and antagonist muscle contraction, less sustained, rhythmic alteration of agonist and antagonist pairs may produce hand tremor. Classification of "primary writing tremor" as a dystonic or tremor disorder remains controversial (57).

Writing tremor helped by botulinum toxin

This man has a task-specific writing tremor on attempting to write or draw freehand. The tremor improved markedly with botulinum toxin injections into his forearm muscles. (Contributed by Dr. Joseph Jankovic.)

Patients with extensor muscle involvement may report increasing difficulty putting the pen on paper, the thumb or fingers lifting off the pen, and a need to lean further and further towards the writing surface to compensate for wrist. In this instance, a faint script may be noted, as the patient has difficulty maintaining contact between the pen and paper. Conversely, a flexor type writer’s cramp will produce bold and illegible script. Flexion of the fingers produces the illegibility by decreasing ability to produce space between letters and loops, whereas wrist flexion increases the boldness of the script. In either situation, patients may adopt a printing style of handwriting, perhaps to allow for each letter to become a discreet component, instead of using more prolonged sequences of activity.

Occupational dystonia is a term used to describe patients with dystonic muscle contractions producing employment disability. Occupations most often associated with these disorders are associated with chronic, stereotyped movements of the hands and fingers. Typists, stenographers, musicians, blackjack dealers, dentists, and surgeons have been reported to have this condition. A unique form of occupational dystonia termed "Blacksmith dystonia" was reported, involving proximal arm dystonia specifically triggered by repetitive hammering movements in blacksmithing (33).

Dystonia (task-specific) related to banjo playing

This banjo player develops right-hand dystonia whenever he starts playing the banjo. (Contributed by Dr. Joseph Jankovic.)
Dystonia (task-specific) related to flute playing

This flutist develops dystonic flexion of the 5th digit whenever she starts playing a flute. (Contributed by Dr. Joseph Jankovic.)
Dystonia (task-specific) related to violin playing

This professional violinist had to cut short his career due to dystonic flexion of the 3rd and 4th digits of his left hand; the dystonic flexion occurs whenever he starts playing the violin. (Contributed by Dr. Joseph Jankovic.)

Rosenkranz and colleagues suggest that different mechanisms may be involved in writers, who use their hands no more than the average worker, and in musicians, where there is prolonged, repetitive use of the hands (66). Similar sports-related dystonias have also been reported in trap shooters, darts players, and golfers. The sudden jerk-like movement of the extensor muscles of the lead forearm, when moving the club toward the ball when putting, is in golfer’s terminology, the "yips" (19). A summary of this phenomenon by Smith and colleagues found that this phenomenon usually affected low-handicap golfers in their mid-40s, usually after 20 to 30 years of golf participation at a frequency greater than 75 rounds annually (75). Adler and colleagues report that yips-affected golfers usually have had greater exposure to the sport (37.6 vs. 25.9 years, p=0.03) and are better players (handicap 3.5 vs. 6.3, p=0.01) than nonaffected golfers (01).

Limb dystonia involving the legs usually produces knee extension, plantar flexion, and toe flexion, but may involve any leg muscle. The appearance of a spontaneously dorsiextended big toe may also be seen within the context of limb dystonia ("Babinski dystonia"-also known as striatal toe). Leg dystonia, in patients beyond 30 years of age, should prompt concern for idiopathic Parkinson disease. However, primary adult-onset focal lower extremity dystonia has been reported (69; 57). In children, the development of this posture may represent the initial onset of primary torsion dystonia or dopa-responsive dystonia.

Prognosis and complications

The most significant prognostic indicator in limb dystonia is age of onset. Patients reporting the onset of symptoms, prior to the age of 18, are much more likely to develop generalized dystonia.

Usually, complications of limb dystonia are related to musculoskeletal changes in the affected extremity. In the leg tendon, contracture may lead to foot eversion or inversion, foot shortening, or Achilles tendon shortening that causes increasing gait disability. Involvement of the forearm and hand may also lead to tendon contracture, but also produces median and ulnar nerve entrapment symptoms.

Clinical vignette

The first subject was a 15-year-old girl who was referred to a psychologist for poor school performance attributed to oppositional defiance disorder; she would not complete her writing assignments. The patient presented with her mother and reported difficulty with writing since first or second grade. She remembers being corrected for her poor handwriting posture by almost all of her elementary teachers but could not make adjustments to hold the pen or pencil correctly. Several attempts at writing implement modifications also did not help. The remainder of her neurologic examination and further, limited work-up at the time were unremarkable. She was given the diagnosis of writer’s cramp and became successful with minor modification of her in-class work and the use of a home computer to complete her assignments.

The second subject was a 70-year old woman with a history of mild hypertension and a previous small, left putamen infarction. She was hospitalized for mild weakness that resolved satisfactorily within several days. Her work-up was otherwise negative, and she began taking 325 mg of aspirin daily. During the 8 months after discharge, she developed right great toe extension, toe abduction and increased plantar arch. She responded to botulinum toxin A or Botox(r) injection of 50 units to the extensor hallucis longus muscle and 30 units to her flexor hallucis brevis muscle.

Biological basis

Etiology and pathogenesis

Until recently, limb dystonia has been classified as primary or secondary based on etiology. Primary limb dystonia refers to a syndrome where dystonia is the only neurologic finding with the exception of tremor. Secondary dystonia refers to a dystonic syndrome with an identifiable cause and is frequently accompanied by other neurologic signs (ie, cognitive dysfunction, pyramidal tract signs, visual disturbances). Revisions replaced the older “primary” and “secondary” labels with isolated dystonia, in which dystonia is the only motor sign apart from possible tremor, and combined dystonia, where dystonia co-occurs with other movement disorders. Axis I details clinical descriptors—age at onset, body distribution, and temporal pattern—whereas Axis II groups etiologies as structural, inherited, acquired, or idiopathic (18; 02).

Table 1. Classification of Dystonias

Axis I: clinical characteristics
	• Age at onset
		- Infancy (under 2 years) - Childhood (3 to 12 years - Adolescence (13 to 20 years) - Early adulthood (21 to 40 years) - Late adulthood (over 40 years)
	• Family history
		- Sporadic - Familial - Unknown
	• Body distribution
		- Focal (one isolated body region) - Segmental (two or more contiguous regions) - Multifocal (two or more noncontiguous regions) - Hemidystonia (half the body) - Generalized (trunk plus two other sites)
	• Temporal dimensions
		Onset - Acute - Subacute - Gradual Course - Static - Progressive - Fluctuating Variability - Paroxysmal - Diurnal variability - None
	• Phenomenology
		Relationship with voluntary movement - Task-specific (occurs only with one specific voluntary motor task) - Action-induced (occurs with a variety of voluntary actions) - Occurs also at rest (unrelated to voluntary movements) - Fixed (continuous and unalleviated) Additional characteristics - Alleviating maneuvers (sensory trick, geste antagoniste) - Tremulous (tremor-like) - Jerky (myoclonic-like)
	• Isolated or combined
		Isolated Combined - With another movement disorder - With other neurologic features - With systemic features
Axis II: etiology and pathogenesis
	• Genetic
		- Autosomal dominant - Autosomal recessive - X-linked - Mitochondrial - Unknown / variant of uncertain significance
	• Acquired
		- Drug- or toxin-induced - Brain injury / stroke - Infection or inflammation - Neoplastic - Other acquired cause
	• Neuroanatomical substrate
		- Focal structural lesion - Multifocal or diffuse lesions - No structural pathology identified
	• Pathogenic mechanism
		- Developmental - Degenerative - Metabolic - Immune / inflammatory - Unknown

Dystonias have been associated with genetic mutation in up to 19% of cases in a exome wide sequencing study of 728 families (87). Early-onset primary limb dystonia is rare, often genetic, and typically starts in one or both lower extremities, eventually generalizing. DYT1 dystonia (DYT-TOR1A) is the most frequent early-onset genetic limb dystonia and is caused by a GAG deletion in the TOR1 gene. In contrast to DYT1 dystonia, DYT6 dystonia (DYT-THAP1) is characterized by onset in cranial-cervical and laryngeal areas, but it also tends to generalize. Other genetic forms of dystonia involving the limb have been designated as DYT4 (DYT-TUB4A); DYT5 (DYT-GCH1), dopa-responsive dystonia; DYT11 (DYT-SGCE), myoclonus dystonia; or DYT12 (DYT-ATP1A3), rapidly progressive dystonia and parkinsonism.

In spite of growing evidence for the genetic inheritance of dystonia, the vast majority of cases of focal primary dystonia are sporadic, with no definite genetic factor having been identified. The current known genes that produce primary dystonia are summarized in Table 2. Whole-exome sequencing revealed several new genes that have been strongly associated with segmental dystonia: TUBB4 (DYT4), CIZ1 (DYT23), ANO3 (DYT24), GNAL (DYT25), and ATP1A2 (DYT27). A couple of newly identified genes have been linked with dystonia: PRKRA, TAF1, KMT2B, VPS16, and VAC14 HPCA (38; 04; 32). EIF2AK and AOPEP have been shown to cause isolated dystonia (81).

Table 2. Clinical and Molecular Information on the Primary Inherited Dystonias

DYT1-TOR1 (Oppenheim dystonia; DYT1)
	• Location: 9q34 (GAG deletion); Torsin A • Inheritance pattern: autosomal dominant (incomplete penetrance) • Phenotype: childhood and adolescent; limb onset
DYT-HPCA (DYT2)
	• Location: 1p35.1 • Inheritance pattern: autosomal recessive • Phenotype: Spanish gypsies; not confirmed
DYT-TAF1 (Lubag; DYT3)
	• Location: Xq13.1, TAF1 • Inheritance pattern: x-linked recessive • Phenotype: parkinsonism-dystonia (Lubag, Philippines)
DYT-TUB4A (DYT4)
	• Location: 19p.13.12-13, TUBB4a • Inheritance pattern: autosomal dominant • Phenotype: whispering dysphonia in Australian family
DYT-GCH1 (Segawa disease; DYT5/DYT14)
	• Location: 14q22.1, GTP cyclohydrolase 1 (DYT5a) and 11p11.5 tyrosine hydroxylase (DYT5b) • Inheritance pattern: autosomal dominant (incomplete penetrance) for DYT5a, autosomal recessive for DYT5b (DYT14) • Phenotype: dopa-responsive dystonia
DYT-THAP1 (DYT6)
	• Location: 8p21-p22, THAP1 • Inheritance pattern: autosomal dominant • Phenotype: Mennonite and Amish dystonia with mixed face, eyes, and neck or limb onset; childhood or adult onset
DYT7
	• Location: 18p • Inheritance pattern: autosomal dominant (incomplete penetrance) • Phenotype: German families; adult neck, face, or limb onset
DYT-MR1 (DYT8)
	• Location: 2q34, MR1 (myofibrillogenesis regulator 1) • Inheritance pattern: autosomal dominant (incomplete penetrance) • Phenotype: paroxysmal nonkinesigenic dyskinesia
DYT-SLC2A1 (DYT9)
	• Location: 1p21, SLC2A1 • Inheritance pattern: autosomal dominant • Phenotype: paroxysmal choreoathetosis with episodic ataxia and spasticity
DYT-PRRT2 (DYT10)
	• Location: 16p11.2-q12.1, PRRT2 • Inheritance pattern: autosomal dominant (incomplete penetrance) • Phenotype: paroxysmal kinesigenic choreoathetosis
DYT-SGCE (myoclonus dystonia; DYT11)
	• Location: 7q21, SGCE, epilson sarcoglycan • Inheritance pattern: autosomal dominant (incomplete penetrance) • Phenotype: myoclonus dystonia; alcohol-responsive
DYT-ATP1A3 (DYT12)
	• Location: 19q13, ATP1A3 • Inheritance pattern: autosomal dominant (incomplete penetrance) • Phenotype: rapid-onset dystonia-parkinsonism
DYT13
	• Location: 1p36.13-32 • Inheritance pattern: autosomal dominant (incomplete penetrance) • Phenotype: Italian family; cranial or cervical dystonia
DYT15
	• Location: 18p11 • Inheritance pattern: autosomal dominant • Phenotype: progressive dystonia, parkinsonism, dysphagia, ataxia • Testing available: no

DYT16 (PRKRA)
	• Location: 2q31.2, stress response protein PRKRA • Inheritance pattern: autosomal recessive • Phenotype: dystonia, parkinsonism


DYT17
	• Location: 20p11.2-q13.12 • Inheritance pattern: autosomal recessive • Phenotype: juvenile onset with torticollis
DYT-SLC2A1 (DYT18)
	• Location: 1p35-p31.3 SLC2A1 gene- GLUT1 • Inheritance pattern: autosomal dominant • Phenotype: paroxysmal exertional dyskinesia (PED)
DYT19
	• Location: 16q13-q22 • Inheritance pattern: autosomal dominant • Phenotype: paroxysmal kinesigenic dyskinesia without epilepsy
DYT20
	• Location: 2q31 • Inheritance pattern: autosomal dominant • Phenotype: paroxysmal nonkinesigenic dyskinesia (PNKD2)
DYT-CIZ1 (DYT23)
	• Location: 9q34 CIZ1 • Inheritance pattern: autosomal dominant • Phenotype: adult onset, cervical dystonia
DYT-ANO3 (DYT24)
	• Location: 11p14.2 ANO3 • Inheritance pattern: autosomal dominant • Phenotype: adult onset, cervical dystonia +/- brachial dystonia
DYT-GNAL (DYT25)
	• Location: 18p11.21 • Inheritance pattern: autosomal dominant • Phenotype: adult onset, cervical dystonia +/- brachial dystonia
DYT-KCTD17 (DYT26)
	• Location: 22q12.3 • Inheritance pattern: autosomal dominant • Phenotype: adult onset, myoclonus-dystonia
DYT-ATP1A2 (DYT27)
	• Location: 2q37.3 COL 6A3 • Inheritance pattern: autosomal recessive • Phenotype: adult onset, cervical dystonia +/- brachial dystonia
DYT- KMT2B (DYT28)
	• Location: 19p13 • Inheritance: autosomal dominant • Phenotype: progressive dystonia in the first decade of life
DYT MECR(DYT 29)
	• Location: 1p35 • Inheritance: autosomal recessive • Phenotype: childhood onset dystonia with optic atrophy and basal ganglia abnormalities (DYTOBG)
DYT- VPS16 (DYT30)
	• Location: 20p13 • Inheritance: autosomal dominant • Phenotype: focal dystonia progressing towards generalized
Modified from (53; 68; 44; 38; 18).

Table 3. Differential Diagnosis of Dystonia

Idiopathic (primary) dystonia
	Sporadic (idiopathic torsion dystonia, ITD)
	Inherited (hereditary torsion dystonia)
		• Autosomal dominant ITD (DYT1TOR1, DYT-GCH1, DYT-THAP1, DYT-ATP1A3) • Other familial dystonias with an identified locus (DYT6, DYT7, DYT13) • Autosomal recessive DYT ATP7B (Wilson), DYT PANK2 (NBIA) • Other familial dystonias with a yet unidentified locus • X-linked DYT/PARK-TAF1
Secondary dystonia
	Dystonia-plus syndromes
		• Myoclonus dystonia • Dopa-responsive dystonia (GTP cyclohydrolase I; 114q22 and tyrosine hydroxylase deficiency; 11p11.5) • Rapid-onset dystonia – parkinsonism (DYT12; 19q13)
	Associated with neurodegenerative and dymyelinating disorders
		• Sporadic
			- Parkinson disease - Progressive supranuclear palsy - Multiple system atrophy - Corticobasal ganglionic degeneration - Multiple sclerosis - Central pontine myelinolysis
		• Inherited
			- Huntington disease - Neuronal brain degeneration with iron accumulation (NBIA) - Hypoprebetalipoproteinemia, acanthocytosis, retinitis pigments, and pallidal degeneration (HARP syndrome) - Joseph disease - Ataxia telangiectasia - Neuroacanthocytosis - Rett syndrome - Intraneuronal inclusion disease - Infantile bilateral striatal necrosis - Familial basal ganglia calcifications - Spinocerebellar degeneration - Olivopontocerebellar atrophy - Hereditary spastic paraplegia with dystonia - X-linked dystonia Parkinsonism or Lubag (pericentromeric) deletion of 18q
	Associated with metabolic disorders
		• Amino acid disorders
			- Glutamic acidemia - Methylmalonic acidemia - Homocystinuria - Hartnup disease - Tyrosinosis
		• Lipid disorders
			- Metachromatic leukodystrophy - Ceroid lipofuscinosis - Dystonic lipidosis ("sea blue" histiocytosis) - Gangliosidoses (GM1-, GM2-variants) - Hexosaminidase A and B deficiency
		• Miscellaneous metabolic disorders
			- Wilson disease - Mitochondrial encephalopathies (Leigh disease, Leber disease) - Lesch-Nyhan syndrome - Triosephosphate isomerase deficiency - Vitamin E deficiency - Biopterin deficiency
	Due to a known specific cause
		• Perinatal cerebral injury and kernicterus (athetoid cerebral palsy, delayed onset dystonia) • Infectious and postinfectious (viral encephalitis, encephalitis lethargica, Reye syndrome, subacute sclerosing panencephalitis, Jakob-Creutzfeldt disease, AIDS, tuberculosis, syphilis, acute infectious torticollis) • Paraneoplastic brainstem encephalitis • Cerebral vascular and ischemic injury • Brain tumor • Arteriovenous malformation • Head trauma and brain surgery • Whiplash injury • Peripheral trauma • Toxins (MN, CO, CS2, methanol, disulfiram, wasp sting) • Drugs (levodopa, bromocriptine, antipsychotic agents, metoclopramide, fenfluramine, flecainide, ergot agents, anticonvulsant agents, certain calcium channel blocking agents)
Other hyperkinetic syndromes associated with dystonia
	Tic disorders with dystonic tics
	Paroxysmal dyskinesias
		• Paroxysmal kinesigenic choreoathetosis • Paroxysmal dystonic choreoathetosis • Intermediate paroxysmal dyskinesia • Benign infantile dyskinesia
Functional dystonia
Pseudodystonia
	Atlantoaxial subluxation Syringomyelia Arnold-Chiari malformation Trochlear nerve palsy Vestibular torticollis Posterior fossa mass Soft tissue neck mass Congenital muscular torticollis Congenital Klippel-Feil syndrome Isaacs syndrome Sandifer syndrome Satoyoshi syndrome Stiff-person syndrome
Modified from (76)

Adult-onset primary limb dystonia affects mainly the upper limb, whereas lower limb involvement is uncommon (45). Musician dystonia has been linked with arylsulfatase G (ARSG) gene locus (39). A systematic review found that KMT2B mutation carriers frequently present with the lower limb dystonia, whereas TOR1A, PRKRA, and HPCA were frequently observed in both upper and lower ones (36). Similarly, THAP1 and ANO3 patients manifest in the upper half of the body (upper limb, neck), whereas onset in GNAL mutations present with neck dystonia.

Limb dystonia may be present, isolated, or in association with dystonia plus syndromes. In dopa-responsive dystonia (DYT-GCH1, DYT 5), dystonic posturing of lower extremities is often present together with parkinsonian features. The most common cause of dopa-responsive dystonia is Segawa disease, an autosomal dominant disorder due to mutation in the GTP cyclohydrolase 1 gene followed by an autosomal recessive form related to mutation of the tyrosine hydroxylase gene. More than 170 pathogenic GCH1 variants have now been catalogued, and clinical presentations are heterogeneous with dystonia, parkinsonism, and mood disorders.

Myoclonus-dystonia (DYT-SGCE, DYT 11) is an autosomal dominant disease that presents with myoclonic jerks of the arms with focal or segmental dystonia and is related to mutations in the epsilon sarcoglycan gene. Over 120 distinct SGCE mutations have been reported, most exhibiting paternal transmission because the maternal allele is normally silenced, causing dystonia and myoclonus in childhood or adolescence, and are frequently associated with psychiatric disorders (47; 64).

In rapid-onset dystonia parkinsonism (DYT-ATP1A3, DYT12), the typical presenting symptom is upper limb dystonia with acute onset. More than 20 mutations have been described and associated with a variety of clinical presentations (38).

The common biological pathways affected in the etiology of dystonia are defects in dopamine signaling, metabolic abnormalities, heavy metal storage, dysregulation of ion channels, abnormal gene regulation, and mitochondrial dysfunction (30).

Acquired dystonias (formerly “secondary dystonias”) are rare, with a prevalence of 7 in 100,000 (55). Acquired limb dystonias are a well-recognized result of structural brain lesions, which most commonly occur in the basal ganglia (46.2%), thalamus (28.1%), and brainstem (22.6%). Quantitative analysis now confirms a limb dystonia subgroup is linked to basal ganglia lesions, a hand dystonia subgroup to thalamic lesions, and a cervical dystonia subgroup to brainstem and cerebellar lesions (06; 13).

Extrapyramidal syndromes, such as Wilson disease, Parkinson disease, progressive supranuclear palsy, and multiple system atrophy, may be associated with limb dystonia. Parkinson disease may present with symptoms of lower limb dystonia. Patients with progressive supranuclear palsy often present with dystonic muscle contraction of the axial muscles, and some patients with corticobasal degeneration will exhibit profound limb dystonia in addition to, and sometimes masking, symptoms of the "alien-limb" phenomenon. Limb dystonia with diurnal fluctuations may be caused by dopa-responsive dystonia. Paroxysmal dystonias in the limbs may be observed in paroxysmal kinesogenic and dystonic choreoathetosis. Tonic spasms of multiple sclerosis are typically transient attacks of hemidystonia of the limbs. Reported secondary causes of dystonia include exposure to DA receptor-blocking drugs ("tardive dystonia"), hypoxic encephalopathy, head trauma, encephalitis, human immunodeficiency virus and other infections, peripheral or segmental nerve injury, reflex sympathetic dystrophy, inherited disorders (eg, Wilson disease), metabolic disorders and other inborn errors of metabolism, mitochondrial disorders, and chromosomal abnormalities (See Table 3).

Central nervous system lesions are well recognized as causes of limb dystonia. A larger analysis of 359 cases found the most common lesion etiologies to be infarcts, hemorrhage, tumors, and inflammatory conditions (13). In this cohort, the mean age of onset was 40.0 years, and the median latency from insult to dystonia was 11 weeks, although latency varied widely, with some cases occurring within a week and others more than a year later. This modern analysis confirms that basal ganglia lesions were most frequent (46.2%), with the putamen most commonly involved. Data-driven methods were used to identify distinct subgroups, and a “hand dystonia” group was linked to thalamic lesions, with 100% of patients in that subgroup having hand dystonia. Large lenticular or caudo-capsulo-lenticular lesions may give rise to foot dystonia (56). Other structural abnormalities associated with limb dystonia include cavernous angioma of the basal ganglia (40), subdural hematoma (21), left frontal meningioma (49), calcification of the head of the right caudate nucleus (48), and cervical cord lesion secondary to multiple sclerosis (83). Movement disorders after severe head injury have been reported in 13% to 66% of patients (34).

Most of our understanding of the mechanisms of dystonia comes from focal hand dystonia studies (77). Task-specific dystonia is considered to be due to a combination of environmental factors and individual vulnerability. Environmental factors like peripheral injury or repetitive use together with abnormal mechanisms of plasticity have been invoked in the pathophysiology of dystonia (58). Some of the best-studied mechanisms include reduced inhibition at cortical, subcortical, and spinal levels, abnormalities of sensory-motor integration, and maladaptive plasticity (37; 22). Writer's cramp is a task-specific dystonia that leads to involuntary hand postures during writing. Whereas prior understanding focused on peripheral physiological phenomena like muscle co-activation activity (28; 09), the modern “motor network model” proposes dystonia is a circuit disorder involving the basal ganglia, cerebellum, thalamus, and cortex. Similarly, the physiological basis has moved from peripheral muscle activity to specific central neuronal dysfunction (31).

The understanding of dystonia pathophysiology has progressed with the advances in electrophysiologic and neuroimaging techniques. These studies have linked dystonia with malfunction in the basal ganglia, sensorimotor network, and cerebello-thalamo-cortical pathway (54). fMRI and PET studies revealed functional abnormalities in patients with dystonia in the primary motor area, supplementary motor area, dorsal premotor cortex, basal ganglia, and sensorimotor areas. A comprehensive meta-analysis concluded there are no reliable gray matter alterations in idiopathic dystonia, suggesting it may be a functional disorder at the network level without consistent macroscopic structural changes (86). Electrophysiological studies using transcranial magnetic stimulation have identified abnormal neurophysiologic changes in the basal ganglia, the sensorimotor cortex, and, more recently, the cerebellum. These changes include: (1) loss of inhibition at multiple levels in the CNS with resulting excess movement, (2) an impairment of somatosensory processing and sensorimotor integration, and (3) maladaptive plasticity of sensorimotor circuits (60).

There is evidence of abnormal inhibition in the nervous system at multiple levels: lack of reciprocal inhibition at the spinal level, abnormal inhibition at the cortical level as measured by transcranial magnetic stimulation, and abnormal surround inhibition as a result of impaired GABA interneurons (37; 58; 12).

The mechanism of impaired motor regulation is now framed within a broader motor network model involving the basal ganglia, cerebellum, thalamus, and cortex. Although early work emphasized abnormal cortical sensory processing, large-scale structural neuroimaging meta-analyses and voxel-based morphometry studies in idiopathic dystonia show that defective sensorimotor integration remains central but reflects dysfunction across distributed circuits (42). Evidence from lesion-induced dystonia and impaired cerebellum-dependent motor learning supports the view that dystonia arises from disordered network interactions rather than isolated cortical changes (13). Another mechanism involved in dystonia pathophysiology is the altered plasticity, now recognized within the updated consensus classification as a defect in neurotransmitter signaling and circuit-level motor learning. The nervous system uses plasticity as a means to adapt flexibly to changes required in a dynamic environment and to facilitate learning and memory. Abnormally enhanced plasticity was demonstrated in patients with dystonia. Studies show subtype-specific abnormalities in cerebellum-dependent tasks, such as conditioned eye-blink reflexes. These findings suggest that dystonia reflects impaired, circuit-specific plasticity within the broader motor network model (02).

Diagnostic workup

The diagnosis of primary dystonia should be considered in any patient with an abnormal posture and a family history of cramps, spasms, tremor, and crippling conditions. Information concerning age at onset, initial and subsequent areas of involvement, course and progression, tremor or other movement disorders, possible birth injury, developmental milestones, and exposure to neuroleptic medications as well as a family history of dystonia, parkinsonism, or other movement disorders should be reviewed. The diagnosis of dystonia now follows the two-axis classification system, beginning with detailed clinical characterization (Axis I) of age at onset, body distribution, temporal pattern, and associated features. Early onset (< 30 years), generalized distribution, or a strong family history strongly suggest a genetic cause. Evidence of other conditions known to produce dystonia, but associated with other neurologic dysfunctions (eg, cognitive, pyramidal, sensory, or cerebellar deficits) should be evaluated along with secondary causes of dystonia. Modern genetic evaluation has shifted from single-gene tests to exome or panel sequencing, though most adult-onset focal dystonias remain idiopathic. Screening for Wilson disease is essential in patients under 50, and targeted metabolic or storage disease testing may be considered (02). Electromyography may be performed if carpal tunnel syndrome is suspected as a complication of the dystonia. Imaging of the brain (MRI) should be performed in adult-onset patients with a short history of limb dystonia to screen for secondary forms of dystonia. F-DOPA scans are useful to differentiate between dopa-responsive dystonia and juvenile Parkinson disease presenting with dystonia.

Management

Therapy of dystonia can be classified in the following categories: (1) pharmacologic treatment, (2) chemodenervation with botulinum toxin, (3) surgical (deep brain stimulation), and (4) physical therapy.

Anticholinergic drugs are effective in most types of dystonia but especially in the focal dystonia. Trihexyphenidyl and benztropine can be used with variable degree of efficacy. Side effects are numerous and include dryness of the mouth, constipation, urinary retention, aggravation of glaucoma, blurred vision, and drowsiness (35). In some patients with a component of tremor, beta-blocking agents may be useful (65). Baclofen or tizanidine are commonly used in treating symptoms of dystonia and may be most appropriate in patients with a history of hypoxic or traumatic brain injury. Benzodiazepines, particularly if patients report sleep difficulty, are useful as adjunct therapy. In one series of 190 patients, approximately one-third of patients experienced some benefit from medical therapy, and included anticholinergics, benzodiazepines, clonazepam, and diazepam (06). Other muscle relaxants with possible beneficial effects for muscular pain in dystonia include cyclobenzaprine, methocarbamol, orphenadrine, or chlorzoxazone. Tetrabenazine, a dopamine depleting drug, has been used in patients with dystonia, particularly those with tardive dystonia, and it represents another option for those patients that do not respond to anticholinergics. Dopaminergic therapy should be used if dopa responsive dystonia is suspected. This form of dystonia is often linked to pathogenic variants in the GCH1 gene and is characterized by diurnal fluctuations in symptoms. The gene NR4A2 has also been associated with levodopa-responsive dystonia. In paroxysmal kinesigenic dyskinesias, carbamazepine in low dose is frequently highly effective (02).

When medical treatment is failing, botulinum toxin is usually the most effective treatment in focal dystonia (41; 24). Botulinum toxin injections are highly effective in the treatment of limb dystonia (10). The American Academy of Neurology concluded in 2008 that botulinum toxin should be offered for focal upper extremity dystonia (level B evidence) and can be considered for lower limb dystonia (level C) (71). An appraisal of the evidence available for use of botulinum toxin in limb dystonia supported a level B recommendation for both abobotulinumtoxinA and onabotulinumtoxinA (25; 72).

A major advance is daxibotulinumtoxinA (DAXI), a novel BoNT formulation designed for extended duration. The pivotal ASPEN-1 phase 3 trial provided class I evidence, demonstrating a median duration of effect of 24.0 weeks for the 125 U dose, approximately twice that of conventional agents, offering the potential for more stable symptom control and a reduced treatment burden (11). Injection strategy is determined by a combination of functional observation, muscle palpation, ultrasound guidance, and electrophysiologic assessment. Muscle identification methods vary from clinician to clinician. Examples include using mirror dystonia as guidance (73; 74) in addition to plain observation of the dystonic posture while performing the task. Data confirming the additional benefit of electromyographic guidance or electrical stimulation remain controversial (50; 05), and functional benefit may be a combination of chemodenervation of muscle fibers as well as intrafusal fibers. Prolonged benefit in subjects with writer’s cramp has been associated with delayed recovery of the tonic vibration reflex, perhaps indicating a physiologic alteration of intrafusal-fiber-mediated sensorimotor integration (82). Because approximately 20% of patients will eventually stop the botulinum injections due to treatment failure it was proposed that ultrasound guidance or electromyography be used in these patients (43).

Because focal hand dystonia is difficult to treat pharmacologically and the injections with botulinum toxin can be challenging, alternative treatments are necessary. Based on the identification of impaired plasticity in the somatosensory cortex of dystonia patients, several rehabilitation techniques have been proposed, such as limb or finger immobilization and sensory motor retraining (89). Advances in our understanding of the pathophysiology of dystonia have led to new treatment strategies, including behavioral training strategies and noninvasive brain stimulation techniques (07).

Transcranial magnetic stimulation has been used in writer’s cramp as a therapeutic approach (52). TMS can be used as a therapeutic tool to treat focal hand dystonia when pharmacological options or injections of botulinum toxin are ineffective (60; 63). Sensorimotor training in conjunction with transcranial direct current stimulation seems to be effective in task-specific dystonia (67; 59). Longer-term cerebellar repetitive TMS combined with therapy produced modest benefits in cervical dystonia, though single-session studies showed limited efficacy in writer’s cramp (31).

In a study of 54 pianists with musician’s dystonia, the following multiple therapies have been tried: retraining (87%), hand therapy (42%), relaxation techniques (38%), physiotherapy (30%), psychotherapy (23%), acupuncture (21%) and body techniques (21%); 81.5% reported improvement, and 5.6% reported complete recovery, but only 43% had objective evidence of improvement in task-specific motor performance (84).

Deep brain stimulation (DBS) should be considered in patients with disabling limb dystonia refractory to medical or botulinum toxin treatment (34). Most often, this therapy is considered in patients with generalized or posttraumatic dystonia; however, patients with segmental or focal dystonia may benefit as well. Many studies have identified GPI as the target of choice for dystonia (17), and controlled studies showed that deep brain stimulation of GPI is efficient in treating dystonia and efficacious 5 years after the surgery (85). However, thalamic and cerebellar circuits are being re-examined within the motor network model as potential targets. In a study of 15 patients with musician’s dystonia who were followed for an average of 2.5 years (up to about 9 years) following ventro-oral thalamotomy, all patients except one (93%) experienced marked improvement in symptoms without deterioration during the follow-up period (26). In a systematic review of 523 patients from 24 studies, the improvement in Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) motor score after GPI deep brain stimulation in idiopathic dystonia was 65.2% (51). Isolated general dystonia, younger age of onset, normal MRI, and no other coexistent movement disorders were associated with better outcomes (79).

Besides deep brain stimulation, lesioning techniques such as MR-guided focused ultrasound have been used with benefit successfully in patients with task specific dystonia (27).

Media

References

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Contributors

All contributors' financial relationships have been reviewed and mitigated to ensure that this and every other article is free from commercial bias.

Authors

Aparna M Prabhu MD MRCP

Dr. Prabhu of Thomas Jefferson University and Jefferson Einstein Medical Center has no relevant financial relationships to disclose.
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Shikhar Khurana MD

Dr. Khurana of Thomas Jefferson University Hospitals has no relevant financial relationships to disclose.
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Editor

Robert Fekete MD

Dr. Fekete of New York Medical College received consultation fees from Acadia Pharmaceutical, Acorda, Adamas/Supernus Pharmaceuticals, Amneal/Impax, Kyowa Kirin, Lundbeck Inc., Neurocrine Inc., and Teva Pharmaceutical, Inc.
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Former Authors

Joseph K C Tsui MD
Joseph Jankovic MD
Mark A Stacy MD
Corneliu Luca MD PhD
Carlos Singer MD

Patient Profile

Age range of presentation: 0 month to 65+ years
Sex preponderance: male=female
Heredity: none
Population groups selectively affected: none selectively affected
Occupation groups selectively affected: Musicians

Telegraphers

Writers

ICD & OMIM codes

ICD-10: Arm and hand dystonia, familial: G24.1x60

Leg and foot dystonia, familial: G24.1x61
ICD-11: Other specified primary dystonia: 8A02.0Y

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Limb dystonia

Associated Disorders

Dopa-responsive dystonia
Multiple system atrophy
Musician's cramp
Occupational dystonia
Parkinson disease
- Progressive supranuclear palsy
- Task-specific dystonia
- Telegrapher's cramp
- Wilson disease
- Writer's cramp
- Yips

Differential Diagnosis

carpal tunnel syndrome
tennis elbow
muscle strain
muscle cramp
fasciitis
- arthritis
- inflammation
- reflex sympathetic dystrophy

Limb dystonia

Cite this article

Introduction

Overview

Key points

Historical note and terminology

Clinical manifestations

Presentation and course

Prognosis and complications

Clinical vignette

Biological basis

Etiology and pathogenesis

Table 1. Classification of Dystonias

Table 2. Clinical and Molecular Information on the Primary Inherited Dystonias

Table 3. Differential Diagnosis of Dystonia

Epidemiology

Prevention

Differential diagnosis

Diagnostic workup

Management

Special considerations

Pregnancy

Anesthesia

Media

References

Contributors

Authors

Editor

Former Authors

Patient Profile

ICD & OMIM codes

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