AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Background

The term chorea comes from Latin, which, in turn, was derived from the Greek word khoreia, a choral dance. The basic Greek word for dance (in Latin letters) is khoros.

Chorea has been defined by the ad hoc Committee on Classification of the World Federation of Neurology as "a state of excessive, spontaneous movements, irregularly timed, non-repetitive, randomly distributed and abrupt in character. These movements may vary in severity from restlessness with mild intermittent exaggeration of gesture and expression, fidgeting movements of the hands, unstable dance-like gait to a continuous flow of disabling, violent movements."

Patients with chorea exhibit motor impersistence (ie, they cannot maintain a sustained posture). When attempting to grip an object, they alternately squeeze and release ("milkmaid's grip"). When they attempt to protrude the tongue, the tongue often pops in and out ("harlequin's tongue"). Patients frequently involuntarily drop objects. Also frequently, patients voluntarily augment the choreiform movements with semipurposeful movements in order to mask the chorea.

Chorea involves proximal and distal muscles. In most patients, normal tone is noted, but in some instances, hypotonia is present. In a busy movement disorder center, levodopa-induced chorea is the most common movement disorder, followed by Huntington disease (HD).

Any discussion of chorea must also address the related terms athetosis, choreoathetosis, and ballism (also known as ballismus).

The term athetosis comes from the Greek word athetos (meaning not fixed). It is a slow form of chorea. Because of the slowness, the movements have a writhing (ie, squirming, twisting, or snakelike) appearance. Choreoathetosis is essentially an intermediate form (ie, moderately slow or moderately rapid chorea). To the extent that the only difference between chorea, choreoathetosis, and athetosis is the rapidity of movement, some neurologists argue that the term athetosis is unnecessary and even confusing. They argue a simpler nomenclature would include fast, intermediate, or slow chorea. While the authors of this article understand the basis of that argument, they also believe that in some cases, the writhing movements are extremely prominent, seemingly even apart from the speed of the movement. Thus, the authors of this article advocate retaining this descriptive term.

Ballism or ballismus is considered a very severe form of chorea in which the movements have a violent, flinging quality. The word ballism comes from the Greek word ballismos, meaning "a jumping about or dancing." Ballism has been defined as "continuous, violent, coordinated involuntary activity involving the axial and proximal appendicular musculature such that the limbs are flung about." This movement disorder most often involves only one side of the body (ie, hemiballism or hemiballismus). Occasionally, bilateral movements occur (ie, biballism or paraballism). Many patients with hemiballism have choreiform movements and vice versa, and hemiballism often evolves into hemichorea. Currently, ballism should be viewed as a severe form of chorea.

Pathophysiology

A simple model of basal ganglia function states that dopaminergic and GABAergic impulses from the substantia nigra and motor cortex, respectively, are funneled through the pallidum into the motor thalamus and motor cortex. These impulses are modulated in the striatum via 2 segregated, parallel, direct and indirect loops through the medial pallidum and lateral pallidum/subthalamic nucleus. Subthalamic nucleus activity drives the medial pallidum to inhibit cortex-mediated impulses, thereby inducing parkinsonism. Absent subthalamic nucleus inhibition enhances motor activity through the motor thalamus, resulting in abnormal involuntary movements such as dystonia, chorea, and tics. A classic example of loss of subthalamic inhibitory drive is ballism.

The most well-studied choreatic syndrome is Huntington chorea; therefore, the pathophysiology of HD as it applies to chorea is the focus of the discussion that follows.

Dopaminergic mechanism

In Huntington chorea, the content of striatal dopamine is normal, indicating that the major pathological alterations lay in the surviving, but diseased, medium-sized, spiny, striatal dopaminergic neurons. Pharmacologic agents that either deplete dopamine (eg, reserpine, tetrabenazine) or block dopamine receptors (eg, neuroleptic medications) improve chorea, giving further support to this observation. Because drugs that decrease the striatal content of dopamine improve chorea, increasing the amount of dopamine worsens chorea, such as the levodopa-induced chorea seen in persons with Parkinson disease (PD).

Cholinergic mechanism

The concept that a critical striatal balance between acetylcholine (Ach) and dopamine is essential for normal striatal function received its greatest acceptance in the understanding of PD. In the early days of PD therapy, anticholinergic medications were used commonly, especially when tremor was the predominant symptom. Other PD symptoms, such as bradykinesia and rigidity, often also improved.

Development of chorea in patients treated with anticholinergic medications such as trihexyphenidyl is a common clinical observation. Furthermore, intravenous administration of physostigmine (a centrally acting anticholinesterase) can temporarily reduce chorea. Similarly, anticholinergic-induced chorea can be overcome promptly by administering physostigmine.

Patients with HD have a patchy reduction of choline acetyltransferase in the basal ganglia. This enzyme catalyzes the synthesis of ACh. A marked reduction of muscarinic cholinergic receptor sites has also been reported. These 2 observations could explain the variability of the response to physostigmine and the limited efficacy of Ach precursors such as choline and lecithin.

Serotonergic mechanism

Manipulation of striatal serotonin may play a role in the genesis of many abnormal movements. Selective serotonin reuptake inhibitors such as fluoxetine may induce or aggravate parkinsonism, akinesia, myoclonus, or tremor. The role of serotonin (5-hydroxytryptamine [5-HT]) in choreiform movements is less clear. The striatum has a relatively high concentration of serotonin. Pharmacologic attempts to either stimulate or inhibit serotonin receptors in persons with Huntington chorea have shown no effect, indicating that the contribution of serotonin in the pathogenesis of chorea is limited.

GABAergic mechanism

The most consistent biochemical lesion in persons with Huntington chorea appears to be a loss of neurons in the basal ganglia that synthesize and contain GABA. The significance of this remains unknown. A variety of pharmacologic techniques have been attempted to increase CNS GABA levels. Valproate acid, which acts in part via a GABAergic mechanism, has, in a limited number of uncontrolled cases, ameliorated not only the agitation sometimes seen in persons with HD but has also improved the movement problem. However, no systematic studies have been conducted on the use of GABAergic agents for HD.

Substance P and somatostatin

Substance P levels have been shown to be markedly decreased in persons with HD, while somatostatin levels are increased. The significance of this remains unknown.

Ballism

This movement disorder usually involves only one side of the body (ie, hemiballism). Hemiballism is usually attributed to lesions of the contralateral subthalamic nucleus, although infarction in the caudate, striatum, lenticular nucleus, or thalamus also has been associated with hemiballism.

Lesions of the subthalamic nucleus cause contralateral hemiballism-hemichorea by reducing the normal excitatory drive from the subthalamic nucleus to the internal segment of the globus pallidus. This reduces the inhibitory output of the globus pallidus on the thalamus, and this disinhibition gives rise to excessive excitatory drive to the cortex, which is expressed as contralateral hyperkinetic movements. However, this disorder often appears in the absence of a lesion in the subthalamic nucleus.

Klawans suggested that increased dopaminergic transmission might play a role in the pathophysiology of this disorder. This hypothesis is supported by the observation that dopamine-receptor blockers and catecholamine-depleting agents often improve hemiballism. While hemiballism and hemichorea are distinguishable on the basis of the type and distribution of movements, they represent 2 different symptoms on a spectrum of the same disease process. Why one patient with basal ganglia dysfunction develops hemiballism and another with similar pathologic changes develops hemichorea is unknown.

Frequency

United States

Although no data are available regarding the incidence of chorea, the incidences of several entities in which chorea is the main clinical feature are well known.

• HD is an autosomal dominant, neurodegenerative disorder in which the defective gene is located on the short arm of chromosome 4. The estimated prevalence of HD in the United States is 5-10 cases per 100,000 people.
• Wilson disease is an autosomal recessive, multisystem disease caused by a mutation in the ATP7B gene, which resides on the long arm (q) of chromosome 13 (13q14.3). This gene codes for an ATPase, which is involved with the transport of copper. Although the gene prevalence (heterozygous carriers who inherited only 1 abnormal gene) has been estimated to be as high as 1%, the disease prevalence is only 30 cases per 1 million people.
• Benign hereditary chorea, a fairly rare disorder in which most of the pedigrees have clearly demonstrated dominant inheritance, has a prevalence of approximately 1 case per 500,000 people.

Race

• George Huntington first described HD transmission in 1872 in successive generations of natives of Long Island, New York. All affected individuals descended from ancestors who had emigrated from East Anglia, England, to the New World in 1649. This disorder is now dispersed widely around the globe.
• HD is best known in white populations. All cases of the disorder have probably occurred from the lineage originating in East Anglia.
• In addition, informative genotypes were obtained from a vast family lineage carrying the gene; they are located in and around Lake Maracaibo, Venezuela.

Age

Chorea may commence at any age. In children, postpump chorea and infectious, inflammatory, and striatal lesions may account for many cases.

• Approximately 10% of patients with HD have onset of the disease when they are younger than 20 years, approximately 6% when they are younger than 21 years, and approximately 3% when they are younger than 15 years; however, the typical peak age at onset is in the fourth and fifth decades of life. Cases have been recognized in patients younger than 5 years. Patients with early onset usually inherited the disease from their father, while patients with later onset are more likely to have inherited the gene from their mother. The relatively low rate of expression in childhood is succeeded by a virtually exponential upsweep in the rate of appearance through the second and third decades of life to reach a plateau that is sustained from the fourth to the seventh decades. Although 27% of cases are first recognized in patients older than 50 years, most of the cases are documented in patients younger than 60 years. Onset has been recorded as late as the eighth decade.
• Neuroacanthocytosis, perhaps the most common form of hereditary chorea, usually manifests clinically in the third and fourth decade (age range is 8-62 y). It should be differentiated from late-onset HD through careful pedigree analysis and neurogenetic testing.
• Senile chorea manifests gradually in late-to-middle life.
• In general, on the basis of age of onset, benign hereditary chorea may be divided into 3 types: (1) early infancy, (2) at approximately age 1 year, and (3) during late childhood or adolescence. The most common age of onset is approximately 1 year, when the child begins to walk. Benign hereditary chorea is now known to be caused by a mutation in the TITF1 gene. Interestingly, this gene contains the code for a transcription factor essential for the organogenesis of the basal ganglia, the lungs, and the thyroid.

CLINICAL

Section 3 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

History

Patients with chorea may not initially be aware of the abnormal movements because they may be subtle. Patients can suppress the chorea temporarily and frequently camouflage some of the movements by incorporating them into semipurposeful activities (ie, parakinesia). The inability to maintain voluntary contraction (ie, motor impersistence), as is seen during manual grip (milkmaid grip) tests or tongue protrusion, is a characteristic feature of chorea and results in the dropping of objects and clumsiness. Muscle stretch reflexes are often hung-up and pendular. In severely affected patients, a peculiar dancelike gait may be noted. Depending on the underlying cause of the chorea, other motor symptoms include dysarthria, dysphagia, postural instability, ataxia, dystonia, and myoclonus. A brief discussion of the clinical manifestations of the most common choreatic diseases is presented.

• Huntington disease
• • Penetrance of HD is 100%. Expression is highly variable, both with respect to clinical manifestations and age of onset. When the disorder emerges early, particularly in patients younger than 20 years, it is most likely to run a rapid course with grave disability due to cognitive decline.
  • The Westphal variant, a rigid dystonic disorder, may be accompanied by seizures and even myoclonus. It is encountered principally among those with childhood onset. In contrast, when the disorder appears late in life, the cardinal manifestation is chorea.
  • The insidious onset of clumsiness and adventitious movements may be wrongly attributed to simple nervousness. Although chorea and other motor disabilities are the most readily recognized manifestations of HD, they may be neither the earliest to appear nor the most disabling manifestations of the disease.
  • Psychological disturbances and personality change are the initial manifestations in greater than 50% of affected persons. Symptoms consistent with a depressive state are the most frequent psychological disturbances.
  • The duration of illness from onset to death is approximately 15 years in the case of adult HD and 8-10 years for the juvenile variant.
• Wilson disease
• • The clinical features are age dependent. In children, the disease is manifested initially by progressive dystonia, rigidity and dysarthria, and hepatic dysfunction, whereas in adults, psychiatric symptoms, tremor, and dysarthria usually predominate.
  • Because Kayser-Fleischer rings are almost always present when neurological symptoms are present, slit-lamp examination of the cornea must be performed to be certain that Wilson disease is excluded in a patient with chorea beginning in childhood or young adulthood. In patients with chorea and negative findings from a slit-lamp examination, serum copper and ceruloplasmin analysis along with a 24-hour copper urine excretion test need to be performed.
• Neuroacanthocytosis
• • Symptoms usually begin with lip and tongue biting (often causing self-injury), orolingual dystonia, motor and phonic tics, generalized chorea, parkinsonism, and seizures. Patients with neuroacanthocytosis may report an inability to feed themselves because of dystonic tongue protrusion every time they try to eat.
  • Other features include cognitive and personality changes, dysphagia, dysarthria, amyotrophy, areflexia, evidence of axonal neuropathy with absent deep ankle tendon stretch reflexes, and elevated serum creatine kinase levels without evidence of myopathy.
• Senile chorea
• • This clinical entity is characterized by a gradual onset of generalized and symmetric chorea with slow progression and specifically excluding mental deterioration, emotional disturbances, or family history.
  • To rule out the possibility of HD, genetic testing is recommended because family history can be inaccurate and distinguishing age-related mental changes from early features of HD in an elderly person may be difficult.
• Sydenham chorea
• • Sydenham chorea is a major manifestation of acute rheumatic fever. With the 1992 modifications of the Jones criteria, it alone is sufficient to enable the physician to make the diagnosis of the first attack of acute rheumatic fever. Sydenham chorea is considered a disease of childhood; however, it also may be seen in adults. Rheumatic chorea is characterized by muscle weakness and the presence of chorea. The patients have the milkmaid grip sign, clumsy gait, and explosive bursts of dysarthric speech. Often, harlequin tongue, which pops in and out when the patient tries to hold it out, can be prominently demonstrated.
  • Psychological symptoms are equally prominent and typically precede the appearance of even the most subtle choreiform movements. Emotional lability is the most common symptom; decreased attention span, obsessive-compulsive symptoms, and separation anxiety disorder also are seen. Symptoms can lag behind the etiologic streptococcal infection by 1-6 months. In adults, generalized poststreptococcal chorea may complicate birth control or pregnancy (chorea gravidarum).
• Benign hereditary chorea
• • This is a rare autosomal dominant genetic disorder characterized by nonprogressive choreiform movements that appear in childhood, without intellectual impairment. It is further distinguished clinically from juvenile HD by the absence of seizures, rigidity, or cerebellar features.
  • Benign hereditary chorea is caused by a mutation in the TITF1 gene. Interestingly, this gene contains the code for a transcription factor essential for the organogenesis of the basal ganglia, the lungs, and the thyroid.
  • It does not shorten the life span of affected patients, but severely affected patients can be markedly disabled by the chorea.

Physical

Because HD is the most clearly defined choreatic disease, its physical findings are described here.

• Huntington disease
• • HD is caused by an expansion repeat (CAG) mutation in the IT15 gene (which codes for the protein called huntingtin) on chromosome 4. Initial signs of chorea generally are flickers in the fingers and ticlike grimaces of the face. Over time, higher-amplitude dancelike movements disrupt voluntary actions of the extremities and interfere with gait. Speech becomes dysrhythmic.
  • Characteristically, the patient is hypotonic, although reflexes may be augmented and clonus may be noted.
  • Voluntary gaze is disturbed early. In particular, saccades may be irregular or of prolonged latency and may require an initial blink for their initiation.
  • Loss of optokinetic nystagmus is common after a decade of progressive disease.
  • Cognitive changes are manifested early as loss of recent memory and impaired judgment. Apraxia is also present. Ultimately, the patient becomes severely demented.
  • Neurobehavioral changes typically consist of personality changes, apathy, social withdrawal, agitation, impulsiveness, depression, mania, paranoia, delusions, hostility, hallucinations, or psychosis.
  • The Westphal variant is dominated by rigidity, bradykinesia, and dystonic postures. Generalized seizures and myoclonus may be seen. Ataxia and dementia are also present.

Causes

• Idiopathic - Physiological chorea of infancy, buccal-oral-lingual dyskinesia, senile chorea
• Hereditary - HD, hereditary nonprogressive chorea (benign hereditary chorea), benign recessively inherited choreoathetosis of early onset, familial inverted chorea, neuroacanthocytosis, familial remitting chorea, nystagmus and cataracts, ataxia-telangiectasia, tuberous sclerosis, familial calcification of basal ganglia, pantothenate kinase–associated neurodegeneration (PKAN) or pantothenate kinase 2 (PANK2) deficiency (previously termed Hallervorden-Spatz disease), Friedreich ataxia
• Hereditary (metabolic) - Wilson disease, glutaric aciduria, Lesch-Nyhan disease, phenylketonuria, acute intermittent porphyria, propionic acidemia, abetalipoproteinemia, hypobetalipoproteinemia, lipid storage diseases
• Other metabolic and endocrine disorders - Kernicterus, hyperthyroidism, hypoparathyroidism, hypoglycemia, nonketotic hyperglycemia, chorea gravidarum, hypomagnesemia, chronic nonfamilial hepatic encephalopathy, anoxic encephalopathy (including postcardiac transplantation), postportocaval anastomosis for portal hypertension
• Paroxysmal - Paroxysmal kinesogenic choreoathetosis, paroxysmal dystonic choreoathetosis
• Infectious - Sydenham chorea, encephalitides, subacute sclerosing panencephalitis, syphilis, enteric cytopathogenic human orphan (ECHO) virus infection, Lyme disease, HIV infection, cerebral toxoplasmosis, Creutzfeldt-Jakob disease, subacute bacterial endocarditis
• Drug induced - Neuroleptics, levodopa, anticholinergics, oral contraceptives, antihistamines, amphetamines, cocaine, phenytoin, tricyclics
• Toxins - Alcohol intoxication and withdrawal, carbon monoxide, manganese, mercury
• Vascular - Cerebrovascular disease (ischemic or hemorrhagic), chronic subdural hematoma, Moyamoya disease, migraine/hemicrania choreatica, Churg-Strauss syndrome, polycythemia vera
• Immunologic - Systemic lupus erythematosus, Behçet disease, primary antiphospholipid antibody syndrome, multiple sclerosis, postcardiac transplantation, postvaccination
• Tumors - Primary, metastatic
• Miscellaneous - Mitochondrial cytopathies, ventriculoperitoneal shunts

DIFFERENTIALS

Section 4 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

WORKUP

Section 5 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Lab Studies

• Diagnosis of the primary choreatic conditions is based on history and clinical findings; however, several laboratory studies are useful, especially in distinguishing the secondary forms of chorea from the primary forms. Some of them are mentioned here.
• • Huntington disease: The only laboratory study presently available to confirm HD is genetic testing. It identifies a gene abnormality in the short arm of chromosome 4, characterized by abnormal repetition of the trinucleotide CAG, the length of which determines the age of onset (anticipation).
  • Wilson disease: A low serum ceruloplasmin level and serum copper values showing increased urinary copper excretion corroborate the diagnosis in most cases. Persistent aminoaciduria, reflecting a renal tubular abnormality, is present in most but not all patients. Liver function test results are usually abnormal. Serum ammonia levels may be elevated. If the diagnosis is still uncertain, liver biopsy can help confirm the diagnosis.
  • Sydenham chorea: The chorea can lag behind the etiologic streptococcal infection by 1-6 months, sometimes as long as 30 years; therefore, antistreptococcal antibody titers may no longer be elevated at presentation. Without documentation of an antecedent streptococcal infection, the diagnosis of Sydenham chorea must be made by excluding other causes.
  • Neuroacanthocytosis: The diagnosis is confirmed by the presence of spiky erythrocytes (acanthocytes) in peripheral blood smears. The serum creatine kinase level may be elevated.
• Other laboratory studies useful in the differential diagnosis of chorea include complement levels, antinuclear antibody titers, antiphospholipid antibody titers, amino acid levels in serum and urine, enzymatic studies from skin fibroblasts, thyrotropin levels, thyroxine values, and parathormone levels.

Imaging Studies

• MRI
• • Patients with HD and chorea-acanthocytosis show decreased signal in the neostriatum, caudate, and putamen. No significant difference has been observed between these diseases. The decreased neostriatal signal corresponds to increased iron deposition. Generalized atrophy, as well as focal atrophy of the neostriatum, predominantly of the caudate, with resulting enlargement of the frontal horns, follows the initial findings of decreased neostriatal signal.
  • Most patients with Sydenham chorea show no abnormalities. However, a study reported volumetric differences in the caudate, putamen, and globus pallidus; they were significantly larger in patients with Sydenham chorea than in controls. Patients with hemiballismus demonstrate signal changes in the contralateral subthalamic nucleus or, less often, the striatum or thalamic nuclei.
  • MRI of the brain of patients with senile chorea shows a decrease in signal intensity throughout the striatum (suggesting iron deposition) and narrowing of the space separating the caudate head and putamen, but no overt atrophy of these structures.
• Positron emission tomography
• • Fluorodopa (F-dopa) uptake is normal or mildly reduced in patients with chorea. HD and chorea-acanthocytosis show bilateral hypometabolism in the caudate nucleus and putamen.
  • Patients with chorea and dementia show decreased glucose metabolism in the frontal, temporal, and parietal cortices.
  • Patients with benign hereditary chorea may or may not show decreased metabolism in the caudate.
  • The finding of normal cerebral glucose metabolism in the striatal region practically excludes HD, this being a useful tool for differential diagnosis. The definite diagnosis of HD is made easily by neurogenetic studies.
  • Hypometabolism in the caudate nucleus and putamen on the contralateral side is seen in patients with hemichorea.

TREATMENT

Section 6 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical Care

• Only symptomatic treatment is available for patients with chorea. Chorea may be a disabling symptom, leading to bruises, fractures, and falls, and may impair the ability of patients to feed themselves. In addition, patients sometimes express a desire for antichorea treatment for cosmetic reasons.
• The most widely used agents in the treatment of chorea are the neuroleptics. The basis of their mechanism of action is thought to be related to blocking of dopamine receptors. Neuroleptics can be classified as typical and atypical. Typical neuroleptics include haloperidol and fluphenazine. Atypical neuroleptics include risperidone, olanzapine, clozapine, and quetiapine.
• Dopamine-depleting agents, such as reserpine and tetrabenazine, represent another option in the treatment of chorea.
• GABAergic drugs, such as clonazepam, gabapentin, and valproate, can be used as adjunctive therapy.
• Intravenous immunoglobulin and plasmapheresis may shorten the course of the illness and decrease symptom severity in patients with Sydenham chorea.
• Chorea following cardiac transplantation has been reported to be responsive to steroid treatment.
• Reports of drug treatment for hemiballism must take into account the high spontaneous remission rate for the disorder. Anecdotal reports must be viewed with caution, unless they can demonstrate that the response is due to the agent (by recurrence of the movements with drug withdrawal). The rarity of this disorder and the severity of its manifestations have precluded placebo-controlled drug trials. Pharmacologic treatment is the same as that prescribed for other choreatic disorders.

Surgical Care

• Deep brain stimulation is an emerging technique that may benefit patients, at least in certain cases.
• • In 2000, Thompson et al reported a reduction in choreiform movements in 2 pediatric cases of chorea. One patient had cerebral palsy from birth secondary to brain hemorrhage. The other, an 11-year-old child, developed chorea subsequent to a thalamic hemorrhage 4 years before. Both children improved after the procedure.
  • Reported in 2003, Krauss et al tested globus pallidus stimulation on 2 patients with dystonia (one adult and one child) and 4 adult patients with essentially static (ie, nonchanging) chorea secondary to cerebral palsy. The dystonia patients markedly improved. Two of the 4 chorea patients showed no improvement, but 2 showed mild improvement.
  • In 2004, Moro et al reported on bilateral globus pallidus internus stimulation on a patient with HD. Stimulation at 130 and 40 Hz improved the chorea, but the stimulation at 130 Hz worsened the bradykinesia. Stimulation of 40 Hz had little effect on the bradykinesia and appeared to increase blood flow (assessed by positron emission tomography scanning) in areas associated with executive functions and judgment.
• Although deep brain stimulation is not yet used routinely for chorea, as it is for PD, exciting progress has been made with this modality.

MEDICATION

Section 7 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

The goals of pharmacotherapy are to reduce morbidity and to prevent complications.

Drug Category: Antipsychotic agents

Block dopamine receptors and appear to have antispasmodic effects.

Drug Name	Fluphenazine (Prolixin)
Description	Blocks postsynaptic mesolimbic dopaminergic D1 and D2 receptors in brain. Exhibits strong alpha-adrenergic and anticholinergic effects. May depress reticular activating system.
Adult Dose	0.5-1 mg/d PO initially
Pediatric Dose	Not established
Contraindications	Documented hypersensitivity; narrow-angle glaucoma
Interactions	May potentiate effects of narcotics, including respiratory depression; lithium increases CNS effects; barbiturates may decrease effects
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Besides extrapyramidal symptoms as described for haloperidol, mild leukocytosis, leukopenia, and eosinophilia occasionally occur; dermatological reactions are common; watch for urinary retention, blurred vision, dry mouth, and constipation as result of anticholinergic effects

Drug Name	Clozapine (Clozaril)
Description	New atypical neuroleptic medication available in 25- and 100-mg tab. Blocks norepinephrine, serotonergic, cholinergic, histamine, and dopaminergic receptors. Mechanism of action still unclear. Affinity for mesolimbic D4 dopamine receptor accounts for striking effects in control of behavioral and psychiatric symptoms with low incidence of extrapyramidal symptoms. Histamine receptor blockade accounts for increased incidence of sleep disturbances.
Adult Dose	Chorea: 12.5 mg PO qd; increase dose weekly to 50-75 mg PO qd Dystonia: Doses of up to 700 mg/d may be needed PD: 25-50 mg PO qd required to control hallucinations Schizophrenia: Higher doses required
Pediatric Dose	Not established
Contraindications	Documented hypersensitivity; history of agranulocytosis; history of pulmonary embolism, diabetes mellitus, hepatitis, narrow-angle glaucoma, bladder retention, prostate enlargement
Interactions	Epinephrine and phenytoin may decrease effects; other dopamine-depleting agents, TCAs, neuroleptics, CNS depressants, guanabenz, and anticholinergics may increase effects
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Monitor for agranulocytosis and orthostatic hypotension; caution in patients who take other drugs that can cause agranulocytosis, such as carbamazepine and ticlopidine; all patients should undergo weekly WBC counts with differential; if WBC falls to <3000/µL or if absolute neutrophil count falls to <1500/µL, interrupt or discontinue therapy; anticholinergic reactions can be quite severe; may cause pulmonary embolism or hepatitis; may elevate LFT results

Drug Name	Olanzapine (Zyprexa)
Description	May inhibit serotonin, muscarinic, and dopamine effects.
Adult Dose	5-10 mg PO qd initially; increase to 10 mg PO qd within 5-7 d; not to exceed 20 mg/d
Pediatric Dose	Not established
Contraindications	Documented hypersensitivity
Interactions	Fluvoxamine may increase effects; antihypertensives may increase risk of hypotension and orthostatic hypotension; levodopa, pergolide, bromocriptine, charcoal, carbamazepine, omeprazole, rifampin, and cigarette smoking may decrease effects
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Agranulocytosis has not been reported to date; watch for orthostatic hypotension and constipation; less risk of extrapyramidal effects than traditional neuroleptics; serum half-life increases by approximately 50% in patients >65 y and can be expected to increase in patients with liver dysfunction; both groups may require smaller-than-average dosages

Drug Name	Risperidone (Risperdal)
Description	Binds to dopamine D2-receptor with 20 times lower affinity than for 5-HT2 receptor. Improves negative symptoms of psychoses and reduces incidence of extrapyramidal adverse effects.
Adult Dose	1 mg PO bid initially; increase slowly to 4-6 mg/d
Pediatric Dose	Not established
Contraindications	Documented hypersensitivity
Interactions	Carbamazepine may decrease effects; may inhibit effects of levodopa; clozapine may increase levels
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Low risk of extrapyramidal adverse effects; may cause extrapyramidal reactions, hypotension, tachycardia, and arrhythmias

Drug Name	Quetiapine (Seroquel)
Description	May act by antagonizing dopamine and serotonin effects.
Adult Dose	25 mg PO bid initially; titrate slowly to effect in 2-3 divided doses; not to exceed 800 mg/d
Pediatric Dose	Not established
Contraindications	Documented hypersensitivity
Interactions	May antagonize levodopa and dopamine agonists; phenytoin, thioridazine, and other liver enzyme inducers may reduce levels
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	May induce orthostatic hypotension associated with dizziness, tachycardia, and syncope; neuroleptic malignant syndrome has been associated with this treatment

Drug Category: Dopamine depleting agents

Deplete CNS of dopamine, thereby reducing chorea.

Drug Name	Tetrabenazine (Nitoman)
Description	Dopamine-depleting agent available worldwide except in United States. Works by depleting dopamine in presynaptic neuron and by blocking postsynaptic dopamine receptor.
Adult Dose	25 mg PO qd initially; increase dose according to clinical response and adverse effects
Pediatric Dose	Not established
Contraindications	Documented hypersensitivity; depression
Interactions	Potentiates effects of other dopamine-depleting agents (ie, reserpine) and of dopamine-blocking agents such as neuroleptics
Pregnancy	X - Contraindicated in pregnancy
Precautions	Patients may develop sedation, anxiety, akathisia, confusion, tremor, and dizziness; use caution in orthostatic and drug-induced hypotension; because tetrabenazine depletes dopamine, tends to worsen symptoms of parkinsonism/PD or drug-induced parkinsonism

Drug Category: Benzodiazepines

Demonstrated to reduce GABA concentrations in the caudate, putamen, substantia nigra, and globus pallidus. By analogy, increased GABA activity might ameliorate chorea.

Drug Category: Anticonvulsants

May help by various neuropharmacological mechanisms. Valproate is a GABAergic agent and thus it may help in the same way as benzodiazepines. Main mechanism of action of carbamazepine appears to be stabilization of inactivated state of voltage-gated sodium channels. This may reduce neuronal firing in many systems and therefore may nonspecifically reduce abnormal movements in some patients.

Drug Name	Carbamazepine (Carbatrol, Tegretol, Epitol)
Description	Has been of symptomatic help in chorea, particularly in Sydenham chorea and chorea gravidarum, but also in other types. Dosage recommendations and cautions are essentially the same in this off-label use as for the more common indication of seizures. When used as an anticonvulsant, mechanism of action may involve depressing activity in nucleus ventralis anterior of thalamus, resulting in reduction of polysynaptic responses and blocking posttetanic potentiation. Reduces sustained high-frequency repetitive neural firing. Potent enzyme inducer that can induce own metabolism. Due to potentially serious blood dyscrasias, undertake benefit-to-risk evaluation before drug instituted. Therapeutic plasma levels are 4-12 mcg/mL for analgesic and antiseizure response. Peak serum levels in 4-5 h. Half-life (serum) in 12-17 h with repeated doses. Metabolized in liver to active metabolite (ie, epoxide derivative) with half-life of 5-8 h. Metabolites excreted through feces and urine.
Adult Dose	200 mg PO bid on day 1 (100 mg qid susp) initially; increase by 200 mg/d or less qwk until best response attained; divide total dose and administer q6-8h; ER tab may be used for bid dosing instead of dosing tid/qid; not to exceed 1200 mg/d Maintenance: Decrease dose gradually to minimum effective level, usually 800-1200 mg/d
Pediatric Dose	<6 years: 10-20 mg/kg/d PO bid/tid (qid with susp); increase qwk to achieve optimal clinical response tid/qid; not to exceed 100 mg/d 6-12 years: 100 mg PO bid (50 mg qid of susp) increase gradually qwk by adding 100 mg/d PO divided tid/qid (bid with ER tab) until best response obtained; not to exceed 1000 mg/d >12 years: Administer as in adults; not to exceed 1000 mg/d in children 12-15 y or 1200 mg/d in >15 y
Contraindications	Documented hypersensitivity; history of bone marrow depression; administration of MAOIs within last 14 d
Interactions	Serum levels may increase significantly within 30 d of danazol coadministration (avoid whenever possible); do not coadminister with MAOIs; cimetidine may increase toxicity, especially if taken in first 4 wk of therapy; may decrease primidone and phenobarbital levels (their coadministration may increase carbamazepine levels)
Pregnancy	D - Unsafe in pregnancy
Precautions	Do not use to relieve minor aches or pains; caution with increased intraocular pressure; obtain CBC count and serum iron baseline prior to treatment, during first 2 mo, and yearly or every other year thereafter; can cause drowsiness, dizziness, and blurred vision; caution while driving or performing other tasks requiring alertness

FOLLOW-UP

Section 8 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Complications

• The severity of the abnormal involuntary movements may cause rhabdomyolysis or local trauma in some patients.
• The swallowing difficulties and tongue dystonia usually present in neuroacanthocytosis patients may cause aspiration pneumonia and early death in some patients.

Prognosis

• Prognosis depends on the cause of the chorea. HD has a poor prognosis, because all patients will die of complications of the disease. Similarly, patients with neuroacanthocytosis may develop aspiration pneumonia, which can cause early death.

MISCELLANEOUS

Section 9 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• In HD, the quality of the genetic counseling is very important. The physician can make errors of omission and commission. The pitfalls and problems associated with genetic testing should be discussed.
• • Some individuals do not want to know ahead of time whether they will develop manifestations of the disease, but others do want to know. Still, others are unsure. Patients have committed suicide in anticipation of the onset of HD. This could lead to a lawsuit. Thus, testing should not be performed in a casual manner and not without adequate discussion.
  • On the other hand, omitting the testing or not informing patients that their offspring have a 50% chance of contracting the disease also could lead to a lawsuit.
  • If one feels uncomfortable discussing these things with the patient, the best plan may be to refer him or her to a medical geneticist who will supervise the testing.

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

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Article Last Updated: Oct 13, 2006