An open-label study of botulinum toxin A for treatment of tardive dystonia

Tardive syndrome: An update and mini-review from the perspective of phenomenology

Tardive syndrome (TS) is a group of movement disorders caused by the long-term use of dopamine receptor blocking agents. The phenotypic presentation of TS is diverse, ranging from the most well-characterized symptom of tardive dyskinesia to other symptoms, including dystonia, akathisia, myoclonus, parkinsonism, tremor, and tics. These tardive symptoms are distinct not only in their phenomenology but also in their clinical outcomes. However, our knowledge of the pathophysiology and management of TS is almost exclusively based on tardive dyskinesia. First-generation antipsychotics have a higher risk of inducing TS and have largely been replaced by second-generation antipsychotics with a lower risk of TS. However, patients with off-label use of second-generation antipsychotics are still at risk of developing TS. Thus, the management of TS remains a challenging and important issue for physicians. In this review, we update the information on the epidemiology, phenomenology, and treatment of TS from the perspective of the specific form of TS.

Management of Tardive Syndrome: Medications and Surgical Treatments

Tardive syndrome (TS) is an iatrogenic, often persistent movement disorder caused by drugs that block dopamine receptors. It has a broad phenotype including movement (orobuccolingual stereotypy, dystonia, tics, and others) and nonmotor features (akathisia and pain). TS has garnered increased attention of late because of the Food and Drug Administration approval of the first therapeutic agents developed specifically for this purpose. This paper will begin with a discussion on pathogenesis, clinical features, and epidemiology. However, the main focus will be treatment options currently available for TS including a suggested algorithm based on current evidence. Recently, there have been significant advances in TS therapy, particularly with the development of 2 new vesicular monoamine transporter type 2 inhibitors for TS and with new data on the efficacy of deep brain stimulation. The discussion will start with switching antipsychotics and the use of clozapine monotherapy which, despite the lack of higher-level evidence, should be considered for the treatment of psychosis and TS. Anti-dyskinetic drugs are separated into 3 tiers: 1) vesicular monoamine transporter type 2 inhibitors, which have level A evidence, are approved for use in TS and are recommended first-choice agents; 2) drugs with lower level of evidence for efficacy including clonazepam, Ginkgo biloba, and amantadine; and 3) drugs that have the potential to be beneficial, but currently have insufficient evidence including levetiracetam, piracetam, vitamin B6, melatonin, baclofen, propranolol, zolpidem, and zonisamide. Finally, the roles of botulinum toxin and surgical therapy will be examined. Current therapies, though improved, are symptomatic. Next steps should focus on the prevention and reversal of the pathogenic process.

The psychopharmacology of catatonia, neuroleptic malignant syndrome, akathisia, tardive dyskinesia, and dystonia

Although highly prevalent, motor syndromes in psychiatry and motor side effects of psychopharmacologic agents remain understudied. Catatonia is a syndrome with specific motor abnormalities that can be seen in the context of a variety of psychiatric and somatic conditions. The neuroleptic malignant syndrome is a lethal variant, induced by antipsychotic drugs. Therefore, antipsychotics should be used with caution in the presence of catatonic signs. Antipsychotics and other dopamine-antagonist drugs can also cause motor side effects such as akathisia, (tardive) dyskinesia, and dystonia. These syndromes share a debilitating impact on the functioning and well-being of patients. To reduce the risk of inducing these side effects, a balanced and well-advised prescription of antipsychotics is of utmost importance. Clinicians should be able to recognize motor side effects and be knowledgeable of the different treatment modalities.

Non-VMAT2 inhibitor treatments for the treatment of tardive dyskinesia

Although VMAT2-inhibitors are now established as first-line treatment for tardive dyskinesia, not all patients respond to, or tolerate them. Numerous other agents have been adopted to treat tardive dyskinesia, but with variable results and generally lower quality methodologic reports. Amantadine is the most promising but benzodiazepines, branched chain neutral amino acids, Vitamin B6, several nutraceuticals, and botulinum toxin injections might help some patients. In all cases, better placebo controlled trials are needed before definitive recommendations can be made.

The Symptomatic Treatment of Acquired Dystonia: A Systematic Review

Background

Acquired dystonia is caused by an acquired or exogenous event. Although the therapeutic armamentarium used in clinical practice is more or less similar to that used for inherited or idiopathic dystonia, formal proof of the efficacy of these interventions in acquired dystonia is lacking.

Methods

The authors attempt to provide a comprehensive and systematic review of the current evidence for medical and allied health care treatment strategies in acquired dystonias. The PubMed, Cochrane Library, MEDLINE, Web of Science, PiCarta, and PsycINFO databases were searched up to December 2015, including randomized controlled trials, patient-control studies, and case series or single case reports containing a report on clinical outcome.

Results

There are level 3 practice recommendations for botulinum toxin injections and globus pallidus pars interna deep brain stimulation for tardive dystonia and dystonic cerebral palsy as well as intrathecal baclofen for dystonic cerebral palsy. There are insufficient and conflicting data on the effect (vs. the hazard) of other pharmacological interventions, and limited work has been done on other forms of neurostimulation and allied health care. Because no class A1 or A2 studies were identified, level 1 or 2 practice recommendations could not be deducted for a specific treatment intervention.

Conclusions

To improve the current medical and allied health care treatment options for patients with acquired dystonia, high-quality trials that examine the efficacy of therapies need to be performed.

Drug-induced movement disorders

Movement disorders are frequently a result of prescription drugs or of illicit drug use. This article focuses on prescribed drugs but briefly mentions drugs of abuse. The main emphasis is on movement disorders caused by dopamine receptor-blocking agents. However, movement disorders caused by other drugs are also briefly discussed.

Neuroleptic-Induced Tardive Cervical Dystonia: Clinical Series of 20 Patients

Background:

Cervical dystonia (CD) may be classified according to the underlying cause into primary or secondary CD. Previous exposure to neuroleptics is one of the main causes of adult-onset secondary dystonia. There are few reports that characterize the clinical features of primary CD and secondary neuroleptic-induced CD. Herein our aim was to investigate a series of patients with neuroleptic induced tardive CD and to describe their clinical and demographic features.

Patients and Methods:

We retrospectively evaluated 20 patients with neuroleptic-induced tardive CD and compared clinical, demographic and therapeutic characteristics to another 77 patients with primary CD. All patients underwent Botulinum toxin type-A therapy.

Results:

We did not identify any relevant clinical and demographic characteristics in our group of patients that could be used to distinguish tardive and primary CD.

Conclusion:

Patients with tardive CD presented demographic characteristics and disease course similar to those with primary CD.

Case report of refractory tardive dystonia induced by olanzapine

Summary

Tardive dystonia (TDt), a cluster of extrapyramidal symptoms that are caused by long-term use of antipsychotic medication, is characterized by difficulty in autonomic movements of skeletal (voluntary) muscles and consequent deformations of the body. TDt is rarely seen among patients taking olanzapine, but olanzapine was the precipitating antipsychotic medication in this 22-year old male patient with schizophrenia who developed lip puckering, persistent involuntary torticollis, muscular pain, axial dystonia and unstable gait after taking a standard dose of olanzapine regularly for about one year. His symptoms did not resolve after his olanzapine was stopped. Four months of treatment with clozapine combined with magnesium valproate, vitamin E, tiapride, and lorazepam did not lead to any improvement in the dystonia.

Antipsychotic Drug Treatment for Patients with Schizophrenia: Theoretical Background, Clinical Considerations and Patient Preferences

The cornerstone in treatment of psychosis is antipsychotic drugs. Treatment options have increased over the years; newer antipsychotic drugs with a proposed increased efficacy regarding negative and cognitive symptoms, but also a shift in side-effects from neurological side-effects to metabolic side-effects have arisen as the new challenge. The basis of successful pharmacological treatment is a fundamental understanding of the mechanisms of action, the desired effects and side-effects of antipsychotic drugs, a good relationship with the patient and a thorough monitoring of the patient before and during treatment. The clinically relevant aspects of antipsychotic drug treatment are reviewed; mechanism of antipsychotic drug action, clinical considerations in treatment, switching antipsychotic drugs, polypharmacy, safety and patient preference.

Successful treatment of tardive lingual dystonia with botulinum toxin: case report and review of the literature

Tardive dyskinesia (TD) is a dreaded side effect of antipsychotic medication. Recommended treatments for TD may provide reliable improvement but can be, in turn, associated with additional adverse reactions. Recently, several reports have suggested that botulinum toxin A (BTX-A) injection in affected muscles may significantly improve TD. Here, we report a case of severe tongue protrusion dystonia secondary to an antipsychotic medication in a young man. Several approaches including clozapine, amisulpride, aripiprazole, ziprasidone, tiapride and clonazepam failed to improve the symptoms. Injection of 50 U of BTX-A (Dysport, Ipsen, Ettlingen, Germany) into each genioglossal muscle dramatically improved tongue protrusion within few days with a sustained effect. If reasonable precautions are taken, the application seems to be well tolerated with only minor side effects. A review of the literature that is part of this article adverts BTX-A injection as a potential beneficial approach of various kinds of TD.

Neurological complications of psychiatric drugs: clinical features and management

This paper reviews the main neurological complications of psychiatric drugs, in particular antipsychotics and antidepressants. Extrapyramidal syndromes include acute dystonia, parkinsonism, akathisia, tardive dyskinesia and tardive dystonia. Extrapyramidal symptoms (EPS) are less frequent with atypical than with conventional antipsychotics but remain common in clinical practice partly due to lack of screening by health professionals. Neuroleptic malignant syndrome (NMS) consists of severe muscle rigidity, pyrexia, change in conscious level and autonomic disturbance but partial forms also occur. NMS is particularly associated with the initiation and rapid increase in dose of high-potency antipsychotics but it has been reported with all the atypical antipsychotics and rarely with other drugs including antidepressants. Serotonin toxicity comprises altered mental state (agitation, excitement, confusion), neuromuscular hyperactivity (tremor, clonus, myoclonus, hyper-reflexia) and autonomic hyperactivity and occurs on a spectrum. Severe cases, termed serotonin syndrome, usually follow the co-prescription of drugs that increase serotonergic transmission by different pathways, for example a monoamine oxidase inhibitor (MAOI) and a selective serotonin reuptake inhibitor (SSRI). Most antipsychotics and antidepressants lower the seizure threshold and can cause seizures; the risk is greater with clozapine than with other atypical antipsychotics and greater with tricyclic antidepressants (TCAs) than with SSRIs. In randomised controlled trials in elderly patients with dementia atypical antipsychotics are associated with a higher risk of stroke and death than placebo. Cohort studies suggest that conventional drugs carry at least the same risk. Cessation of treatment with antipsychotics and antidepressants can lead to a wide range of discontinuation symptoms which include movement disorders and other neurological symptoms. Clinicians need to be familiar with strategies to reduce the risk of these adverse events and to manage them when they arise. Their occurrence needs to be balanced against the benefits of psychiatric drugs in terms of efficacy and improved quality of life in a range of disorders.

Tardive Syndromes in the Elderly

Tardive syndromes are characterized by abnormal involuntary movements that occur after prolonged exposure to drugs that block dopamine receptors. The prevalence and incidence of tardive syndromes are much higher in elderly individuals, and the number of elderly patients receiving antipsychotics has been increasing. This article summarizes the clinical phenomenology, pathophysiology, epidemiology, and treatment of these disorders in elderly individuals.

Botulinum toxin: Clinical use

Since its development for the use of blepharospasm and strabismus more than 2.5 decades ago, botulinum neurotoxin (BoNT) has become a versatile drug in various fields of medicine. It is the standard of care in different disorders such as cervical dystonia, hemifacial spasm, focal spasticity, hyperhidrosis, ophthalmological and otolaryngeal disorders. It has also found widespread use in cosmetic applications. Many other indications are currently under investigation, including gastroenterologic and urologic indications, analgesic management and migraine. This paper is an extensive review of the spectrum of BoNT clinical applications.

Tardive dystonia

Tardive dyskinesia is a movement disorder that develops after exposure to dopamine receptor blocking agents. Less well-appreciated are other, more recently described tardive syndromes that are phenomenologically distinct from tardive dyskinesia and respond to different treatments. Patients may simultaneously have more than one tardive syndrome. Major subtypes of tardive syndromes include tardive dyskinesia, characterized by orobuccolingual, truncal, or appendicular, choreiform movements; tardive dystonia, characterized by sustained, stereotyped muscle spasms of a twisting or turning character; and tardive akathisia, characterized by an inner sense of restlessness or unease. The sensation often is unpleasant and may be accompanied by repetitive, purposeless movements (stereotypies), such as pacing. Less common tardive syndromes include tardive myoclonus, tardive tourettism, and tardive tremor. Tardive syndromes often are a source of great distress and disability to patients and may be permanent, despite discontinuing the responsible medication. Prevention, early detection, and prompt management are the major clinical focus. When a patient develops a tardive syndrome appropriate actions include 1) review of the primary diagnosis that prompted starting a dopamine receptor blocking agent; 2) characterization of the movement disorder(s); 3) where possible, discontinuation of dopamine blocking agent or replacement with a less potent alternative agent; 4) gradual withdrawl of the offending drug because some patients have an exacerbation of a tardive syndrome after abrupt withdrawal; and 5) assessment of the severity of symptoms and development of a treatment plan based on the phenomenology, with the goal of maximizing patient comfort and function. Although tardive dyskinesia typically develops after chronic exposure to dopamine receptor blocking agents, it, and other variants (such as tardive dystonia) can develop very rapidly after treatment. There seems to be no minimal safe duration of exposure for the development of a tardive syndrome. It is important to recognize that anti-emetics, which are dopamine receptor blockers, such as prochlorperazine, promethazine and metoclopramide, can cause tardive syndromes. Clinicians should become familiar with antipsychotic agents that have a lower risk of causing tardive syndromes, such as clozapine, quetiapine, and olanzapine. We review treatment options for tardive dystonia.

Mouvements anormaux d’origine médicamenteuse : les syndromes tardifs

Persistent drug-induced movement disorders (tardive syndromes) remain an important clinical problem and consist of a variety of involuntary movements appearing in a patient exposed to a dopamine-blocking agent. The current state of knowledge on this topic is summarised in this article. Clinical aspects (tardive dyskinesia, tardive dystonia and other forms), prevalence, risk factors, prevention and management are discussed.

Treatment of severe neuroleptic-induced tardive torticollis

Background

The aim of this paper is to describe a case of severe neuroleptic-induced tardive torticollis successfully treated with a combination of clozapine, clonazepam and botulinum toxin-A.

Case Report

The patient, a 30-year old man with a seven-year history of delusional disorder experienced severe right torticollis with painful tightness of the neck and elevation of the shoulder. At this time he was receiving haloperidol 20 mg, trifluoperazine 5 mg, zuclopenthixol 20 mg and biperidine 4 mg daily. The combination therapy with clozapine and clonazepam and the long-term use of botulinum toxin-A resulted in a complete remission of dystonic movements.

Conclusions

The present observations provide evidence indicating that this combination therapy may be of benefit in patients with severe neuroleptic-induced tardive torticollis.

Classification and treatment of tardive syndromes

BACKGROUND

Tardive syndromes are a group of delayed-onset abnormal involuntary movement disorders induced by a dopamine receptor blocking agent. There are several phenomenologically distinct types of TS.

REVIEW SUMMARY

The term tardive dyskinesia has been used to refer to the TS that presents with rapid, repetitive, stereotypic movements mostly involving the oral, buccal, and lingual areas. Tardive dystonia can be focal, segmental, or generalized. It commonly affects the face and neck followed by the arms and trunk. It usually results in retrocollis when it involves the neck and trunk arching backwards when it involves the trunk. Tardive akathisia is characterized by a feeling of inner restlessness and jitteriness with an inability to sit or stand still. Other tardive syndromes include tardive tics, myoclonus, tremor, and withdrawal-emergent syndrome. It remains unclear whether tardive parkinsonism truly exists. The only way to prevent TS is to avoid its etiologic agents. Chronic use of dopamine receptor blocking agents should be limited as much as possible to patients with chronic psychoses. In general, for mild TS, reducing the neuroleptic dose, switching to an atypical agent, or discontinuing antipsychotic treatment altogether in the hope of facilitating remission is recommended. For moderate to severe TS, tetrabenazine or reserpine may be the most effective agent. Neuroleptics should be resumed to treat TD in the absence of active psychosis only as a last resort for persistent, disabling, and treatment-resistant TD.

CONCLUSIONS

The severity of the TS and the absolute need for antipsychotic therapy often dictate the treatment approach for this disorder.

Antipsychotic-Induced movement disorders in the elderly: epidemiology and treatment recommendations

We reviewed the epidemiological aspects of antipsychotic-induced movement disorders as they pertain to older patients. The incidence and prevalence of drug-induced parkinsonism and tardive dyskinesia (TD) are significantly greater in the older patient than in the younger patient whereas akathisia seems to occur evenly across the age spectrum and dystonia is uncommon among older patients. The literature on risk factors associated with treatment-emergent movement disorders is highly variable. Treatment practices vary across the age range and the interaction between age and antipsychotic dosage confounds our understanding of the relative importance of treatment-related risk factors. However, there is general agreement that pre-existing extrapyramidal signs (EPS) increase the vulnerability of the patient to developing significant drug-induced movement disorders. Elderly patients with dementia are at greater risk than patients without dementia for persistent drug-induced EPS. Management of drug-induced movement disorders in the older patient requires careful consideration of the contraindications imposed by such agents as anticholinergics and beta-blockers. At present, well-controlled double-blind studies of second-generation antipsychotics such as clozapine, risperidone. olanzapine or quetiapine for reducing the risk of treatment-emergent movement disorders in the elderly have not been published. However, open-label studies of atypical antipsychotics demonstrate a markedly lower incidence of both EPS and TD compared with conventional antipsychotic treatment in the elderly. There is emerging literature in support of atypical antipsychotics for the treatment of existing drug-induced movement disorders. More controversial is the use of adjunctive antioxidants in newly treated patients who are vulnerable to drug-induced movement disorders. While the evidence is mixed in support of antioxidants for the treatment of TD, the possibility remains that prophylactic use of antioxidants may help reduce the incidence of TD. The development of a drug-induced movement disorder often reduces the quality of life in an elderly patient. Effective pharmacological management requires cooperation from the patient and family, which can be fostered early in the patient's care through proper informed consent. The risks and benefits of antipsychotic treatment in the elderly patient need to be communicated to the patient and family. At the present time, there is no consistently effective treatment for patients with TD once it develops. Therefore, attention should focus on its prevention and close monitoring.

Tardive Dyskinesia

Although there are many published studies on the treatment of tardive dyskinesia (TD), relatively few treatments have proven to be consistently useful in clinical practice. Reviewed critically, most treatments have produced only slight to moderate benefit in less than half the patients treated. Emphasis instead is on prevention, prompt detection, and management of early and potentially reversible cases. If a patient develops dyskinesia while taking an antipsychotic drug (APD), ideal management is immediate discontinuation of the APD, if this is psychiatrically feasible. The manifestations of TD should be documented and the patient examined to exclude other possible causes of dyskinesia. APDs should then be withheld in the hope that the dyskinesia will disappear. Although the dyskinesia may fade within several weeks, it has the potential to recur if APD treatment is reintroduced. Psychiatric reevaluation to consider alternative psychiatric diagnoses or treatments is strongly advised. If there is no alternative to reintroducing an APD for psychiatric treatment, then an atypical neuroleptic should be considered. Because dyskinesia is very often not disturbing enough to require treatment, the need for treatment of TD should be carefully assessed. For mild dyskinesia, low doses of a benzodiazepine (eg, clonazepam) may reduce the amount of both dyskinesia and associated anxiety. Anticholinergic drugs are unhelpful and may aggravate TD but, similar to their effect in idiopathic dystonia, may be effective in tardive dystonia. Botulinum toxin injections are of considerable value in managing localized forms of tardive dystonia, such as retrocollis or blepharospasm. Tetrabenazine and reserpine are presynaptic dopamine depletors that may have considerable efficacy in TD, especially tardive dystonia; however, their use is often limited by side effects. Based on the rationale that TD may be due to formation of free radicals, vitamin E has been used for treatment of TD, with mixed results. In some patients with persistent and disabling TD that fails to remit even after the patient is no longer taking an APD, it may be necessary to resume treatment eventually with a typical APD. This approach should be considered only as a last resort to suppress TD, however, because it carries the risk of preventing remission and possibly aggravating TD. In this case, further attempts to taper and discontinue the APD are recommended. At present, there is no evidence that established TD continues to progress in severity with continued APD exposure. This nonprogressive character of TD may provide to be a consolation to the patient and family and is also of potential medical-legal importance.

Tardive and idiopathic oromandibular dystonia: a clinical comparison

OBJECTIVE

Most patients with tardive dystonia have a focal onset involving the cranial-cervical region. Because of its resemblance to idiopathic cranial dystonia, a common form of dystonia, it often poses a diagnostic problem. To compare clinical features and response to botulinum toxin (BTX) injections between patients with tardive and idiopathic oromandibular dystonia (OMD).

METHODS

Patients seen in a movement disorder clinic who satisfied the inclusion criteria for tardive or idiopathic OMD were studied. The clinical variables and responses to BTX between the two groups of patients were compared. In the tardive group, we also compared the clinical variables between those with oro-facial-lingual stereotypies, and those without.

RESULTS

Twenty four patients with tardive OMD and 92 with idiopathic OMD were studied. There were no differences in the demographic characteristics. Most were women, with duration of symptoms longer than 8 years. The mean duration of neuroleptic exposure was 7.1 (SD 7.9) years. Jaw closure was the most frequent subtype of OMD (tardive=41.7%, idiopathic=51.1%). Idiopathic patients were more likely to have coexistent cervical dystonia (p<0.05), whereas isolated OMD was significantly higher in tardive patients (p<0.05). Limb stereotypies, akathisia, and respiratory dyskinesia were seen only in the tardive OMD. Frequency of oro-facial-lingual stereotypy was significantly higher in the tardive than the idiopathic group (75.0% v 31.5%, p<0.0001). The peak effect of BTX was similar in both groups.

CONCLUSIONS

Oro-facial-lingual stereotypies were significantly more frequent in the tardive than the idiopathic group. Presence of stereotypic movements in the limbs, akathisia, and respiratory dyskinesias in patients with OMD strongly suggests prior neuroleptic exposure. Dystonia in tardive OMD is more likely to be restricted to the oromandibular region, whereas in patients with idiopathic OMD, there is often coexistent cervical dystonia. BTX is equally effective in both groups of patients.

The current status of tardive dystonia

Tardive dystonia (TDt), a persistent dystonia associated with exposure to neuroleptic drugs, is an uncommon disorder. It differs from tardive dyskinesia (TDk) in epidemiology, clinical features, risk factors, pathophysiology, course, prognosis, and treatment outcome. TDt seems to develop faster and is more painful, distressing, and disabling than tardive dyskinesia. In this article, evidence is reviewed on the face, descriptive, construct, and predictive validity of this iatrogenic complication of antipsychotic drugs. It is suggested that TDt should not be lumped together with TDk. It deserves a separate nosological status as an independent diagnostic category. The subclassification of TDt into various subtypes based on coexistence of other movement disorders is suggested.

Dystonia

Many different disorders have dystonia as the only or primary sign. The list of causes for dystonia increases yearly and now includes three mapped loci for primary torsion dystonia, although other susceptibility genes are suspected. Study of one of these primary torsion dystonia loci (DYT1) has culminated in the cloning of a gene which codes for a novel protein, torsin A. Physiological and positron emission tomography analyses suggest that dystonia results from impaired inhibition at cortical and subcortical levels; these physiological changes may in turn be due to striatal dysfunction and a mismatch or imbalance between the direct and indirect pathways. Future study of normal and mutant torsin A, as well as the identification of other primary torsion dystonia genes, should help elucidate the mechanisms underlying dystonia.

Clinical comparison of tardive and idiopathic cervical dystonia

It has been suggested that tardive cervical dystonia may be clinically indistinguishable from the idiopathic form and that the diagnosis rests solely on documenting an exposure to dopamine antagonist medications. To investigate this, we performed a retrospective evaluation of patient records on 102 patients with idiopathic and 20 patients with tardive cervical dystonia seen in our Movement Disorder Clinic over the past 8 years. Several clinical and demographic variables were compared and a number of differences were observed. The presence of extracervical involvement, retrocollis, and spasmodic head movements were individually found to be predictive of tardive cervical dystonia. Torticollis, laterocollis, and trick maneuvers were predictive of idiopathic cervical dystonia. Head tremor (42.2%) and family history of dystonia (9.8%) were present only in the idiopathic group. Cervical muscle hypertrophy was significantly more common in the idiopathic group (100% versus 75%). No difference was found between the two groups in their response to treatment with botulinum toxin A. These results indicate that clinical differences between idiopathic and tardive cervical dystonia exist. These differences may help to distinguish them in the clinical setting, improve diagnostic accuracy, and support the existence of a causal relationship between exposure to dopamine antagonist medications and chronic dystonia.

Drug-induced movement disorders

Drug-induced movement disorders are often unrecognized, especially when not due to dopamine receptor blockers. This review discusses acute, subacute, and chronic syndromes. Pathophysiology relates almost always to dopaminergic transmission. Patient-dependent vulnerability and drug-dependent sensitivity are contributing factors. Young patients are more prone to acute reactions, and tardive or chronic conditions are more frequent in the elderly. Subclinical Parkinsonism can be unmasked by medication exposure. Treatment of tardive dyskinesia remains a challenging task for the clinician, but novel antipsychotics and dopamine depleting agents can be beneficial.