What is the difference between Acute Dystonia and Tardive Dyskinesia (TD), a condition characterized by involuntary, repetitive body movements?

From the Guidelines

Acute dystonia and tardive dyskinesia are distinct movement disorders associated with antipsychotic medications, with acute dystonia being reversible and responsive to anticholinergic medications, whereas tardive dyskinesia is often irreversible and requires prevention strategies and treatment with VMAT2 inhibitors. The key differences between acute dystonia and tardive dyskinesia lie in their timing, presentation, and management. Acute dystonia occurs early in treatment, usually within hours to days, and presents as sustained muscle contractions causing abnormal postures, often affecting the neck, eyes, tongue, or jaw 1. It responds rapidly to anticholinergic medications like benztropine (1-2mg IV/IM) or diphenhydramine (25-50mg IV/IM). In contrast, tardive dyskinesia develops after months or years of antipsychotic use and manifests as involuntary, repetitive movements typically affecting the face, mouth, and tongue, though it can involve the extremities and trunk 1.

Some of the main points to consider when managing these conditions include:

• The use of anticholinergic medications for acute dystonia
• The importance of prevention strategies for tardive dyskinesia, such as using the lowest effective dose of antipsychotics and preferring atypical over typical antipsychotics
• Regular monitoring with standardized assessments like the AIMS scale to detect early signs of tardive dyskinesia
• The potential use of VMAT2 inhibitors like valbenazine or deutetrabenazine for the treatment of tardive dyskinesia. The underlying mechanism for acute dystonia involves dopamine blockade causing relative cholinergic excess, while tardive dyskinesia results from dopamine receptor hypersensitivity after prolonged blockade, explaining their different time courses and treatment approaches 1.

Given the potential for significant morbidity and impact on quality of life associated with these conditions, it is essential to prioritize prevention and early detection of tardive dyskinesia, and to manage acute dystonia promptly and effectively. This can be achieved by following established guidelines and using evidence-based treatments, such as those recommended by the American Academy of Child and Adolescent Psychiatry 1.

From the Research

Definition and Characteristics

• Acute dystonia is a movement disorder characterized by sustained muscle contractions, frequently causing twisting and repetitive movements, or abnormal postures 2.
• Tardive dyskinesia is a movement disorder characterized by irregular, stereotyped, and choreiform movements associated with the use of antipsychotic medication 3.
• Tardive dyskinesia encompasses a broad spectrum of hyperkinesias associated with exposure to neuroleptics, and dystonia is one of the most common expressions of tardive dyskinesia 2.

Causes and Risk Factors

• Tardive dyskinesia is caused by the blockade of dopamine receptors by antipsychotic drugs 4.
• The chronic use of dopamine receptor blocking agents, most commonly antipsychotics, can lead to a movement disorder called tardive dyskinesia 5.
• Exposure to dopamine receptor blocking agents (DRBAs) such as antipsychotics or antiemetics is associated with a spectrum of movement disorders including tardive dyskinesia 6.

Diagnosis and Differential Diagnosis

• The differential diagnosis of tardive dyskinesia is based on history of DRBA exposure, recent discontinuation or dose reduction of a DRBA, and movement phenomenology 6.
• Common diagnostic challenges are the abnormal behaviors and dyskinesias associated with advanced age or chronic mental illness, and other movement disorders associated with DRBA therapy, such as akathisia, parkinsonian tremor, and tremor related to use of mood stabilizing agents 6.
• Duration of exposure may help rule out acute drug-induced syndromes such as acute dystonia or acute/subacute akathisia 6.

Treatment Options

• Preventing tardive dyskinesia is of primary importance, and clinicians should follow best practice for prescribing antipsychotic medication, including limiting the prescription for specific indications, using the minimum effective dose, and minimising the duration of therapy 3.
• The first-line management of tardive dyskinesia is the withdrawal of antipsychotic medication if clinically feasible 3.
• Switching from a first-generation to a second-generation antipsychotic with a lower D2 affinity, such as clozapine or quetiapine, may be effective in reducing tardive dyskinesia symptoms 3.
• Valbenazine is a relatively newer option for the treatment of tardive dyskinesia in adults, and is thought to function as a highly selective inhibitor of the VMAT2 vesicular monoamine transporter resulting in decreased availability of dopamine in the presynaptic cleft 5.
• Electroconvulsive therapy may be an effective treatment option for tardive dyskinesia and dystonia refractory to valbenazine treatment 4.