Psychiatry · Extrapyramidal Symptoms
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Tardive dyskinesia is a hyperkinetic movement disorder caused by long-term exposure to dopamine receptor-blocking agents.
The pathophysiology involves dopamine receptor supersensitivity in the nigrostriatal pathway following chronic blockade.
Classic clinical presentation includes involuntary orofacial movements such as lip smacking, tongue protrusion, and jaw grinding.
The first-line management step is to discontinue or taper the offending antipsychotic or switch to a second-generation antipsychotic with lower risk, such as quetiapine or clozapine.
Valbenazine and deutetrabenazine are the FDA-approved VMAT2 inhibitors indicated for the treatment of moderate to severe tardive dyskinesia.
Tardive dyskinesia is a chronic condition that may become irreversible if the offending agent is not identified and managed early.
The Abnormal Involuntary Movement Scale (AIMS) is the standardized clinical tool used to monitor and quantify the severity of dyskinetic movements.
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A 62-year-old male with a history of schizophrenia presents for a follow-up visit. He has been maintained on haloperidol for the past 8 years. During the interview, the physician observes repetitive lip smacking, tongue thrusting, and involuntary choreoathetoid movements of the extremities. The patient reports these movements have been present for several months and are causing him social distress. His mental status is stable with no evidence of acute psychosis.
What is the most appropriate pharmacologic intervention for this patient's condition?
Valbenazine
The patient exhibits classic signs of tardive dyskinesia due to long-term typical antipsychotic use; VMAT2 inhibitors like valbenazine are the indicated treatment when the offending agent cannot be discontinued.
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Etiology / Epidemiology
Caused by long-term dopamine receptor blockade from antipsychotics. Older age and female sex are primary risk factors.
Clinical Manifestations
Involuntary orofacial movements including lip smacking and tongue protrusion. Repetitive, choreoathetoid movements.
Diagnosis
Clinical diagnosis using the AIMS scale. No specific lab values; ruling out other movement disorders is required.
Treatment
Discontinue or switch to clozapine. Use valbenazine or deutetrabenazine for persistent cases.
Prognosis
Often irreversible if not caught early. Early detection is the only way to prevent permanent disability.
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Epidemiology & Etiology
Occurs in patients on chronic antipsychotic therapy, particularly first-generation agents. Risk increases with cumulative dose and duration of exposure. Elderly patients are at significantly higher risk for developing permanent symptoms.
Pertinent Anatomy
Involves the nigrostriatal pathway within the basal ganglia. Dysregulation of the striatum leads to the characteristic hyperkinetic movements.
Pathophysiology
Chronic blockade of postsynaptic D2 receptors leads to receptor supersensitivity and upregulation. This results in a relative excess of dopaminergic activity in the basal ganglia. The imbalance between dopamine and acetylcholine manifests as involuntary, repetitive movements.
Clinical Manifestations
Patients present with orofacial dyskinesia, including lip smacking, tongue protrusion, and grimacing. Limb involvement may include choreoathetoid movements or piano-playing finger motions. Red flag: symptoms may worsen or emerge upon dose reduction or discontinuation of the offending agent.
Diagnosis
Diagnosis is clinical, supported by the Abnormal Involuntary Movement Scale (AIMS). Clinicians must perform a thorough medication review to confirm exposure. Rule out metabolic, infectious, or structural causes of movement disorders before confirming.
Treatment
First step is to taper and discontinue the offending antipsychotic if clinically feasible. If psychiatric stability requires continued treatment, switch to clozapine due to its low risk profile. For persistent cases, valbenazine or deutetrabenazine (VMAT2 inhibitors) are the first-line pharmacologic treatments. Contraindication: Avoid anticholinergics, as they may worsen symptoms.
Prognosis
Symptoms are irreversible in up to 50% of cases if not identified early. Routine AIMS monitoring every 6 months is required for all patients on long-term antipsychotics to ensure early detection.
Differential Diagnosis
Drug-induced Parkinsonism: presents with bradykinesia and rigidity, not chorea
Huntington's disease: presents with family history and cognitive decline
Tourette syndrome: presents with vocal tics and onset in childhood
Wilson's disease: presents with liver dysfunction and Kayser-Fleischer rings
Acute dystonia: presents with sustained muscle contractions, not repetitive movements