How do you differentiate between akathisia and tardive dyskinesia in a patient with a history of antipsychotic medication use?

Differentiating Akathisia from Tardive Dyskinesia

Akathisia is a subjective sense of severe restlessness with pacing and agitation that occurs early in treatment (days to weeks), while tardive dyskinesia consists of involuntary rhythmic movements primarily in the orofacial region that develops after prolonged antipsychotic exposure (months to years). 1, 2

Timing of Onset

The most reliable distinguishing feature is when the symptoms appear:

• Akathisia develops during the initial treatment phase, typically within days to weeks after starting antipsychotic medication or increasing the dose 1, 2
• Tardive dyskinesia emerges after prolonged antipsychotic use, typically after months or years of treatment 1, 2

A critical caveat: tardive akathisia exists as a variant that develops after long-term treatment, complicating this distinction 3, 4. In one series, 34% of tardive akathisia cases developed within 1 year of treatment 3.

Nature of the Symptoms

Akathisia Characteristics:

• Subjective component is fundamental: an inner sense of restlessness, severe tension, and compulsion to move 5, 6
• Movements are semi-voluntary: the patient moves to relieve the subjective distress 6
• Manifests as pacing, inability to sit still, marching in place, crossing/uncrossing legs, trunk rocking 5, 3
• Often misinterpreted as psychotic agitation or anxiety, leading to inappropriate dose increases 5

Tardive Dyskinesia Characteristics:

• Movements are involuntary and rhythmic: the patient cannot suppress them voluntarily 2, 6
• Characterized by athetoid or choreic movements, typically rapid involuntary facial movements including blinking, grimacing, chewing, or tongue movements 5, 1
• Primarily affects the orofacial region (buccolingual-masticatory area) but can involve any body part 5, 2
• Does NOT present with tremor as a primary feature 7

Location of Movements

• Akathisia: predominantly affects the legs and trunk, with complex stereotyped movements like marching in place, leg crossing, trunk rocking 3
• Tardive dyskinesia: primarily orofacial (tongue protrusion, lip smacking, chewing movements), though choreiform limb movements can occur 5, 6

Associated Features

Akathisia:

• May occur alongside other acute extrapyramidal symptoms (dystonia, parkinsonism) 5, 2
• Causes severe subjective distress and is a common reason for medication noncompliance 5
• Associated with increased suicide risk due to the overwhelming urge to move and severe distress 8

Tardive Dyskinesia:

• Often occurs in isolation without other extrapyramidal symptoms 2
• Patient may be unaware of the movements initially 6
• Up to 50% of youth receiving neuroleptics may experience some form of tardive or withdrawal dyskinesia 5, 1

Response to Treatment

This is a critical differentiating factor:

Akathisia Management:

• Responds to lowering the antipsychotic dose if clinically feasible 5, 1
• β-blockers or benzodiazepines provide relief 5, 1
• Anticholinergic agents are not consistently helpful for akathisia 5

Tardive Dyskinesia Management:

• Does NOT respond to anticholinergics (these are contraindicated) 7
• Worsens or unmasks with antipsychotic dose reduction initially 1
• Requires VMAT2 inhibitors (valbenazine or deutetrabenazine) as first-line pharmacotherapy for moderate to severe cases 1, 7
• May persist indefinitely even after medication discontinuation 1, 2

Risk Factors

Akathisia:

• Young age, male gender 5, 2
• High-potency typical antipsychotics 2
• Higher doses 2

Tardive Dyskinesia:

• Older age, female gender 1
• Prolonged antipsychotic exposure 1
• Presence of acute EPS may predict later TD 1
• Diabetes mellitus, affective disorders 1

Practical Assessment Algorithm

When evaluating a patient on antipsychotics with movement abnormalities:

1. Document baseline movements using the Abnormal Involuntary Movement Scale (AIMS) before attributing symptoms to medication 1, 2

2. Ask about subjective distress: If the patient reports an overwhelming inner restlessness and urge to move, suspect akathisia 6, 8

3. Assess voluntary control: Ask the patient to suppress the movements. If they can temporarily suppress them or the movements relieve subjective distress, suspect akathisia 6

4. Check timing: Onset within days to weeks suggests akathisia; onset after months to years suggests tardive dyskinesia 1, 2

5. Observe location: Predominantly leg/trunk movements with pacing suggest akathisia; orofacial movements (tongue, lips, jaw) suggest tardive dyskinesia 5, 3

6. Look for other EPS: Concurrent dystonia or parkinsonism suggests acute akathisia rather than tardive dyskinesia 2

Critical Pitfall

Tardive akathisia exists as a distinct entity that shares features of both conditions: it develops after long-term treatment like TD but presents with akathisia symptoms 3, 4. These patients often have concurrent signs of tardive dyskinesia and may require years for symptom abatement (mean 2.7 years) 3. Catecholamine-depleting drugs (reserpine, tetrabenazine) showed the best response in tardive akathisia, with improvement in 87% and 58% respectively, though complete abatement occurred in only 33% at follow-up 3.