What is the Abnormal Involuntary Movement Scale (AIMS) and how is it used?

The Abnormal Involuntary Movement Scale (AIMS): Overview and Application

The Abnormal Involuntary Movement Scale (AIMS) is a standardized clinical assessment tool designed to detect and monitor tardive dyskinesia, consisting of a 12-item scale where items 1-7 assess involuntary movement severity across body regions on a 0-4 rating scale.

What is the AIMS Scale?

The AIMS is a clinician-administered rating scale developed to:

• Detect and monitor tardive dyskinesia (TD)
• Assess the severity of abnormal involuntary movements
• Document changes in movement disorders over time
• Evaluate treatment efficacy for movement disorders

The scale is considered the gold standard for evaluating treatment efficacy in TD clinical trials 1 and is widely used in clinical practice to monitor patients on antipsychotic medications.

Structure of the AIMS Scale

The AIMS consists of 12 items:

• Items 1-7: Assess severity of involuntary movements across different body regions
• Items 8-10: Global judgments about the movements
• Items 11-12: Questions about dental status (which can affect the assessment)

Rating Scale for Items 1-7:

• 0 = No dyskinesia
• 1 = Low amplitude, present during some but not most of the exam
• 2 = Low amplitude and present during most of the exam (or moderate amplitude and present during some of the exam)
• 3 = Moderate amplitude and present during most of exam
• 4 = Maximal amplitude and present during most of exam

Body Regions Assessed (Items 1-7):

1. Facial and oral movements

   • Muscles of facial expression (e.g., movements of forehead, eyebrows, periorbital area, cheeks)
   • Lips and perioral area (e.g., puckering, pouting, smacking)
   • Jaw (e.g., chewing movements, jaw opening, lateral movements)
   • Tongue (rate only increase in movement both in and out of mouth, NOT inability to sustain movement)

2. Extremity movements

   • Upper limbs (arms, wrists, hands, fingers)
   • Lower limbs (legs, knees, ankles, toes)

3. Trunk movements

   • Neck, shoulders, hips (e.g., rocking, twisting, squirming, pelvic gyrations)

How to Administer the AIMS

1. Preparation:

   • Have the patient seated in a chair with hands on knees, legs slightly apart, and feet flat on floor
   • Ask the patient to remove shoes and socks
   • Observe the patient unobtrusively at rest

2. Examination procedure:

   • Ask the patient about the current condition of their teeth and dentures
   • Ask if they notice any movements in their mouth, face, hands, or feet
   • Have the patient sit with hands hanging unsupported (observe for movements)
   • Ask the patient to open their mouth (observe tongue at rest)
   • Ask the patient to protrude their tongue (observe for abnormalities)
   • Ask the patient to tap their thumb with each finger as rapidly as possible for 10-15 seconds (observe facial and leg movements)
   • Have the patient stand up (observe trunk, legs, and entire body)
   • Have the patient extend both arms outstretched in front with palms down (observe trunk, legs, and mouth)
   • Have the patient walk a few paces, turn, and walk back to the chair (observe hands and gait)

3. Scoring:

   • Rate the highest severity observed for each body region
   • Rate movements that occur upon activation one less than those observed spontaneously
   • Complete all examination procedures before making ratings

Clinical Application and Interpretation

When to Use the AIMS:

• Baseline assessment before starting antipsychotic medication
• Regular monitoring every 3-6 months for patients on antipsychotics 2
• More frequent monitoring for high-risk patients (elderly, females, those with previous movement disorders)
• When TD is suspected or reported by patient/caregiver

Interpretation:

• TD diagnosis: Typically defined as at least mild symptoms (score ≥2) in ≥2 anatomical areas, OR moderate or greater symptoms (score ≥3) in ≥1 area 3
• AIMS total score: Sum of items 1-7, ranging from 0-28, with lower scores indicating improvement
• Clinical significance: A change of 2 points or more on the total score is generally considered clinically meaningful

Common Pitfalls and How to Avoid Them:

1. Inadequate observation time: Ensure sufficient time to observe movements during all examination procedures
2. Failure to distinguish TD from other movement disorders: Be familiar with differential diagnoses (e.g., akathisia, drug-induced parkinsonism)
3. Inconsistent rating: Training and experience significantly improve inter-rater reliability 4
4. Not accounting for dental status: Poor-fitting dentures can mimic or mask oral movements
5. Failure to document baseline: Always perform AIMS before starting antipsychotics

Clinical Implications

The AIMS is crucial for:

• Early detection of TD, which is essential as early intervention may prevent progression
• Monitoring treatment response to VMAT2 inhibitors like valbenazine or deutetrabenazine 2, 5
• Guiding medication adjustments (e.g., dose reduction, switching medications)
• Documentation for clinical and legal purposes

Research shows that implementing structured AIMS training significantly improves documentation compliance in clinical settings, with one study showing an increase from 3% to 87% after a one-hour training session 6.

While the AIMS remains the standard assessment tool, it has limitations in capturing the full impact of TD on patients' lives. Newer assessment tools like the Tardive Dyskinesia Impact Scale (TDIS) can complement the AIMS by providing patient-reported outcomes 1.

Conclusion

The AIMS scale is an essential tool for clinicians who prescribe antipsychotic medications. Regular and proper use of this scale can lead to earlier detection of TD and more timely interventions, potentially improving patient outcomes and quality of life.