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Assessment Tool: SAS — Simpson-Angus Rating Scale

The SAS quantifies antipsychotic-induced parkinsonism across 10 motor domains. Rate each item after observing the patient's gait and performing structured passive movement tests. The mean SAS score (total divided by 10) above 0.3 indicates clinically significant extrapyramidal symptoms. EPS can be misdiagnosed as depression — accurate identification prevents inappropriate escalation of antipsychotic dose.

SAS — Simpson-Angus Rating Scale

A validated 10-item clinician-rated scale for quantifying antipsychotic-induced parkinsonism (drug-induced EPS). Each item is rated 0–4; total score is divided by 10 to produce a mean score. Developed by George Simpson and John Angus (1970). Mean SAS score > 0.3 suggests clinically significant extrapyramidal symptoms.

Mean score interpretation (Total ÷ 10)

≤ 0.3

Normal / clinically insignificant EPS

> 0.3

Clinically significant antipsychotic-induced EPS

Clinical note: Antipsychotic-induced parkinsonism can be misdiagnosed as depression (masked facies, slowed movement, apparent apathy). Differentiating drug-induced EPS from worsening psychiatric illness is critical to avoid inappropriate antipsychotic escalation.
1. Gait

Patient is asked to walk

2. Arm Drop

Patient and examiner raise both arms 90° and let them fall to sides

3. Shoulder Shaking

Patient is seized by the shoulder and shaken

4. Elbow Rigidity

Passive movement of elbow with patient seated; rate right/left worst

5. Wrist Rigidity

Passive movement of wrist (flexion/extension)

6. Leg Pendulousness

Patient sits on edge of table; legs swing freely

7. Head Rotation

Flex head against resistance of examiner's hands

8. Glabella Tap

Series of firm taps on glabella of forehead at a speed of approximately 2 per second

9. Tremor

Observe patient while standing and during walking

10. Salivation

Observe during interview and walking