Asessing the presence and severity of drug-induced Parkinsonism (Extrapyramidal Side Effects - EPS).
Monitoring patients on first-generation and high-potency second-generation antipsychotics.
Evaluating the effectiveness of anticholinergic rescue medications (e.g., benztropine).
Standardized reporting of motor side effects in clinical trials.
Section 2
Formula & Logic
Scoring Component
The SAS consists of 10 items assessing gait, arm dropping, shoulder shaking, elbow rigidity, wrist rigidity, head rotation, glabella tap, tremor, salivation, and akathisia. Each item is rated from 0 to 4.
Diagnostic Threshold
Mean Score > 0.3
Indicator of clinically significant Parkinsonism
Calculation
Total score divided by 10 (number of items)
Section 3
Pearls/Pitfalls
Rigidity Focus
The SAS is heavily weighted towards muscle rigidity and gait, making it more specific for Parkinsonism than simple tremor assessments.
Clinical Pearls
The "Glabella Tap" (Meyerson's sign) is a primitive reflex; persistent blinking despite instructions is a hallmark of Parkinsonian pathology.
Wrist and elbow rigidity should be tested via passive range of motion with the patient in a relaxed state.
If the mean score exceeds 0.3, consider reducing the antipsychotic dose or switching to an agent with lower D2 affinity (e.g., quetiapine, clozapine).
Section 4
Next Steps
Clinical Management
01
Mean > 0.3: Review current medication regimen. Distinguish from "negative symptoms" which can mimic motor retardation.
02
Prophylaxis: Routine SAS monitoring every 3-6 months for patients on maintenance antipsychotics.
03
Intervention: If motor symptoms interfere with function (salivation, gait instability), initiate anticholinergic therapy or dose titration.
Section 5
Evidence Appraisal
Primary Reference
A rating scale for extrapyramidal side effects
Simpson GM et al. • Acta Psychiatrica Scandinavica. Supplementum. 1970;Vol 212. pp. 11-19. The original publication of the scale.
Section 6
Literature
George Simpson
Developed by Dr. George Simpson and colleagues. It has remained a standard tool for over 50 years for assessing movement disorders in psychiatry.
