Assessment of extrapyramidal symptoms during acute neuroleptic treatment

Acute administration of traditional neuroleptic drugs is often accompanied by the emergence of extrapyramidal symptoms (EPS). The use of a standardized scale to measure EPS can assist the clinician in assessing the occurrence and severity of these adverse reactions. The current work presents the interrater reliability and validity of the Yale Extrapyramidal Symptom Scale (YESS)--an eight-item, easy-to-administer scale for assessing emergence, severity, and type of side effects that commonly occur during acute treatment.

Interrater reliability (Study 1) and validity (Study 2) of the scale were studied using two independent samples of acutely psychotic patients treated with neuroleptic drugs. Study 1: Interrater reliability was assessed by comparing the YESS ratings of two clinicians blind to the other's rating and to the patient's drug regimen and dose. Study 2: Validity was studied by examining whether YESS items correlated with other EPS measures (convergent validity) but not with psychotic symptoms that may be confused with EPS (discriminant validity).

Interrater agreement between clinicians was good to excellent. YESS items correlated with assessments used to measure symptoms of Parkinson's disease and akathisia and generally showed low nonsignificant correlations with ratings of symptoms of psychosis.

The current work presents a brief EPS scale for the assessment of commonly occurring neuroleptic-induced extrapyramidal side effects. It was demonstrated that the YESS could be used reliably across clinician raters and that the YESS is a valid measure for assessing EPS during acute treatment.