Pronator drift test

Historical Background

Jean Alexandre Barré first described a sensitive leg sign in 1919 for detecting subtle pyramidal paresis, with the patient prone and one leg flexed at the hip and knee. His 1920 paper introduced the upper limb test—arms outstretched, eyes closed, palms supinated—which later became known as Barré sign or pronator drift. Giovanni Mingazzini had described a similar arm‑drift phenomenon several years earlier, and the coexistence of these names reflects how the sign evolved within neurology.


Clinical Mechanism

In upper motor neuron lesions, the supinator muscles weaken more than the pronators. As a result, the affected arm gradually drifts downward and the palm turns inward. Clinicians often teach that pronation represents an evolutionarily older, subcortically driven movement pattern that emerges when pyramidal control is impaired.


Diagnostic Utility

Studies have shown that the pronator drift test is highly sensitive and specific for detecting mild unilateral cerebral lesions. A related observation—downward drift without pronation—has been reported as a strong indicator for distinguishing functional weakness from organic weakness.


NIHSS Link

New‑onset pronator drift is a classic sign of acute ischemic stroke and is incorporated into the arm‑drift item of the NIH Stroke Scale.


Recommended Video

A clear demonstration of the technique (arms extended, palms up, eyes closed) is available here:

https://www.youtube.com/watch?v=2MkNKTXp7L8


Key Reference

Barré’s original description of the upper‑limb test appeared in his 1920 article 

La signe de la déviation radiale et l’épreuve de la pronation de l’avant‑bras in Revue Neurologique.

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