In medicine, pronator drift (also known as pyramidal drift) refers to a pathologic sign seen during a neurological examination. Jean Alexandre Barré is credited with having first described it; thus it is sometimes known as the Barré test or sign. A positive result indicates spasticity. This sign can appear due to an upper motor neuron lesion or various other conditions (including inborn errors of metabolism) which include spasticity as a symptom.
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Description
The patient is asked to hold both arms fully extended at shoulder level in front of them, with the palms upwards, and hold the position. If they are unable to maintain the position the result is positive. Closing the eyes accentuates the effect, because the brain is deprived of visual information about the position of the body and must rely on proprioception. Tapping on the palm of the outstretched hands can accentuate the effect.
Interpretation
This is a test of upper motor neuron disease.
If a forearm pronates, with or without downward motion, then the person is said to have pronator drift on that side reflecting a contra-lateral pyramidal tract lesion. A lesion in the ipsilateral cerebellum or ipsilateral dorsal column usually produces a drift upward, along with slow pronation of the wrist and elbow.