Pronator Drift

Definition

A routine procedure in a neurological examination in which patients are asked to extend both arms anteriorly and hold them at shoulder height with the palms facing up (supine position) for at least 10 s while keeping their eyes closed. The pathological response is for one of the arms to drift (up, down, or out) and/or for the hand to begin to pronate (turn palm down). Such a response can be indicative of either an upper motor neuron lesion anywhere along the neuroaxis or from a disturbance of proprioception anywhere from the parietal cortex down. An upward or lateral drift of the arm, with or without pronation, tends to be more suggestive of a proprioceptive than a motor (weakness) deficit, although a downward drift does not rule out a problem with proprioception.

A manifestation of upper motor neuron (UMN) disease is seen when the affected patient is unable to maintain a posture of outstretched hands held in the palms-up (supine) position with the eyes closed. In the...