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doi: 10.1097/01.NURSE.0000428333.01107.94

Assessing for pronator drift

Rank, Wendi MSN, RN, CNRN, CRNP

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Wendi Rank is a board member of the Philadelphia chapter of the American Association of Neuroscience Nurses.

The author has disclosed that she has no financial relationships related to this article.

Can you explain the significance of pronator drift in a neurologic assessment?—AL, ILL.

Wendi Rank, MSN, RN, CNRN, CRNP, replies: Assessing for pronator drift helps you evaluate motor function in a patient who's awake and able to follow directions. Evaluation of the motor system is part of a good general neurologic assessment of a patient with a neurologic diagnosis or comorbidity, or acute neurologic deficits.1

The motor assessment should include assessment of muscle bulk, strength, and tone. Assessment of gait, posture, involuntary movements, and coordination should also be performed. The motor assessment can yield valuable information about the function and integration of such structures as the frontal lobe, cerebellum, and spinal cord.1

To assess for pronator drift, explain to your patient what he or she needs to do. Depending on the patient's condition, ask him or her to stand or sit. Ask the patient to close his or her eyes, then to stretch out both arms with the palms facing up. (See Testing for pronator drift.) Your patient should maintain this position for 20 to 30 seconds. Observe both arms. If your patient's motor pathway is intact, the arms should remain in this position equally.2

Patients with a slight weakness in one arm won't be able to keep the affected arm raised, and ultimately the palm may begin to pronate, or turn downward. (See Picturing pronator drift.) This is pronator drift, which indicates abnormal function of the corticospinal tract (the upper motor neurons in the brain and spinal cord that mediate voluntary muscle movement) in the contralateral hemisphere. In some patients, the arm may remain supinated but drop lower than the unaffected arm, and the fingers and elbow might flex. Pronator drift may occur in patients with cerebral injury such as stroke or cervical spine injury.1,2

Other abnormal findings include an arm that moves up or laterally. This is a sign of loss of proprioception (position sense), which is mediated by the spinothalamic tract.1,2

Be sure the patient keeps his or her eyes closed during the exam, and don't ask the patient to raise the arms until after closing the eyes. If the patient can see the drift, the brain will use the sensory input to correct it.

If your patient's arms remain equally raised and supinated, instruct him or her to keep the arms up and eyes closed, and use your fingers to tap both arms briskly downward. In a patient with intact proprioception, muscle strength, and coordination, both arms will return to the starting position.

Document whether or not you observe drift, and if so, which arm drifts and the direction of the drift. Pronator drift must be interpreted in context with the remainder of your assessment. Further diagnostic testing, such as computed tomography or magnetic resonance imaging, may be indicated, particularly if this is a new deficit. Notify the healthcare provider if the patient has a pronator drift that hasn't been documented in a prior assessment.2

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Figure. Testing for ...
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1. Hickey J.The Clinical Practice of Neurological and Neurosurgical Nursing. 6th ed. Philadelphia, PA: Wolters Kluwer Health/Lippincott Williams and Wilkins; 2009.

2. Rank W.Simplifying neuro assessment. Nurs Made Incredibly Easy! 2010;8(2):15–19.

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Bickley LS, Szilagyi PG.Bates' Guide to Physical Examination and History Taking. 10th ed. Philadelphia, PA: Wolters Kluwer Health/Lippincott Williams and Wilkins; 2009.

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