When limited by the number of motor tests that can be performed on a patient suspected of having a stroke, the pronator drift may be your best bet! This test may be positive in as many as 94% of patients within a week of having a stroke (1). An advantage of this maneuver is that it can point to subtle lesions in the corticospinal tract (CST) often missed by formal strength testing.
To perform the test, ask the patient to hold his or her arms straight out in front with palms facing upwards and eyes closed for 20-30 seconds. Slight pronation of one hand and flexion of the elbow suggests mild drift. Additional downward drift of the entire arm may also be present with more severe deficits (2). Interestingly, if one arm drifts upward this suggests a lesions outside the CST, possibly a cerebellar or parietal lesion, which may be equally concerning.
- Louis ED, King D, Sacco R, et al. Upper motor neuron signs in acute stroke: prevalence, interobserver reliability, and timing of initial examination. J Stroke Cerebrovasc Dis 1995;5:49-55. https://www.ncbi.nlm.nih.gov/pubmed/26486559
- Campbell, WW. In DeJong’s The Neurologic Examination-6th Ed, p389-392, 2005. Lippincott Williams&Wilkins, Philadelphia.
Contributed by Alexis Roy, Harvard Medical Student, Boston, MA.