Objective To examine a new neurological sign that uses synergistic oppositional movements of the arms to evaluate for non-organic upper extremity weakness.

Methods Patients with unilateral arm weakness were tested in a standing or sitting position with the elbows flexed at 30°. The examiner held both forearms near the wrists while asking the patient to flex or extend the normal arm at the elbow and simultaneously feeling for flexion or extension of the contralateral (paretic) arm. In patients with organic paresis, there was not a significant detectable force of contralateral opposition of the paretic limb. Patients with non-organic arm weakness had detectable strength of contralateral opposition in the paretic arm when the normal arm was tested.

Results The test was first performed on 23 patients with no complaint of arm weakness. Then, 31 patients with unilateral arm weakness were tested (10 with non-organic weakness and 21 with organic weakness). The elbow flex-ex sign correctly identified the cause of weakness in all cases.

Conclusions The elbow flex-ex sign is useful in differentiating between functional and organic arm paresis.