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.
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Clinicians frequently encounter patients with physical exam findings that are not explained by organic pathology. Such symptoms may account for 10–30% of referrals to outpatient neurology clinics.1 ,2 The Hoover sign is a well-known test first described in 1908 to examine for non-organic weakness of the lower extremities by using synergistic movements of the legs.3 Other described tests similarly use this principle of complementary opposition by examining contralateral abduction and adduction at the hip to test for non-organic lower extremity weakness.4 ,5 Described tests for upper extremity function use synkinesias6 ,7 instead of complementary opposition. We observed upper extremity contralateral synergistic limb movements during flexion and extension at the elbow. These movements appear to keep the torso in a stable position while one arm is working against resistance. The elbow flex-ex sign uses this pattern of complementary opposition to evaluate for non-organic paresis of the proximal upper extremity.
The elbow flex-ex sign was first performed on patients with no complaint of arm weakness. The test was then performed on patients presenting to the outpatient neurology clinic with unilateral upper extremity weakness. The patients were examined by two physicians. EIT examined all of the patients. EB or TLL served as the second examiner. The examining physicians agreed on the interpretation of data gathered from performing the elbow flex-ex sign in all cases. EIT has been using the flex-ex sign routinely in all patients presenting to the clinic with upper extremity weakness and recording the findings. Our institutional review board approved a retrospective collection of the chart data for analysis.
The test was performed in 21 patients with organic weakness and 10 patients with non-organic weakness. Organic paresis was diagnosed using neuroimaging, electrodiagnostic studies and coexisting neurological examination findings (such as hyperreflexia or the Babinski sign). Non-organic weakness was diagnosed when there were physical exam findings (such as give-way weakness or symmetrical reflexes) arguing against organic pathology and neuroimaging or electrodiagnostic studies failed to find a specific aetiology. For each patient, the diagnosis was reached by consensus between at least two of the physicians caring for the patient (taken from a pool of EIT, EB, JW and TLL).
Performing the elbow flex-ex sign
The elbow flex-ex sign was performed in two parts while the patient was in either a standing or sitting position with the elbows flexed at a 30° angle. The examiner performed the elbow flex-ex sign by holding both forearms near the wrists. For the test's first part, the patient was asked to flex or extend the normal arm at the elbow while the examiner, also holding the resting (paretic) arm, felt for extension or flexion of the paretic arm (see figure 1A). In patients with organic paresis, there was not a significant detectable force of contralateral opposition of the paretic limb when asking the patient to move the normal arm. However, patients with non-organic weakness showed detectable strength of contralateral opposition in the paretic arm when the normal arm was tested for strength (thus showing involuntary synergistic oppositional movement of the paretic arm). The weakness was judged non-organic if the paretic arm displayed greater or normal strength during the complementary opposition manoeuvre than during manual testing. As a second part of the test, the patient was asked to flex the paretic arm at the elbow (see figure 1B), while the examiner felt for contralateral extension of the normal arm. Patients with non-organic weakness displayed poor strength of extension of the contralateral (normal) limb whereas patients with organic weakness showed normal effort of the contralateral arm during elbow flexion and extension. A supplementary video file, available online only, provides demonstration of the flex-ex sign.
Findings in patients without upper extremity weakness
The elbow flex-ex sign was first performed on patients who had no complaint of weakness before testing on patients with weakness. This was done to confirm that when a patient was asked to flex or extend at one elbow, the examiner could detect the presence of expected synergistic movements in the opposite arm. Of the 23 subjects examined, 22 (96%) demonstrated synergistic opposite muscle movement in the contralateral arm. The test did not detect evidence of organic weakness or non-organic weakness in these subjects.
Findings in patients with unilateral upper extremity weakness
A total of 31 patients presenting to the outpatient neurology clinic were examined. Of these, 21 were found to have organic paresis of the upper extremity after a thorough neurodiagnostic workup and 10 patients were diagnosed as having non-organic weakness. The elbow flex-ex sign was performed as part of the routine physical exam in all patients before a formal diagnosis was determined. In a majority of patients with either organic or non-organic weakness (including 7 of 10 of those with non-organic weakness), the test was performed prior to initiation of neurodiagnostic work-up. During the first part of the flex-ex test, all 21 patients with organic aetiology of arm weakness had no detectable or severely reduced muscle movement in the paretic arm when asked to move the normal arm whereas the 10 patients with non-organic unilateral upper extremity paresis had findings during the elbow flex-ex sign that were consistent with non-organic weakness (table 1). The first part of the elbow flex-ex sign showed 100% sensitivity and 100% specificity for differentiating between organic and functional upper extremity paresis. The second part of the two-part test (which relied on detecting synergistic movement of the normal arm) was not sensitive or specific.
This study demonstrates that the elbow flex-ex sign could be useful in differentiating between functional and organic paresis in patients presenting with unilateral upper extremity weakness. The flex-ex sign was designed with two parts, similar to Hoover's test. The newly described sign correctly differentiated between organic and non-organic arm weakness in all patients tested when interpreting results of the sign's first part.
Previously described signs
Tests previously described to distinguish between functional and organic upper extremity weakness include two using synkinesias, which are involuntary synchronous contraction movements of muscles in one limb when the same muscles are purposefully contracted in the contralateral limb.8 Tinazzi et al6 published a method that used synkinetic movements by measuring finger abduction strength simultaneously in both hands. When abducting against maximal resistance using the unaffected hand, it was possible to differentiate between organic and non-organic paresis by detecting any movement in the contralateral (symptomatic) hand. Another test has been described that uses synkinesias of shoulder adduction, based on the principle that when shoulder adduction is tested on one side, the contralateral side in normal individuals is also expected to adduct.7
Hoover attempted adaptation of his lower extremity sign, which uses involuntary synergistic movements of the legs (such as involuntary hip extension during contralateral voluntary hip flexion) for use in the upper extremities. However, he reportedly did not consistently observe such a sign in the upper limbs.9
Ziv et al10 used Hoover's concept of complementary opposition in the legs and applied it to the arms by using a computer to measure isometric force of arm movement while the patient was supine. The patient flexed the unaffected arm while held in an extended position and the strength of extension in the affected arm was quantitatively measured. During involuntary extension of the unaffected arm, the measured strength of the affected arm was absent in organic paresis and present in non-organic paresis.
Flex-ex sign compared with other tests
Our elbow flex-ex sign may be an important addition to bedside tests examining for non-organic paresis in the upper extremity. While Tinazzi et al's sign using synkinetic movements during finger abduction tests distal muscles, our test provides a way to examine for functional paralysis of proximal muscles. It may also be easier for the clinician at the bedside to differentiate between forces of larger proximal muscles rather than relying on strength of synkinetic finger abduction, which could be a subtler finding.
When compared with Ziv's test, ours is more likely to be of use to the average clinician because Ziv's test uses specialised computer equipment. Our test can more easily be performed at the bedside in the acute setting. Also, it may be easier to perform a test of arm strength while the patient is sitting or standing. The elbow flex-ex sign allows for patient examination in upright positions, whereas to perform Ziv's test while the patient is supine may be more awkward due to reaching over the patient to test both arms simultaneously.
The primary limitation for this study is that, like another recently published sign for examining non-organic lower extremity weakness,4 the examiners were not blinded to the patient's symptoms or to the aetiology of weakness. However, the exam was carried out at initial patient intake for most patients and therefore the correct diagnosis at the time the elbow flex-ex sign was performed was not known, making it less likely that weakness aetiology would impact physician interpretation of the flex-ex sign. Another possible limitation of our sign is that it relies primarily on the examiner detecting differences in strength by feel, whereas another sign in the lower extremities4 also used visual cues by observing for leg movement. Because neurologists detect level of strength by feel during the routine neurological exam, we expect that they could perform our test. Only the first component of our two-part test was sensitive and specific, possibly because it is easier to detect differences in the strength of a ‘paretic’ limb rather than feeling for subtle differences in normal limb strength.
The principles of contralateral opposition and/or synkinesia could be used to develop additional tests for non-organic weakness. For example, during evaluation of patients without weakness, we assessed contralateral opposition in the arms during shoulder abduction. While examining deltoid strength with the elbows bent and arms held at a horizontal level, downward pressure was applied to one arm while feeling for contralateral involuntary adduction of the opposite limb. This additional test still requires validation, but may be helpful in evaluating for functional upper extremity proximal weakness.
Functional symptoms can mimic neurological disorders11 and detection of non-organic symptoms is important because patients with unexplained symptoms are frequent users of healthcare resources.12 Because up to a third of patients in the neurology clinic have symptoms that are not solely explained by organic disease,2 physical exam techniques to detect non-organic weakness are needed. Such exam methods need to be sensitive and specific because it is undesirable to falsely label a patient as hysterical. There are reports of incorrect diagnoses of functional disorders being made when there is underlying organic pathology.13 There are previously described signs in the upper6 and lower3 ,4 extremities that appear reliable in making such distinctions. Like these previously published signs, the elbow flex-ex sign is a sensitive and specific tool to detect non-organic paresis.
The elbow flex-ex sign may be a useful tool to differentiate between organic and functional weakness of the upper extremity. Our findings suggest that a larger prospective study should be considered to validate these findings.
Thank you to Emmanuel H During, MD, John Jefferson, MD, Mani K Nezhad, MD, and Anishee Shah, MD, for assistance in making the online supplementary demonstration video.
Review history and Supplementary material
This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.
Files in this Data Supplement:
- Data supplement 1 - Online video
Contributors TLL authored the manuscript and assisted with data analysis. EIT designed the flex-ex maneuver, assisted with manuscript revisions, provided guidance for discussion with reviewers, performed study design, and gathered patient data. EB performed study design and gathered patient data. JW, JMC, DSE and AM assisted with study design and data interpretation as well as providing guidance for the manuscript.
Competing interests None.
Ethics approval Cedars-Sinai Medical Center IRB.
Provenance and peer review Not commissioned; externally peer reviewed.
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