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Importance of clinical tests to detect non-organic paresis
  1. Masahiro Sonoo
  1. Correspondence to Professor Masahiro Sonoo, Department of Neurology, Teikyo University School of Medicine, Tokyo 1738605, Japan; sonoom{at}med.teikyo-u.ac.jp

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Non-organic symptoms and signs have been one of the main targets of neurology for more than a century. The Babinski sign, the most renowned milestone in neurological symptomatology, has been also devised to differentiate between organic and non-organic hemiparesis. Conversion disorders, so-called ‘hysteria’, continues to be a nightmare of neurologists even in this modern era. In fact, development of various sophisticated imaging studies increased the number of tests that might be performed to exclude organic disorders. The medical costs consumed during evaluation of patients with conversion disorders is enormous in most countries. In this regard, the demand for positive clinical signs for conversion disorders that need no special equipments but only trained skills of neurologists would not be lessened,1 and the addition of a new sign that is sufficiently reliable to an inventory of neurological signs to detect conversion disorders would be always welcome.

Lombardi et al2 describe a new sign to detect unilateral upper extremity non-organic paresis, ‘the elbow flex-ex test’. This test uses the complementary opposition of the paretic arm, as a part of synergic movement during the elbow flexion/extension of the normal arm (first part). In this sense, this test is comparable with Hoover test3 and Sonoo abductor test4 in the lower limb, but is different from, for example, abductor finger sign by Tinazzi et al,5 which use synkinetic, and not synergic, movements of fingers in both hands. Both the sensitivity and specificity of the first part of this new test have been reported to be 100% reliable. One of the key points that determine whether such a sign is reliable is how the synergic relation of relevant movements is robust. I personally tested their sign in normal subjects, and confirmed that the elbow flexion/extension of one arm and elbow extension/flexion of the other arm were closely linked synergically, which indicates that this test must be sufficiently reliable.

I would like to add a few further comments. The authors did not explain the meaning of this synergic movement. From the experiments in normal subjects, I came to be convinced that this synergic opposition following flexion/extension of one arm is necessary to prevent anterior/posterior sway of the trunk, or the whole body. If the subject opens his/her stance back and forth and can prevent the sway of the body by the power of the legs, this synergic opposition is not observed. This supposed mechanism can explain why the second part of their test was unsuccessful. Weak flexion/extension of the affected arm would be balanced by a similarly weak power of the other arm, whether the aetiology is organic or non-organic. Lastly, my experience tells that non-organic weakness of the upper limb is frequent in distal muscles, for example, finger or wrist movements, but rarely involves elbow flexion/extension. There may be some racial differences; the Japanese, who assign great value to skilled manual work, may easily develop conversion disorders in this region. In any case, it is evident that this test requires weakness of elbow flexion/extension.

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Footnotes

  • Competing interests None.

  • Provenance and peer review Commissioned; internally peer reviewed.

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