Objectives: To test a new neurological sign, the "abductor sign," which can distinguish between organic and non-organic leg paresis using synergic movements of the bilateral hip abductors.
Methods: The subjects were 33 patients presenting with paresis of one leg, 17 of organic origin and 16 of non-organic origin (hysteria). To test the abductor sign, the examiner told the patient to abduct each leg, and opposed this movement with his hands placed on the lateral surfaces of the patient's legs. The leg contralateral to the abducted one showed opposite actions for organic paresis and non-organic paresis: for example, when the paretic leg was abducted, the sound leg stayed fixed in organic paresis, but moved in the hyperadducting direction in non-organic paresis. Hoover's sign was used for comparison in the same patients.
Results: The abductor sign gave the correct classification for all 33 cases. Hoover's sign was reliable if the results were carefully interpreted, but it was non-diagnostic for 16 patients because of strong hip extensors and in two because of strong hip flexors. Two patients with non-organic paresis succeeded in tricking the examiner by pretending full effort to lift the paretic leg.
Conclusions: The abductor sign is a useful test to detect non-organic paresis, because (1) it is difficult for a hysterical patient to deceive the examiner, (2) the hip abductor is one of the most commonly involved muscles in pyramidal weakness, and (3) the results are easily visible as movement or non-movement of the unabducted leg.