Objective: To study applicability of Hoover’s sign to diagnostics of functional component in PD.

Background: It has been reported that Parkinson’s Disease (PD) patients have a higher prevalence of functional neurological symptoms. The placebo effect is powerful in PD also. Thus, a development of a diagnostic test for psychogenic contribution to PD becomes of a special importance. Hoover’s sign is a useful clinical test in differentiating asymmetric functional and organic hemiparesis. For idiopathic PD asymmetry of motion is common and can persist for several years. In this work we studied abilities of Hoover’s Sign as a method for identifying psychogenic (functional) component in PD.

Method: We used Hoover’s Sign (test). Thirty-two PD female patients with asymmetric  movements and thirty healthy control patients were examined. The voluntary pressure by a heel (VP) and reflectory pressure (RP) have been measured on both sides. The Hoover index (HI) was calculated as a ratio RP/VP. If the HI is high (the  reflectory pressure is more to the strength exhibited during the strength test), then the patient is thought to be hysterical.

Results: The HI in the control group was 1,0±0,2 and for unaffected extremities of the PD patients was 1,1±0,2. On the affected side («bad side»), the behavior of the PD patients is different from healthy control with a high degree of confidence. HI was measured as high as 2,0±0,4. The HI increase was not caused by unwillingness to perform active  movements. On the contrary, the PD patients diligently followed the directions and were willing to show the maximum results. Surprisingly, the PD patients are able to reflectorily exert a higher pressure on the scale compared to healthy people. This fact can be explained by a phenomenon of increase of physiological synkinesia and parallel movements.  Among 32 patients, there was not a single case of HI increase due to a large decrease of  VP.

Conclusion: The Hoover’s sign failed to confirm the presence of a functional component in PD. This result may possibly be due to insensitivity of the method for the patients with PD, or the idea about universal involvement of a functional component in PD is not entirely correct. It is necessary to consider that heightened physiological synkinesia may play a pathological role in patient’s movements.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/hoovers-sign-in-parkinsons-disease/