Force Control Deficits in Individuals with Parkinson’s Disease, Multiple Systems Atrophy, and Progressive Supranuclear Palsy

Kristina A. Neely,Cynthia L. Comella,David E. Vaillancourt,Peggy J. Planetta,Janey Prodoehl,Christopher G. Goetz,Daniel M. Corcos,Kathleen L. Shannon,Per Svenningsson

doi:10.1371/journal.pone.0058403

Abstract

ObjectiveThis study examined grip force and cognition in Parkinson’s disease (PD), Parkinsonian variant of multiple system atrophy (MSAp), progressive supranuclear palsy (PSP), and healthy controls. PD is characterized by a slower rate of force increase and decrease and the production of abnormally large grip forces. Early-stage PD has difficulty with the rapid contraction and relaxation of hand muscles required for precision gripping. The first goal was to determine which features of grip force are abnormal in MSAp and PSP. The second goal was to determine whether a single variable or a combination of motor and cognitive measures would distinguish patient groups. Since PSP is more cognitively impaired relative to PD and MSAp, we expected that combining motor and cognitive measures would further distinguish PSP from PD and MSAp.MethodsWe studied 44 participants: 12 PD, 12 MSAp, 8 PSP, and 12 controls. Patients were diagnosed by a movement disorders neurologist and were tested off anti-Parkinsonian medication. Participants completed a visually guided grip force task wherein force pulses were produced for 2 s, followed by 1 s of rest. We also conducted four cognitive tests.ResultsPD, MSAp, and PSP were slower at contracting and relaxing force and produced longer pulse durations compared to controls. PSP produced additional force pulses during the task and were more cognitively impaired relative to other groups. A receiver operator characteristic analysis revealed that the combination of number of pulses and Brief Test of Attention (BTA) discriminated PSP from PD, MSAp, and controls with a high degree of sensitivity and specificity.ConclusionsSlowness in contracting and relaxing force represent general features of PD, MSAp, and PSP, whereas producing additional force pulses was specific to PSP. Combining motor and cognitive measures provides a robust method for characterizing behavioral features of PSP compared to MSAp and PD.

Highlights

Parkinson’s disease (PD) is characterized by bradykinesia, rigidity, tremor, and postural instability
PD, multiple system atrophy (MSAp), and progressive supranuclear palsy (PSP) were slower at contracting and relaxing force and produced longer pulse durations compared to controls
A receiver operator characteristic analysis revealed that the combination of number of pulses and Brief Test of Attention (BTA) discriminated PSP from PD, MSAp, and controls with a high degree of sensitivity and specificity

Summary

Introduction

Parkinson’s disease (PD) is characterized by bradykinesia, rigidity, tremor, and postural instability. These signs are routinely identified in a clinical exam, detecting additional features that differentiate PD from other forms of Parkinsonism can be more difficult. Atypical Parkinsonian disorders, such as the Parkinsonian variant of multiple system atrophy (MSAp) and progressive supranuclear palsy (PSP), can mimic signs of PD and the correct diagnosis may only become clear as the disease progresses [1,2]. Clinical drug trials treating PD have mistakenly included patients with atypical Parkinsonism [1]. Correct diagnosis is important for the patient and caregiver to make decisions regarding treatment and long-term planning, and to establish coping and support mechanisms. It is important to explore behavioral tests that may provide distinguishing characteristics [3]

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