Laterality, region, and type of motor dysfunction correlate with cognitive impairment in Parkinson's disease

Abstract

We studied the relationship between two screening cognitive measures and off motor Unified Parkinson's Disease Rating Scale (UPDRS) scores in 108 Parkinson's disease patients. Multiple regressions were conducted to examine the UPDRS subscores' unique contributions to cognitive function. When including bradykinesia, rigidity, and postural/gait instability subscores, only bradykinesia predicted Mini Mental Status Examination (MMSE), normalized β = −0.57, t(104) = −3.31, P < 0.01, and Dementia Rating Scale‐2 (DRS‐2), normalized β = −0.45, t(104) = −2.55, P < 0.05. Tremor was not included in the regression analyses because it did not correlate with cognitive function. When including axial and appendicular subscores, only the axial subscore predicted MMSE, normalized β = −0.39, t(105) = −3.19, P < 0.01, and DRS‐2 scores, normalized β = −0.40, t(106) = −3.28, P < 0.01. When including left‐sided and right‐sided subscores, only the right‐sided symptoms predicted DRS‐2 scores, normalized β = −0.28, t(105) = −2.45, P < 0.05, and showed a trend toward predicting MMSE scores, normalized β = −0.22, t(105) = −1.95, P = 0.054. We therefore found that right‐sided symptoms (for laterality), axial symptoms (for region), and bradykinesia (for type of symptoms) were thebest predictors of cognitive function. © 2006 Movement Disorder Society