Motor Disorders in Alzheimer?s Disease and Mild Cognitive Impairment

Blaise Christe
Neuropsychology and Movement Disorders Units, Department of Neurology, Geneva University H

Orestes V. Forlenza
Laboratory of Neuroscience (LIM27), Department and Institute of Psychiatry, Hospital das Clinicas, Faculty of Medecine, University of Sao Paulo, Brazil

Daniel Fuentes
Psychology and Neuropsychology Unit, Department and Institute of Psychiatry, Hospital das Clinicas, Faculty of Medecine, University of Sao Paulo, Brazil

Monica S. Yassuda
Laboratory of Neuroscience (LIM27), Department and Institute of Psychiatry, Hospital das Clinicas, Faculty of Medecine, University of Sao Paulo, Brazil

Wagner F. Gattaz
Laboratory of Neuroscience (LIM27), Department and Institute of Psychiatry, Hospital das Clinicas, Faculty of Medecine, University of Sao Paulo, Brazil

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     Last modified: February 28, 2007

Abstract
Although some studies reported akinetic features in a significant percentage of patients, motor disorders in Alzheimer?s disease (AD) and Mild Cognitive Impairment (MCI) are rarely taken into account in clinical practice, indeed regarded as diagnostic criterion of exclusion. This study was interested in this somewhat paradoxal situation by evaluating in a detailed way the motor efficiency of AD and MCI patients. METHOD: AD patients (N=13), MCI patients (N=19) and control (CTRL) subjects (N=23) were evaluated using the Purdue Pegboard and a digitizing tablet-based instrument. The four tasks of Purdue Pegboard ? dominant hand, non-dominant hand, both hands, assembly ? were administered. The tasks of digitizing tablet-based instrument ? execution, speed programming, speed-accuracy programmming, planning ? were performed with dominant and non-dominant hands. Temporal, spatial and sequential constraints underlying these tasks allowed to focus, with distinct measures, on the diversified aspects of akinesia, including bradykinesia, hypometria and altered sequential movements. RESULTS: Except for the dominant hand task, the Purdue Pegboard results were systematically better for CTRL subjects compared to MCI patients. Except for assembly task, they were significantly better for MCI patients compared to AD patients. With regard to the assembly task and AD, we did not carry out inferential statistics because of the limited sample (N=3, 76% of failure). Concerning the digitizing tablet, analyses of movement time in a typical speed-accuracy trade-off setting did not reveal any significant slowing of MCI patients compared to CTRL subjects. Movement time was significantly longer for non-dominant hand of AD patients compared to MCI patients, and constantly longer for AD patients compared to CTRL subjects. Results concerning constant error did not reveal any hypometria, but on the contrary a general tendency toward target center overshoot. This tendency was significantly higher for AD patients compared to MCI patients and CTRL subjects only for dominant hand movements in condition with poor spatial constraints. Sequencing difficulties were exemplified in planning tasks by a significant higher effective capacity for CTRL subjects compared to MCI patients. No inferential statistics were carried out for AD patients because of the high rate of failure in this task (54% for dominant hand, N=6, and 69% for non-dominant hand, N=4). CONCLUSION: These results confirm the presence of motor disorders in AD and MCI, showing bradykinetic components and altered sequential movements. Above all, they strongly support the idea that motor disorders should not be regarded any more as a diagnostic criterion of exclusion.