Incidental Lewy body disease: electrophysiological findings suggesting pre-clinical Lewy body disorders

Abstract

Objective: Evaluate electrophysiologic findings in incidental Lewy body disease (ILBD).

Methods: ILBD, Control, and Parkinson's disease (PD) subjects had electrophysiological evaluation within 2 years prior to autopsy. Data analyzed included surface electromyography (EMG) of upper extremity muscles during rest and muscle activation, and electroencephalography (EEG) recording at rest. For EMG, gross tracings and spectral peaks were analyzed. EEG measures analyzed were background frequency and power in delta, theta, alpha, and beta bands.

Results: Three of ten ILBD subjects (30%) showed unilateral rhythmic EMG discharges at rest without a visually apparent rest tremor. The ILBD resting EMG frequency was lower than in the Control group with no overlap (P=.03) and close to that of the PD group. The ILBD group had significantly lower background rhythm frequency than the Control group (P=.001) but was greater than the PD group (P=.01).

Conclusions: The electrophysiologic changes in ILBD cases are between those of Control and PD, suggesting that these findings may reflect changes correlating with ILBD as a possible precursor to PD.

Significance: Electrophysiologic changes in ILBD may assist with the identification of a preclinical stage for Lewy body disorders and help the development of a therapeutic agent for modifying Lewy body disease progression.

Copyright © 2011 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Figures

Figure 1

Surface EMG rest discharges from a PD subject (top), and surface EMG rest discharges and their Fast-Fourier Transform (FFT) averaged spectra from an ILBD subject (bottom). Top-Surface EMG polygraphy of left wrist flexors and left abductor pollicis brevis from a PD subject. Bottom-Surface EMG polygraphy of left wrist flexors and left abductor pollicis brevis and their FFT averaged spectra show a distinct at about 5 hertz for both muscles from an ILBD Subject. Note that the PD rest tremor discharges are much larger than for the ILBD rest tremor discharges that have no visible rest tremor.

Figure 2

Frequency value plots among Control, ILBD, and PD for rest and activation EMG discharges and EEG background frequency.