Central Motor Fatigue in Parkinson’s Disease and the Effect of Levodopa: A transcranial Magnetic Stimulation Study

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Lou, Jau-Shin, M.D., Ph.D.
Oregon Health Sciences University, Portland, OR

Abstract

The responses of various PD symptoms to levodopa therapy have always varied because other neurotransmitter systems may be involved as well. Dr. Jau-Shin Lou will do a pilot study on the common complaint, fatigue. They will use transcranial magnetic stimulation in both patients and matched control subjects to determine the pathophysiology underlying fatigue, both mental and physical, and hope to thus be better able to plan appropriate therapy for the patients.This is a good example of the reason such studies can only be done in major medical centers in which up-to-date electrophysiologic equipment is available with onlyminimal added expense for specific measuring devices.

Progress Report (as of 8/2002)

Dr. Lou presented the results of his study at The Parkinson Study Group 15th Annual Symposium entitled "Etiology, Pathogenesis and Treatment of Parkinson's Disease and Other Movement Disorders" in Chicago in September 2001. Because patients with Parkinson’s disease often complained of excessive fatigue during physical activity, they conducted the study to see if this fatigue is associated with abnormal brain response to transcranial magnetic stimulation (TMS). During TMS, a brief magnetic field is delivered through the scalp and responses recorded from the muscle. They found that PD patients have larger muscle responses evoked by TMS than normal controls before, during and after exercise. Furthermore, those patients who developed more fatigue with exercise have larger responses. A small amount of carbidopa/levodopa reduced the amplitudes of the muscle responses to almost normal. They concluded that abnormal brain response to TMS is associated with excessive fatigue during exercise. These abnormal responses to TMS may be used to monitor the fatigue associated with exercise in PD patients in therapeutic trials.

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