Evaluation of fatigue in Parkinson's disease patients with stimulated single fiber electromyography

Munksgaard 2001.Objectives – Fatigue is a disabling and dopa-resistant symptom inParkinson’s disease (PD). Pathological studies have shown that bothperipheral and central cholinergic systems are involved in PD.Electrophysiological investigation showed decremental muscleresponses following repetitive nerve stimulation (RNS). We hypothe-sized that fatigue in PD patients may be secondary to cholinergic defectat the neuromuscular level. Material and methods – Twenty PD patientswith disabling fatigue symptoms were enrolled. We used stimulatedsingle fiber electromyography (s-SFEMG) to evaluate the neuromus-cular junction of these patients. For every patient, at least 15 musclefibers were tested at the rate of 10 Hz with the method described byTrontelj et al. The individual mean consecutive difference (i-MCD) wasobtained from 100 constant consecutive single fiber potentials. Thei-MCD values in each patient were averaged to obtain the mean MCD(m-MCD). Results – None of the 20 PD patients with disabling fatiguesymptoms had an m-MCD over 29 ms or more than 10% of the i-MCDvalues over 41 ms. The neuromuscular junction was intact in terms ofnormal jitter (expressed as MCD) and an absence of blocking.Conclusion – Our findings indicate that the cholinergic system at theneuromuscular level is not affected in PD patients with fatiguesymptoms.W. J. Hwang, T. S. Lin