Electrophysiological Investigation of Fatigue in Electrical Injury Patients (P02.019)

Abstract

Objective: To investigate central and peripheral fatigue in electrical injury (EI) patients. Background Although experiential fatigue is common with EI patients, little is known about the cause of this fatigue. Design/Methods: EI patients and age and sex-matched healthy volunteers completed fatigue severity scale questionnaire (FSSQ). The study is designed to measure central and peripheral fatigue. Motor evoked potentials (MEP) and M-waves were measured using surface electromyogram of right abductor digiti minimi (ADM) using transcranial magnetic stimulation (TMS) and ulnar nerve stimulation (UNS) at rest and during maximal voluntary contraction (MVC). Fatigue was induced using 2 minutes of MVC and subjects were followed for 15 minutes of recovery. The experiment was repeated with inflated blood-pressure (BP) cuff during the first 75 seconds of recovery to maintain muscle ischemia. Results: 8 EI patients and 8 volunteers were studied (all men, 46±7.8 years vs. 45.5±7.3 years). FSSQ confirmed greater experiential fatigue reported by EI patients compared to healthy volunteers (p=0.04). Cortical silent period was prolonged in patients compared to volunteers (177ms vs. 145ms, p=0.04). Drop in MEP amplitude with consecutive TMS at rest (5 pulses at 0.3Hz) was observed immediately after exercise but was present only for EI patients with BP cuff after 2 minutes of recovery (p Conclusions: Prolonged cortical silent period in EI patients suggests that GABA-B receptor-mediated cortical inhibition may be increased with EI. BP-induced delay in recovery from decrease in amplitude of consecutive MEP9s demonstrates greater peripheral fatigue in EI patients after exercise. Higher increase in M-wave area post-exercise suggests greater decrease in conduction velocity of muscle action potential with exercise in EI patients. In conclusion, experiential fatigue reported by EI patients is shown to have both central and peripheral components. Supported by: Catherine Manson Chair in Movement Disorder. Disclosure: Dr. Udupa has nothing to disclose. Dr. Kashigar has nothing to disclose. Dr. Fish has nothing to disclose. Dr. Chen has received personal compensation for activities with Allergan, Inc., Medtronic, Inc., Biovail, EMD Serono, Merz Pharma, the American Academy of Neurology, the Douglas Mental Health University Institute, Movement Disorders Society, the University of Pittsburg, Merz, CHIR, the Michael J. Fox Foundation for Parkinson9s Research, the Dystonia Medical Research Foundation, and has provided expert testimony and affidavit in welding related litigations. Dr. Chen has received research support from Medtronic, Inc.