Katsumi Kurokawa    Department   Kawasaki Medical School  Kawasaki Medical School, Department of General Internal Medicine 1,    Position   Professor
Language	English
Title	Far-Field Potentials (FFPs) Contaminating Ulnar CMAPs: Investigation from the 2L/IO Method
Conference	2009 Asian and Oceanian Congress of Clinical Neurophysiology
Conference Type	International society and overseas society
Presentation Type	Speech
Lecture Type	General
Publisher and common publisher	◎Kurokawa Katsumi, Sonoo Masahiro, Higashihara Mana, Kurono Hiroko, Hatanaka Yuki, Shimizu Teruo
Date	2009/04/16
Venue (city and name of the country)	Seoul, Korea
Society abstract	Clinical Neurophysiology 120(Suppl.),S24 2009
Summary	Background We’ve investigated the far-field potential (FFP) components contaminating median, ulnar and radial compound muscle action potential (CMAP). The waveforms of FFPs were quite different among nerves and their generating mechanism is still unclear. In the present study, we aimed to elucidate the generating mechanism of FFPs in ulnar and median CMAPs by investigating the 2L-IO method (2nd lumbricalis and 1st palmar interosseous recording; Preston’s method). Materials and Methods Subjects were five healthy volunteers. We placed electrodes over the bellies of the 2L/IOP1, ADM, IOD1 and APB muscles, and at the tip of the digits II, V and I. The common proximal reference was placed at the forearm. We recorded the CMAPs following supramaximal stmulation of the median and ulnar nerves at the wrist. We also obtained routine CMAPs of each muscle. Results Ulnar nerve stimulation elicited large FFPs with negative-positive-negative three phases at the tip of the index finger, even larger than those over the little finger, whereas those following median nerve stimulation were small. The onset latencies of both the negative FFPs over the finger tips and the CMAPs of IOP1 and IOD1 by the belly-proximal recordings following ulnar nerve stimulation were similar, and were earlier than those of routine IOP1 and IOD1 CMAPs with distal references. Conclusions The present and other studies of ours have suggested that at least the initial negative phase of the ulnar FFPs is generated by the interosseous muscles. The early onset of these negative FFPs indicates that they were generated by the commencement of the action potentials at these muscles, instead of their termination.