The Incrementing Responses of Compound Muscle Action Potentials (Waxing Phenomenon) in Normal Subjects

• Published in: Rihabiritēshon igaku Vol. 36; no. 2; pp. 112 - 118
• Main Authors: AKASHI, Ken, TSUBAHARA, Akio, KAWAMOTO, Sadanori, FUJITA, Aoi
• Format: Journal Article
• Language: English
• Published: The Japanese Association of Rehabilitation Medicine 1999
• Subjects: Eaton-Lambert syndrome; fatigue test; high frequent repetitive stimulation; incrementing response; nerve conduction study
• ISSN: 0034-351X; 1880-778X
• DOI: 10.2490/jjrm1963.36.112

Repetitive stimulations to the median and ulnar nerves were carried out to elucidate the mechanism of incrementing responses of compound muscle action potentials (CMAPs), the so-called “waxing phenomenon” in 10 normal subjects. The amplitude and area (integral calculus) of each CMAP were calculated, and the relationship between the shapes of the CMAPs and filter institutions on repetitive stimulation was investigated. There were incrementing responses of amplitude in the median and ulnar nerves with high frequency repetitive stimulation (20Hz and 30Hz). Incrementing responses of amplitude were always recognized in the median nerves with high frequency repetitive stimulation except for the high-cut filter setting (200Hz), which was extremely lower than normal. We postulate that the conduction time between Ca2+ uptake and the release of acetylcholine (Ach) in the nerve terminals becomes shorter only in the slower conducting peripheral nerve fibers, or that the propagation velocities of muscle fibers change during repetitive stimulation. However, the change of volume conduction should be also taken into consideration.