Conduction in ulnar nerve bundles that innervate the proximal and distal muscles: a clinical trial

Abstract

BackgroundThis study aims to investigate and compare the conduction parameters of nerve bundles in the ulnar nerve that innervates the forearm muscles and hand muscles; routine electromyography study merely evaluates the nerve segment of distal (hand) muscles.MethodsAn electrophysiological evaluation, consisting of velocities, amplitudes, and durations of ulnar nerve bundles to 2 forearm muscles and the hypothenar muscles was performed on the same humeral segment.ResultsThe velocities and durations of the compound muscle action potential (CMAP) of the ulnar nerve bundle to the proximal muscles were greater than to distal muscles, but the amplitudes were smaller.ConclusionsBundles in the ulnar nerve of proximal muscles have larger neuronal bodies and thicker nerve fibers than those in the same nerve in distal muscles, and their conduction velocities are higher. The CMAPs of proximal muscles also have smaller amplitudes and greater durations. These findings can be attributed to the desynchronization that is caused by a wider range of distribution in nerve fiber diameters.Conduction parameters of nerve fibers with different diameters in the same peripheral nerve can be estimated.

Üst Ve Alt Ekstremi̇tede Ayni Si̇ni̇r Tarafindan İnerve Olan Proksi̇mal Ve Di̇stal Kaslardan Kaydedi̇len F Dalgasi: Yeni̇ Bi̇r Yöntem Olabi̇li̇r Mi̇?

“…When the minimum latencies of the F-wave recorded from the distal and proximal muscles in the lower and upper extremities were compared, it was found that the minimum latencies of the Fwave recorded from the proximal muscles (FUP and FPP) were longer than the minimum F-wave latencies recorded from the distal muscles (FUD and FPD). In previous studies comparing nerve conduction velocities, conduction velocity was found to be higher in proximal muscles with greater mass then the distal small muscles even they are innervated by the same nerve [6,12,13]. Considering the physiology of the Fwave, it is conceivable that the F-wave latency recorded from the proximal muscle should be shorter.…”

“…The reason for the higher nerve conduction velocity in the proximal segments compared to the distal segments may be the thinning of the nerve fiber diameter from proximal to distal, the shortening of the internodal segments in the nerve fibers in the distal segments, and the lower extremity temperature in the distal compared to the proximal segments [5]. If a peripheral nerve is stimulated at the same site and electrophysiological recordings are made from two different muscles located proximally and distally, it is possible to comment on the conduction parameters of nerve fibers with the same course and in the same peripheral nerve but of different diameters [5,6].…”

Comparison of the Nerve Conduction Parameters in Proximally and Distally Located Muscles Innervated by the Bundles of Median and Ulnar Nerves

“…The values of CMAP amplitude from the proximal stimulus were significantly lower than those from the distal stimulus. In another trial with ulnar nerves, Oğuzhanoğlu et al [ 3 ] detected that the arm segment amplitude values were lower than the forearm segment amplitude values in the hypothenar region recordings, and authors attributed this findings to temporal dispersion. This study showed that the same findings also apply to the median nerve in addition to ulnar nerve findings.…”

“…The intensity of the stimulus was slowly increased up to the point at which the CMAP amplitude did not increase any more. Following a 25s% increase in the maximal value of stimulus, this point was determined to be the level of supramaximal stimulation [ 3 ].…”

“…The motor unit size and the nerve fiber diameter correlate with the size of the muscle they innervate [ 3 , 4 ]. Therefore, it might be predictable that the nerve fibers of muscles with larger mass and proximal localization are larger and faster [ 5 ].…”