European Journal of Anatomy

Official Journal of The Spanish Society of Anatomy
Cover Volume 20 - Number 1
Eur J Anat, 20 (1): 1-17 (2016)

Median nerve motor entry points in the forearm - clinical application

Ehab M. El Zawawy1, Nancy M. El Sekily1, Wael A. Fouad2, Mohamed H. Emam3, Marwa M. Hassan3

1Department of Anatomy and Embryology, Faculty of Medicine, Alexandria University, Alexandria, Egypt, 2Department of Neurosurgery, Faculty of Medicine, Alexandria University, Alexandria, Egypt, 3Department of Physiotherapy, Faculty of Medicine, Alexandria University, Alexandria, Egypt

ABSTRACT Superficial forearm flexors receive primary and secondary branches from the median nerve (mn). These branches vary in number, size and motor entry points (m) into the muscles. Knowledge of these points is essential for maximal compound muscle action potential (cmap) recording from these muscles. Spasticity of these flexors is treated using botulinum toxin (bt) injection or selective partial neurotomy (spn) of the nerve branches to the spastic muscles. Twenty human cadaveric forearms were dissected. The location of the motor entry points of the median nerve to the superficial forearm flexor muscles was expressed as a distance from the medial (me) and lateral (le) epicondyles of the humerus. Fifty apparently healthy volunteers (25 males and 25 females) underwent cmap recording from the superficial forearm flexors. Thirty patients (15 males and 15 females) with spastic hyperflexion of the wrist and fingers underwent bt injection or spn. Pronator teres (pt) had 2-4 m, flexor carpi radialis (fcr) had 1-3 m and flexor digitorum superficialis (fds) had 3-8 m. Variable shapes of the cmap were recorded from them (monophasic, biphasic or multiphasic). Based on the anatomical results, bt injection was done at 5 points (p1-p5); pt was injected at p1, fcr was injected at p2, and fds is a large muscle and was injected at p3, p4, p5 (proximal, middle, distal), giving good results in 85% of cases; spn was done in severe cases refractory to bt injection with excellent to good results in 80% of cases. The patterns of branching of mn differ from the classically described patterns. Therefore, revising the innervation patterns of the superficial forearm flexors is mandatory, since the variations observed are more diverse than has been described. Identification of the branches and the motor entry points of mn are essential for cmap recording from the superficial forearm flexors, bt injection, spn and tendon transfer.

Keywords: Branching patterns, Forearm flexors, Compound muscle action potential recording, Botulinum toxin

European Journal of anatomy
ISSN 2340-311X (Online)