Motor innervation of the trapezius muscle: A histochemical study

Controversy exists as to the significance of the cervical plexus as efferent to the trapezius muscle. We have sought to further study this question and to add to anatomic and electrophysiologic evidence of a histochemical perspective.The accessory nerve and the cervical plexus branches from 18 neck dissections were studied by histochemical staining for acetylcholinesterase (motor nerve) and carbonic anhydrase (sensory nerve) activity. The motor controls were either accessory nerve, ansa hypoglossi or hypoglossal nerve, and for sensory controls the greater auricular nerve.Eleven of 18 necks (61%) contained evidence of motor axons in the branches of the cervical plexus. Motor axons were noted mainly in C3 and or C4.There is confirmatory histochemical evidence that a significant proportion of cervical spinal nerves to the accessory nerve or trapezius contain motor nerves.