An exploratory study on the presence of sensory nerves in the caudal part of the trapezius

Intramuscular onabotulinumtoxinA (BTX) injections and nerve decompression surgery both aim to release compressed sensory nerves and are used in the treatment of migraine/headaches. Although for many BTX injection sites, sensory nerves and their potential entrapment sites have been established, for the trapezius this information is incomplete. A macro- and microscopic cadaveric study was performed in which the suprascapular part of the trapezius was explored for the presence of piercing or penetrating nerves and whether these nerves contained sensory nerve fibers. One side of six human cadavers were dissected to reveal trapezius-associated nerves in its suprascapular part. Schematic overview drawings were made of nerves either piercing or penetrating the trapezius in this region. Piercing or penetrating cervical nerves were resected and microscopically studied for the presence of sensory nerve fibers. For this suprascapular region, correlating potential entrapment sites of the supraclavicular nerves were detected. In all specimens, plexuslike connections between the accessory nerve and branches of the cervical plexus, varying between CII-CV, were observed to innervate the trapezius at locations that showed overlap with BTX injection sites. Moreover, all these nerves contained sensory nerve fibers as confirmed by immunohistochemical staining with the sensory nerve marker CGRP. The presence of potential entrapment sites for supraclavicular nerves and other cervical nerve branches might explain why BTX injection in the suprascapular part of the trapezius show therapeutic effectivity in the treatment of migraine/headaches