Distribution of Neuron Cell Bodies in the Intraspinal Portion of the Spinal Accessory Nerve in Humans.

The spinal accessory nerve is often identified as a purely motor nerve innervating the trapezius and sternocleidomastoid muscles. Although it may contain proprioceptive neurons found in cervical spinal levels C2-C4, limited research has focused on the histology of the spinal accessory nerve. The objective of the present study was to examine the spinal accessory nerve to determine if there are neuronal cell bodies within the spinal accessory nerve in humans. Cervical spinal cords were dissected from eight cadavers that had previously been used for dissection in other body regions. The segmental rootlets were removed to quantify the neuron cell bodies present at each spinal level. Samples were embedded in paraffin; sectioned; stained with hematoxylin and eosin; and examined using a microscope at 4×, 10×, and 40× magnification. Digital photography was used to image the samples. Neuronal cell bodies were found in 100% of the specimens examined, with non-grossly visible ganglia found at spinal levels C1-C4. The C1 spinal level of the spinal accessory nerve had the highest number of neuron cell bodies.