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The accessory nerve, also known as the eleventh cranial nerve, cranial nerve XI, or simply CN XI, is a cranial nerve that supplies the sternocleidomastoid and trapezius muscles. It is classified as the eleventh of twelve pairs of cranial nerves because part of it was formerly believed to originate in the brain.
It projects bilaterally down the spinal cord and triggers the ventral horn of the cervical spinal circuits, particularly controlling lower motor neurons associated with the spinal accessory nerve (CN XI). Additionally, the pathway projects superiorly to the paramedian pontine reticular formation, indirectly innervating the nuclei of CN VI and ...
The spinal accessory nucleus lies within the cervical spinal cord (C1-C5) in the posterolateral aspect of the anterior horn. The nucleus ambiguus is classically said to provide the "cranial component" of the accessory nerve .
There are several options of treatment when iatrogenic (i.e., caused by the surgeon) spinal accessory nerve damage is noted during surgery. For example, during a functional neck dissection that injures the spinal accessory nerve, injury prompts the surgeon to cautiously preserve branches of C2, C3, and C4 spinal nerves that provide supplemental innervation to the trapezius muscle. [3]
The spinal root of accessory nerve (or part) is firm in texture, and its fibers arise from the motor cells in the lateral part of the anterior column of the gray substance of the medulla spinalis as low as the fifth cervical nerve.
The pyramidal pathways, such as corticospinal and some corticobulbar tracts, may directly innervate motor neurons of the spinal cord or brainstem. This is seen in anterior (ventral) horn cells or certain cranial nerve nuclei. Whereas the extrapyramidal system centers around the modulation and regulation through indirect control of anterior ...
The point of his new accessory is to keep his brain and his feet in active communication. “The nerves that run from the spinal cord to the legs and feet are some of the longest in the body ...
From here, the accessory nerve courses through the posterior triangle of the neck to enter the anterior border of the trapezius muscle at a point located approximately at the junction of the middle and lower thirds of the anterior border of this muscle. The spinal accessory nerve can often be found 1 cm above Erb's point. [4]