The accessory nerve is a cranial nerve responsible for controlling the muscles in the neck and shoulders. It is spelled with three syllables: ac-ces-so-ry. The first syllable, "ac," is pronounced /æk/, the second, "ces," is pronounced /ˈsɛs/, and the final syllable, "sory," is pronounced /ˈsɔri/. The "c" in "accessory" is pronounced as a "k" sound because it comes before an "e" followed by an "s." Correct spelling of medical terms is important to ensure clear communication among healthcare professionals.
The accessory nerve, also known as the cranial nerve XI or the spinal accessory nerve, is one of the twelve pairs of cranial nerves that originates in the brainstem, specifically the medulla oblongata and the upper cervical spinal cord. This nerve is primarily responsible for controlling the movement of specific neck and shoulder muscles, known as the sternocleidomastoid and trapezius muscles.
The accessory nerve is considered a motor nerve because its main function involves providing motor impulses to the aforementioned muscles. It supplies the necessary innervation for movement and coordination of the head, neck, and shoulders, aiding in actions such as rotation and flexion.
The name "accessory nerve" stems from its unique course compared to other cranial nerves. Unlike most cranial nerves, which directly exit the skull, the accessory nerve mainly arises from the spinal cord, specifically at the level of the spinal cord's first five or six segments. This peculiar origin point allows the nerve fibers to travel upwards and enter the skull before ultimately joining the other cranial nerves.
An injury or impairment of the accessory nerve can result in weakened or limited movement of the muscles under its control. This condition is known as accessory nerve palsy and may cause difficulties in performing everyday activities that involve head and neck motion. Rehabilitation techniques, including physical therapy and exercises, are often employed to restore and improve the affected muscle function.
The word "accessory" comes from the Latin word "accessorius", which means "adjunct" or "secondary". The term "nerve" comes from the Latin word "nervus", meaning "sinew" or " tendon". The "accessory nerve" is so named because it was initially believed to be an auxiliary nerve, supplying only a secondary function. However, it is now understood to play a more significant role in motor functions, such as controlling certain muscles in the neck and shoulder.