Review Note

Last Update: 04/23/2024 09:06 PM

Current Deck: MRCS::Anatomy

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Accessory Nerve

The {{c1::cranial}} root of the accessory nerve arises from the {{c1::caudal two thirds of the nucleus ambiguus}} and the {{c1::caudal four fifths of the dorsal nucleus of the vagus}}.
The {{c1::cranial}} root emerges as {{c1::four rootlets}} from the {{c1::dorsolateral surface of the medulla oblongata}} below those of the {{c1::vagus}}. It then traverses the {{c1::jugular foramen}}.
On exiting the jugular foramen it separates from its {{c1::spinal}} part. Whereupon its {{c1::cranial}} fibres join those of the {{c1::vagus}} to innervate some of the {{c1::palatal muscles}}.
The fibres arising from the spinal root exit near the junction between the {{c1::spinal cord}} and the {{c1::medulla}}. The fibres pass rostrally to unite with the cranial roots to exit through the {{c1::jugular foramen}}. As outlined above, these separate on exiting the foramen.
The spinal part then crosses the {{c1::transverse process of the atlas}}, and is crossed by the {{c1::occipital artery}} as it does so.
It descends obliquely, medial to the {{c1::styloid process, stylohyoid, and the posterior belly of digastric}}. It then reaches the upper part of {{c1::sternocleidomastoid}} to enter its upper surface.
It typically exits this muscle a little above the midpoint of the posterior aspect of it. This point is usually {{c1::4-6cm below the tip of the mastoid process}}.
It crosses the {{c1::posterior triangle on the levator scapulae}} separated from it by the {{c1::prevertebral layer of deep cervical fascia}}. At this point, the nerve is superficial and related to the {{c1::superficial cervical lymph nodes}}.
Approximately {{c1::3-5 cm above the clavicle}} it passes behind the anterior border of {{c1::trapezius}} which it innervates.

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