Spinal nerve C3
Nervus spinalis C3
- Related terms: Third cervical nerve; C3
Definition
The third cervical spinal nerve C3 is a mixed nerve, carrying both motor and sensory fibers. It arises from the C3 spinal segment of the spinal cord.
a) Roots
Like other nerves, the spinal nerve C3 is formed by the union of two roots:
1. Posterior (dorsal) root:
This root carries sensory fibers from peripheral structures in the neck and upper back to the spinal cord's dorsal gray horn.
2. Anterior (ventral) root:
This root contains motor fibers that originate in the spinal cord's anterior gray horn and transmit commands to muscles in the neck and upper back.
b) Mixed spinal nerve and rami
The anterior and posterior roots unite at the intervertebral foramen to form the mixed C3 spinal nerve, which exits between the C2 and C3 vertebrae. It then divides into two primary rami:
1. Anterior (ventral) ramus:
This ramus provides motor and sensory innervation to the neck region. It also connects with the sympathetic trunk via the gray ramus communicans, which carries postganglionic sympathetic fibers.
2. Posterior (dorsal) ramus:
This ramus innervates the deep muscles of the posterior neck and provides sensory innervation to the skin of the back of the neck.
A. ANTERIOR RAMUS OF SPINAL NERVE C3:
The anterior ramus of the spinal nerve C3 emerges from the vertebral canal through the intervertebral foramen between the C2 and C3 vertebrae. This mixed nerve, carrying both motor and sensory fibers, contributes to the cervical plexus by interconnecting with the anterior rami of C1, C2, and C4.
Key functions and innervations
Motor Innervation (Somatic Efferent Fibers): | Sensory Innervation (Somatic Afferent Fibers): | ||
The anterior ramus of spinal nerve C3, which forms part of the cervical plexus, supplies motor innervation to the following muscles: Sternocleidomastoid (accessory nerve and branches from anterior rami of C2, C3), trapezius (proprioceptive fibers from C3, C4). Levator scapulae (C3, C4 direct branches, and C4, C5 via the dorsal scapular nerve). middle scalene (C3-C7) muscles. Pre-vertebral muscles, such as the longus colii (it's vertical part). Diaphragm, via the phrenic nerve (C3, C4, C5). Anterior neck muscles, including the sternohyoid (C1-C3), sternothyroid (C1-C3), and omohyoid muscles (C1-C3). | The sensory fibers of the anterior ramus of spinal nerve C3 innervate the skin of the C3 dermatome, which encompasses the lower neck region, potentially extending to the mastoid process. Sensory fibers are conveyed through the supraclavicular nerve (C3, C4, C5), great auricular nerve (C2, C3), and transverse cervical nerve (C2, C3). | ||
B. POSTERIOR RAMUS OF SPINAL NERVE C3:
The posterior ramus of the C3 is the posterior branch of the spinal nerve C3.
Lateral branch: | Medial branch (greater occipital nerve): | ||
The lateral branch of the posterior ramus of the C3 spinal nerve runs through the paraspinal muscles, where it supplies motor fibers to the iliocostalis cervicis muscle, and then becomes superficial, providing sensory innervation to the skin overlying the posterior neck region. | The third occipital nerve is the medial branch of the posterior ramus of the spinal nerve C3. It provides sensory innervation to the skin of the lower occiput and upper cervical region, and motor innervation to the semispinalis capitis muscle. Emerging between the C2 and C3 vertebrae, the third occipital nerve ascends and pierces the semispinalis capitis and splenius capitis muscles. It then continues superiorly, piercing the trapezius muscle before becoming subcutaneous. The third occipital nerve is closely related to the greater occipital nerve, which is the medial branch of the posterior ramus of the C2 spinal nerve. Both nerves contribute to the sensory innervation of the scalp and can be involved in occipital neuralgia. |
C. ADDITIONAL STRUCTURES ASSOCIATED WITH SPINAL NERVE C3:
a) Recurrent Meningeal Nerve (Meningeal branch):
The recurrent meningeal nerve (or meningeal branch) originates from either the C3 spinal nerve or one of its rami. This small nerve re-enters the vertebral canal through the intervertebral foramen and provides sensory innervation to:
The meninges (protective coverings of the spinal cord),
The annulus fibrosus of the intervertebral discs,
The vertebral bodies and periosteum,
Adjacent blood vessels.
b) Sympathetic connections:
The spinal nerve C3 connects to the sympathetic trunk through the gray ramus communicant. The gray ramus communicant enables the postganglionic sympathetic fibers to reach peripheral targets such as sweat glands and blood vessels.
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SUMMARY TABLE
STRUCTURES INNERVATED BY THE SPINAL NERVE C3 | |||
ANTERIOR RAMUS | POSTERIOR RAMUS | ||
MOTOR STRUCTURES | SENSORY STRUCTURES | MOTOR STRUCTURES | SENSORY STRUCTURES |
Sternocleidomastoid (accessory nerve, C2, C3), trapezius (C3, C4). Levator scapulae (C3, C4, C5). middle scalene (C3-C7). longus colii (vertical part). Diaphragm (C3, C4, C5). Sternohyoid (C1-C3), sternothyroid (C1-C3), and omohyoid muscles (C1-C3). | C3 dermatome of skin encompassing the lower neck region and may extend to the mastoid process at the back. | Semispinalis capitis, splenius capitis, iliocostalis cervicis, trapezius muscle. | Skin in the lower occiput and upper cervical region. |
References
Drake, R.L., Vogl, A.W., and Mitchell, A.W.M. (2010). ‘Chapter 8: Head and Neck’, in Gray’s anatomy for students. (2nd ed.) Churchill Livingstone Elsevier, Philadelphia PA 19103, pp.955, 970, 974.
Saito T, Steinke H, Hammer N, Li ZL, Kawata S, Yasuda M, Wakao N, Koyasu H, Itoh M. Third primary branch of the posterior ramus of the spinal nerve at the thoracolumbar region: a cadaveric study. Surg Radiol Anat. 2019 Aug;41(8):951-961.
Drake, R.L., Vogl, A.W., and Mitchell, A.W.M. (2010). ‘Chapter 8: Head and Neck’, in Gray’s anatomy for students. (2nd ed.) Churchill Livingstone Elsevier, Philadelphia PA 19103, pp.875.
Saglam L, Coskun O, Kale A, Gayretli O. A Comprehensive Study of the Potential Compression Points of the Third Occipital Nerve and Its Possible Clinical Interests. Plast Reconstr Surg. 2024 Dec 1;154(6):1220e-1228e.
Tubbs RS, Mortazavi MM, Loukas M, D'Antoni AV, Shoja MM, Chern JJ, Cohen-Gadol AA. Anatomical study of the third occipital nerve and its potential role in occipital headache/neck pain following midline dissections of the craniocervical junction. J Neurosurg Spine. 2011 Jul;15(1):71-5.
Zhang J, Tsuzuki N, Hirabayashi S, Saiki K, Fujita K. Surgical anatomy of the nerves and muscles in the posterior cervical spine: a guide for avoiding inadvertent nerve injuries during the posterior approach. Spine (Phila Pa 1976). 2003 Jul 1;28(13):1379-84
