Cervical Plexus Overview

Study Notes

Cervical Plexus

Network of nerve fibers supplying the head, neck, and trunk.
Formed by the anterior (ventral) rami of spinal nerves C1-C4.
Located in the posterior triangle of the neck, at the mid-sternocleidomastoid muscle level.
Situated opposite the upper 4 cervical vertebrae.
Lies on the scalenus medius, covered by the sternocleidomastoid muscle.

Formation of Cervical Plexus

Each cervical nerve, except the first, divides into upper and lower branches.
These branches unite with branches of adjacent cervical nerves to form loops.
Each nerve communicates with the one above and below it, forming loops.
Communicating fibers from the superior cervical ganglion in the sympathetic trunk are present, known as “gray rami communicantes.”

Muscular Branches

Segmental branches to prevertebral muscles:
- Rectus capitis anterior & lateralis
- Longus capitis
- Longus colli
- Scalenes
C1 loop (to hypoglossal):
- Superior root of Ansa Cervicalis:
  - Infrahyoid muscles
  - Thyrohyoid & geniohyoid muscles
Branches from C2 & 3:
- Sternocleidomastoid (SCM)
Branches C3 & 4:
- Trapezius
C2 & 3:
- Inferior Root of Ansa cervicalis
  - Spirals around the lateral side of the internal jugular vein
Phrenic nerve:
- C3, 4, 5
- Supplies the diaphragm
- Accessory Phrenic nerve

Cutaneous Branches

Lesser Occipital Nerve:
- C2
- Curves around and ascends along the posterior border of the SCM.
- Supplies the skin of the back of the upper neck and scalp posterior to the ear.
- Gives off an auricular branch, supplying the skin over the upper SCM and auricle.
Great Auricular Nerve:
- Largest cutaneous nerve
- C2 & C3
- Winds around the posterior border of the SCM.
- Ascends beneath the platysma to the parotid gland, where it divides into anterior and posterior branches.
  - Anterior branch: Skin of the face over the parotid gland, communicates with the facial nerve.
  - Posterior branch: Skin over the mastoid process, communicates with the smaller occipital, auricular branch of the vagus, and the posterior auricular branch of the facial nerves.
Transverse Cervical:
- C2 & C3
- Divides beneath the platysma into ascending and descending branches.
  - Ascending branches: skin of the upper and front part of the neck.
  - Descending branches: skin of the side and front of the neck, as low as the sternum.
Supraclavicular Nerves:
- C3 & C4
- Emerge beneath the posterior border of the SCM.
- Descend the posterior triangle of the neck beneath the platysma and deep cervical fascia.
- Supply skin to:
  - Medial branches: Sternal angle and sternoclavicular joint.
  - Intermediate branches: Skin anterior to the clavicle to the anterior axial line.
  - Lateral branches: Over the acromion and upper half of the deltoid, posterior shoulder joint to the scapular spine (posterior axial line).

Cervical Nerves

Upper 3 cervical nerves: Meningeal branches
- Supply the posterior cranial fossa.
- C1 ascends with the hypoglossal nerve, and C2 with the vagus nerve
C1 does not supply any skin.
Anterior divisions of the cervical nerves (except the first) lie on the grooved upper surfaces of the transverse processes of the vertebrae.
Anterior division of C1 (suboccipital nerve) passes from the vertebral canal above the posterior arch of the atlas and runs forward around the lateral aspect of its superior articular process medial to the vertebral artery.
The anterior divisions of the upper 4 cervical nerves unite to form the cervical plexus.
Each receives a gray ramus communicans from the superior cervical ganglion of the sympathetic trunk.