Cervical plexuses

1. Cevical Plexux

2. Contents
1. Formation
2. Branches
3. Course and Distribution
4. Clinical Notes.

3. Formation
• The cervical plexus is a conglomeration of cervical
nerves formed by the anterior (ventral) rami of
spinral nerves C1-C4. These are the roots of
cervical plexus.
• The 5th cervical nerve may also be considered as
part of the plexus due to its contribution in the
formation of one of the motor branches of the
cervical plexus, the phrenic nerve.

4. Cont...
• The cervical plexus is formed in the neck region. It lies
deep to the sternocleidomastoid muscle, and anterolateral
to the levator scapulae.
• Each cervical nerve communicates with one another in a
superior-inferior fashion close to their origins, thus C2
accepts communicating fibres from C1, C3 from C2 and
so on.

5. Cont..
• These communicating fibres are the contributions from the
Sympathetic Trunk (sympathetic nervous system) to the cervical
plexus and are known as the “gray rami” communicates.
• Each cervical nerves (except the first, C1) then divide into two
branches:an ascending branch and a descending branch. They
subsequently unite with branches of adjacent cervical nerves to
form loops. Loops and branches from the cervical nerves
contribute to the fromation of the cervical plexus.

6. Branches
• Sensory
There are four sensory branches originating from the
loops formed between the anterior rami of spinal rami of spinal
nerves C2 and C3, and C3 and C4.
Branches from the loop between C2 and C3:
1. Lesser Occiital Nerve (formed by C2)
2. Great auricular Nerve (formed by C2 and C3)
3. Transverse Cervical Nerve (formed by C2 and C3)
Branches from the loop between C3 and C4:
1. Supraclavicular Nerve ( formed by C3 and C4)

7. Motor
• Ansa Cervicalis (C1-C3)
• It is a nerve loop innervating the infrahyoid muscles in the
anterior cervical triangle.
• Phrenic Nerve (C3-C5)
• It supplies the diaphragm and the pericardium of the
heart. Additional muscle branches are also given off to
provide innervation to several prevertebral,
sternocleidomastoid and trapezious muscles.
• Phrenic Nerve mainly contributed by C4 with little fibres
from C3 and C5.

8. Course and Distribution
Sensory Branches
• Lesser Occipital Nerve: This branch is formed by the second
cervical nerve only, and courses to supply the skin of the neck
and the scalp posterosuperior to the clavicle.
• Great Auricular Nerve: This branch originates from the C2 and
C3 nerves. It courses upwards in diagonal fashion and crosses
the sternocleidomastoid muscle onto the parotid gland. It then
divides and innervates the skin over the parotid gland, the
posterior aspect of the auricle, and an area of skin extending from
the angle of the mandible to the mastoid process.

9. Cont..
• Transverse Cervical Nerve: The transverse cervial nerve is formed by
axons from the second and third cervical nerves. It supplies the skin covering
the anterior triangle of the neck. This branch curves arround the middle of the
posterior border of the sternocleidomastoid muscle and crosses it deep to the
platysma muscle.
• Supraclavicular nerves: These branches are formed by the C3 and C4
Spinal Nerves, and emerge as a common trunk under cover of the
sternocleidomastoid muscle. This divides into three branches (medial,
intermediate and lateral) to the skin of the neck. Some branches also cross
the clavicle to supply skin over the shoulder.

10. Motor Branches
• The ansa cervicalis: ( or ansa hypoglossi) is a loop of
the nerves from cervical plexus. It lies superficial to the
internal jugular vein in the carotid triangle.
• Branchyes from ansa cervicalis innervate most of the
infrahyoid muscles, including the sternothyroid muscle.
• Throhyoid muslce is also an infrahyoid muslce and
geniohyoid muscle which is a suprahyoid muscle are
innervated by cervical spinal nerve 1 via the hypoglossal
nerve.

11. Cont...
• Phrenic Nerve: Originate chiefly from the 4th cervical
nerve C4 but receives contributions from the 3rd and 5th
cervical nerves (C3 and C5).
• It is formed at the superior part of the lateral border of the
anterior scalene muslce, at the level of the superior
border of the thyroid cartilage.
• The phrenic nerve contains motor, sensory, and
sympathetic nerve fibres. It provides the sole motor
supply to the diaphragm as well as sensation to its central
part. In the thorax phrenic nerve innervates the

12. Clinical Notes
• Phrenic Nerve Severance
Severance (injury) of phrenic nerve results in paralysis
of diaphragm. Temporary paralysis of the diaphragm also
results from phrenic nerve block. In this condition, the
anaesthetic is injected around the nerve where it lies on the
anterior surface of the middle third of the anterior scalene
muscle.

13. Cont...
• Cervical Plexus Block
Nerve block is measure to inhibit nerve impulse
conductance, usually for regional anaesthesia prior to
surgical operations. In a cervical plexus block, an
anaesthetic agent is injected at several points along the
posterior border of the sternocleidomastoid muscle, mainly
at the junction of its superior and middle thirds the nerve
point of the neck. Because the phrenic nerve supplying the
diaphragm pericardium is also paralysed by cervical plexus
block, this procedure is not performed on patients with