Superficial structures of the neck: Cervical plexus

Definitions & Key takeaways

The cervical plexus is an important plexus of nerves that provide innervation to the head and neck. This plexus is located anteromedial to the levator scapulae and middle scalene muscles and deep to the sternocleidomastoid muscle. The cervical plexus forms from the anterior rami of spinal nerves C1, C2, C3, and C4. It is a mixed nerve plexus as it provides both sensory and motor nerve fibers. The sensory fibers provide sensation to the skin of the neck, upper chest, and shoulder regions, while the motor fibers provide innervation to the muscles in the neck, chest, and shoulder regions.

Chapters:

Watch video only

Introduction0:00–0:20

The cervical plexus is an important plexus of nerves which provide innervation to the head and neck. This plexus is located anteromedial to the levator scapulae and middle scalene muscles and deep to sternocleidomastoid - or SCM.

Roots0:20–1:09

Now, the anterior rami of the spinal nerves C1, C2, C3 and C4 form the roots of the cervical plexus, which is an irregular series of nerve loops and the branches that arise from these loops.
Each participating ramus, except the first, splits into ascending and descending branches which unite with branches from neighboring spinal nerves to form the loops.
The superficial branches of the plexus, which initially pass posteriorly are cutaneous, or sensory, branches which innervate the skin, and the deep branches of the plexus, which includes the roots of the phrenic nerve and the ansa cervicalis, pass anteromedially and are motor branches which innervate the muscles of the neck.
The cutaneous branches of the cervical plexus emerge around the middle of the posterior border of the SCM, and they supply the skin of the neck, superolateral thoracic wall, shoulder and scalp between the auricle and the external occipital protuberance.

Sensory (cutaneous) branches1:09–2:53

Now let’s look at the four cutaneous nerves that innervate these areas. There are three nerves branching from the C2 and C3 loop.
The lesser occipital nerve, which contains fibers from C2 supplies the skin of the neck and scalp posterosuperior to the auricle.
The great auricular nerve contains fibers from both C2 and C3 and ascends across the SCM to the inferior pole of the parotid gland, where it divides to innervate the skin over - and the sheath surrounding - the parotid gland, the mastoid process, the posteroinferior part of the auricle and an area of skin that extends from the angle of the mandible to the mastoid process.
There is also the transverse cervical nerve which also contains fibers from C2 and C3. It curves around the middle of the posterior border of SCM, passing anteriorly and horizontally across it, deep to the external jugular vein and the platysma to innervate the skin covering the anterior triangle.
The branches of the cervical plexus that arise from the C3 and C4 nerve loop are the supraclavicular nerves which contain fibers from C3 and C4 and emerge as a common trunk deep to the SCM.
These branches send smaller branches to the skin of the neck that cross the clavicle and supply the skin over the shoulder.
And finally, there are the motor branches of the cervical plexus that include the ansa cervicalis and the phrenic nerves which arise from the loops of cervical plexus, as well as branches that arise from the roots of the brachial plexus such as dorsal scapular nerve mainly from C5, but sometimes also from C4 which innervates the levator scapulae and rhomboid muscles, and the long thoracic nerve, from C5 to C7 which innervates the serratus anterior muscle.

Motor branches2:53–5:09

The ansa cervicalis is a loop formed by the union of the superior root of the ansa cervicalis, which is composed of fibers from C1 and C2 and ,can be seen briefly joining the hypoglossal nerve, and the inferior root of the ansa cervicalis composed of fibers from C2 and C3.
The ansa cervicalis innervates the infrahyoid muscles, specifically the omohyoid, sternothyroid and sternohyoid, but not the thyrohyoid which is innervated by a motor nerve which derives solely from C1 fibers that travel along - or hitchhike with - the hypoglossal nerve before descending as the nerve to thyrohyoid.
Another motor nerve which derives from C1 fibers that travel with the hypoglossal nerve is the nerve to geniohyoid which innervates, well, the geniohyoid muscle.
The phrenic nerve originates mainly from the C4 nerve with contributions from C3 and C5 nerves. It contains motor, sensory and sympathetic nerve fibers.
Each phrenic nerve forms at the superior part of the lateral border of the anterior scalene muscle at the level of the superior border of the thyroid cartilage, and descends obliquely with the internal jugular vein across the anterior scalene.
The phrenic nerves provide the sole motor supply to the diaphragm. You can remember this fact - and the nerve roots that form the phrenic nerve - by the mnemonic “C3, 4 and 5 keep the diaphragm alive!”.
The phrenic nerves also provide sensory innervation to the central part of the diaphragm as well as the mediastinal pleurae and pericardium.
Before we hit the recap, let’s take a quick break and try to identify the sensory and motor branches of the cervical plexus.Alright, let’s do a quick recap.

Quiz5:09–5:23

The cervical plexus forms from the anterior rami of spinal nerves C1, C2, C3 and C4 and has two types of branches: cutaneous and motor branches.

Review5:23–5:55

The cutaneous branches are represented by the lesser occipital nerve, great auricular nerve, transverse cervical nerve and supraclavicular nerves, and the motor branches are represented by the ansa cervicalis, phrenic nerves, nerve to thyrohyoid and nerve to geniohyoid.
nerve and supraclavicular nerves, and the motor branches are represented by the Ansa. Cervicalis.
Phrenic nerves nerve to the thyroid