Cervical plexus: what it is and what are its parts

The cervical plexus is a structure found in the neck, made up of four of the 31 pairs of spinal nerves., cervical nerves. These nerves are involved in the transmission of sensory stimulation and also the control of various muscles located in the face and upper chest.

Next, we will take a more in-depth look at this plexus, what structures it makes up, what its functions are, and the cervical plexus block technique used in anesthesiology.

• Related article: "Parts of the Nervous System: functions and anatomical structures"

What is the cervical plexus?

The cervical plexus is a structure formed by the conglomeration of the anterior rami of the first four pairs of spinal nerves, that is, the cervical nerves, these are C1, C2, C3 and C4, although some authors also include C5 in the plexus.

The roots of these four nerves unite in front of the transverse processes of the first three cervical vertebrae, forming three arches. The plexus is limited by the paravertebral muscles and the vascular bundle medially, while which laterally delimits the levator scapulae muscle and the muscle sternocleidomastoid.

structure and function

Before going into more detail about how the cervical plexus is organized, it is necessary to mention how the four types of nerves that make it up come together.

The first cervical nerve, that is, C1, exits through the intervertebral foramen and gives off two branches, one anterior and one posterior.. The anterior branch runs inferiorly. The second nerve, C2, also gives off two branches, one ascending and one descending, and anastomoses (joins) with C1 to form the Atlas loop. The descending branch of C2 anastomoses with the ascending branch of C3, forming the loop of the Axis, while C4 unites with the anterior branch of the infra-adjacent nerve, forming the Third Loop.

The cervical plexus is divided into two types of branches, according to their degree of depth.. On the one hand we have the superficial branches, which specialize in capturing stimuli sensory, and on the other we have the deep branches, which are involved in the activation of muscles.

superficial branches

As we have already commented, the superficial branches are of the sensitive type. These superficial branches emerge at the level of the middle third of the posterior border of the sternocleidomastoid muscle, and are visible in the posterior triangle. They meet over the sternocleidomastoid muscle, forming the superficial cervical plexus..

The superficial cervical plexus is a modality that collects sensation from part of the head, neck, and upper part of the thorax. This is achieved thanks to the existence of sensitive, or cutaneous, branches that are located in these parts. Within the superficial branches the following nerves can be found:

1. Lesser occipital nerve (C2)

It is derived from the C2 root, although in some individuals it also receives part of the C3 roots. It is responsible for providing cutaneous sensation of the posterosuperior scalp.

2. Great auricular nerve (C2 and C3)

Its anterior branch supplies facial skin over the parotid gland, which communicates with the facial nerve. The posterior branch of the great auricular nerve innervates the skin over the mastoid and the posterior part of the auricular nerve.

3. transverse neck nerve

Its ascending rami rise reaching the submandibular region.. Here it forms a plexus with the cervical branch of the facial nerve below the platysma.

The descending branches pierce this platysma and distribute, anterolaterally, to the inferior part of the sternum.

4. Supraclavicular nerves (C3 and C4)

These nerves pass through the posterior part of the sternocleidomastoid, dealing with skin sensation in the supraclavicular fossa and upper thorax.

• You may be interested in: "Choroid plexuses: anatomy, functions and pathologies"

deep branches

The deep branches of the cervical plexus form the deep cervical plexus which, unlike the superficial, this is mostly motor, with the exception of the phrenic nerve that contains some sensory fibers. It is made up as follows:

• Medial branches: innervate the long muscle of the head and neck.
• Lateral branches (C3-C4): levator scapulae muscle and rhomboids.
• Ascending rami: rectus capitis and lateral rectus capitis muscles.
• Descending branches: union of the roots of C1, C2 and C3.

Within the descending branches we can highlight two structures, which are the most important of the deep cervical plexus.o: the cervical loop and phrenic nerve.

1. cervical loop

The cervical loop originates from branches of C1, C2, and C3, and consists of two roots, one upper and one lower.

The first reaches the hypoglossal nerve as it descends into the neck. The second descends laterally to the jugular vein, then bends forward and anastomoses with the superior root.

The cervical loop acts on the infrahyoid muscles, which depress the hyoid bone, an essential action for swallowing and speaking. These muscles are:

• omohyoid muscle.
• sternohyoid muscle.
• sternothyroid muscle.
• thyrohyoid muscle.

2. phrenic nerve

It originates mainly from C4, but also has branches of C3 and C5. Provides motor innervation to the diaphragm, although it also has sensory and sympathetic fibers.

The phrenic nerve arises on the upper portion of the lateral border of the anterior scalene, at the level of the upper border of the thyroid cartilage. Then, descends obliquely down the neck, passing in front of the anterior scalene muscle.

On the right side it passes in front of the second portion of the subclavian artery, and on the left side it crosses the first portion of the same artery.

Superficial cervical plexus block

In surgery, the cervical plexus block technique is used to provide the appropriate conditions to carry out interventions on the parathyroid gland. without resorting to general anesthesia. This anesthetic technique favors early discharge of patients who undergo excision of the parathyroid gland.

It is especially indicated for short-term surgeries, with little complexity and in cooperative patients without previous medical problems. However, it is also indicated in patients who present a high risk of complications in the event that they are operated under general anesthesia.

Despite its advantages, it can be said that It presents, although few, adverse effects. These include ipsilateral phrenic nerve palsy, which causes paralysis of the diaphragm, Horner's syndrome, and facial nerve palsy. Anesthetic may accidentally be injected into the epidural or intradural space, causing total spinal anesthesia.

Bibliographic references:

• Blanco-Aparicio M, Montero-Martínez C, Couto-Fernández D, Pernas B, Fernández-Marrube M, Verea-Hernando H (2010). Unilateral Painful Diaphragm Paralysis as the Only Sign of Amyotrophic Neuralgia. Arch Bronconeumol, 46(7):390-392.
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