Cervical Plexus: What It Is And What Its Parts Are
The cervical plexus is a structure found in the neck, made up of four of the 31 pairs of spinal nerves, the cervical nerves. These nerves are involved in transmitting sensory stimulation and also controlling various muscles located in the face and upper chest.
Below we will see in more depth this plexus, what structures it makes up, what its functions are and the technique of blocking the cervical plexus, used in anesthesiology.
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 join 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 laterally it is delimited by the levator scapulae muscle and the sternocleidomastoid muscle.
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 are joined.
The first cervical nerve, that is, C1, exits through the intervertebral foramen and gives two branches, one anterior and one posterior The anterior branch runs inferiorly. The second nerve, C2, also gives two branches, one ascending and the other descending, and anastomoses (joins) with C1 forming the handle of the Atlas. The descending branch of C2 anastomoses with the ascending branch of C3, forming the loop of the Axis, while C4 joins 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 sensory stimuli, and on the other we have the deep branches, which are involved in muscle activation.
Superficial branches
As we have already mentioned, the superficial branches are sensitive. 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 sensitivity from part of the head, neck and upper part of the chest. It achieves this thanks to the existence of the 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. Responsible for providing cutaneous sensation of the posterosuperior scalp
2. Great auricular nerve (C2 and C3)
Its anterior branch innervates the skin of the face on 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 does so with that of the pinna.
3. Transverse neck nerve
Its ascending branches 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 are distributed, anterolaterally, to the lower part of the sternum.
4. Supraclavicular nerves (C3 and C4)
These nerves pass through the back of the sternocleidomastoid, taking care of the sensitivity of the skin in the supraclavicular fossa and the upper part of the chest
deep branches
The deep branches of the cervical plexus form the deep cervical plexus, which, Unlike the superficial nerve, this is mostly motor, with the exception of the phrenic nerve, which contains some sensory fibers It is made up as follows:
Within the descending branches we can highlight two structures, which are the most important of the deep cervical plexus or: the cervical loop and the phrenic nerve.
1. Cervical loop
The cervical loop originates from branches of C1, C2 and C3, and It consists of two roots, one upper and one lower
The first reaches the hypoglossal nerve as it descends towards 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 action essential for swallowing and speaking. These muscles are:
2. Phrenic nerve
It originates mainly from C4, but also has branches from 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 scalenus, at the level of the upper border of the thyroid cartilage. Then, descends obliquely down the neck, passing in front of the anterior scalenus 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 that 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 the early discharge of patients who undergo parathyroid gland excision.
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 have a high risk of complications if they undergo surgery under general anesthesia.
Despite its advantages, it must be said that presents, although few, adverse effects These include ipsilateral phrenic nerve palsy, which causes paralysis of the diaphragm, Horner’s syndrome, and facial nerve palsy. The anesthetic can be accidentally injected into the epidural or intradural space, causing total spinal anesthesia.
