The cervical plexus is a structure located 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 in the control of various muscles located in the face and upper chest.
Below we will take a closer look at this plexus, what structures it forms, what are its functions, and the technique of cervical plexus blocking, which is used in anesthesiology.
What is the cervical plexus?
The cervical plexus is a structure formed by the conglomeration of the anterior branches of the first four pairs of spinal nervesThat is, the cervical nerves, these are C1, C2, C3 and C4, although some authors also include it in the plexus at C5.
The roots of these four nerves meet in front of the transverse processes of the first three cervical vertebrae, forming three arches. The plexus is bounded by the paravertebral muscles and the vascular bundle medially, while laterally it is bounded by the elevator scapular muscle and the sternoclidomastoid muscle.
Structure and function
Before going into more detail about the organization of the cervical plexus, it is necessary to mention how the four types of nerves that compose it come together.
The first cervical nerve, i.e. C1, exits through the intervertebral foramen and gives two branches, an anterior and a posterior. The anterior branch runs in a lower direction. The second nerve, C2, also gives two branches, one ascending and one descending, and anastomoses (joints) with C1 forming the handle of the Atlas. The descending branch of C2 anastomoses with the ascending branch of C3, forming the handle of the axis, while C4 joins with the anterior branch of the infra-adjacent nerve forming the third handle.
The cervical plexus is divided into two types of branches, depending on their degree of depth. On the one hand, we have the superficial branches, which specialize in capturing sensory stimuli, and on the other hand, we have the deep branches, which are involved in the activation of muscles.
As we have already mentioned, the superficial branches are of the sensitive type. These superficial branches emerge at the height of the middle third of the posterior border of the sternoclidomastoid muscle, and are visible in the posterior triangle. They meet on the sternoclidomastoid muscle, forming the superficial cervical plexus.
The superficial cervical plexus is a modality that captures the sensitivity of part of the head, neck and upper chest. This is achieved through the existence of sensitive branches, or skin, which are found in these parts. In the superficial branches, the following nerves can be found:
1. Minor occipital nerve (C2)
It is derived from the root of C2, although in some individuals it also receives part of the roots of C3. It is responsible for the skin sensation of the postero-superior scalp.
2. Large atrial nerve (C2 and C3)
Its anterior branch innervates the facial skin above the parotid gland, which communicates with the facial nerve. The posterior branch of the great atrial nerve innervates the skin of the mastoid, and the posterior does so with that of the atrium.
3. Transverse nerve of the neck
Its ascending branches rise to reach the submandibular region. Here it forms a plexus with the cervical branch of the facial nerve below the platysma.
The descending branches pierce this platysm and are distributed anterolaterally to the lower part of the sternum.
4. Supraclavicular nerves (C3 and C4)
These nerves run through the back of the sternoclidomastoid, take care of the sensitivity of the skin at the supraclavicular fossa and upper chest.
The deep branches of the cervical plexus form the deep cervical plexus which, unlike the superficial, this is mainly motor, with the exception of the phrenic nerve which contains some sensory fibers. It is compliant as follows:
- Medial branches: innervate the long muscle of the head and neck.
- Lateral branches (C3-C4): scapular and rhomboid lifting muscle.
- Ascending branches: inferior anterior rectus muscles and lateral rectus muscles.
- Descending branches: union of the roots of C1, C2 and C3.
In the descending branches we can highlight two structures, which are the most important of the deep cervical plexusor: the cervical handle and the phrenic nerve.
1. Cervical asa
The cervical handle comes from the branches of C1, C2 and C3, i it consists of two roots, one upper and one lower.
The first reaches the hypoglossal nerve going down to the neck. The second descends laterally into the jugular vein, then leans forward and anastomoses with the upper root.
The cervical handle acts on the infrahyoid muscles, which depress the hyoid bone, a key action for swallowing and speaking. These muscles are:
- Homohyoid muscle.
- External hyoid muscle.
- Sternothyroid muscle.
- Video tape.
2. Phrenic nerve
It mainly comes from C4, but also has branches from C3 and C5. It provides motor innervation to the diaphragm, although it also has sensitive and sympathetic fibers.
The phrenic nerve arises on the upper part of the lateral border of the anterior scalene, at the height of the upper border of the thyroid cartilage. after, it descends obliquely along the neck, passing in front of the anterior scalene muscle.
On the right side, it passes in front of the second part of the subclavian artery, and on the left side, it crosses the first part of this same artery.
Superficial cervical plexus obstruction
In surgery, the cervical plexus block technique is used to provide the right conditions for performing procedures on the parathyroid gland. without resorting to general anesthesia. This anesthetic technique promotes the early discharge of patients operated on for excision of the parathyroid gland.
It is particularly indicated for surgeries of short duration, with little complexity and in patients in collaboration and without previous medical problems. However, it is also indicated in patients at high risk of complications if they are operated on under general anesthesia.
Despite its advantages, it must be said that has side effects, although rare. Among them are ipsilateral phrenic nerve palsy, which causes diaphragm paralysis, Horner’s syndrome, and facial nerve palsy. The anesthetic can be accidentally injected into the epidural or intradural space, causing total spinal anesthesia.
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