Cervical plexus and its branches: structure and function

It is difficult to overestimate the importance and importance of the cervical plexus. Its branches set in motion a part of the respiratory muscles and provide the support function of the neck muscles . Therefore, in the pathology of the cervical plexus, a part of the vital functions can be broken.

Anatomy

The cervical nervous plexus is a paired complex formed by the anterior branches of the upper cervical spinal nerve roots. Its branches are supplemented by three arcuate loops connecting the roots together, forming a plexus.

Some sources combine it with the humerus, consisting of the lower half of the cervical nerve roots and the two upper pectoral roots. These sources mention the cervico-brachial plexus, consisting of spinal nerves of the cervical segments of the spinal cord, as well as the two upper pectoral spinal nerves.

Topography

Knowing the topography of the cervical plexus helps to understand which pathological conditions lead to a disruption of the functions of its roots. For specialists, this information is valuable in that, knowing the projection of the plexus, it is easier to avoid a negative impact on it during various medical manipulations.

The cervical plexus is located at the level of the upper four vertebrae of the cervical region. Being covered from the lateral side and from the front by the sternocleidomastoid muscle, it lies from the antero-lateral side of the group of deep muscles of the neck.

Structure and functions

Since the branches of the cervical plexus contain both afferent and efferent nerve fibers, they perform both sensory and motor functions.

Accordingly, if the structures of the cervical plexus are affected, both of these regions will suffer.

Motor branches

Muscular, or motor, nerves of the cervical plexus, branching in the muscles located near the muscles, set them in motion; And in addition, participate in the formation of the so-called cervical loop, consisting of a descending branch of the sublingual nerve and nerve fibers from the roots of the nerve plexus. Its function is to innervate the muscles located below the hyoid bone.

It should also be mentioned that both the trapezius, and the sternocleidose-mastoid muscle are also innervated by the nerve fibers that depart from the motor roots of the cervical plexus.

Sensitive department

Sensitive innervation of the cervical plexus is provided by the so-called cutaneous branches of the plexus, namely the large auricular nerve, the small nerve of the occiput, the transverse cervical and supraclavicular nerves.

Diaphragmatic nerve

This is another branch of the cervical plexus, which has an interesting feature: in the diaphragmatic nerve there are both motor fibers that branch into the diaphragm and drive it, and sensitive, providing innervation of the pericardium, pleura and peritoneum.

This nerve is recognized as the most important branch of those that form the cervical plexus, as it is directed to the diaphragm, and its defeat inevitably leads to paresis of the diaphragm of varying severity or its paralysis. This condition is clinically manifested by respiratory failure, down to its severe degree.

In a number of cases, when the cervical plexus is affected, and in particular, the diaphragmatic nerve, the pathology is manifested by clonic convulsions in the diaphragm, which appear externally in the form of hiccups.

Blood supply

The main source of nutrition structures of the upper part of the cervical spine are small branches of the vertebral artery, which, starting from the subclavian artery, rises along the spine upward, entering the cavity of the skull and giving off along all its length small branches for blood supply to the anatomical formations of the cervical spine.

Pathology of the cervical plexus

Symptoms of the defeat of the cervical nervous plexus are manifested in the form of motor, sensory and trophic disorders. The complexity of the symptomatology is due to the combination in this formation of nerve fibers having different functions. Infringements concern bodies to which gives for an innervation of a branch a cervical plexus. Its anatomy is such that when all of the roots are affected, all three functions suffer.

Possible defeats

1. Traumatization, for example, with dislocations or subluxations of the cervical vertebrae, bruises or birth trauma in newborns.
2. Compression syndrome in case of compression with neoplasm, bone fragments, hematoma or bandage (with incorrectly immobilized limb).
3. Infectious and inflammatory lesion, which can undergo the cervical plexus of the spinal nerves after the transmitted infections (herpetic infection, influenza, angina, syphilis).
4. Toxic etiology of cervical plexitis. This variant of defeat is possible with systematic abuse of alcohol or in case of poisoning with heavy metals.
5. Pronounced hypothermia (hypothermia) can cause inflammation of the nerve trunks.
6. Allergic or autoimmune damage, when the aggressive action of the cells of the immune system is erroneously directed to the body's own nervous tissue.
7. Chronic systemic diseases, leading to disruption of nerve supply.

Manifestations

Among the lesions and diseases of the cervical plexus can be identified:

• One-sided.
• Two-sided.

All cases when the cervical plexus and its branches are affected are characterized by motor, sensory and trophic disorders in the corresponding innervation zone. Pathology passes in its development the following stages:

• Neuralgic stage. Manifestations are associated with irritation of nerve trunks. A typically acute onset in the form of sharp soreness in the lower lateral part of the face with irradiation into the auricle and occipital region, as well as inconstant irradiation into the hand to the fingertips. The localization of the pain syndrome corresponds to the side of the lesion. Soreness increases significantly with active and passive movements; The state of rest can bring some relief, but the pain at rest, and even at night, does not completely disappear. The pain is accompanied by paresthesias, cooling of the skin and a temperature sensitivity disorder in the innervation zone of the affected nerve roots.
• The paralytic stage. The stage of paresis and paralysis (depending on the severity of the lesion) is characterized by signs of impaired functions of the cervical nerves that make up the cervical plexus. Because of the defeat of the diaphragmatic nerve, hiccups are noted and, due to the uncoordinated work of the muscles, difficulty, disruption in coughing; Disorders of voice formation, respiration - up to pronounced dyspnea and in severe cases of respiratory disorders, up to respiratory failure. Trophic disorders cause swelling and bluish staining of the skin, a change in their turgor; In addition, sweating is broken in the direction of its amplification. The long duration of the disease can lead to atrophic changes in the muscles of the shoulder girdle, resulting in the formation of habitual dislocations of the shoulder joint; Or paralysis of the musculature of the neck, a severe degree of which leads to loss of the neck muscles ability to perform their functions: the head of the patient in severe cases can lean forward so that the chin abuts the sternum. With such deep lesions, active movements with the help of the affected muscles are impossible; Such a patient can not raise his head independently.
• Stage of recovery. At this stage, the disturbed nervous functions begin to gradually recover. In a number of cases, recovery is observed incomplete, with residual phenomena in the form of paresis or paralysis of the peripheral type (flaccid character) and atrophic changes in the musculature (the formulation for the diagnosis of residual phenomena in the form of a peripheral paresis should contain an indication of the affected nerve root).

Residual phenomena:

• Flaccid (peripheral) paresis or paralysis of the muscles of the neck and shoulder girdle, habitual dislocations of the shoulder joint and the characteristic position of the head due to weakness of the cervical musculature.
• Muscle Tone Disorder; Cramps and spasms in the innervated by the branches of the cervical plexus muscle groups.
• Sensory disorders in the form of paresthesias and painful hyperesthesia in the zone of sensitive innervation of the plexus.
• Trophic disorders of the skin and soft tissues in the affected areas.

Anesthesia

Anesthesia of the cervical plexus allows for operative interventions on the neck, thyroid gland, blood vessels of the brachiocephalic group in traumas, gunshot wounds, oncological diseases.

Since anterior to the median line of the neck, the branches of the cervical plexus are anastomosed, anesthesia of the sensitive roots behind the edge of the sternocleidomastoid muscle should be made from both sides. Such anesthesia makes it possible to perform large interventions on the tissues of the deep layers of the neck (including laryngectomy, removal of oncological neoplasms).

In order to enhance the effect of anesthesia of the branches of the cervical plexus, additional blockage of the superficial nerve branches that extend to the frontal surface of the neck is allowed.

To perform all these manipulations, anesthesia is performed by anterior access, since the use of lateral access (injection of anesthetic solution into subdural space) is associated with a high probability of developing rather serious complications, therefore, the side-access technique is not used, if possible.