It is difficult to overestimate the importance and importance of the cervical plexus. Its branches set in motion part of the respiratory muscles and provide the support function of the neck muscles . Therefore, in the pathology of the cervical plexus, part of the vital functions may be impaired.
Anatomy
The cervical nerve plexus is a paired complex formed by the anterior branches of the superior cervical spinal nerve roots. Its branches are complemented by three arcuate loops connecting the roots that form the plexus.
Some sources combine it with the brachial, consisting of the lower half of the cervical nerve roots and two upper thoracic. These sources mention the cervico-brachial plexus, consisting of the spinal nerves of the cervical segments of the spinal cord, as well as the two upper thoracic spinal nerves.
Topography
Knowing the topography of the cervical plexus helps to understand what pathological conditions lead to a violation 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 effect on it during various medical manipulations.
The cervical plexus is located at the level of the upper four vertebrae of the cervical spine. Being covered from the lateral side and in front of the sternocleidomastoid muscle, it lies on the front-side side of the group of deep neck muscles.
Structure and function
Since the branches of the cervical nerve plexus contain both afferent and efferent nerve fibers, they perform both sensitive and motor functions.
Accordingly, with damage to the structures of the cervical plexus, both of these areas will suffer.
Motor branches
The muscular, or motor, nerves of the cervical plexus, branching in nearby muscles of the neck, set them in motion; and in addition, they take part in the formation of the so-called cervical loop, consisting of a descending branch of the hyoid nerve and nerve fibers coming 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 sternocleidomastoid muscles are also innervated by nerve fibers extending from the motor roots of the cervical plexus.
Sensitive department
The sensitive innervation of the cervical plexus is provided by its so-called cutaneous branches, namely, the large ear nerve, the small nerve of the occiput, the transverse cervical and supraclavicular nerves.
Phrenic nerve
This is another branch of the cervical plexus that has an interesting feature: in the composition of the phrenic nerve there are both motor fibers branching in the diaphragm and setting it in motion, as well as sensory ones, which provide 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 goes 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, up to its severe degree.
In some cases, when the cervical plexus is affected, and in particular, the phrenic nerve, the pathology is manifested by clonic convulsions in the diaphragm, which externally manifest as hiccups.
Blood supply
The main source of nutrition for the structures of the upper cervical spine are small branches of the vertebral artery, which, originating from the subclavian artery, rises along the spine, entering the cranial cavity and giving small branches along its length for blood supply to the anatomical formations of the cervical spine.
Pathology of the cervical plexus
Signs of damage to the cervical nerve plexus are manifested in the form of motor, sensory and trophic disorders. The complexity of the symptoms is due to the combination in this formation of nerve fibers having different functions. Violations relate to organs to which the cervical plexus gives for innervation of the branch. Its anatomy is such that with the defeat of each of the roots all three functions suffer.
Possible defeats
- Injury, for example, with dislocations or subluxations of the cervical vertebrae, bruises or birth injuries in newborns.
- Compression syndrome with compression by a neoplasm, bone fragments, a hematoma or a bandage (with improperly performed limb immobilization).
- Infectious and inflammatory lesion, which may be subjected to the cervical plexus of the spinal nerves after infections (herpes infection, influenza infection, tonsillitis, syphilis).
- Toxic etiology of cervical plexitis. This variant of the lesion is possible with systematic abuse of alcohol or in the case of heavy metal poisoning.
- Severe hypothermia (hypothermia) can cause inflammation of the nerve trunks.
- An allergic or autoimmune lesion, when the aggressive effects of cells of the immune system are mistakenly directed to the body’s own nervous tissue.
- Chronic systemic diseases leading to malnutrition of nerve trunks.
Manifestations
Among the lesions and diseases of the cervical plexus can be distinguished:
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. Typically an acute onset in the form of a sharp pain in the lower lateral part of the face with irradiation to the auricle and occipital region, as well as intermittent irradiation in the arm up to the tips of the fingers. The localization of the pain syndrome corresponds to the side of the lesion. Soreness increases significantly with active and passive movements; a state of rest may bring some relief, but the pain at rest, even at night, does not completely disappear. The pain is accompanied by paresthesia, cooling of the skin and a disorder of temperature sensitivity in the innervation zone of the affected nerve roots.
- Paralytic stage. The stage of paresis and paralysis (depending on the severity of the lesion) is characterized by signs of dysfunction of the cervical nerves that make up the cervical plexus. Due to damage to the phrenic nerve, hiccups are noted and, due to uncoordinated work of muscles, difficulties, disturbances during coughing; disorders of voice formation, breathing - up to severe shortness of breath 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 disturbed in the direction of its amplification. A long duration of the disease can lead to atrophic changes in the muscles of the shoulder girdle, which will result in the formation of habitual dislocations of the shoulder joint; or paralysis of the neck muscles, a severe degree of which leads to the loss of the ability of the neck muscles to perform their functions: in severe cases, the patient’s head can lean forward so that the chin is adjacent to the sternum. With such deep lesions, active movements with the help of the affected muscles are impossible; such a patient cannot raise his head independently.
- Recovery stage. At this stage, impaired nerve function begins to recover gradually. In some cases, the recovery is incomplete, with residual phenomena in the form of paresis or paralysis of the peripheral type (flaccid nature) and atrophic changes in the musculature (the formulation for the diagnosis of residual phenomena in the form of peripheral paresis should contain an indication of the affected nerve root).
Residual effects:
- 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 neck muscles.
- Muscle tone disorder; cramps and spasms in muscle groups innervated by the branches of the cervical plexus.
- Sensory disturbances in the form of paresthesias and pain 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 surgical interventions on the neck, thyroid gland, blood vessels of the brachiocephalic group with injuries, gunshot wounds, and oncological diseases.
Since the branches of the cervical plexus are anastomosed in front of the midline of the neck, anesthesia of the sensitive roots behind the edge of the sternocleidomastoid muscle should be performed on both sides. Such anesthesia allows you to perform, including large interventions on the tissues of the deep layers of the neck (including laryngectomy, removal of cancerous tumors).
In order to enhance the effect of anesthesia of the branches of the cervical plexus, additional blocking of the superficial nerve branches extending to the frontal surface of the neck is allowed.
To perform all these manipulations, anesthesia is performed with front access, since the use of lateral access (injection of the anesthetic solution into the subdural space) is associated with a high probability of the development of rather serious complications, therefore, the lateral access technique, if possible, is not used.