The cervical plexus is a plexus of nerves of the spinal cord, located in the cervical region and composed of mixed nerve fibers. Thus, for example, the plexus is as much involved in the sensory innervation of the ear skin as it is in the motor innervation of the diaphragm. Diseases of the plexus are grouped together as plexopathies.
What is the cervical plexus?
In medicine, a plexus is a fine meshwork of blood vessels or nerve fibers. Accordingly, the cervical plexus is a nerve fiber plexus made up of branches of the spinal nerves. As such, the nerves of the spinal cord are referred to. The cervical plexus contains spinal nerves of the spinal cord segments C1 to C4. In addition, some portions of segments C5 meet in the plexus. Between the scalenus anterior and medius muscles, the branches of the nerve plexus extend down into the deep cervical region. Medicine distinguishes sensitive nerve branches from motor nerve branches. The sensitive branches conduct stimulus perceptions. The motor fibers, on the other hand, reach effectors such as muscles or organs and send movement commands to these effectors from the central nervous system. The cervical plexus contains both nerve fiber qualities. Its motor fibers are involved in innervation of the hyoid muscles, diaphragmatic muscles, and cervical muscles. The sensitive branches innervate the ear and neck and the skin between the clavicle and shoulder. The cervical plexus is a somatic nerve plexus. This type of nerve bundle should be distinguished from vegetative nerve bundles, which usually move along arteries.
Anatomy and structure
Anatomically, the cervical plexus corresponds to the mixed cervical nerve plexus and thus to a confluence of anterior branches of the first four spinal nerves. Its superficial branches correspond to the sensory portions. The deep portions are motor branches. The plexus has connections to the border cord, hypoglossal nerve, and accessorius nerve. Its superficial sensitive branches lie on the cervical fascia and emerge in a star shape from the posterior border of the sternocleidomastoid muscle. The sensory branches are mainly the nervus occipitalis minor, the nervus auricularis magnus, the nervus transversus colli, and the nervi supraclaviculares. In addition, the supraclavicular intermediary nerve and the supraclavicular lateral nerve are included. The sensory branches are divided into ascending and descending branches of the central nervous system depending on their course. The motor branches of the plexus include primarily the phrenic nerve, the ramus musculi sternocleidomastoidei, the ramus musculi trapezii, and the ansa cervicalis, also called the cervical loop. The confluence of nerves is reticular and corresponds to storage in fiber bundles.
Function and tasks
The functions of the cervical plexus are sensory and motor innervation of parts of the neck, chest, and face. For example, through motor innervation of the diaphragm, the plexus enables diaphragmatic movement as part of respiratory motion. Motorically, the plexus also innervates the sternocleidomastoid and trapezius muscles. Thus, it gives motility to the trapezius muscle of the upper spine and the cervical muscle on the building side. With the cervical loop, the plexus makes the sublingual muscles mobile. The same applies to the muscles located in front of the cervical spine, the scapula elevator, the head turner and the staircase muscles of the rib cage. In addition, through the movement of the chin-tongue muscle, the plexus is relevant to the act of swallowing. To all of the above muscles, movement commands from the central nervous system are transmitted through the plexus, causing the muscles to contract or relax. In addition, the cervical plexus supplies ascending sensory branches to the skin behind the ear, the auricle, adjacent skin areas, the anterior surface of the neck, and the skin below the chin. Its descending sensitive branches innervate the lower neck region between the shoulder and clavicle. Sensory nerve branches transmit stimuli such as pain, temperature sensation or muscle tension information into or out of the central nervous system. The confluence of the individual nerve branches in the somatic cervical plexus also results in an exchange of fibers between individual spinal cord nerve segments.
Diseases
Diseases of nerve plexuses such as the cervical plexus cause mixed sensory and motor deficits and disorders. Several nerve roots intertwine in the plexus, so symptoms of plexus disease are usually not due to a single nerve. For example, motor deficits such as muscle weakness, misguided or failed reflexes, muscle pain, spastic phenomena, and or paralysis can occur when the motor branches in the cervical plexus are disrupted. Depending on which of the branches are affected, the failure may involve the diaphragm, tongue, neck or chest. The deficits may be associated with skin sensation if the sensory branches are also affected. Such sensations include tingling and numbness, for example, on the skin between the shoulder and collarbone. Plexus disorders are also called plexopathies and are usually caused by compression or trauma. Metastatic cancer can also be responsible for cervical plexopathy. The same is true for some metabolic diseases, so especially diabetes. In connection with a plexopathy of the cervical plexus, a bilateral failure of the diaphragm-supplying nerve structures is particularly dangerous. If the motor innervation of the diaphragm is impaired in the plexus on both sides of the body, or even fails completely, this results in a diaphragmatic herniation. The affected patient can no longer take a deep breath due to the diaphragmatic protrusion and therefore has the feeling of suffering from shortness of breath. Failure of individual nerves from the cervical plexus may also correspond to neuropathy or be caused by some other neurogenic disease.
