The auricular magnus nerve is a sensitive nerve of the cervical plexus. The nerve supplies sensation to the dorsal ear skin and portions of the scalp. Damage to the nerve results in sensory disturbances.
What is the auricular nerve magnus?
The cervical nerve plexus is better known to medical professionals as the cervical plexus. It consists of the anterior branches or rami of spinal nerves from segments C1 to C4 and also carries portions of spinal nerves from segment C5. The nerve branches of the plexus run between the scalenus anterior muscle and the scalenus medius muscle down into the deeper neck region. In addition to motor and mixed nerves, the cervical plexus carries a number of purely sensory nerves. These include, for example, the auricularis magnus nerve, also known as the great auricular nerve. The nerve originates from the second and third cervical segments C2 and C3 in the spinal cord, making it a sensory spinal nerve whose fibers of origin articulate with other cervical nerves in the cervical plexus. Sensory nerves show an afferent course. They thus transport excitation upward toward the central nervous system, while efferent nerves transport excitation in the other direction and thus out of the central nervous system. The auricular magnus nerve is the largest of the ascending nerve branches in the cervical plexus. Since the auricularis magnus nerve does not consist of only one ramus throughout, calling it one nerve is actually misleading. It is more specifically two nerve branches of the same nerve.
Anatomy and structure
The greater auricular nerve originates from the anterior branches of the second and third spinal nerves. From there, the sensory nerve winds around the sternocleidomastoid muscle. At the punctum nervosum or Erb’s point, the nerve reappears along with transverse collateral nerve, lesser occipital nerve, and supraclavicular nerve, and appears at the posterior border of the skeletal muscle. In its course, the nerve, like many other nerves of the cervical plexus, pierces the superficial cervical fascia. After piercing, it continues on the muscle in a cranial direction under the platysma and reaches the parotid gland. At this point, the auricular magnus nerve divides into an anterior and a posterior branch or ramus. In the parotid region, the sensitive nerve cord communicates with fibers of the facial nerve. The auricularis magnus nerve is a purely sensory nerve. Motor nerves can never be purely motor efferent, but always contain sensitive afferent fibers as well. In contrast, in sensitive nerves, the exclusivity of the sensitive fiber type is the rule. Like all other nerve fibers, the auricular nerve is encased in glial cells and corresponds to an appendage of neurons.
Function and tasks
The function of sensory nerves is to transport excitation to the central nervous system. Sensory nerves are connected in the periphery with so-called receptors. The receptors perceive stimuli such as pressure, touch, temperature, and pain and transfer these stimuli into the language of the central nervous system depending on the stimulus intensity. This occurs through the formation of an action potential, which travels along the afferent sensory nerve fibers eventually out of the tissue into the central nervous system. There, the final processing of the signal begins and the stimulus perception reaches, for example, consciousness. Purely sensitive nerves are not designed to conduct depth sensitive information. Depth sensitivity consists of stimulus perceptions of the muscle spindle and Golgi tendon organ. It is composed of information about the current position of joints and muscles and is carried to the central nervous system by the ascending portions of mixed sensory-motor nerves. Thus, the purely sensory nerves have nothing to do with depth sensitivity. Accordingly, the auricular nerve only transmits temperature, pain and touch stimuli. It takes over the sensitive innervation of the dorsal skin parts in the area of the auricle and the scalp behind the ear. It also provides sensory supply to the skin above the mastoid process and also innervates an area of skin above the parotid gland and masseter muscle.
Diseases
Because of its extraordinary length, the auricularis magnus nerve is used as a donor nerve by reconstructive surgery. Thus, in reconstructive surgical procedures, it serves from time to time as an interposition for reconstruction of shorter nerve defects.However, the auricular nerve itself can also be affected by defects. In the case of a lesion of its tissue, sensory disturbances occur in the supply areas mentioned above. These disturbances can manifest themselves in various ways. In addition to numbness, sensory disturbances such as disturbed pain or warm/cold sensation can occur. Persistent tingling may also be a symptom. Peripherally mediated sensory disturbances occur, for example, when the cervical nerve plexus between the scalenus anterior and scalenus muscles is jammed. This may be the case after an increase in the size of the two muscles, which may be due to excessive strain, for example. Peripherally mediated sensory disturbances also occur in the context of polyneuropathies and are due to demyelination of peripheral nerve branches. Such demyelination degenerates the insulating cells around the nerves. Stimuli are thus still detected, but the excitation generated in response to the stimulus perception is partially or completely lost on its way to the central nervous system. Trauma, peripheral inflammation, infection, or malnutrition and poisoning can also result in sensory disturbances. Centrally mediated sensory disturbances of the auricular nerve are usually associated with injury to the associated spinal nerve and may be due, for example, to spinal cord infarcts or the autoimmune disease multiple sclerosis.
