The lesser occipital nerve is a sensitive nerve of the cervical plexus that contains fibers from spinal cord segments C2 and C3. It is responsible for the sensitivity of the skin behind the ears. Sensory disturbances occur when the nerve is damaged.
What is nervus occipitalis minor?
The cervical plexus is also known as the cervical plexus. It is a confluence of anterior nerve branches of spinal cord nerves one to four. The plexus corresponds to a somatic plexus and allows fiber exchange of individual spinal cord segments. It is located anterior to the origins of the scalenus medius muscle and the levator scapulae muscle and is associated with the hypoglossal nerve, the accessorius nerve, and the border cord. Located in the cervical plexus is the lesser occipital nerve, also known as the lesser occipital nerve. Its origin is in the first spinal nerves. It is a sensitive nerve branch containing fibers from spinal cord segments C2 and C3. Its area of supply corresponds to the skin surfaces behind the ear. The nerve is bilateral and is purely sensory. Unlike motor nerves, purely sensory nerves do not carry any motor nerve fibers in addition to their sensory fibers. Motor nerves, on the other hand, never contain exclusively motor fibers, but always carry sensitive fiber portions as well. The purely sensitive occipital nerve minor is not required in all species. For example, domestic animals such as dogs and cats do not possess an occipital nerve minor.
Anatomy and structure
The nervus occipitalis minor originates from the branches of the second and third spinal nerves and winds from there around the sternocleidomastoid muscle. Together with the transverse collateral, auricular magnus, and supraclavicular nerves, the occipital nerve emerges in the punctum nervosum and thus posterior border of the skeletal muscle. At the posterior edge of the muscle, it ascends in a cranial direction. It is therefore an afferent nerve because of its ascending course. Near the skull, the sensory nerve pierces the superficial fascia of the neck. From here, it runs along the skull in a cranial direction and extends to its supply area within the retroauricular region. In this area, the afferent nerve communicates with the auricularis magnus, occipitalis major, and auricularis posterior nerves. The cervical plexus, apart from the occipital minor nerve, consists of the sensitive branches the auricular magnus, transverse colli and supraclavicular nerves. The sensitive supply area of all these nerves is located at the posterior part of the head and neck, so that all of the mentioned parts pierce the cervical fascia at the punctum nervosum.
Function and tasks
Nerves carry bioelectrical signals throughout the body. Unlike efferent nerves, afferent nerves do not conduct signals from the central nervous system in to individual target organs in the body. They receive much more signals from individual body tissues and conduct these signals into central nervous system in the form of an action potential. Sensory nerves such as the nervus occipitalis minor are connected to receptors in the skin. More specifically, the nervus occipitalis minor is the thermoreceptors, nociceptors and mechanoreceptors located in the skin behind the ears. These receptors perceive pain, temperature, pressure and other touch stimuli in their receptive area and generate an action potential of varying intensity depending on the strength of the stimulus. These sensations from the receptors travel along the sensitive nerve from the body to the central nervous system. The task of purely sensitive nerves does not include the conduction of depth-sensitive sensations. Irritations of the muscle spindle and the Golgi tendon organ are mediated by the sensitive fibers of motor nerves and do not fall within the task of nerves such as the nervus occipitalis minor. Thanks to the nerve, only temperature stimuli, touch or pain sensations behind the ear reach our consciousness. If this were not the case, we would be less able to react to danger stimuli and would not notice, for example, if the hair behind our ears caught fire.
Diseases
When there is damage to the lesser occipital nerve, sensory disturbances of the skin behind the ear occur. These sensory disturbances may correspond, for example, to a persistent tingling sensation.Numbness, altered sensation of pain and temperature behind the ear or absolute insensibility at this site may also occur after damage to the sensitive nerve. Peripheral damage to the nerve may be associated with poisoning, malnutrition, metabolic diseases such as diabetes, with trauma or infection. When the myelin sheath around peripheral nerves is degraded, the nerve loses its conductivity, which can progress to absolute loss of function. This phenomenon is known as polyneuropathy and may occur in association with the above causes or with ideopathic cause. An even more common phenomenon is nerve compression syndrome. Nerve compression can be caused by tumors, but accidents or anatomical bottlenecks can also promote nerve entrapment. The nervus occipitalis minor can be pinched together with other nerves of the cervical plexus, for example by the musculus scalenus medius and the musculus levator scapulae. This is predominantly the case when the mentioned muscles hypertrophy. Such hypertrophy may have various causes and may, for example, be a response to increased stress on the muscles. Another cause of sensory disturbances behind the ear may be spinal cord lesions of segments C2 and C3. Primary causes of such lesions include trauma, spinal cord infarction, and spinal cord inflammation. Inflammation in the spinal cord is usually bacterial or autoimmunologic in origin and thus can occur, for example, in the setting of the autoimmune disease MS.
