The transverse collateral nerve is a purely sensory nerve of the cervical-thoracic region. It originates from spinal cord segments C1 and C2. Damage to the nerve or spinal cord may result in complete loss of skin sensation in the corresponding area.
What is the transverse collateral nerve?
Depending on how many sensitive fibers and how many motor fibers a nerve contains, it is called a motor, sensitive, or mixed nerve. A sensitive nerve is the transverse collateral nerve. This is the transverse cervical nerve, which contains only sensitive fibers and thus serves to conduct stimulus information afferently. Afferent in this context means that the nerve conducts information from the body periphery to the central nervous system. The transverse collateral nerve is a sensitive branch of the superior cervical plexus. This mixed plexus is also known as the cervical plexus. As a sensory branch of the plexus, the nerve arises directly from the spinal cord, where it originates from segments C1 and C2. The nerve is involved in the sensory supply of the skin in the region of the throat. Its supply area extends from the neck to the sternum. In its course, the transverse collateral nerve divides into anterior and posterior branches, with all branches corresponding to purely sensory nerve branches. The second and third spinal nerves are considered the starting points of the nerve.
Anatomy and structure
The transverse collateral nerve winds around the sternocleidomastoid muscle. At the punctum nervosum, or Erb’s point, the nerve, along with the supraclavicular, lesser occipital, and greater auricular nerves, shows up at the posterior margin of the muscle, from where it runs ventrally and crosses the sternocleidomastoid muscle toward the anterior margin. In doing so, it undercuts the external jugular vein to pierce the superficial cervical fascia. Under the platysma, the sensitive nerve becomes smaller branches with mixed descending and ascending courses. These branches distribute in the lateral anterior neck region. The ascending branches are called rami superiores and run toward the mandible where, together with the ramus colli from the facial nerve, they become a loop of nerves under the platysma known as the ansa cervicalis superficialis. With some fibers, the nevus transverus colli pierces the platysma and thus distributes finely branched in the anterior superior cervical region. The descending branches of the nerve are called rami inferiores and pierce the platysma to distribute in the skin of the anterior lower neck region.
Function and tasks
Like all sensitive nerves, the sensitive fibers of the transverse volli nerve conduct sensations or stimuli that are registered by so-called receptors. Receptors are sensory cells for the perception of pain, temperature, and touch. At a certain stimulus intensity, the receptors form a so-called action potential and thus translate the sensation into the language of the central nervous system. The fibers of the transverse colliculus nerve receive this signal and take on the function of a wire. Like a cable, they conduct the registered stimuli from the neck and chest region in the direction of the central nervous system. Depending on the direction of their excitation conduction, this is also referred to as afferent fibers. All branches of the transverse collateral nerve consist exclusively of afferent fibers, since the nerve is an exclusively sensitive nerve. In German, sensory nerve branches are distinguished from sensory fibers. Instead of conducting excitation of sensory organs such as the eyes, ears, or nose, as sensory fibers do, sensitive nerves such as the transverse colliculus nerve are not necessarily involved in conducting excitation of sensory organs. Because sensitive fibers also contain specialized nerve endings for stimulus reception, this distinction has not become common in other languages. Unlike motor nerves, purely sensitive nerves actually contain only sensitive fibers. Motor nerves also contain portions of sensitive fibers that transmit stimuli such as muscle tone to the central nervous system. Sensations from the muscles or information about muscle tone in the cervical and thoracic regions are not conducted by the transverse collateral nerve, because the sensitive portions of the nerves that each supply motor information serve for this purpose.
Diseases
Nerve diseases such as polyneuropathy can cause lesions of the transverse collateral nerve.Such lesions lead to insensitivity of the chest and neck area up to complete loss of skin sensations. In polyneuropathies, only peripheral nerves are affected by damage. Often the neurogenic diseases are accompanied by a preceding poisoning, a metabolic disorder such as diabetes or vitamin deficiency. Myelin coats the nerve fibers to ensure their conductivity. In polyneuropathies, however, the myelin around peripheral nerves degenerates so that existing stimuli are no longer sent to the central nervous system, or are sent only with delay or with qualitative impairment. Among the sensory disturbances due to demyelination processes are numbness, tingling sensations or impairment of the hot-cold sensation. Discomfort is also caused by the transverse collateral nerve after damage to the spinal cord and thus to the central nervous system. Conduction failures or disturbed stimulus sensations occur in this nerve primarily after damage to spinal cord segments C1 and C2, whose fibers the sensitive nerve contains. Such spinal cord damage can be traumatic, but can also occur as a result of tumors, inflammatory processes and spinal cord infarctions. Among the most common inflammations of the spinal cord are those caused by autoimmunology in the context of multiple sclerosis. Nerve compression syndromes can also limit the conduction of the transverse collateral nerve. In these compression syndromes, the nerve becomes entrapped in an anatomic narrowing. Often, an entire plexus of nerves is affected by such entrapments. In the transverse collateral nerve, this superior plexus would be the cervical plexus.
