Injury to the<unk><unk>  can happen in numerous environments. These may include contact sports, motor vehicle accidents, and birth. Although these are but a common few events, there is one of two mechanisms of injury that remain constant during the point of injury. The two mechanisms that can occur are traction and heavy impact. Traction, also known as stretch injury, is one of the mechanisms that cause<unk> . The nerves of the<unk><unk>  are damaged due to the forced pull by the widening of the shoulder and neck. This is a closer look at the traction mechanism at the cervical spine. The arrowed red line represents the stretch of the nerves. Depending on the force, lesions may occur. Anatomy This image shows the anterior view of the five<unk><unk>  nerves on the human arm. The<unk><unk>  is made up of spinal nerves that are part of the peripheral nervous system. It includes sensory and motor nerves that innervate the upper limbs. The<unk><unk>  includes the last four cervical nerves (C5-C8) and the 1st thoracic nerve (T1). Each of those nerves splits into smaller trunks, divisions, and cords. The lateral cord includes the musculocutaneous nerve and lateral branch of the median nerve. The medial cord includes the medial branch of the median nerve and the ulnar nerve. The posterior cord includes the axillary nerve and radial nerve. Traction Traction occurs from severe movement and causes a pull or tension among the nerves. There are two types of traction: downward traction and upward traction. In downward traction there is tension of the arm which forces the angle of the neck and shoulder to become broader. This tension is forced and can cause lesions of the upper roots and trunk of the nerves of the<unk><unk> . Motorcycle accidents and sports injuries usually cause this type of injury to<unk><unk> . Upward traction also results in the broadening of the scapulo-humoral angle but this time the nerves of T1 and C8 are torn away. Humeral fractures and shoulder dislocations can also cause this type of injury with high energy injuries. Root avulsion or nerve rupture may occur during severe trauma, inappropriate surgical positioning, or inappropriate use of surgical retractors. There are two mechanisms for root avulsion injury: peripheral and central mechanism. In peripheral mechanism, traction is transmitted to the rootlet, however dura mater will be torn with the rootlet intact because the dura is less elastic when compared to the rootlet. Pseudomeningocele can be shown on cervical myelography. On the other hand, through central mechanism, the head and neck is pushed along with the spinal roots of the<unk><unk>  to the opposite site of the body, leading to direct nerve root injury but the dura sheath remains intact. In this case, anterior roots are more prone than posterior roots for avulsion, thus the C8 and T1 nerve roots are more prone to injury. Root avulsion injury can be further divided based on the location of the lesion: pre- and postganglionic lesions. In a preganglionic lesion, the sensory fibre remain attached to the cell body of the sensory ganglion, thus there is no wallerian degeneration of the sensory fibre, thus sensory action potential can still be detected at the distal end of the spinal nerve. However, those who get this type of lesion have sensory loss over the affected nerve roots. In this case, surgical repair of the lesion is not possible because the proximal nerve tissue is too short for stitching to be possible. For postganglionic lesions, the cell body of the sensory ganglion is detached from the spinal nerve, leading to wallerian degeneration of the sensory fibre. Thus, no action potential detected at the distal end of spinal nerve. However, surgical repair is possible because proximal nerve tissue has enough length for stitching. Impact Heavy impact to the shoulder is the second common mechanism to causing injury to the<unk><unk> . Depending on the severity of the impact, lesions can occur at all nerves in the<unk><unk> . The location of impact also affects the severity of the injury and depending on the location the nerves of the<unk><unk>  may be ruptured or avulsed. When passing through between the clavicle and first rib, the<unk><unk>  may be crushed in the costoclavicular space. This is usually due to direct trauma to the shoulder or neck region as a result of motorvehicular accidents, occupational injuries or sports injuries. The<unk><unk>  may also be compressed by surrounding damaged structures such as bone fragments or callus from the clavicular fracture, and hematoma or pseudoaneurysm from vascular injury. Cervical rib, prominent transverse process, and congenital fibrous bands can also compress the<unk><unk>  and cause thoracic outlet syndrome. During the delivery of a baby, the shoulder of the baby may graze against the pelvic bone of the mother. During this process, the<unk><unk>  can receive damage resulting in injury. The incidence of this happening at birth is 1 in 1000. This is very low compared to the other identified<unk> es.
Brachial plexus injury
Posterior cord syndrome
Diastematomyelia
Spinal cord injury
Central cord syndrome
Syringomyelia
Accessory nerve disorder
Cernunnos deficiency