Повреждения плечевого сплетения: причины, механизмы и классификация.

A brachial plexus injury (BPI), also known as brachial plexus lesion, is an injury to the brachial plexus, the network of nerves that conducts signals from the spinal cord to the shoulder, arm and hand. These nerves originate in the fifth, sixth, seventh and eighth cervical (C5–C8), and first thoracic (T1) spinal nerves, and innervate the muscles and skin of the chest, shoulder, arm and hand. Brachial plexus injuries can occur as a result of shoulder trauma (e. g. dislocation), tumours, or inflammation, or obstetric. Obstetric injuries may occur from mechanical injury involving shoulder dystocia during difficult childbirth, with a prevalence of 1 in 1000 births. "The brachial plexus may be injured by falls from a height on to the side of the head and shoulder, whereby the nerves of the plexus are violently stretched. The brachial plexus may also be injured by direct violence or gunshot wounds, by violent traction on the arm, or by efforts at reducing a dislocation of the shoulder joint". The rare Parsonage–Turner syndrome causes brachial plexus inflammation without obvious injury, but with nevertheless disabling symptoms.

Injury to the brachial plexus 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.

The brachial plexus 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 brachial plexus 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 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 brachial plexus. 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 brachial plexus 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. This is very low compared to the other identified brachial plexus injuries. Consequently, the future of peripheral nerve MR imaging (including imaging brachial plexus injuries) is likely to be based on diffusion weighted imaging, such as diffusion tensor techniques, which are of significant potential clinical utility and can enable the production of easily interpreted 3D reconstructions of the spinal cord and brachial plexus such as this. Several weeks/months after BPI, EMG examination can provide additional information about whether the muscle is denervated. These examinations are painful, highly user dependent and lack normal values so cannot be relied upon.

The severity of brachial plexus injury is determined by the type of nerve damage. Neurapraxia: The mildest form of nerve injury. It involves an interruption of the nerve conduction without loss of continuity of the axon. Recovery takes place without wallerian degeneration. Axonotmesis: Involves axonal degeneration, with loss of the relative continuity of the axon and its covering of myelin, but preservation of the connective tissue framework of the nerve (the encapsulating tissue, the epineurium and perineurium, are preserved). Neurotmesis: The most severe form of nerve injury, in which the nerve is completely disrupted by contusion, traction or laceration. Not only the axon, but the encapsulating connective tissue lose their continuity. The most extreme degree of neurotmesis is transsection, although most neurotmetic injuries do not produce gross loss of continuity of the nerve but rather, internal disruption of the nerve architecture sufficient to involve perineurium and endoneurium as well as axons and their covering. It requires surgery, with unpredictable recovery. A more recent and commonly used system described by the late Sir Sydney Sunderland, divides nerve injuries into five degrees: first degree or neurapraxia, following on from Seddon, in which the insulation around the nerve called myelin is damaged but the nerve itself is spared, and second through fifth degree, which denotes increasing severity of injury. With fifth degree injuries, the nerve is completely divided. The exercises mentioned above can be done to help rehabilitate from mild cases of the injury. However, in more serious brachial plexus injuries surgical interventions can be used. Function can be restored by nerve repairs, nerve replacements, and surgery to remove tumors causing the injury. Another crucial factor to note is that psychological problems can hinder the rehabilitation process due to a lack of motivation from the patient. On top of promoting a lifetime process of physical healing, it is important to not overlook the psychological well being of a patient. This is due to the possibility of depression or complications with head injuries.

There are many treatments to facilitate the process of recovery in people who have brachial plexus injuries. Improvements occur slowly and the rehabilitation process can take up to many years. Many factors should be considered when estimating recovery time, such as initial diagnosis of the injury, severity of the injury, and type of treatments used. Some forms of treatment include nerve grafts, medication, surgical decompression, nerve transfer, physical therapy, and occupational therapy. A study has also shown that a sensory motor deficit in the upper limbs after a brachial plexus injury can affect the corporal balance in the vertical positioning. Examined patients had a lower score in the Berg balance scale, a greater difficulty in maintaining in the unipodal stance during one minute and leaned the body weight distribution to the side affected by the lesion. Patients also exhibited a greater variability in the postural oscillation, evaluated by the directional stability index. The results alert the clinical community about the necessity to prevent and treat secondary effects of this condition. In studies about the effectiveness of additional effect of modified constraint induced movement therapy (MCIMT), it was found that MCIMT helped improved the range of motion, shoulder function and it has the potential to promote functional gains for children with BPBI.

Brachial plexus injury is found in both children and adults, but there is a difference between children and adults with BPI.

The prevalence of brachial plexus injuries in North American adults in the 1900s was about 1.2%.

OBPP, also known as obstetrical brachial plexus palsy, occurs primarily in young children at a rate of 0.38 to 1.56 per 1000 live births depending on the type of care and the average birth weight of infants in different regions of the world. Brachial plexus injury risks for newborns are increased with gained birth weight, birth delivery where a vacuum is assisted, and not being able to handle glucose.

BPI has shown to occur in 44% to 70% of traumatic injuries, such as motorcycle accidents, sporting activities, or workplace accidents. and with ihg injury injuries such as motorcycle accidents, root avulsion from the spinal cord is the most common pattern of injury (~72% prevalence of at least 1 root avulsion) Most closed infra clavicular injuries due to shoulder dislocation are managed non operatively initially and data shows that most fail to recover sensory function but recover some motor function. For milder injuries involving buildup of scar tissue and for neurapraxia, the potential for improvement varies, but there is a fair prognosis for spontaneous recovery, with a 90–100% return of function.