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21 Brachial plexus injuries – outline and approach G.Biswas MS, Prabhu Anand Raj MS Department of Plastic Surgery, Postgraduate Institute of Medical Education and Research, Chandigarh, India - 160012 Introduction T he Brachial plexus constitute afferent motor and efferent sensory nerves supplying the upper extremities. It is situated in a very vulnerable anatomical position between the neck and shoulder. Injury to this plexus, which is often due to traction, results in various degrees of motor and sensory deficit to the involved upper limb. This results in loss of function and its catastrophic consequences. Two different groups of patients are observed in Brachial plexus injuries, which differ in presentation and also in the approach in management. Obstetric Brachial plexus injuries are a result of traction injury during a difficult delivery of a child. Adult Brachial plexus injuries are usually a consequence of motor vehicles accidents. Etiology of both these types of injuries are however similar, resulting from a forceful traction at the neck shoulder angle. The experience of the authors in the management of 196 brachial plexus injuries is represented. Anatomic Considerations Brachial plexus is formed by the cervical spinal roots C5-T1 and occasionally C4 (prefixed) or T2 (post fixed) may also contribute to the plexus. From proximal to distal, the levels of the brachial plexus correspond to the branching pattern and consist of roots, trunks, divisions, cords, terminal cord branches and peripheral nerves. The roots travel between the anterior and middle scalene muscles and join in a consistent manner to form three trunks, which is located inferiorly in the posterior triangle of neck. The upper and lower trunks are formed by the union of C5 and C6 and of C8 and T1, respectively where as the middle trunk is a continuation of the C7. All three trunks divide into an upper and posterior division as they pass underneath the clavicle. The division travel beneath the pectoralis minor where they form three cords. The cords are named by their position according to their position relative to the axillary artery. Correspondence : DR. G.Biswas Department of Plastic Surgery, Postgraduate Institute of Medical Education and Research, Chandigarh, India - 160012 e-mail : [email protected] The anterior divisions of the upper and middle trunks form the lateral cord; the anterior division of the lower trunk forms the lower cord. The posterior divisions of all three trunks form the posterior cord, which receives contributions from all the spinal levels (C5-T1). The major peripheral nerves of the upper limb arise as the terminal branches of these cords where as the muscles of the shoulder girdle are innervated from the branches from the cord, trunk, and root levels. The lateral cord and the medial cord each makes a contribution, these join together to form the median nerve. The musculocutaneous and ulnar nerve are the terminal branches of the lateral and medial cords, respectively. The median nerve is formed by the sensory contribution from the lateral cord and motor contribution from the medial cords. The axillary and radial nerves are terminal cord branches of the posterior of the posterior cord. The functioning of the muscles, which are innervated by the branches from the root level, are helpful in diagnosing root avulsion injuries. These branches include the long thoracic nerve (C5-C7), which supplies the serratus anterior, the dorsal scapular nerve (C5-C6), which supplies the levator scapulae and the rhomboid muscles, the phrenic nerve (C4-C5), and the nerve to the subclavius muscle. Prescence of function in this muscle group, denotes an intact root with a good surgical prognosis. Biswas et al. Epidemiology Trauma to the brachial plexus results in loss of motor function and sensation of the involved upper extremity. These devastating injuries involve young male patients in as many as 90 % of cases. Most of the cases are caused by motor vehicle accidents, and motorcycle accidents are implicated in up to 84% of cases. Brachial plexus injuries occur in 0.67% to 1.3% in motor vehicle accidents, but this figure rises to 4.2% in motorcycle accidents. Motorcycle accidents subject the brachial plexus to greater traction forces because the body is unprotected; motorcycle accidents are more likely to cause root avulsion, where as motor vehicle accidents produce crush injuries. Common causes also include pedestrian/motor accidents industrial accidents, and gunshot wounds. Traction on the brachial plexus can also occur from falling objects, in sports including cycling injuries skiing injuries or falling from a height or down stairs. In our series 96% of the injuries sustained were due to motor cycle accidents and the rest 4% were due to fall of heavy object on neck , penetrating injuries as well as iatrogenic injury to the neck following lymph node biopsy. Mechainism of Injury There are three basic mechanisms of injury to the brachial plexus: 1. Traction of the upper extremity in the downward direction. This causes damages to the upper roots and trunks. Motor cycle accidents and sport like skiing causes injury in this manner. 2. Upper extremity traction in the cephalad direction widens the scapulo-humeral angle and produces damage to the lower plexus. 3. The brachial plexus may also be crushed in the costoclavicular space as it passes between the clavicle and the first rib. This seen most commonly in motor vehicle accident, heavy object falling on the shoulder, bone fragments or hematoma or pseudoaneurysm Root Avulsion The mechanism of root avulsion can be central or peripheral. In the peripheral mechanism, traction on the spinal nerve is transmitted to the rootlet and its dura mater sheath, results in a separation of the root from the spinal cord. This results in an irreparable damage to the root. With a central mechanism, the head and neck are subject 22 to traumatic force such that the cervical spine and cord are pushed to the opposite side. The traction force is directly transmitted to the ipsilateral spinal root and not the dural sheath. This leads to a disruption of the nerve and not the dura. Root avulsion can be further differentiated based on the location of the lesion relative to the dorsal root ganglion. Pre or supra ganglionic lesions occur proximal to the dorsal root ganglions. Diagnosis and Recognition The patient with brachial plexus injury presents to the emergency with multisystem trauma. The ABC's of trauma remain the first priority and life-threatening injuries should be ruled out. The brachial plexus injury is diagnosed by the conscious patient, but in an unconscious patient the diagnosis is usually delayed. Usually a diagnosis of Brachial Plexus injury can be made in the emergency department but a definitive localization of the site of the lesion can only be undertaken after about 2-3 weeks, when the edema and pain subsides History A detailed history of the mechanism of injury is obtained to try and determine the type of lesion i.e, Avulsion versus traction or crush versus compression. The arm position at the time of injury may indicate the site of plexus injury. If the arm is abducted above 90 degrees the lower plexus C8-T1 are more severely injured and if the upper extremity is pulled downward, the C5 and C6 suffer maximal. Physical Examination The upper trunk and extremities are carefully inspected for asymmetry in posture and muscle atrophy. Specific observations are made including shoulder subluxation, winging of the scapula, loss of the anterior axillary fold. The Horner's syndrome, which reflects injury to the preganglionic fibers serving the hand and neck region, is a valuable sign in severe traction injuries to the brachial plexus. The eye is examined for the presence of ptosis, meiosis and anhydrosis. If present it indicates injury to the white rami of the T1 root to the stellate ganglion and signifies a partial or complete avulsion of the T1 root and other neighbouring roots as well All muscles of the shoulder girdle and involved in the upper extremity and are graded on a scale of 0-5.A detailed sensory examination is completed including touch, pain, static, two –point discrimination, joint position, and vibration are recorded. Brachial plexus injuries 23 Pb Journal of Orthopaedics Vol-X, No. 1, 2008 The next step is to determine the passive range of motion of all the joints. This is carried out for the cervical spine, shoulder joint, and all the distal joints of the upper extremity. The last test to be performed is eliciting Tinel's sign. On percussing each peripheral nerve from distal to proximal the patient perceives a tingling sensation. This indicates the site of distal active fibers of that particular nerve that has connectivity to the central nervous system. Investigation Plain X-rays diagnose fractures that may give clue about the underlying injury. A transverse process fracture of the cervical region may suggest injury or avulsion of the corresponding root. Electodiagnostic studies include Electromyography (EMG), nerve conduction velocity, and sensory potentials. Needle EMGs are carried out to identify the functional status of the muscle. Fibrillation potentials indicate continuing muscle degeneration where as motor unit potential indicates progressive reinnervation. It may take as long as 4-6 weeks after injury before fibrillation potentials appear on EMGs. Sensory conduction studies are carried out to ascertain the functional status of afferent fibers along the median ulnar and radial nerves. Nerve conduction studies should only be performed after 4 to 6 weeks post injury. MRI is advantageous as it is non invasive and patient need not be sedated. Different types of tissues including muscle nerve and vascular structures can be readily distinguished. The MRI is especially advantages for imaging the distal brachial plexus injury. Presence of pseudomeningoceles i.e., out pouching of the dura at the level of roots is and indication of root avulsion. Principles of Management All patients, with the exception of penetrating injuries, are managed conservatively, unless disruption of brachial plexus is observed more distally. For less severe cases in which the brachial plexus remains intact, Observation for 3 months is warranted for signs of regeneration or muscle renervation. If no signs of recovery is forthcoming then surgical exploration of the plexus is indicated. In penetrating injuries it is mandatory to explore and repair the plexus primarily. Priorities of function in brachial plexus reconstruction Physical therapy Maintaining passive range of motion in the paralytic upper extremity is critical for all patients whether their management is conservative or operative. Operative Management Primary repair may be carried out if there is a clear transection of the brachial plexus structures. An end-to-end neurorhapy may be performed if there is no tension at the repair site. Secondary repair is performed in closed plexus injuries and in patients in whom primary repair was not indicated. Repair is usually performed within 8-12 weeks . The minimal goal is to restore a stable shoulder joint and to restore elbow flexion and median nerve sensibility. Exploration of the plexus is performed through a supraclavicular approach, extending it below the clavicle in case of distal injury. If the roots are intact, primary reconstruction of the plexus with cable nerve grafts are indicated. Often in situation of multilevel injury, the roots may be dissected to the best motors to provide early reinnervation, ignoring the plexus architecture. For example roots may be dissected to the suprascapular nerve of Musculocutaneous nerves for early restoration of shoulder and elbow movement. When intraplexal donors are not available as in the case of root avulsion. Nerve transfers are done using nerves that can be expended. Distal nerves of the spinal accessory nerve, the phrenic (in adults), intercostals contra lateral C7, part of ulnar are some of the donor nerves used to neurotize paralyzed nerve components. Results of such nerve repair shows a 60- 70 % recovery of M3+ power, after approximately 12-16 months. In long standing paralysis, of over a year following injury options are limited, as degenerative changes in motor end plates have set in, and the effector organ( muscles ) have become fibrosed. In such situation the microsurgical transfer of motor units (example gracilis muscle with its nerve and blood supply) are transferred to the affected upper limb and innervated by a donor nerve. This provides basic function to shoulder and elbow . Hand functions are poor. Muscle transfers, arthrodesis, distraction osteotomies, tenodesis are other procedures necessary in secondary reconstructions. Patients require extensive rehabilitation. The psychosocial trauma in these patients are difficult to gauge as it affects the livelihood of the individual, who is more often than not young. Patients need to be well motivated and realistic. The earlier pessimistic approach has been replaced by a new optimism, as results in centers managing these injuries are now encouraging. Biswas et al. Refernces : 1. Julia K. Tenzin, Marios D. Vekris, Panayiotis N. Soucacos. Outcomes of Brachial Plexus Reconstruction in 204 patients with devastating paralysis, PRS 1991; 104, (5): 1221-1240. 2. C Oberlin, D Beal, S Leecharenjvongs, A. Solan. M.C. Dange et al.Nerve transfer to biceps muscle using part of ulnar nerve for C5- C6 avulsion of Brachial Plexus. Anatomical study and report of ten cases. Journal of Hand Surgery 1994; 19 A, 3: 232- 237. 24 3. A.O. Nanakan, Vincent R. Heritz. Neurotization in Brachial Plexus injures Indication and result. Clinical Orthopedic and related research. 1988; 237: 43-56. 4. Jules. K. Tenzis and Hallene Maragh. Strategies in the microsurgical management of Brachial Plexus injures. Clin in Plast Surg 1989; 605606. 5. Thomas.H.H Tang and Susan E Mackinnon. Brachial Plexus Injures. Clin Plast Surg 2003; 267-288.