Traumatic Brachial Plexus Lesions: Clinical Aspects, Assessment, and Timing of Surgical Repair

Types and Mechanisms of Injury

The typical patient with a brachial plexus injury is a young man involved in a motorcycle accident. Although his helmet in many cases saves his life, it is not useful to prevent lesions to the brachial plexus when he strikes the ground.

The extent of injury is due to the level of energy and to the direction of the force relative to the limb and shoulder. Low-energy injuries (e.g., fall onto the shoulder) cause mostly reversible injuries (stretch), while high-energy (e.g., motorcycle accident) is associated with more significant injuries (rupture and avulsion).

Closed injuries produce stretch/contusion lesions and are the most frequent type of TIBP (73%). ⁴ The vast majority of cases of closed TIBP are related to accidents with high-power engines, mainly motorcycles (79%) ⁵ and are usually associated with a traction mechanism, where the arm and shoulder are forcefully distracted away from the neck or trunk. Sudden caudal traction of the shoulder and arm usually injures first the upper roots of the plexus (C5, C6 and/or C7) and cranial traction involves mainly the lower roots (C8 and T1). All roots can be damaged when a massive momentum is transferred, resulting in a flail upper limb. The force of the impact is projected first to the structures with a straighter course from the spine to the arm (C8 and T1 roots and their continuation as the inferior trunk). The structures with a longest anatomical course from fixed points in the neck to fixed points in the shoulder and arm (C5 and C6 roots and their continuation as superior trunk) receive the last impact of the force. The C7 root and associated middle trunk receive an intermediate impact. As a consequence, the lower structures of the brachial plexus suffer more significant injuries (e.g., root avulsion) than more proximally located elements. It should be remembered that the same patient can injury several different elements of the brachial plexus, in varying severity.

Open TIBP is less frequent (27%) ⁴ and can be produced by lacerations and gunshot wounds. Lacerations of the plexus can result from sharp transections (knives or glass) or blunt transection (automobile metal, fan and motor blades, animal bites, or open fractures of the shoulder) and can either transect a portion (most common) or the entire plexus. Vascular lesions are frequently associated with laceration injuries. The penetrating injuries caused by gunshot wounds are also often associated with vascular injuries. Low-velocity missile wounds from handguns usually produce lesions-in-continuity, but can also transect elements. The force associated with the injury varies and depends on the missile caliber, velocity, and angle of entry of the bullet. Missile injuries produced by low-velocity shell fragments damage the nerve elements by direct impact and tend to be associated with less damage to the plexus. High-velocity gunshot injuries damage the nerve elements through three different mechanisms: direct impact (rare), shock wave effects, and cavitation effects. The latter two mechanisms provoke compression and stretching of the nerve. ⁶These lesions are more intense and usually fail to recover spontaneously.

Based on his experience over 18 years with 1,068 patients, Narakas ⁷ developed an epidemiological rule on brachial plexus lesions called “the seven seventies rule”: approximately 70% were motor vehicle accidents; of these accidents, 70% involved motorcycles or bicycles. Of the cycle riders, 70% had multiple injuries: 70% were supraclavicular injuries. Of the supraclavicular injuries, 70% had at least one root avulsed, 70% of the avulsed roots involved the lower nerve root level (C7, C8, T1), and 70% of the avulsions cases developed chronic pain.

16.3 Location of the Injury

Traumatic brachial plexus lesions in adults can be supraclavicular or infraclavicular. Supraclavicular lesions (72%) ⁴ involve spinal nerves and brachial plexus trunks. The subdivision of these lesions in relation to the dorsal root ganglion (preganglionic and postganglionic) has a prognostic value and helps in the elaboration of the treatment planning. Preganglionic lesions essentially point to a permanent loss of that root without possibility of direct repair, while postganglionic lesions are amenable to repair since they represent distal axons which can regenerate. There are signs and physical findings that suggest a preganglionic injury ⁸: (1) absence of Tinel’s sign in supraclavicular region (absence of proximal spinal nerve stump); (2) Horner’s syndrome (sympathetic ganglion injury/T1 level); (3) injury to very proximal nerves such as dorsal scapular nerve (atrophy of rhomboid muscles), long thoracic nerve (winged scapula), and phrenic nerve (ipsilateral hemidiaphragm paralysis); (4) cervical paraspinal muscle weakness and denervation (seen in electromyography [EMG] studies), and loss of posterior neck sensation (dorsal rami of cervical nerve roots injury); (5) pseudomeningocele in image studies (development of meningeal diverticulum after healing of torn nerve root sleeve); (6) intact sensory nerve action potentials in the area of sensory deficit (absence of wallerian degeneration of the sensory axons owing to the position of sensory nerve cells in the dorsal root ganglion); and (7) severe pain in an anesthetic extremity. Pre- and postganglionic injuries may coexist, the full extent of the lesion being difficult to perceive until surgical exploration is undertaken. Infraclavicular lesions (28%) ⁴ usually occur at the cord and terminal branches’ levels. Combined supra/infraclavicular lesions are possible and seem to occur in 10% of patients. ⁷

The motor neurologic deficits can be separated according to each root involved ( ▶ Table 16.1), but usually they are organized in patterns according to the level of the injury. ⁹ Supraclavicular injuries can produce four patterns of injury: (1) upper arm type (C5/C6 nerve roots/upper trunk) produces loss of shoulder abduction and of elbow flexion, together with loss of sensation in the shoulder, outside of the arm, and the thumb; (2) the extended upper arm type (C5/C6/C7 nerve roots/upper and middle trunks), besides the same loss of movement in shoulder and elbow as the previous pattern, also presents loss of elbow extension and sometimes of wrist extension (variable as C8 too also supplies the wrist extensors); (3) in the lower upper arm type (C8, T1 nerve roots/inferior trunk), patients will maintain shoulder and elbow strength but will lose hand function associated with hand numbness in at least the ring finger and small finger; and (4) in total arm type (C5–T1/all trunks), the patient presents a complete paralysis of the entire upper limb, usually referred as “flail arm.” Infraclavicular injuries also can produce three different patterns of injury: (1) lateral cord/musculocutaneous nerve pattern produces loss of elbow flexion, (2) in medial cord/median and ulnar nerves pattern, the patient loses finger flexion and intrinsic hand function; and (3) in posterior cord/axillary and radial nerves, the patient loses shoulder abduction (partially) and elbow and wrist extension.

**Table 16.1** Roots-relevant gross motor function
Root	Motor function
C5	Shoulder abduction, extension, and external rotation; some elbow flexion
C6	Elbow flexion, forearm pronation and supination, some wrist extension
C7	Diffuse loss of function in the extremity without complete paralysis of a specific muscle group, elbow extension, consistently supplies the latissimus dorsi
C8	Finger extensors, finger flexors, wrist flexors, hand intrinsics
T1	Hand intrinsics

Sensory examination is also important in locating the lesion, as deep pressure sensation may be the only clue to continuity in a nerve with no motor function or other sensation. When the examiner apply a full pinch to the nail base and pull the patient’s finger outward, any burning sensation suggests continuity of the tested nerve. The thumb is related to C6 root, the middle finger to C7, and the little finger to C8.

16.4 Pain

Pain is present in up to 80% of adult patients who sustained a brachial plexus injury. ¹⁰ Usually, it is reasonably controlled with drugs and subsides within months. When the pain is intense and starts early, a diagnosis of differentiation and probable root avulsion is made. This severe neuropathic pain reacts poorly to conventional therapy and has two distinct features: constant burning background pain and periodic sharp paroxysms of shooting pain. A considerable number of patients with root avulsions and this severe type of pain will need a procedure for intraspinal coagulation of the dorsal root entry zone as their definitive treatment.

16.5 Evaluation of Brachial Plexus Function and Diagnosis

The aim of the evaluation of brachial plexus function is to determine as accurately as possible the localization and extent of the lesion. Based on the information derived from this evaluation, a decision whether the patient is a candidate for early surgery or for a period of further observation usually can be made. Physical, electrophysiological, and imaging evaluations should be done. Whatever the clinical picture, all patients with traumatic paralysis of the brachial plexus who have not shown signs of recovery by the 30th day after the injury should undergo additional work-up, including electrodiagnostic tests and image evaluations, in order to come to a decision regarding surgery.

16.5.1 Physical Evaluation

Patients should be evaluated early on, but this is often not possible owing to delayed referral or because in many cases the brachial plexus lesion is only one part of a multisystemic trauma, and either the deficits are overlooked or their evaluation is deferred while life-threatening injuries are treated. ¹¹ The standard advanced trauma life support protocol should be followed. Abrasions to the head, helmet, or shoulder suggest supraclavicular injury, while Horner’s syndrome (ptosis, enophthalmos, and miosis) suggests a lower plexus lesion with lesion of the sympathetic ganglion at T1 level. Diminished or absent pulses suggest vascular injury. The early patient’s postinjury neurological status permits the determination by the nerve surgeon of the neurological evolution in subsequent clinical evaluations. Details about the mechanism of injury as well as associated injuries are essential for lesion localization and treatment planning. Information about the type and severity of pain is also important and should be documented. Having in mind the possibility of associated spine and spinal cord lesions, a thorough neurological examination should be done. The active and passive ranges of motion of the upper limb should be recorded, as well as the presence or absence of reflexes. The motor power of every muscle related to the brachial plexus of the injured limb should be evaluated and documented according to the Medical Research Council System Scale from grade 0 to grade 5. When performing the motor examination, keep in mind that most individual muscles have contributions from multiple cervical levels. The sensibility of the affected limb is also evaluated and documented. The examination of some key sensory areas may give precise information about the affected nerve roots ( ▶ Table 16.2). It is important to note what is real loss of sensation and what the patient perceives as altered sensation. Dry skin is a sign of loss of sweating-motor function. The production of a shooting nerve–like sensation when the examiner taps along the affected plexus elements (Tinel’s sign) suggests an injury farther from the spinal cord. Over time, if the location of the Tinel sign moves down the arm toward the hand, it is a sign that the injury is repairing itself.

**Table 16.2** Key sensory areas
Root	Key sensory area
C5	Skin over deltoid
C6	Thumb and index finger
C7	Middle finger
C8	Ulnar two fingers but particularly little finger
T1	Inner arm

This clinical evaluation will permit diagnosing if the plexus is totally or partially compromised. However, it is important to bear in mind that this gradation is not static and that brachial plexus injuries are, in the great majority of cases, a blend of complete and incomplete injured elements. The clinical course should be followed by means of repeated (monthly) clinical examinations.

16.5.2 Image Studies

Plain X-rays of the neck and shoulder can depict first and second rib fractures, clavicle fracture, fracture of the transverse process of the cervical spine, fracture of the scapula, and shrapnel from gunshot wounds, associated with the brachial plexus injury. Chest X-rays produced after inspiration and expiration can demonstrate the presence of hemidiaphragm elevation and immobility suggesting a phrenic nerve injury and possible proximal C5 injury ( ▶ Fig. 16.1). Computed tomography myelography (CTM) has a reported accuracy greater than 90%, ¹²^, ¹³ especially when combined with data from clinical examination, in the demonstration of nerve root status (presence, disruption, or absence) and of pseudomeningocele formation ( ▶ Fig. 16.2). For demonstration of those diverticulum consequent to healing of torn nerve sleeve filled with intrathecal contrast, the exam should be done at least 1 month after the injury to allow time for its formation and to allow edema and blood clots in the area of the nerve root to resolve. Although highly suggestive, these pseudomeningoceles do not provide proof of rootlet avulsion and this examination presents false-positive and false-negative results ranging from 5 to 10%. The drawbacks of the CTM are the possibility to demonstrate only proximal lesions (until the intervertebral foramina) ( ▶ Fig. 16.3) and its invasive nature. Although CTM is still considered to be the “gold standard” by some authors for studying root lesions, the noninvasive nature and the image details of the entire brachial plexus are responsible for the increasing popularity of magnetic resonance imaging (MRI). Techniques such as fast imaging using steady-state acquisition, MR neurography, and high-field 3-T MRI can demonstrate spinal nerve root lesions with high resolution, matching the diagnostic accuracy of CTM. ¹³^, ¹⁴ Besides providing a noninvasive means of detecting nerve root avulsion and easily demonstrating abnormal cerebrospinal fluid collection of pseudomeningoceles in T2-weighted images ( ▶ Fig. 16.4), MRI can also show spinal cord edema (an indirect sign of nerve root avulsion), postganglionic lesions such as postinjury fibrosis and neuromas, and associated inflammation or edema ( ▶ Fig. 16.5). Although MRI probably will become the most important method for evaluation of brachial plexus injuries, the possibility of false-positives is still a disadvantage of the technique. Associated injury to major vessels has been reported in TBPI to be as high as 23% in some series. ⁷ They are more frequently in infraclavicular lesions, usually involving subclavian artery and vein or the axillary artery. In cases of suspected arterial damage, a conventional angiography, CT angiography, or MR angiography should be performed. An angiography should always be done in cases of gunshot wound to the plexus because of the possibility of early vascular lesion and posterior formation of a pseudoaneurysm.

Fig. 16.1 Chest X-rays after inspiration (a) and expiration (b) demonstrating elevation and immobility of the right hemidiaphragm, suggesting a phrenic nerve injury.

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