Outcomes of treatment for adult brachial plexus injuries

Summary box

1

Clean, sharp lacerations of the brachial plexus should be repaired within 72 hours. Blunt transections are best repaired in a delayed fashion.
2

Progressive neurologic deficits may be indicative of an enlarging hematoma, arteriovenous fistula, or pseudoaneurysm.
3

Blunt or traction injuries of the brachial plexus that show no evidence of spontaneous recovery have favorable outcomes after surgical intervention.
4

Use of intraoperative nerve action potential recordings is critical for assessing extent of nerve injury and serves to guide the surgeon’s decision-making.
5

Functional outcomes from spontaneous recovery or operative intervention are significantly improved by the use of physical and occupational therapies and secondary reconstructive procedures.
6

Of brachial plexus traction injuries, C5 and C6 injuries have the most favorable outcomes with regard to spontaneous recovery (30%), followed by C5, C6, C7 injuries (16%), and C5–T1 injuries (4%).
7

With brachial plexus traction injuries that progress to surgical intervention, C5 and C6 injuries have the best functional outcomes.
8

C5–T1 lesions remain difficult to repair surgically, and operations are considered salvage-like in nature.
9

Functional outcomes after brachial plexus injuries are improving with advancements in nerve transfer techniques.
10

A limited time window exists for optimal nerve regenerative support and subsequent functional recovery.

Introduction

Management of brachial plexus (BP) injuries has changed significantly over the past century, especially with regard to our understanding of neurobiology, pathophysiology, and pathology of nerve injuries and regeneration, as well as the microsurgical repair of injured nerves. Advancements in the clinical diagnosis of nerve lesions, development of comprehensive and evidence-based treatment algorithms, and optimization of the intraoperative decision-making process resulting from the introduction of intraoperative nerve action potential (NAP) recordings paved the way for better management of patients inflicted with peripheral nerve and BP injuries. Another benefit of a rather standardized treatment approach is the ability to systematically study clinical outcomes of patients with nerve injuries after microsurgical repair. Multiple series of functional outcomes after nerve injuries have been reported, both in civilian populations and in war veterans. In this chapter, we discuss briefly our approaches in the management of patients with BP injuries, with particular emphasis on clinical outcomes after microsurgical repair.

Causes of surgical nerve injuries

The BP can be injured either directly as in stab injuries where elements of the BP are sharply transected, or indirectly as in stretch injuries. Recently, traumatic nerve injuries have been classified based on the biomechanics of the injuring processes ( Figure 24.1 (part 1)). This classification is different from the neuropathologic classification of nerve injuries by Sunderland ( Table 24.1 ), as it emphasizes the mechanism of injury, which is important in deciding the best treatment option for a given nerve injury. BP injuries most often are caused by high energy forces that result in injuries such as transection, contusion, stretch, traction, and/or avulsion. However, BP injuries may also result from compressive neuropathies such as thoracic outlet syndrome, which are due to chronic or repetitive low energy forces ( Figure 24.1 (part 2)). BP injuries from injections, radiation, and thermal energy involve rather heterogenous combinations of different injuring factors, but for the purposes of analysis, they are grouped together as a complex group of nerve injuries ( Figure 24.1 (part 3)).

Table 24.1

Nerve injury grading (Sunderland Grading Scale)

Injury grade	Myelin	Axon	Endoneurium	Perineurium	Epineurium
I (Neuropraxia)*	+/−
II (Axonotmesis)*	+	+
III	+	+	+
IV	+	+	+	+
V (Neuromesis)*	+	+	+	+	+

+ denotes anatomical structures affected by injury. * Seddon grading system

Approach to clinical diagnosis

As with every other surgical discipline, the importance of detailed but relevant clinical patient history and mastery of physical examination of the patient as it relates to lesions of the BP cannot be overemphasized. Mastery of these skills combined with prudent use of ancillary tests, such as electromyography (EMG) and imaging studies, will guide the treating physician to an accurate diagnosis and localization of BP injuries ( Table 24.2 ). It is of utmost importance to entertain a broad differential diagnosis and perhaps only accept the diagnosis of BP injury once other causes of upper extremity dysfunction have been considered. This approach is especially important when dealing with controversial diagnostic entities such as Parsonage-Turner and thoracic outlet syndrome. Once a diagnosis of BP injury has been established, surgical treatment of the lesion is dictated by nature of the injury (open versus closed), acuity of the injury (early versus delayed presentation), and findings on clinical, electrodiagnostic, and imaging studies ( Figure 24.2 ).

Table 24.2

Role of nerve conduction studies and imaging in the diagnosis of nerve lesions

With regard to EMG, the following should be emphasized:

▸

EMG should be more than just conduction studies and must include muscle sampling.
▸

Patients can have clinical muscle function despite de-innervational changes.
▸

Patients can have persistent paralysis despite nascents or reduction in denervational changes, such as fibrillation and denervation potentials.
▸

Muscles related to neighboring nerves or plexus elements can show persistent EMG changes despite good function.
▸

Conduction studies are not always useful, especially for ulnar nerve and brachial plexus cases.

Imaging studies are important, but:

▸

MRI is most useful for tumors; occasionally it may also be useful for entrapments and injury.
▸

To date, in most institutions, MRI is not yet a substitute for CT-myelogram, especially when investigating root avulsions.
▸

Don’t forget plain x-rays! It is possible to pick up parrot’s beak of the C7 spinous process or humeral condyle on plain x-rays.

Indications and relative contraindications for surgery

Lacerations of the BP

Transection of the BP may occur when soft tissues surrounding the BP sustain lacerating injuries. These injuries tend to be either sharp or blunt. Sharp injuries to the BP are often caused by stab injuries inflicted by knives, falls through glass windows, or by exploding glass in factory or automobile accidents. Blunt injuries are caused by automobile metal fragments, fan or motor blades, chain saws, and animal bites around the neck.

Patients with lacerating injuries to the BP often have associated vascular injuries and/or airway difficulties; therefore, all initial efforts should be directed toward stabilizing the patient’s potential life-threatening orthopedic or vascular injuries. Securing the patient’s airway, breathing, and hemodynamic stability take precedence over any nerve injuries. Once initial resuscitative efforts are completed, the fundamental goal of managing lacerating injuries of the BP is to establish an accurate diagnosis as soon as possible in an attempt to improve prognosis.

Once diagnosis of a laceration of the BP has been established, urgency of treatment is dictated by the nature of the open wound and the cleanliness of the transected nerve edges:

(a)

Sharp nerve transection in a stable, clean soft tissue environment requires primary end-to-end neurorrhaphy within 72 hours.
(b)

Progressive neurologic deficit with/without progressive pain syndrome may be indicative of an enlarging hematoma, arteriovenous fistula, or pseudoaneurysm and indicates early intervention with participation by a vascular surgeon.
(c)

Nerve laceration within a severely contaminated wound requires aggressive and repeated irrigation and debridement of the wound to remove all necrotic tissues and eliminate risk of sepsis. Delayed repair of the nerve injury is employed, and the method of repair varies from neurolysis, direct end-to-end repair, graft repair and/or nerve transfers, depending on intraoperative findings and NAPs.
(d)

Blunt injury to nerve endings at the injury site requires secondary repair. If possible one can “tack down” nerve stumps with a suture to adjacent fascial or muscle planes so that retraction of the nerves is lessened and secondary repair can be achieved by epineurial suture repair instead of graft repair.

Gunshot wound to BP

Gunshot injuries to the BP constitute the second largest category of injuries involving the BP after stretch/contusion. Gunshot wounds to the BP hardly ever require immediate nerve repair because they most often cause neurmas-in-continuity, although in 10% to 15% of cases, blunt transection of BP elements occurs.

Indications for elective nerve repair of gunshot injuries to the BP are listed below:

(a)

Complete loss of function persistent in the distribution of one or more elements.
(b)

No improvement detected clinically or by electrodiagnostic studies in the early months following injury.
(c)

Loss of function in the distribution of at least one element usually helped by operation, such as C5, C6, C7, the upper or middle trunk, or the lateral or posterior cords or their outflows.
(d)

Surgery is not performed on injuries restricted to the lower trunks unless pain is a severe problem.
(e)

Incomplete loss of function complicated with pain not alleviated pharmacologically.
(f)

Pseudoaneurysm, clot, or fistula involving the plexus.
(g)

True causalgia requiring sympathectomy.

Stretch Injuries to the BP

Stretch injuries constitute the most common type of injury to the BP and are usually caused by motor vehicle accidents, particularly those involving motorcycles. Stretch injuries to the BP can occur during sports and/or recreational activities such as football, bicycling, skiing, wrestling, gymnastics, and even golf. Regardless of the cause of injury, the biomechanics of stretch injuries always involve distractive forces in which the head and neck are usually pushed in one direction and shoulder and arm in another direction. This results in severe stretch to soft tissues, including nerve and, less frequently, vessels.

Management of stretch injuries to the BP has evolved significantly over the last century, beginning with predominantly non-surgical and musculoskeletal reconstructive operations and amputations to direct surgical repairs. Over the last 2 decades, our understanding of the pathophysiology of poor regeneration and functional recovery has improved significantly and, with it, the evolution of innovative approaches to microsurgical management of BP injuries. Likewise, better understanding of the natural history of BP injuries with regard to the potential for spontaneous recovery and timing of microsurgical repair has improved our capability to optimize patient benefit from surgical treatment. A combination of suboptimal clinical results despite excellent direct microsurgical repair, and our appreciation of proximo-distal discrepancy in the reinnervation of denervated muscles after BP injuries, created a receptive audience for Narakas when he re-popularized neurotization (ie, nerve transfers) procedures about 3 decades ago. We have adopted an approach to perform direct microsurgical repair for BP injuries whenever feasible, supplemented with neurotization procedures. Our indications for surgical exploration and repair of BP stretch injuries are as follows:

(a)

Lack of clinical or electrodiagnostic evidence of spontaneous recovery 3 to 4 months after injury.
(b)

Possibility of a direct repair of at least a portion of the BP elements favorable for repair, usually C5, C6, C7 and their more distal outflows.
(c)

Lack of contraindications for surgical exploration.

Approach to intraoperative management of BP lesions

Microsurgery

The key principles in nerve surgery include (1) thorough understanding of the topographic anatomy of the injured nerve ( Figures 24.3, 24.4, 24.5 ); (2) mastery of the required incision and surgical approaches ( Figures 24.6, 24.7 ); (3) adequate surgical exposure of the proximal and distal stumps of the injured nerves as well as the associated nerve branches and blood vessels ( Figures 24.8, 24.9 ); (4) adequate magnification with the use of either the operating microscope or surgical loupes; (5) use of micro-instruments to minimize surgical trauma to the already traumatized nerves and/or branches; (6) careful application of bipolar coagulation only to the epineurial and intrafascicular bleeding points to minimize damage to the nerve itself.

Intraoperative nerve action potential (iNAP)

Lack of clinical and electrodiagnostic evidence of functional recovery 3 to 4 months after nerve injury are indications of lack of adequate reinnervation of denervated muscles and/or remyelination to generate muscle contractions. The senior author (DGK) pioneered the application of iNAP to the evaluation of axonal regeneration across a segment of damaged nerves. Intraoperative evaluation of axonal regeneration using iNAP is important, because it prevents inadvertent resection of nerves that still have the potential for spontaneous recovery. Appropriate intraoperative surgical decisions can be made with regard to the need for surgical resection of severely damaged nerves that have no response on iNAP (flat) and the subsequent need for direct or graft repair, or neurolysis, and continuation of observant non-surgical treatment if the damaged nerves have positive NAPs. Intraoperative NAPs can also help determine the proximal extent of healthy axons in injured nerves.

In addition, iNAP allows for early evaluation of nerve injuries and a determination of the extent of nerve damage. It can be applied 2 to 3 months after most focal injuries, and 3 to 4 months in less-focal lesions caused by stretch/contusion or gunshot injuries. With its application, the surgeon can sort out the management strategy for approximately 70% of nerve injuries in which nerve segments appear continuous with a variable amount of swelling and/or epineurial scar and yet are nonfunctional. NAP recordings can document the extent of a partial injury or prove that there is a neurapraxic block in the early weeks after the injury. When iNAP is applied months after injury, it can differentiate an axonotmetic lesion (positive NAP across the lesion) from a neurotmetic injury (negative NAP across the lesion).

Nerve repair techniques and nerve grafts

The surgical objective of the repair of any severed peripheral nerve involves either microsurgical realignment of the injured nerve stumps (ie, primary neurorrhaphy) or the use of an autologous nerve graft to bridge a larger defect. A thorough understanding of the surgical anatomy of BP exposure at supraclavicular, clavicular, and infraclavicular levels allows the surgeon to expose key elements of the BP, even after stretch injuries where there is abundant scar tissue formation ( Figures 24.10, 24.11, 24.12, 24.13, 24.14, 24.15 ). Wide exposure of BP elements and the application of iNAP guide the surgeon’s decision-making process with regard to microsurgical repair of injured nerves with or without nerve grafting. The nerve grafting technique was first reported between the years 1870 and 1900, but Hanno Millesi re-popularized the concept of using nerve grafts to bridge large defects to avoid the detrimental effects of suturing nerve stumps under tension. His work demonstrated that nerve grafting without tension was superior to epineurial suture under tension, and that tension at the repair site induces scar formation. Therefore, nerve repair without tension is most desirable, because the more scar tissue present at the repair site, the less satisfactory is functional recovery. Tension across a direct suture repair decreases blood flow and promotes proliferation of connective tissue within the nerve, which may block effective axonal regeneration. Acute, excessive stretch may cause intraneural hemorrhage resulting in scar formation and axoplasmic degeneration; subsequent maturation of scar tissue may shrink and constrict nerve fibers and may result in formation of a neuroma-in-continuity. However, whenever there are small-to-moderate gaps, it may be preferable to mobilize nerve ends to allow direct nerve repair (without tension), which results in better functional recovery than graft repair.

Nerve grafting techniques include the use of either a free nerve graft or a vascularized nerve graft in the form of pedicle grafts or as a free vascularized graft transfer. Nerve grafts can be classified according to their biological origin. Autografts are harvested from the same individual, allografts (or homografts) come from an individual of the same species, and xenografts (or heterografts) originate from another species. Autografts, which are the “gold standard” for nerve grafting surgery, are harvested from the same patient and do not pose immunological problems. Currently, donor nerves used for nerve grafting are commonly expendable sensory nerves that can be harvested without significant morbidity, except for some loss of sensation at the donor site. Commonly used donor nerves include the sural nerve, lateral antebrachial cutaneous nerve, anterior division of the medial antebrachial cutaneous nerve, dorsal cutaneous branch of the ulnar nerve, and superficial sensory branch of the radial nerve. The choice of donor nerve to be used is dictated by the cross-sectional area of the nerve to be repaired, length of the nerve gap, and extent of donor site morbidity. The primary donor nerve for free grafting is the sural nerve, which can be harvested to a length of 30 cm or more and is easily accessible. The use of nerve grafts obtained from another human being is warranted in situations when repair of a large defect created by a BP or sciatic nerve injury is limited by an inadequate number of available segments from autograft. However, because allografts trigger immunological response and there is risk of rejection, the use of immunosuppressive treatment is required to prevent rejection. Hence, patients receiving this type of nerve graft must be willing to accept the potentially dangerous side effects of the chemotherapeutic agents used. Xenografts are derived from animals of another species and are also used in situations similar to that for allografts and also require the use of immunosuppressive therapy. The use of xenografts is, thus far, limited to experimental studies in animals.

A posterior subscapular approach to the supraclavicular BP is not used as often as anterior approaches but provides an excellent surgical option to gain access to supraclavicular BP ( Figures 24.16–24.21 ).