Traumatic Brachial Plexus Injuries: Practice Essentials, Anatomy, Pathophysiology (original) (raw)

Practice Essentials

High-energy trauma to the upper extremity and neck can cause a variety of lesions to the brachial plexus. Most common are traction injuries, in which the head and neck are moved away violently from the ipsilateral shoulder; injuries may also be caused by compression between the clavicle and the first rib, penetrating trauma, or direct blows. Recognition may be delayed by other injuries, particularly to the spinal cord and head. [1, 2]

The treatment of lesions of the brachial plexus has changed from shoulder fusion, elbow bone block, and finger tenodesis following World War II to far greater functional restoration made possible by advances in nerve repair and microsurgery. [3]

The natural history of becoming "one-handed" within 2 years has been replaced by early exploration, neurolysis, nerve grafting, neurotization, and free muscle transfers, as well as tendon transfers, for shoulder and elbow function and for wrist or hand prehension. Advances in diagnostic imaging, nerve transfers, electrophysiologic testing, nerve root repair, nerve rootlet replantation, and free muscle transfers have made this a dynamic but highly specialized field. [4, 5, 6]

Because the topic is a complex one, this article focuses primarily on traction injuries, the most common type in adults. Such injuries usually are catastrophic for the affected individual. Loss of useful function of the upper extremity is common, but early repair and reconstruction are providing far greater restoration than was previously possible.

Anatomy

The brachial plexus is formed from the spinal nerves or roots, the coalescence of the ventral (motor) and the dorsal (sensory) rootlets as they pass through the spinal foramen. The dorsal root ganglion contains the cell bodies of the sensory nerves; the cell bodies for the ventral nerves lie within the spinal cord.

Typically, the brachial plexus is formed from C5-T1; in some cases there is a contribution from C4 (prefixed, 28-62%) or T2 (postfixed, 16-73%). All nerve supply to the upper extremity passes through this plexus. The brachial plexus starts at the scalenes, courses under the clavicle, and ends at the axilla. It is typically composed of five roots, three trunks, six divisions (two from each trunk), three cords, and terminal branches.

The five roots are named according to the level with which they correspond. The C5-C7 roots give off branches to form the long thoracic nerve, and the C5 root gives branches to form the dorsal scapular nerve. C5 and C6 give branches to form the superior trunk, C7 the middle trunk, and C8 and T1 the inferior trunk.

Each of the three trunks has two divisions. One division of each of the trunks forms the posterior cord. The anterior division of the superior trunk and the anterior division of the middle trunk form the lateral cord. The anterior division of the inferior trunk forms the medial cord. The medial, lateral, and posterior cord designations refer to the relations of these structures to the axillary artery.

The superior trunk gives off the suprascapular nerve and a nerve to the subclavius. The posterior cord has the upper and lower subscapular nerves, with the thoracodorsal nerve between them. The lateral pectoral nerve emanates from the lateral cord, and the medial pectoral nerve emanates from the medial cord, but with a connection between the pectoral nerves. The posterior cord then becomes the axillary and radial nerves.

The lateral cord continues as the musculocutaneous nerve; a branch from the medial and lateral cords becomes the median nerve; and a branch from the lateral branch joins the medial cord continuation as the ulnar nerve, after the medial cord gives off the medial brachial cutaneous and the medial antebrachial cutaneous nerves.

The cords and branches are distal to the clavicle; the roots and trunks are proximal. The plexus lies in close proximity to the axillary artery, which exits between the anterior and middle scalenes. Knowledge of this anatomy may allow localization of lesions from the physical examination.

Many different approaches to the brachial plexus have been followed. Surgeons' preferences are largely shaped by their training and by the goals of a particular procedure. In any approach, the clavicle can be a barrier to visualization.

Millesi described an approach that uses three anterior incisions with the patient in the supine position. [7] In this approach, a sagittal incision is made on the lower neck and two transverse incisions are made more distally, following skin tension lines. By moving the clavicle and looking at the plexus from both a cephalad and a caudad direction, the operator can visualize the upper, middle, and lower trunks of the brachial plexus and avoid osteotomy of the clavicle. The spinal nerves of the upper plexus can also be visualized with this approach.

Pathophysiology

In traction-type brachial plexus injuries, the head and neck are moved away violently from the ipsilateral shoulder. Upper-plexus injuries (C5 and C6) usually predominate if the arm is at the side because the first rib acts as a fulcrum to direct the traction forces preferentially in line with the upper plexus.

When the arm is moved violently and abducted overhead, the lower elements (C8-T1) typically are injured because the force is directed in line with C7. A lower-plexus lesion predominates when the arm is raised because the coracoid acts as a fulcrum in a similar fashion. Lower-plexus lesions may be more common, in part because of the well-formed transverse radicular ligaments that help resist traction forces at C5, C6, and C7; C8 and T1 lack these ligaments.

Traction forces can result in preganglionic or postganglionic injuries. Preganglionic injuries refer to lesions proximal to the dorsal root ganglion, which is in the spinal canal, and the foramen. They may be central or direct from the spinal cord or intradural. Preganglionic lesions do not cause wallerian degeneration or neuroma formation, because the axons remain in continuity with the cell bodies in the dorsal root ganglion. Postganglionic lesions are defined as any lesions distal to the spinal ganglion and are physiologically similar to other peripheral nerve injuries.

Etiology

The common mechanism for traction injuries of the brachial plexus is violent distraction of the entire forequarter from the rest of the body. These injuries usually result from a motorcycle accident or a high-speed motor vehicle accident (MVA). A fall from a significant height may also result in brachial plexus injury, either of the traction type or from a direct blow; penetrating injuries and low- or high-velocity gunshot wounds also are seen.

In traction-type injuries, the crucial prognostic factor is whether the injury is proximal or distal to the dorsal root ganglion (ie, preganglionic or postganglionic). A preganglionic root avulsion means that the cell bodies of the sensory nerves are pulled from the cord, diminishing the possibility of recovery or surgical reconstruction. These are differentiated from distal ruptures—postganglionic stretch injuries—in which cell bodies are still in continuity with their axons.

Epidemiology

Reliable information on the incidence of traumatic brachial plexus injuries has been difficult to obtain; the exact incidence has not been precisely defined. In 1992, Goldie and Coates suggested that 450-500 closed supraclavicular injuries occur each year in the United Kingdom. [8]

A systematic review of the literature demonstrated that patients had a mean age of 26.4 years, 90.5% were male, and manual labor was the most represented occupation. [9] The mean total indirect cost of traumatic brachial plexus injury in the Monte Carlo simulations was 1,113,962perpatientoverthepostinjurylifetime(median,1,113,962 per patient over the postinjury lifetime (median, 1,113,962perpatientoverthepostinjurylifetime(median,801,723; interquartile range, $22,740-2,350,979).

On the basis of 18 years of experience with 1068 patients, Narakas developed his rule of "seven seventies," as follows [10] :

• Approximately 70% were MVAs
• Of the MVAs, 70% were motorcycles or bicycles
• Of the cycle riders, 70% had multiple injuries
• Of the multiple injuries in cycle riders, 70% were supraclavicular injuries
• Of the supraclavicular injuries, 70% had at least one root avulsed
• Of the avulsed roots, 70% were lower C7, C8, T1
• Of the 70% avulsed roots, 70% of those were associated with chronic pain

Prognosis

The prognosis for traumatic brachial plexus injuries is highly variable. It depends not only on the nature of the injury but also on the age of the patient and the type of procedure performed.

Doi et al reported achieving reliable grasping of the hand and voluntary control of the shoulder and elbow after complete avulsion of the brachial plexus. [11] They achieved these impressive results using a double free muscle transfer technique.

Kandenwein et al presented 134 cases that were treated surgically for traumatic brachial plexus lesions. [12] In this group, the percentage of patients with grade 3 or better motor strength progressed from 2% preoperatively to 52% postoperatively, an enormous improvement over historical results. Graft reconstruction performed better than neurotization.

The Core Outcomes in Nerve Surgery (COINS) Consortium, citing the difficulty of comparing outcome data from different studies of brachial plexus and upper-extremity (BPUE) nerve injuries, has proposed a core outcome set (COS) for these injuries (the COS-BPUE). [13] The COS-BPUE includes 36 data points/outcomes; lists appropriate instruments, methods of testing, and definitions; specifies a minimum follow-up duration (24 mo); and provides optimal time points for assessment (preoperatively; 3, 6, 12, and 24 mo postoperatively).

Patient Education

Brachial plexus injury significantly influences psychological well-being and daily functioning. As a result, patients experience a high prevalence of posttraumatic stress disorder (PTSD), depression, and suicidal ideation. Patients with brachial plexus injury have a high prevalence of psychological concerns and challenges that will require continued attention throughout treatment. [14]

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Author

Coauthor(s)

Curtis T Adams, MD, JD Resident Physician, Department of Orthopaedics, Albany Medical Center

Disclosure: Nothing to disclose.

Abdulreman Arain, MD, MS Resident Physician, Department of Orthopedic Surgery, Albany Medical Center

Disclosure: Nothing to disclose.

Keegan P Cole, MD Resident Physician, Department of Orthopedic Surgery, Albany Medical Center

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Samuel Agnew, MD, FACS Associate Professor, Departments of Orthopedic Surgery and Surgery, Chief of Orthopedic Trauma, University of Florida at Jacksonville College of Medicine; Consulting Surgeon, Department of Orthopedic Surgery, McLeod Regional Medical Center

Samuel Agnew, MD, FACS is a member of the following medical societies: American Association for the Surgery of Trauma, American College of Surgeons, Orthopaedic Trauma Association, Southern Orthopaedic Association

Disclosure: Nothing to disclose.

Chief Editor

Murali Poduval, MBBS, MS, DNB Orthopaedic Surgeon, Senior Consultant, and Subject Matter Expert, Tata Consultancy Services, Mumbai, India

Murali Poduval, MBBS, MS, DNB is a member of the following medical societies: Association of Medical Consultants of Mumbai, Bombay Orthopedic Society, Indian Orthopedic Association, Indian Society of Hip and Knee Surgeons

Disclosure: Nothing to disclose.

Additional Contributors

Jeffrey L Visotsky, MD Assistant Professor, Department of Clinical Orthopedic Surgery, Northwestern University, The Feinberg School of Medicine

Jeffrey L Visotsky, MD is a member of the following medical societies: American Academy of Orthopaedic Surgeons, American Association for Hand Surgery, American Association for Physician Leadership, American College of Surgeons, American Medical Association, American Society for Surgery of the Hand, Arthroscopy Association of North America, Chicago Medical Society, Illinois State Medical Society

Disclosure: Received consulting fee from Depuy for speaking and teaching; Received honoraria from Pegasus for board membership.

Mark R Foster, MD, PhD, FACS President and Orthopedic Surgeon, Orthopedic Spine Specialists of Western Pennsylvania, PC

Mark R Foster, MD, PhD, FACS is a member of the following medical societies: American Academy of Orthopaedic Surgeons, American College of Surgeons, American Physical Society, Christian Medical and Dental Associations, Eastern Orthopaedic Association, North American Spine Society, Orthopaedic Research Society, Pennsylvania Orthopaedic Society

Disclosure: Nothing to disclose.

Acknowledgements

The authors and editors of Medscape Drugs & Diseases gratefully acknowledge the contributions of previous authors Christopher Chaput, MD, and Robert Probe, MD, to the development and writing of this article.