Brachial Plexus Compressive / Entrapment

Disease/ Disorder

Definition

The brachial plexus is vulnerable to intrinsic and extrinsic compression or entrapment and perioperative damage. Compressive neuropathies are caused by direct pressure on nerves. Entrapment neuropathy describes a compressive neuropathy caused by the patient’s own body.

Etiology

Intrinsic brachial plexus compression

• Primary brachial plexus tumors
  • Schwannomas, neurofibromas, and neurofibrosarcomas occur as solitary tumors. ¹
  • Multiple tumors may occur in patients with neurofibromatosis type 1.
  • Rarely cause symptomatic plexopathies, but they may present with pain or clinical deficits related to the location of the plexus affected.
• Metastatic tumors
  • Infiltration from lung and breast metastases occur most frequently via lymphatics from the axilla, typically affecting the lower trunk. ^2,3
• Radiation-induced plexopathy
  • Proposed mechanisms of action include occlusion of microvasculature, direct injury to myelin sheath/axon, endoneural and perineural fibrosis, typically affecting the upper trunk^2,4
  • Less commonly, radiation induced sarcomas can occur.²
  • See Radiation Plexopathy topic for further information.

Extrinsic brachial plexus compression

• Thoracic outlet syndrome (TOS)
  • Subtypes include true (classic) neurogenic TOS, vascular TOS and nonspecific TOS. 
  • See Thoracic Outlet Syndrome topic for further information regarding vascular TOS and non-specific TOS.
• True Neurogenic TOS
  • Causes include congenital fibrous bands, rudimentary cervical ribs, trauma, scalene mediated entrapment, and abnormal posturing.
  • Lower plexus becomes stretched and angulated superiorly due to fibrous band from first thoracic rib to C7 rib or elongated C7 transverse process⁵
  • Presents with slowly progressive, unilateral, atrophic weakness of the thenar muscles and ulnar-innervated hand and forearm muscles, and pain in a lower trunk distribution (particularly T1).⁵
  • Motor weakness may not be apparent initially due to muscle fiber reinnervation by collateral sprouting of surviving nearby nerve fibers.⁵
• Traumatic Neurovascular TOS
  • Rare, often secondary to mid-shaft clavicular fracture
  • Medial cord most susceptible to injury as it passes behind the middle segment of the clavicle
• Rucksack palsy acutely presents with pain, numbness in medial aspect of arm, forearm, and hand weakness in ulnar and median-innervated muscles.⁶
  • Caused by wearing a backpack or carrying a heavy load on the shoulders for a prolonged time period.
  • Presents with painless shoulder/arm weakness and sensory changes, usually unilaterally.
  • Most common nerves involved include long thoracic, axillary, suprascapular, and musculocutaneous nerves.⁷
• Neoplasms
  • Compression occurs due to direct extension of breast, lung, or thyroid tumors, and less commonly lipomas.⁸ 
  • Shoulder pain is the most common presenting symptom.
  • Masses typically invade the inferior trunk, due to proximity to axillary lymph nodes and superior sulcus of lung.³
  • Pancoast syndrome, seen typically with non-small cell lung cancer in the superior sulcus, causes lower plexus symptoms and Horner syndrome.⁹
• Trauma
  • Fractures, falls, objects falling on the shoulder, shoulder dislocation, and sports injuries are among many causes of traumatic plexus compression.
  • See Traumatic Brachial Plexopathy topic for further information.

Perioperative brachial plexus injuries/compression

• Positioning
  • Malpositioning causes traction or pressure on the plexus. Overhead arm positioning with shoulder in external rotation and abduction > 90 degrees causes stretch and compression of the plexus over the head of the humerus and the coracoid. ¹⁰
  • Patients usually present with weakness and paresthesias in an upper plexus distribution, occasionally bilaterally.
  • Prone positioning to improve oxygenation with arms in overhead position in the ICU setting has also been associated with compressive plexopathy.¹¹ 
• Postmedian sternotomy plexopathy
  • Sternotomies cause traction injuries to the C8 anterior primary ramus from fracture or upward displacement of the first rib.
  • C8 median, radial, and ulnar-innervated muscles show weakness.¹²
• Axillary node dissections and orthopedic surgeries involving the clavicle/shoulder
  • Plexopathies result from direct injury or edema causing compression/entrapment.
  • Abduction greater than 90 degrees of an externally rotated and extended arm, stretches the plexus over the head of the humerus and the coracoid process.¹⁰
• Neonatal brachial plexus palsy (NBPP)
  • Caused by excessive lateral traction applied to the fetal head during delivery.
  • Occurs unilaterally with 3 presenting patterns: upper plexus, upper and middle plexus, and panplexus.
  • See Neonatal Brachial Plexus Injury topic for further information

Epidemiology including risk factors and primary prevention

• The prevalence of cancer-associated plexopathies is 0.4%.¹³ Neurofibromas and schwannomas are the most frequent benign tumors, but direct extension of breast or lung cancer is more common.¹
• Radiation therapy to chest, neck, or axillary region increases risk for radiation-induced plexopathy, dose of <6000 cGy reduces risk.²
• Rucksack palsy has been reported in soldiers, boy scouts, hikers, and manual laborers.¹³
• Neurogenic TOS has an estimated incidence of 1 per 1,000,000 and a female to male ratio of 9 to 1.⁵
• Iatrogenic plexopathies related to surgery account for 7% to 10% of brachial plexopathies.¹⁴
• Positioning strategies during surgery reduce plexopathies. When possible, the head and neck should be kept in a neutral position without allowing lateral flexion, arms should be positioned by the patient’s side, and use of wrist restraints and shoulder plates should be limited. The patient’s position should be monitored throughout the procedure.¹⁰

Patho-anatomy/physiology

The most common pathology is axonal loss causing Wallerian degeneration and loss of the axon distally. Some injuries cause focal demyelination, which has no electrodiagnostic or structural effect on the distal nerve.¹

The lesion site determines the following clinical patterns.¹

• Panplexus
  • Weakness, sensory loss, and decreased or absent reflexes in the entire arm.
  • Serratus anterior and rhomboids are usually spared if roots are intact.
• Upper trunk
  • Weakness primarily in C5-C6 innervated muscles, such as deltoid, biceps, brachioradialis, supraspinatus, and infraspinatus.
  • Pronator teres (C6-C7) and triceps (C6-C8) may be affected due to partial upper trunk innervation.
  • Sensory changes in the lateral arm and lateral forearm (axillary and lateral antebrachial cutaneous nerve distribution), as well as lateral hand and thumb (median and radial sensory branches).
  • Biceps and brachioradialis reflexes may be abnormal, depending upon the severity of injury.
• Middle trunk
  • Rare, mimics C7 radiculopathy as middle trunk is formed directly from C7 root.
  • Weakness in the triceps, flexor carpi radialis, extensor digitorum communis, and pronator teres.
  • Sensory changes in the middle finger and posterior forearm.
  • Abnormal triceps reflex.
• Lower trunk
  • Weakness in ulnar-innervated muscles, median C8-T1-innervated muscles (i.e. abductor pollicis brevis, flexor pollicis longus, flexor digitorum profundus), and radial C8-innervated muscles (i.e. extensor indicis proprius, extensor pollicis brevis).
  • Sensory changes in the medial arm, medial forearm, medial hand and digits 4 and 5.
  • Pure lower trunk plexopathy should not have reflex abnormalities.
• Lateral cord
  • Weakness in pronator teres, flexor carpi radialis, and biceps.
  • Sensory changes in the lateral forearm, lateral hand and digits 1 through 3.
  • Abnormal biceps reflex.
• Posterior cord
  • Weakness in the arm and wrist extensors, deltoid, and latissimus dorsi.
  • Sensory changes in the lateral arm, posterior arm, posterior forearm, and radial dorsal hand.
  • Abnormal triceps and brachioradialis reflexes.
• Medial cord
  • Almost identical to lower trunk plexopathy, except for intact radial C8 fibers.
  • Weakness in all ulnar muscles and C8-TI median muscles, (i.e., abductor pollicis brevis, flexor pollicis longus, and flexor digitorum profundus).
  • Finger extensors are intact due to radial nerve sparing.
  • Sensory changes in the medial arm, medial forearm, medial hand and digits 4 and 5.

Specific secondary or associated conditions and complications

• Erb-Duchenne palsy
  • Most common type of brachial plexopathy in newborns.
  • Characterized by weakness of shoulder abduction, elbow flexion, and arm supination.
  • Limb hangs at the side, medially rotated, forearm extended, and pronated.
  • Seen in upper trunk (C5, C6) plexopathies.
• Klumpke palsy
  • Characterized by weakness of the hand intrinsic muscles and ulnar-innervated muscles, with preservation of upper arm muscles
  • Results in supination of the forearm and flexion of the wrist and fingers (claw hand).
  • Seen in lower trunk (C8, T1) plexopathies.
• Radial nerve palsy
  • Characterized by forearm extensor weakness causing wrist drop.
  • Seen in posterior cord plexopathies.

Essentials of Assessment

History

• A thorough medical history should be obtained, including medical, surgical, family, and social histories.
• Determine the onset of the symptoms and any association (surgery, radiation, injury, recreational activity, delivery) or whether the symptoms began insidiously without a known cause. Ask about pain, weakness, and sensory changes.

Physical examination

Thorough musculoskeletal and neurologic examinations should be performed testing manual muscle strength, sensation, and reflexes.

Functional assessment

Plexus lesions cause varying functional abnormalities and palsies. Evaluate patients’ ability to carry out activities of daily living.

Imaging

Magnetic resonance imaging (MRI) provides detailed soft tissue visualization. Contrast-enhanced images are obtained for suspected neoplasm, radiation injury, abscesses, and following peripheral nerve surgery. Non-contrast studies are sufficient for acute traumatic injuries and compressive neuropathy. Chest and spine plain radiographs can detect major osseous abnormalities. Computerized tomography (CT), used in patients who cannot undergo MRI, provides greater detail for bony abnormalities. Ultrasound is an increasingly used modality and subsequently discussed in Cutting Edge Concepts and Practice.¹⁵

Supplemental assessment tools

Electrodiagnostic (EDx) evaluation (nerve conduction studies (NCS) and needle electromyography (EMG)) can help to localize the lesion, and assess severity of injury, chronicity and evaluate for reinnervation.

Sensory NCS are more important than motor NCS in identifying plexus lesions. Sensory nerve action potential (SNAP) amplitudes can help identify if a lesion is proximal or distal to the dorsal root ganglion (DRG). SNAPs may be abnormal in plexus lesions, as these are distal to the DRG, but will be normal in nerve root lesions that are located proximal to the DRG. Compound muscle action potential (CMAP) amplitudes may be affected in both plexus and root lesions. It is important to note that CMAP amplitude is the main prognostic factor in plexopathy because it reflects the degree of axon loss.¹ Other notable electrodiagnostic factors to consider include:

• Distal SNAPs are normal in myelopathy.
• Root lesions from far lateral disks may cause abnormal SNAPs, similar to plexopathies.
• Nerve conduction studies may be normal in small fiber neuropathy.
• F responses may have limited usefulness in the assessment of brachial plexopathies, as the upper extremity muscles tested are often innervated by multiple myotomes. With the presence of motor nerve fibers from unaffected myotomes, a normal F response may be obtained, as an abnormal F response requires all or most of the motor fibers to be affected.¹

Needle EMG of proximal and distal muscles is performed for further lesion localization.

The following abnormal electrophysiologic patterns can be seen:¹

• Upper trunk
  • Low or absent lateral antebrachial cutaneous (LAC) SNAP amplitude, compared to contralateral side.
  • Radial sensory and median sensory studies may be abnormal.
  • Median and ulnar motor NCS and F responses are normal. EMG abnormalities are usually seen in deltoids, biceps, brachioradialis, supraspinatus and infraspinatus muscles, and may also occur in the triceps, pronator teres, and flexor carpi radialis muscles.

• Middle trunk  
  • Radial and median SNAPs may be abnormal, particularly when recording over the middle finger.
  • Median and ulnar motor NCS are normal.
  • EMG abnormalities may be seen in the pronator teres, triceps, flexor carpi radialis muscles.
• Lower trunk
  • Ulnar digital sensory nerves, dorsal ulnar cutaneous, and medial antebrachial cutaneous (MAC) SNAPs are typically abnormal.
  • Median and ulnar motor NCS may be abnormal.
  • EMG abnormalities may be seen in ulnar-innervated muscles, as well as median and radial-innervated muscles containing C8/T1 fibers i.e.: flexor pollicis longus, abductor pollicis brevis, and extensor indicis proprius.
• Lateral cord
  • LAC and median SNAPs are abnormal.
  • Ulnar and median motor NCS are normal.
  • EMG abnormalities may be seen in the biceps, pronator teres, and flexor carpi radialis.
• Posterior cord
  • Radial SNAP is usually abnormal.
  • Median and ulnar motor and sensory NCS are normal.
  • EMG abnormalities may be seen in distal and proximal radial innervated muscles, i.e., brachioradialis, triceps, extensor indicis proprius, extensor carpi radialis.
• Medial cord
  • Ulnar sensory, dorsal ulnar cutaneous, and MAC SNAPs are abnormal.
  • Median and ulnar motor NCS may be abnormal.
  • EMG abnormalities seen in all ulnar-innervated muscles and distal median-innervated muscles containing C8-T1 fibers, i.e., APB, flexor pollicis longus.

Early predictions of outcomes

• Axonal loss, chronic lesions, and muscle atrophy are associated with worse injury and outcome. Presence of fibrillation potentials and positive sharp waves, graded from 0 to 4, can help indicate the severity of axonal loss and active muscle denervation. However, higher grades do not necessarily correspond to the degree of denervation or worse injuries. Maintaining distal CMAP amplitude indicates minimal axon loss and an early prognostic predictor for recovery.
• Focal demyelinating injuries without axon loss, also referred to as neurapraxia, have a better prognosis and recovery.
• NCS/EMG are specific but not sensitive in identifying lesions, limiting their prognostic value.
• After surgery for neurogenic TOS, motor recovery is limited as collateral sprouting is already maximal and the distance between lesion and denervated muscles is long.⁵
• Two thirds of rucksack palsies recover fully within 2 to 5 months.⁷
• Classic postoperative paresis and postmedian sternotomy plexopathy generally have rapid and complete recovery.¹⁴

Rehabilitation Management and Treatments

Available or current treatment guidelines

• Several classes of medications are available for both nociceptive and neuropathic pain management:
  • NSAIDs can be used to treat nociceptive causes, if there are no bleeding risks or other contraindication.
  • Anti-epileptics:  gabapentin and pregabalin
  • Antidepressants: tricyclic antidepressants (such as amitriptyline, nortriptyline, desipramine) and selective norepinephrine and serotonin reuptake inhibitors (duloxetine and venlafaxine).
  • Mixed opioid agonists with norepinephrine reuptake inhibition properties (tramadol and tapentadol), and pure opioid agonists.¹⁶
• Occupational and physical therapies can help restore function reduce pain. Treatments may include:
  •  Regional muscle strengthening, range of motion, stretching, functional bracing/splinting, and physical modalities.
  • Antigravity benefits of aquatic therapy may facilitate recovery of movement.
• Specific treatments depend upon the underlying etiology.
  • Environmental and activity modifications reduce symptoms in rucksack palsy or postural TOS.^6,7
  • Surgical intervention may be required in the setting of neoplasm, neurogenic TOS, and fractures.
  • Neurogenic TOS is treated can be treated with conservative management with physical therapy or scalene injections. When conservative management fails surgical removal of the first rib or band sectioning can be performed.⁵
  • Surgical management includes primary nerve repair, nerve grafting, nerve transfer, functional free muscle transfer transfers. No specific guidelines exist regarding who should be referred for surgery. Timing of surgery and distance of the lesion to recipient muscle(s)are particularly important, as early reconstruction will impede ability for spontaneous recovery, but delay may risk irreversible muscle atrophy.¹⁷

Surgically related plexopathy is usually managed conservatively, with focus on symptom control and functional optimization. At different disease stages

Open nerve injuries

• Transected nerves should be repaired soon after injury (days) to reduce fibrosis, reduce tension, and maximize regrowth.
• If nerve transection exists secondary to fracture, fracture should be reduced. Direct end to end or end to side nerve repair may be performed in cases of sharp nerve division with minimal gaps less than 2.5cm, otherwise grafting may be necessay.¹⁸

Closed nerve injuries

• If by 6 weeks from the time of injury there is no spontaneous recovery, further evaluation should be obtained with imaging and EDx study.
• If there is no evidence of reinnervation by 3-6 months from the time of injury, surgical exploration of the nerve and neurolysis may be considered.¹⁸

Coordination of care

Communicate with other physicians, therapists, orthotists, and nurses is critical in the delivery of patient centered care.

Patient & family education

Patients and family should be educated on the cause of impairment, strategies to mitigate complications, treatment options and expected recovery course.

Emerging/unique interventions

The Disabilities of the Arm, Shoulder, and Hand questionnaire is a reliable instrument to measure upper extremity function and symptoms. The Active Movement Scale assesses motor function in infants with NBPP.

Translation into practice: practice “pearls”/performance improvement in practice (PIPs)/changes in clinical practice behaviors and skills

• NCS/EMG evaluation can help localize lesions, assess chronicity and, severity and offer information regarding prognosis.
• Axon loss lesions typically have a worse prognosis than demyelinating neuropraxic injuries.
• Clinical patterns found on physical examination may localize a plexus lesion.
• Sensory studies play a particularly important role in lesion localization, particularly when evaluating for lesions proximal to the DRG (i.e., nerve root avulsion, radiculopathy) and lesions distal to the DRG (i.e., brachial plexus, individual peripheral nerves). Healthy patients may have SNAP responses within reference range. In these situations, 50% amplitude drop compared to the contralateral side is considered abnormal. Preservation of distal CMAP responses may predict earlier recovery.

When in doubt, early referral to the nerve surgeon is recommended, particularly with complete or severe injuries, as nerve transfer surgery is most successful when performed within the first 3 to 6 months after injury. ¹⁹

Cutting edge concepts and practice

• Neuromuscular ultrasound (NMUS) is of interest for diagnosis and image-guided therapy in plexopathies. NMUS can visualize the movement of structures and identify lesions and masses. It relies on operator skills, which could be a limitation.¹⁵
• Magnetic resonance neurography (MRN), usually available in large academic institutions, increases visualization of individual plexus segments and peripheral nerves. In one study, MRN was found to change preclinical impression in 75.2% of patients, and substantially impacted care in 28% of patients.²⁰ MRN can help further differentiate cervical radiculopathy secondary to osteoligamentous degenerative changes   and/or cervical disc herniation which can present similar to brachial plexopathies. Postsurgical recovery can also be assessed via T2 nerve signal intensity and signs of muscle degeneration.²¹ Advances in nerve surgery have focused on reducing tension on the nerve, which is considered to be the most important factor in peripheral nerve repair.¹⁷ This has led to the development of nerve conduits using allograft and autograft strategies. Due to the high donor site morbidity in autograft techniques, alternative methods are being studied, including stem cell implantation and use of growth factors to promote axonal regeneration.²²

Gaps in the Evidence-Based Knowledge

Several studies found high satisfaction with surgical treatment, whereas others demonstrate comprehensive rehabilitation improves outcomes. However, these studies tend to be small, resulting in a lack of adequately powered, good outcome data on long-term functional outcomes after surgery and rehabilitation.^19,22,23 Guidelines for optimal candidates for surgery and timing for surgical intervention are currently being studied with the use of robotic surgery in the treatment of neurogenic compression in TOS.^24,25

References

1. Preston DC, Shapiro B. Electromyography and Neuromuscular Disorders: Clinical Electrophysiologic Correlations. Philadelphia, PA: Elsevier; 2005.
2. Khadilkar SV and Khade SS. Brachial plexopathy. Ann Indian Acad Neurol. 2013 Jan-Mar; 16(1):12-18
3. Custodio C. Electrodiagnostics in cancer rehabilitation. Phys Med Rehabil Clin N Am. 2017:28:193-203
4. Stubblefield MD. Neuromuscular complications of radiation therapy. Muscle & Nerve. 2017: 1031-1040
5. Ferrante MA and Ferrante ND. The thoracic outlet syndromes: Part 1. Overview of the thoracic outlet syndromes and review of true neurogenic thoracic outlet syndrome. Muscle & Nerve. 2017:6
6. Ferrante MA and Ferrante ND. The thoracic outlet syndromes: Part 2. The arterial, venous, neurovascular and disputed thoracic outlet syndromes. Muscle & Nerve. 2017:10
7. Makela JP, Ramstad R, Mattila V, Pihlajamaki H. Brachial plexus lesions after backpack carriage in young adults. Clinical Orthopaedics and Related Research. 2006:452:205-209
8. Gembruch, Oliver et al. “Lipomas as an Extremely Rare Cause for Brachial Plexus Compression: A Case Series and Systematic Review.” Journal of brachial plexus and peripheral nerve injury 16.1 (2021): e10–e16. Web.
9. Patel, D.K., Gwathmey, K.G. Neoplastic nerve lesions. Neurol Sci 2022 Feb 23 43, 3019–3038.
10. Thomas J. Post-operative brachial plexus neuropraxia: A less recognized complication of combined plastic and laparoscopic surgeries. Indian J Plast Surg. 2014 Sep-Dec; 47(3):460-464.
11.  Goettler CE, Pryor JP, Reilly PM. Brachial plexopathy after prone positioning. Crit Care. 2002 Dec;6(6):540-2. doi: 10.1186/cc1823. Epub 2002 Sep 17. PMID: 12493078; PMCID: PMC153436.    
12. Das S, Ganju A, Tiel RL, Kline DG. Tumors of the brachial plexus.Neurosurg Focus. 2007;22:E26.
13. Nylund T, Mattila VM, Salmi T, Pihlajamaki HK, Makela JP. Recovery of brachial plexus lesions resulting from heavy backpack use: a follow-up case series.BMC Musculoskelet Disord. 2011;12:62.
14. Desai KR, Nemcek AA. Iatrogenic brachial plexopathy due to improper positioning during radiofrequency ablation. Semin Intervent Radiol. 2011;28(2):167-170
15. Bykowski J, Aulino JM, Berger KL et al. ACR appropriateness criteria® plexopathy. J Am Coll Radiol. 2017;14(5S):S225-S233
16. Gilron I, Baron R, Jensen T. Neuropathic pain: Principles of diagnosis and treatment. Mayo Clinic Proc. 2015;90(4):532-545
17. Griffin JW, Hogan MV, Chhabra AB, Deal DN. Peripheral nerve repair and reconstruction. The Journal of Bone and Joint Surgery, 2013: 2144-2151
18. Houdek MT, Shin AY. Management and complications of traumatic peripheral nerve injuries. Hand Clin 31:2015:151-163
19. Robinson LR, Binhammer P. Role of electrodiagnosis in nerve transfers for focal neuropathies and brachial plexopathies. Muscle Nerve. 2022 Feb;65(2):137-146. doi: 10.1002/mus.27376. Epub 2021 Jul 31. PMID: 34331718.
20. Fisher S, Wadhwa V, Manthuruthil C. Clinical impact of magnetic resonance neurography in patients with brachial plexus neuropathies. Br J Radiol. 2016;89(1067)
21. Ku V, Cox C, Mikeska A, MacKay B. Magnetic Resonance Neurography for Evaluation of Peripheral Nerves. J Brachial Plex Peripher Nerve Inj. 2021 May 14;16(1):e17-e23.
22. Fowler JR, Lavasani M, Huard J, Goitz RJ. Biologic strategies to improve nerve regeneration after peripheral nerve repair. Journal of Reconstructive Microsurgery. 2014    
23. Palispis WA and Gupta R. Surgical repair in humans after traumatic nerve injury provides limited functional neural regeneration in adults. Experimental Neurology.2017:106-114
24. Fowler JR, Lavasani M, Huard J, Goitz RJ. Biologic strategies to improve nerve regeneration after peripheral nerve repair. Journal of Reconstructive Microsurgery. 2014
25. Weaver, M.L.; Lum, Y.W. New Diagnostic and Treatment Modalities for Neurogenic Thoracic Outlet Syndrome. Diagnostics 2017:7(28).

Original Version of the Topic

Thiru M. Annaswamy, MD, MA, Jeremy Jones, MD. Brachial Plexus Compressive / Entrapment. 9/20/14

Previous Revision(s) of the Topic

Julia Reilly, MD and Jennifer A. Baima, MD. Brachial Plexus Compressive / Entrapment. 7/16/2018

Author Disclosure

Laura Huang, MD
Nothing to Disclose

Robin Mata, DO, MPH
Nothing to Disclose

Lizeth Caldera, BS, MS
Nothing to Disclose