Axillary Nerve Injury


Article Author:
Joseph Tessler


Article Editor:
Raja Talati


Editors In Chief:
Jasleen Jhajj
Cliff Caudill
Evan Kaufman


Managing Editors:
Avais Raja
Orawan Chaigasame
Carrie Smith
Abdul Waheed
Khalid Alsayouri
Trevor Nezwek
Radia Jamil
Patrick Le
Anoosh Zafar Gondal
Saad Nazir
William Gossman
Hassam Zulfiqar
Steve Bhimji
John Shell
Matthew Varacallo
Heba Mahdy
Ahmad Malik
Sarosh Vaqar
Mark Pellegrini
James Hughes
Beata Beatty
Nazia Sadiq
Hajira Basit
Phillip Hynes
Tehmina Warsi


Updated:
5/4/2019 2:41:20 PM

Introduction

Peripheral nerve injury can vary wildly in severity and presentation, ranging from mild soreness to severe muscle weakness. Axillary nerve injuries typically respond well to conservative management, though surgical intervention may be required. Failure to accurately diagnose and manage patients may lead to life-long disability that can affect the overall quality of life. While axillary nerve lesions are somewhat rare, it should be a consideration when patients present with shoulder weakness and sensory loss.

Anatomic Course

The axillary nerve diverges from the posterior cord of the brachial plexus anterior to the subscapularis muscle, running posterior to the axillary artery. It then travels inferior to the glenohumeral joint capsule and passes through the quadrangular space with the posterior humeral circumflex artery. The axillary nerve proceeds to split into anterior and posterior divisions. The anterior division supplies motor innervation to the anterior and middle heads of the deltoid. The posterior division provides motor innervation to the posterior deltoid and teres minor before eventually terminating as the superior lateral cutaneous nerve and innervating the lateral shoulder.[1] The axillary nerve is a bilateral upper extremity peripheral nerve and receives significant contributions from C5 and minor contributions from C6.[2]

Functional Anatomy

As stated above, the axillary nerve innervates the deltoid and teres minor muscles. The deltoid muscle, divided into three parts performs and assists in a variety of actions. The primary function of the deltoid muscle is glenohumeral abduction, performed by the middle muscle belly. The anterior muscle belly assists in glenohumeral flexion and internal rotation. The posterior muscle belly assists in glenohumeral extension and external rotation.[3] The teres minor functions in glenohumeral external rotation.[4] Also, the deltoid and teres minor stabilize the glenohumeral joint, with the teres minor contributing a greater role as a part of the glenohumeral rotator cuff.[5] Lastly, the axillary nerve transmits afferent, sensory input from the lateral shoulder.[1] Several studies have claimed the axillary nerve innervates the long head of the triceps brachii, but a recent cadaver study by Wade et al. showed no axillary nerve innervation to the triceps brachii.[6]

Etiology

Axillary nerve injury typically presents with other brachial plexopathies. Axillary neuropathies are due to traumatic injuries, traction injuries, quadrilateral space syndrome, and brachial neuritis (also called neuralgic amyotrophy or Parsonage-Turner syndrome).[3]

Epidemiology

An axillary nerve mononeuropathy is a rare event, occurring in about 0.3 to 6% of all brachial plexus injuries.[2] Axillary nerve injuries constitute 6 to 10% of all brachial plexus injuries during shoulder surgery.[7] Recent research showed that the risk of axillary nerve injury after glenohumeral dislocation increased with age. Approximately 65% of patients over 40 years of age were diagnosed by electromyography (EMG) with an axillary nerve lesion.[8] Brachial neuritis has an estimated incidence of 1 to 3 per 100000 annually with a female predilection.[9]

History and Physical

The principle presenting symptoms are a weakness in glenohumeral abduction with or without numbness to the lateral shoulder area. Patients may also present with weakness in glenohumeral external rotation; however, this may not be apparent due to the ability of the infraspinatus. In patients presenting after dislocation or fracture, signs of trauma will be evident on physical exam. Nevertheless, patients may not report muscle weakness or paresthesia due to the presence of acute pain and limited range of motion.[2] Compressive neuropathy may occur after blunt trauma to the deltoid muscle. Atraumatic neuropathy preceded by localized pain presents in brachial neuritis.[2][10] Patients with quadrilateral space syndrome (QSS) present with vascular symptoms such as cyanosis and pallor of the distal upper extremity, and splinter hemorrhages in addition to neurologic symptoms.[11]

Evaluation

A proper history is essential in determining the correct intervention necessary. At the very least, the provider should obtain information on symptom onset, palliative and provoking factors, quality of the symptoms, radiation of symptoms to other regions, the severity of pain (if applicable), and timing. Key questions to consider are trauma, focal weakness, numbness and tingling, cyanosis, limitations in the range of motion, and pain.

The physical exam should begin with a visual inspection of the upper extremity, noting the presence or absence of trauma. The provider should palpate the ipsilateral neck and upper extremity for tenderness and muscle tone, followed by an evaluation of passive and active ranges of motion. Next, a neurologic exam focused on the axillary nerve and shoulder should also include an assessment of the spinal accessory, suprascapular, long thoracic, musculocutaneous, and radial nerves.[2] Several specialty clinical tests that evaluate the deltoid and teres minor muscles exist that may guide providers during assessment for axillary nerve injury in the absence of trauma, muscle strain, or known tendinopathies. The swallow-tail, deltoid extension lag, and Bertelli tests have been used to examine deltoid muscle weakness.[12][13] The external rotation lag, drop arm, and Patte tests evaluate the function of the teres minor muscle.[14]

Radiographs of the shoulder can help identify fractures involving the shoulder region after traumatic events. Shoulder magnetic resonance imaging (MRI) should be ordered if compressive neuropathy or inflammatory processes are suspected, or in cases of chronic neuropathy that has resulted in muscle atrophy. The gold standard for diagnosis confirmation is EMG. Additionally, EMG findings can help establish a patient's baseline in order to evaluate recovery.[2] 

Treatment / Management

Most axillary nerve injuries are treatable conservatively; however, select cases should require surgical management. For atraumatic injuries, a baseline EMG should take place within 1 month, and treatment with physical therapy (PT) should commence. In traumatic shoulder injury involving the axillary nerve, most patients may recover with non-operative treatment; however, there is the possibility of permanent paralysis. Surgical intervention can be considered in closed trauma if EMG shows no improvement after 3 months; however, acute nerve lesions warrant expedited surgical management. Neurorrhaphy, neurolysis, and nerve grafting are all possible surgical options. In patients with chronic muscle atrophy, muscle transfer may be a therapeutic option.[2]

Differential Diagnosis

The following should be potential differentials when considering an axillary nerve lesion[2][15]:

  • Cervical radiculopathy
  • Thoracic outlet syndrome
  • Rotator cuff tear
  • Brachial plexopathy
  • Quadrilateral space syndrome
  • Brachial neuritis
  • Glenohumeral fracture/dislocation
  • Subacromial impingement syndrome
  • Herpes zoster

Prognosis

Most injuries to the axillary nerve are considered low-grade following glenohumeral dislocation and will often result in complete recovery within 7 months.[8] A systematic review showed 85% of nerve graft patients and 79% of nerve transfer patients reached muscle strength grades 4/5 or greater at 18 to 24 months post-op.[16]

Complications

Chronic axillary nerve lesions result in permanent numbness to the lateral shoulder region, atrophy of the deltoid and teres minor muscles, and possibly chronic neuropathic pain.

Postoperative and Rehabilitation Care

Rehabilitation Care:

Frizziero et al. developed a rehabilitation protocol for axillary nerve injury which divides into two phases over two months. The initial phase focused on restoration of scapular kinesis, glenohumeral stabilization, and strengthening of the deltoid muscle. The second phase focused on a return to function with particular attention to motor, postural, and proprioceptive control.[17]

Deterrence and Patient Education

Patient Education[8][18]:

  • The axillary nerve is the most common damaged nerve in glenohumeral dislocation
  • Low-grade axillary nerve injuries should resolve within 12 weeks
  • High-grade axillary nerve injuries require surgical intervention
  • Athletes in contact sports are at an increased risk of axillary nerve injury by traumatic processes that result in compression and lesion

Enhancing Healthcare Team Outcomes

Injury to the axillary nerve is a serious and common complication of glenohumeral dislocation. Complex dislocations (those associated with secondary injury to other bones, nerves, vessels, or tendons) should be identified as soon as possible by the primary care provider and nurse practitioner to minimize long-term deficits. Studies have shown an increased risk of axillary nerve injuries if dislocations have not been reduced within 12 hours. If prolonged axillary nerve deficits persist, surgical intervention is required, with better results seen with early intervention.[8] Iatrogenic axillary nerve injury is also commonly reported during surgical osteosynthesis, especially when utilizing the anterolateral approach.[19] Koshy et al. found no significant differences in post-op muscle strength recovery to 4/5 between patients undergoing surgical nerve transfers versus nerve grafting.[16]

Management of axillary nerve injuries is best with an interprofessional, multi-disciplinary team, including physicians/mid-level practitioners, nursing, and physical therapists, and in cases where medication is part of the regimen, pharmacists as well.


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    Contributed by Joseph Tessler, DO
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Axillary Nerve Injury - Questions

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A 25-year-old male presents to the physician's clinic following an automobile accident 6 months ago. On physical examination, the provider notices the asymmetry between the left and right deltoid muscles. Which of the following nerves has been paralyzed?

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Your patient has fallen and dislocated his shoulder joint. In an effort to test the function of the nerve which is related to the surgical neck of the humerus, and remembering that you cannot expect him to contract any muscle which acts across his dislocated shoulder, you test the sensation of the skin:



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A 17-year-old female presents to the emergency department due to a traumatic injury from skateboarding. Her initial shoulder radiographs reveal a humeral fracture at the level of surgical neck. It is suspected that she has also suffered a nerve lesion. Which activity might the patient have trouble engaging in?



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A patient is brought into the emergency room at the county hospital with a gunshot wound through his posterior axillary fold close to the humerus. The wound is bleeding profusely, and the patient cannot lift his arm away from the side of his body. Examination indicates that the deltoid muscle is paralyzed and there is sensory loss of the proximal lateral upper extremity. Pain on movement is not excessive. What is the probable explanation?



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A 33-year-old male presents to the clinic with a chief complaint of right arm weakness for 1 week. Patient states he was playing flag football when a player on the opposing team accidentally tackled him to the ground on his right side. On physical exam, the patient has difficulty sustaining shoulder abduction but has no trouble initiating the action. All other shoulder movements appear normal. Given the presentation, where might the patient perceive decreased sensation to light touch?



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A 33-year-old male presents to the clinic today with a chief complaint of left shoulder weakness for 3 months. The patient states he works in construction and had an incident where some equipment was swung and accidentally hit him in the back of the shoulder. Radiographs taken at the time were negative for an acute fracture. On exam, the patient has a positive external rotation lag sign and positive Bertelli sign. The patient has full passive range of motion of the shoulder. What is the best initial diagnostic test to order at this time?



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Axillary Nerve Injury - References

References

Isaacs J,Cochran AR, Nerve transfers for peripheral nerve injury in the upper limb. The bone     [PubMed]
Steinmann SP,Moran EA, Axillary nerve injury: diagnosis and treatment. The Journal of the American Academy of Orthopaedic Surgeons. 2001 Sep-Oct;     [PubMed]
Moser T,Lecours J,Michaud J,Bureau NJ,Guillin R,Cardinal É, The deltoid, a forgotten muscle of the shoulder. Skeletal radiology. 2013 Oct;     [PubMed]
Williams MD,Edwards TB,Walch G, Understanding the Importance of the Teres Minor for Shoulder Function: Functional Anatomy and Pathology. The Journal of the American Academy of Orthopaedic Surgeons. 2018 Mar 1;     [PubMed]
Wheelock M,Clark TA,Giuffre JL, Nerve Transfers for Treatment of Isolated Axillary Nerve Injuries. Plastic surgery (Oakville, Ont.). 2015 Summer;     [PubMed]
Bokor DJ,Raniga S,Graham PL, Axillary Nerve Position in Humeral Avulsions of the Glenohumeral Ligament. Orthopaedic journal of sports medicine. 2018 Dec;     [PubMed]
Wade MD,McDowell AR,Ziermann JM, Innervation of the Long Head of the Triceps Brachii in Humans-A Fresh Look. Anatomical record (Hoboken, N.J. : 2007). 2018 Mar;     [PubMed]
Seror P, Neuralgic amyotrophy. An update. Joint, bone, spine : revue du rhumatisme. 2017 Mar;     [PubMed]
Sato T,Tsai TL,Altamimi A,Tsai TM, Quadrilateral Space Syndrome: A Case Report. The journal of hand surgery Asian-Pacific volume. 2017 Mar;     [PubMed]
Bertelli JA,Ghizoni MF, Abduction in internal rotation: a test for the diagnosis of axillary nerve palsy. The Journal of hand surgery. 2011 Dec;     [PubMed]
Werthel JD,Bertelli J,Elhassan BT, Shoulder function in patients with deltoid paralysis and intact rotator cuff. Orthopaedics     [PubMed]
Collin P,Treseder T,Denard PJ,Neyton L,Walch G,Lädermann A, What is the Best Clinical Test for Assessment of the Teres Minor in Massive Rotator Cuff Tears? Clinical orthopaedics and related research. 2015 Sep;     [PubMed]
Avis D,Power D, Axillary nerve injury associated with glenohumeral dislocation: A review and algorithm for management. EFORT open reviews. 2018 Mar;     [PubMed]
Aktas I,Akgun K,Gunduz OH, Axillary mononeuropathy after herpes zoster infection mimicking subacromial impingement syndrome. American journal of physical medicine     [PubMed]
Van Eijk JJ,Groothuis JT,Van Alfen N, Neuralgic amyotrophy: An update on diagnosis, pathophysiology, and treatment. Muscle     [PubMed]
Koshy JC,Agrawal NA,Seruya M, Nerve Transfer versus Interpositional Nerve Graft Reconstruction for Posttraumatic, Isolated Axillary Nerve Injuries: A Systematic Review. Plastic and reconstructive surgery. 2017 Nov;     [PubMed]
Kongcharoensombat W,Wattananon P, Risk of Axillary Nerve Injury in Standard Anterolateral Approach of Shoulder: Cadaveric Study. Malaysian orthopaedic journal. 2018 Nov;     [PubMed]
Perlmutter GS,Leffert RD,Zarins B, Direct injury to the axillary nerve in athletes playing contact sports. The American journal of sports medicine. 1997 Jan-Feb;     [PubMed]
Frizziero A,Vittadini F,Del Felice A,Creta D,Ferlito E,Gasparotti R,Masiero S, Conservative treatment after axillary nerve re-injury in a rugby player: a case report. European journal of physical and rehabilitation medicine. 2018 Dec 21;     [PubMed]

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