Accessory Nerve (CN XI) Injury


Article Author:
Sanad AlShareef


Article Editor:
Bruce Newton


Editors In Chief:
Rodrigo Kuljis
Oleg Chernyshev
Aninda Acharya


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Avais Raja
Orawan Chaigasame
Carrie Smith
Abdul Waheed
Khalid Alsayouri
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James Hughes
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Nazia Sadiq
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Phillip Hynes
Tehmina Warsi


Updated:
6/2/2019 11:36:26 PM

Introduction

Cranial nerves are attached to the brain and then travel outside the skull via foramina to innervate various structures. Cranial nerve XI is also known as the accessory nerve. According to the morphology characteristics of the cranial root of the accessory nerve, it is made of the union of two to four short filaments, making the cranial roots of the accessory nerve then two to nine rootlets join the spinal root to form the nerve. The cranial roots of CN XI could be possibly considered as part of the vagus nerve when factoring in the function of the two nerves, not only morphology. Both the cranial roots of the accessory nerve and the vagus nerve originate from nucleus ambiguus and dorsal nucleus of the vagus nerve and travel to the laryngeal muscles, supplying the motor fibers.[1] As the accessory nerve travels down and away from the brain, the cranial and spinal pieces of the nerve come together to form the spinal accessory nerve (SAN). The SAN is formed by the fusion of cranial and spinal contributions within the skull base and exits the skull through the jugular foramen adjacent to the vagus nerve.[2] The SAN descends alongside the internal jugular vein, coursing posterior to the styloid process, posterior belly of the digastric muscle, and sternocleidomastoid muscle (SCM) prior to entering the posterior cervical triangle. As the accessory nerve leaves through the jugular foramen along with glossopharyngeal nerve (CN IX) and vagus nerve (CN X), accessory nerve travels to the SCM, either superficial or deep, and then enters trapezius muscle, where a major trunk of the accessory nerve converges with C2, C3, or both. The traveling pathway of this nerve provides a functional significance to the structures in the posterior neck. However, the accessory nerve is prone and vulnerable to injury due to its long and superficial nature, Injury to the accessory nerve could be from blunt trauma, incidental, or most commonly, iatrogenic reasons.[3]

Etiology

The most common cause for cranial nerve 11 injury is iatrogenic, such as lymph node biopsies that involve the posterior triangle of the neck, neck surgeries including removal of tumor, carotid or internal jugular vein surgeries, neck dissection (including radical, selective, and modified), or cosmetic surgery (e.g., facelift) from the mechanical stress exerted on the neck due to positioning throughout the procedure. Other causes are penetrating trauma such as knife or gunshot trauma, blunt trauma from pressure, stress to the neck area, due to a vigorous movement, or acromioclavicular joint dislocation affecting SCM. Other possible sources of injury are neurological causes in which the nerve or the foramen it passes through are affected, leading to CN XI palsy. Examples are a tumor at jugular foramen which causes cranial nerve palsies such as Collet-Sicard syndrome, involving the lower cranial nerves IX, X, XI, and XII, and Vernet syndrome, involving the lower cranial nerves IX, X, and XI.[3] Syringomyelia, brachial neuritis, poliomyelitis, and motor neuron disease are other possible causes of CN XI injury. Other examples are traction palsies to brachial plexus and thoracic outlet.[4][5][6] Due to the various causes of this nerve injury, the age of presentation could be anywhere between a couple of months old to the elderly.

Epidemiology

Cranial nerve XI injury mostly occurs due to iatrogenic causes that involve posterior and lateral cervical triangles surgeries such as lymph biopsy from the area. The high likelihood of SAN injury with posterior and lateral neck surgeries led to exploring the various options with neck dissections such as radical, selective, and modified neck dissections in different studies. According to a retrospective study by Popovski et al., SAN injury rate postoperatively is the highest, with radical neck dissections at 46.7% compared to selective neck dissections at 42.5% and 25% in modified neck dissections.[4][5][6][7] Other studies suggest preservation of other structures such as the nerve, muscles, and veins would lead to fewer dysfunctions compared to more extensive procedures in the neck zones in which only the nerve preserved. Although other causes of cranial nerve XI injury are uncommon, they are explored as part of etiology.

History and Physical

The most common and primary complaint of SAN injury is pain, more specifically, shoulder pain and weakness. Radiation of pain is to the upper back, neck, and ipsilateral arm. Pain is exacerbated with weight on the injured shoulder without being supported. The traction and straining of the muscles rhomboids and levator scapulae that work to compensate for the nerve injury could lead to more pain and decreased strength in the injured side. The combination of the pain and decreased strength would limit the range of motion of the involved shoulder.[3]

The most common sign is the noticeable asymmetry on inspection of the shoulder and upper back. The patient would present with a diminished ability to hold the shoulder in abduction motion, involved-shoulder drooping, and ipsilateral scapular winging (in which medial side of the scapula is more prominent than the unaffected side). A limited active range of motion might eventually progress to a worsening of the passive range of motion causing adhesive capsulitis. Other possible findings are atrophy of trapezius (depending on the length of time of the injury) and internally rotation of the humeral head.

Evaluation

Ultrasound such as high-resolution ultrasonography (HRUS) has been used to confirm the target nerve and visualize the structures surrounding the nerve. Ultrasound is meaningful in detecting some change to the muscles, such as atrophy, and reducing possible damage during the administration of injections and medication to the affected area by guiding to correct targeted area while visualizing with the ultrasound. Ultrasonography is not helpful in detecting the actual transection of the nerve.[2][8]

Moreover, electromyography (EMG) and nerve conduction studies are unnecessary for the diagnosis; however, it would be helpful to distinguish and quantify the degree of damage by doing serial EMGs.

Electromyography (EMG) has shown that the trapezius muscle is the main muscle responsible for shoulder elevation and, by means of its upper bundle, it participates in the arm elevation movement. Nonetheless, this movement also involves the participation of the deltoid, supra-spinal, and infra-spinal muscles. For these reasons, arm elevation paresis secondary to spinal nerve mononeuropathy may be missed by clinicians because the movement may be compensated by the action of the other muscles responsible for arm elevation.[8]

Treatment / Management

The algorithm for management is divided between immediate therapy and delayed management. The severity and the cause of the SAN injury would be factors in determining whether the treatment is surgical, such as reanastomosis and nerve grafting, or nonsurgical, such as nonsteroidal anti-inflammatory drugs (NSAIDs), nerve stimulation and local/ regional nerve blocking and physical therapy and rehabilitation. Immediate therapy should be considered for severe presentation such as penetrating traumas and iatrogenic traumas. In a study in which half of the patients received primary nerve repair and half of the patients received nerve graft,  it was found that the recovery time ranged between 4 to 10 months.[9][10][11] However, one of the most important contributors to a better prognosis is early referral and intervention which leads to a more accurate diagnosis. Also, early operative intervention has better results in regaining functionality; whereas, delayed diagnosis and treatment run the risk of less effective treatment and less predictable results.[9][12][13][14]

Differential Diagnosis

  • Long thoracic nerve injury causing paralysis or weakness of the serratus anterior muscle presents as winging of the scapula that is worse with lift-forward flexion of the arm or pushing the outstretched arm against a wall. This is different from CN XI injury which has winging of the scapula with the abduction of the arm.
  • Rotator cuff injury has a similar presentation when lifting the arm behind the head, except this injury does not present with winging of the scapula.
  • Shoulder girdle arthritis and pain syndrome is absent muscular atrophy and winging of the scapula.
  • Whiplash injury could cause neck pain and cervical spine rigidity and limited neck motion secondary to spasm and pain.

Enhancing Healthcare Team Outcomes

A patient with injury to the SAN may present with neck pain, asymmetrical shoulders, inability shrug the shoulder or weakness in the neck area. It is important for the nurse practitioner and primary care provider to refer this patient to a neurologist to determine the cause and treatment. Coordination of care for the patient with physical therapy and occupational therapy play a significant role in better recovery and improved outcomes.


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Accessory Nerve (CN XI) Injury - Questions

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What are the diseases that can affect the eleventh cranial nerve?



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A 30-year-old athlete presents with a 5-month history of pain in the right side of the neck, ipsilateral anterior shoulder, and chest. On exam, strength testing is normal. Initial radiographs, MRI, and nerve conduction testing of the neck, paraspinal, and trapezius muscles show no pathological changes. What could be the cause of this persistent pain, without signs of decreased muscle strength?



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What is the blood supply, if severed, that would affect the spinal roots of the accessory nerve?



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A 35-year-old male presented with chronic, daily headaches localized to occipital area and radiate to shoulders bilaterally. Symptoms are not responsive to analgesic medications. He reports occasional gait instability and episodes of dizziness. MRI of brain and spine showed Chiari malformation type II. The patient undergoes foramen magnum decompression. At the four weeks follow-up visit, patient reports left-sided shoulder weakness with dropping of the left shoulder. After careful examination, the patient is diagnosed with spinal accessory nerve injury, What could be the cause of the nerve injury in this case?



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A right-handed 40-year-old female with a past medical history of breast cancer stage status post lumpectomy with sentinel lymph node removal two years ago, hypertension, and fibromyalgia presented to the clinic with a chief complaint of right shoulder pain and difficulty raising right arm and shoulder above the head. She noticed the symptoms starting a couple of weeks ago. She denies trauma. She works as an office assistant at a law firm office. She leads mostly a sedentary life. She reports she went on a 3 hours rock climbing trip while carrying heavy climbing gear across her body about a month ago. On physical exam, you notice winging of scapula, and weakened abduction. What is the most likely cause of the CN XI injury?



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A professional baseball player with uncontrolled diabetes presents with an inability to turn his neck and shrug his shoulders. The patient reports the dysfunction started after a lymph node biopsy in the posterior triangle of the neck. Which of the following cranial nerves (CN) is most likely affected?



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Accessory Nerve (CN XI) Injury - References

References

Liu HF,Won HS,Chung IH,Kim IB,Han SH, Morphological characteristics of the cranial root of the accessory nerve. Clinical anatomy (New York, N.Y.). 2014 Nov     [PubMed]
Bodner G,Harpf C,Gardetto A,Kovacs P,Gruber H,Peer S,Mallhoui A, Ultrasonography of the accessory nerve: normal and pathologic findings in cadavers and patients with iatrogenic accessory nerve palsy. Journal of ultrasound in medicine : official journal of the American Institute of Ultrasound in Medicine. 2002 Oct     [PubMed]
Popovski V,Benedetti A,Popovic-Monevska D,Grcev A,Stamatoski A,Zhivadinovik J, Spinal accessory nerve preservation in modified neck dissections: surgical and functional outcomes. Acta otorhinolaryngologica Italica : organo ufficiale della Societa italiana di otorinolaringologia e chirurgia cervico-facciale. 2017 Oct     [PubMed]
Kim DH,Cho YJ,Tiel RL,Kline DG, Surgical outcomes of 111 spinal accessory nerve injuries. Neurosurgery. 2003 Nov     [PubMed]
Bordoni B,Dulebohn SC, Neuroanatomy, Cranial Nerve 11 (Accessory) null. 2018 Jan     [PubMed]
Lanišnik B, Different branching patterns of the spinal accessory nerve: impact on neck dissection technique and postoperative shoulder function. Current opinion in otolaryngology     [PubMed]
Prim MP,De Diego JI,Verdaguer JM,Sastre N,Rabanal I, Neurological complications following functional neck dissection. European archives of oto-rhino-laryngology : official journal of the European Federation of Oto-Rhino-Laryngological Societies (EUFOS) : affiliated with the German Society for Oto-Rhino-Laryngology - Head and Neck Surgery. 2006 May     [PubMed]
Brown H,Burns S,Kaiser CW, The spinal accessory nerve plexus, the trapezius muscle, and shoulder stabilization after radical neck cancer surgery. Annals of surgery. 1988 Nov     [PubMed]
Milenović A,Knežević P,Boras VV,Gabrić D,Rogulj AA,Virag M, [INFLUENCE OF NECK DISSECTION ON THE CORRESPONDING MOTOR AND SENSORY NERVES]. Lijecnicki vjesnik. 2015 Jul-Aug     [PubMed]
Giordano L,Sarandria D,Fabiano B,Del Carro U,Bussi M, Shoulder function after selective and superselective neck dissections: clinical and functional outcomes. Acta otorhinolaryngologica Italica : organo ufficiale della Societa italiana di otorinolaringologia e chirurgia cervico-facciale. 2012 Dec     [PubMed]
Salerno G,Cavaliere M,Foglia A,Pellicoro DP,Mottola G,Nardone M,Galli V, The 11th nerve syndrome in functional neck dissection. The Laryngoscope. 2002 Jul     [PubMed]
Paoloni JA,Milne C,Orchard J,Hamilton B, Non-steroidal anti-inflammatory drugs in sports medicine: guidelines for practical but sensible use. British journal of sports medicine. 2009 Oct     [PubMed]
Göransson H,Leppänen OV,Vastamäki M, Patient outcome after surgical management of the spinal accessory nerve injury: A long-term follow-up study. SAGE open medicine. 2016     [PubMed]
Ronconi G,Spagnolo AG,Ferriero G,Giovannini S,Amabile E,Maccauro G,Ferrara PE, [Case report: Iatrogenic shoulder pain syndrome following spinal accessory nerve injury during lateral cervical neck dissection for tongue cancer: the role of rehabilitation and ethical-deontological issues]. Igiene e sanita pubblica. 2017 May-Jun     [PubMed]

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