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Phrenic Nerve Injury

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Last Update: August 13, 2020.

Continuing Education Activity

The phrenic nerve is among the most important nerves in the body due to its role in respiration. The phrenic nerve provides the primary motor supply to the diaphragm, the major respiratory muscle. Phrenic nerve injury, such as may occur from cardiothoracic surgery, can lead to diaphragmatic paralysis or dysfunction. The presentation of phrenic nerve injury is non-specific, and the diagnosis may easily be missed. Phrenic nerve injury can be identified by a number of imaging modalities including ultrasound, electromyography, and fluoroscopy. This activity reviews the etiology, presentation, evaluation, and management of phrenic nerve injuries and reviews the role of the interprofessional team in evaluating, diagnosing, and managing the condition.

Objectives:

  • Describe the pathophysiology and various potential etiologies of phrenic nerve injury.
  • Outline the evaluation and differential diagnoses for a patient presenting with suspected phrenic nerve injury.
  • Summarize the possible treatment options for phrenic nerve injury based on specific etiology.
  • Explain the importance of improving care coordination among the interprofessional team to improve outcomes for patients with an injury to the phrenic nerve.
Earn continuing education credits (CME/CE) on this topic.

Introduction

The phrenic nerve is among the most important nerves in the body due to its role in respiration. The phrenic nerve provides the primary motor supply to the diaphragm, the major respiratory muscle. Phrenic nerve injury, such as may occur from cardiothoracic surgery, can lead to diaphragmatic paralysis or dysfunction. The presentation of phrenic nerve injury is non-specific, and the diagnosis may easily be missed. Phrenic nerve injury can be identified by a number of imaging modalities including ultrasound, electromyography, and fluoroscopy[1]

Ultrasound is ideal and emerging as a diagnostic test for this condition as the modality is non-invasive, poses no risk of ionizing radiation, is easily reproducible, low cost and may be performed at the bedside. This is especially ideal for critical patients. Ultrasound is more commonly being used to evaluate phrenic nerve injury due to its ability to evaluate the function and structure of the diaphragm. Ultrasound of the diaphragm can help clinicians identify diseases caused by phrenic nerve injury including diaphragmatic paralysis and diaphragmatic dysfunction. Ultrasound can sometimes identify the etiology behind the disease and provide data for determining prognosis[2]. Diaphragmatic ultrasound is also useful in the assessment of prolonged mechanical ventilation and assessment of the failure of weaning from mechanical ventilation[3]. This modality can additionally help select patients for early surgical plication (which can decrease intensive care unit length of stay and ventilator-associated pneumonia)[4].

Etiology

Injury of the phrenic nerve can occur by multiple mechanisms. One common etiology of phrenic nerve injury is from surgery, primarily thoracic and cardiac surgery[5]. The left phrenic nerve descends anteriorly between the pericardium and mediastinal pleura. Therefore, it can be injured while dissecting near the area of an internal thoracic artery. Canbaz et al. identified that a major factor that causes injury during cardiac surgery is the icy slush that is used for myocardial protection. The phrenic nerve can also be damaged from blunt or penetrating trauma[6], metabolic diseases like diabetes[7], infectious causes such as Lyme disease and herpes zoster[8][9], direct invasion by tumor[10], neurological diseases such as cervical spondylosis and multiple sclerosis, myopathy (i.e., muscular dystrophy) and immunological disease (e.g., Guillain-Barre syndrome)[11]

Phrenic nerve injury may present as diaphragmatic dysfunction, unilateral diaphragmatic paralysis, or bilateral diaphragmatic paralysis. One of the most frequent causes of unilateral diaphragmatic paralysis is iatrogenic. In bilateral diaphragmatic paralysis, one of the most common causes is a motor neuron disease, including amyotrophic lateral sclerosis and post-polio syndrome[12].

Epidemiology

Few studies have shown that diaphragmatic paralysis occurs more often in male individuals. Scharf et al. found that 1% to 7% of patients with significant blunt trauma present with a diaphragmatic injury. Up to 3% of abdominal injuries also involve the diaphragm[13].

History and Physical

The diagnosis of phrenic nerve injury requires high suspicion due to nonspecific signs and symptoms including unexplained shortness of breath, recurrent pneumonia, anxiety, insomnia, morning headache, excessive daytime somnolence, orthopnea, fatigue, and difficulty weaning from mechanical ventilation. In unilateral diaphragmatic paralysis, the patient is often asymptomatic at rest and has dyspnea only during exertion. This unilateral diaphragmatic paralysis is typically found incidentally on chest radiograph[10][14][15]. In comparison, patients with bilateral diaphragmatic paralysis always present with shortness of breath[15][16][17][18][19].

On physical examinations, findings may include decreased breath sounds on the affected side, dullness to percussion of the affected side of the chest and inward movement of the epigastrium during inspiration.

Evaluation

Phrenic nerve injury can be evaluated with multiple modalities, for example, esophageal and gastric manometry, diaphragmatic electromyography or ultrasound. Diaphragmatic ultrasound is primarily performed with a low-frequency curvilinear transducer. A high-frequency linear transducer is the best choice for an intercostal view since it has a small footprint that can fit between the ribs.

Patients are typically examined in the supine position during spontaneous inspiration and expiration. The pleural and peritoneal membranes should be visualized during imaging of the diaphragm for thickness measurements. The supine position limits any compensatory active expiration by the anterior abdominal wall, which may mask paralysis[20].

On ultrasound, the diaphragm appears as a thick echogenic line[21]. The left hemidiaphragm can be evaluated through the splenic window. The right hemidiaphragm is visualized through the liver window. Interestingly, pathologic conditions such as a left upper quadrant mass, splenomegaly or hepatomegaly may make an evaluation of the left hemidiaphragm easier[22]. Diagnostic criteria for diaphragmatic paralysis include paradoxical movement or significantly decreased diaphragmatic excursion[23].

Diaphragm thickness and thickening during respiration can be assessed with ultrasound, typically with a high-frequency linear transducer. The ultrasound transducer is placed at the anterior axillary line between the seventh and eighth or eighth and ninth ribs, which is the Zone of Apposition (ZOA). Diaphragm thickness can be used to assess for atrophy, especially as might occur while on mechanical ventilation. Diaphragmatic thickness values less than 0.2 cm at the end of expiration are considered to define diaphragmatic atrophy. In healthy volunteers, the average thickness of the diaphragm is typically between 0.22 to 0.28 cm, however in a paralyzed diaphragm, the diaphragmatic thickness is reported to be less, between 0.13 to 0.19 cm. The Thickening Fraction can also be calculated and used as a predictor of success of weaning from mechanical ventilation[24][25][24].

Treatment / Management

Most patients with asymptomatic unilateral diaphragmatic paralysis do not require treatment. When identified, the underlying cause should be treated[26]. Surgical options are considered if the underlying cause is treated and the patient still has symptoms, or if the patient has bilateral diaphragmatic paralysis. There are various treatment options including plication and phrenic nerve stimulation. Plication of the affected site is a very useful treatment method that allows weaning from mechanical ventilation. Plication is preferably performed in unilateral diaphragmatic paralysis in non-morbidly obese patients[27].  Phrenic nerve stimulation is performed in intact phrenic nerve without evidence of myopathy. This procedure can be performed in patients with bilateral diaphragmatic paralysis with cervical spine injuries[28].

Differential Diagnosis

Since the symptoms of phrenic nerve injury are not specific, we have to consider all causes of shortness of breath including pulmonary, cardiac, metabolic, and hematologic causes. In bilateral diaphragmatic paralysis, the following additional diagnoses should be considered: anterior horn cells and neuromuscular junction diseases[29].  Hypoventilation secondary to cervical spine disease is also difficult to differentiate from phrenic nerve dysfunction.

Prognosis

The mortality and morbidity of phrenic nerve injury or diaphragmatic paralysis depend on the underlying causes and status of pulmonary function[26]. Generally speaking, unilateral diaphragmatic paralysis has a good prognosis unless the patient is experiencing severe shortness of breath. If recovery occurs in bilateral diaphragmatic paralysis, it usually takes more than one year for partial or full recovery[19][30].

Enhancing Healthcare Team Outcomes

There is potentially significant mortality and morbidity associated with phrenic nerve injury. Recovery is heavily dependent on an interprofessional effort of nurses, respiratory therapists, and clinicians educating and motivating the patients while providing quality care.

Continuing Education / Review Questions

Chest x-ray of a patient who sustained traumatic root avulsion brachial plexus injury

Figure

Chest x-ray of a patient who sustained traumatic root avulsion brachial plexus injury. Note the elevated right hemidiaphragm indicating associated phrenic nerve injury. The patient also sustained fractures to the right midshaft clavicle and right 1st (more...)

CXR demonstrating right clavicle fracture, elevated right hemi-diaphragm associated with phrenic nerve injury

Figure

CXR demonstrating right clavicle fracture, elevated right hemi-diaphragm associated with phrenic nerve injury. Contributed by Zhongyu Li, MD PhD

References

1.
Houston JG, Fleet M, Cowan MD, McMillan NC. Comparison of ultrasound with fluoroscopy in the assessment of suspected hemidiaphragmatic movement abnormality. Clin Radiol. 1995 Feb;50(2):95-8. [PubMed: 7867276]
2.
Yeh HC, Halton KP, Gray CE. Anatomic variations and abnormalities in the diaphragm seen with US. Radiographics. 1990 Nov;10(6):1019-30. [PubMed: 2259759]
3.
Kim WY, Suh HJ, Hong SB, Koh Y, Lim CM. Diaphragm dysfunction assessed by ultrasonography: influence on weaning from mechanical ventilation. Crit Care Med. 2011 Dec;39(12):2627-30. [PubMed: 21705883]
4.
Kunovsky P, Gibson GA, Pollock JC, Stejskal L, Houston A, Jamieson MP. Management of postoperative paralysis of diaphragm in infants and children. Eur J Cardiothorac Surg. 1993;7(7):342-6. [PubMed: 8396949]
5.
Tripp HF, Bolton JW. Phrenic nerve injury following cardiac surgery: a review. J Card Surg. 1998 May;13(3):218-23. [PubMed: 10193993]
6.
Bell D, Siriwardena A. Phrenic nerve injury following blunt trauma. J Accid Emerg Med. 2000 Nov;17(6):419-20. [PMC free article: PMC1725484] [PubMed: 11104246]
7.
White JE, Bullock RE, Hudgson P, Home PD, Gibson GJ. Phrenic neuropathy in association with diabetes. Diabet Med. 1992 Dec;9(10):954-6. [PubMed: 1478044]
8.
Derveaux L, Lacquet LM. Hemidiaphragmatic paresis after cervical herpes zoster. Thorax. 1982 Nov;37(11):870-1. [PMC free article: PMC459448] [PubMed: 6298966]
9.
Abbott RA, Hammans S, Margarson M, Aji BM. Diaphragmatic paralysis and respiratory failure as a complication of Lyme disease. J Neurol Neurosurg Psychiatry. 2005 Sep;76(9):1306-7. [PMC free article: PMC1739811] [PubMed: 16107377]
10.
Piehler JM, Pairolero PC, Gracey DR, Bernatz PE. Unexplained diaphragmatic paralysis: a harbinger of malignant disease? J Thorac Cardiovasc Surg. 1982 Dec;84(6):861-4. [PubMed: 6292583]
11.
Gibson GJ. Diaphragmatic paresis: pathophysiology, clinical features, and investigation. Thorax. 1989 Nov;44(11):960-70. [PMC free article: PMC462156] [PubMed: 2688182]
12.
Czapliński A, Strobel W, Gobbi C, Steck AJ, Fuhr P, Leppert D. Respiratory failure due to bilateral diaphragm palsy as an early manifestation of ALS. Med Sci Monit. 2003 May;9(5):CS34-6. [PubMed: 12761460]
13.
Al-Thani H, Jabbour G, El-Menyar A, Abdelrahman H, Peralta R, Zarour A. Descriptive Analysis of Right and Left-sided Traumatic Diaphragmatic Injuries; Case Series from a Single Institution. Bull Emerg Trauma. 2018 Jan;6(1):16-25. [PMC free article: PMC5787359] [PubMed: 29379805]
14.
Lisboa C, Paré PD, Pertuzé J, Contreras G, Moreno R, Guillemi S, Cruz E. Inspiratory muscle function in unilateral diaphragmatic paralysis. Am Rev Respir Dis. 1986 Sep;134(3):488-92. [PubMed: 3752705]
15.
Hart N, Nickol AH, Cramer D, Ward SP, Lofaso F, Pride NB, Moxham J, Polkey MI. Effect of severe isolated unilateral and bilateral diaphragm weakness on exercise performance. Am J Respir Crit Care Med. 2002 May 01;165(9):1265-70. [PubMed: 11991876]
16.
Laroche CM, Carroll N, Moxham J, Green M. Clinical significance of severe isolated diaphragm weakness. Am Rev Respir Dis. 1988 Oct;138(4):862-6. [PubMed: 3202460]
17.
Sandham JD, Shaw DT, Guenter CA. Acute supine respiratory failure due to bilateral diaphragmatic paralysis. Chest. 1977 Jul;72(1):96-8. [PubMed: 872664]
18.
Kumar N, Folger WN, Bolton CF. Dyspnea as the predominant manifestation of bilateral phrenic neuropathy. Mayo Clin Proc. 2004 Dec;79(12):1563-5. [PubMed: 15595343]
19.
Hughes PD, Polkey MI, Moxham J, Green M. Long-term recovery of diaphragm strength in neuralgic amyotrophy. Eur Respir J. 1999 Feb;13(2):379-84. [PubMed: 10065685]
20.
Houston JG, Angus RM, Cowan MD, McMillan NC, Thomson NC. Ultrasound assessment of normal hemidiaphragmatic movement: relation to inspiratory volume. Thorax. 1994 May;49(5):500-3. [PMC free article: PMC474874] [PubMed: 8016774]
21.
Nason LK, Walker CM, McNeeley MF, Burivong W, Fligner CL, Godwin JD. Imaging of the diaphragm: anatomy and function. Radiographics. 2012 Mar-Apr;32(2):E51-70. [PubMed: 22411950]
22.
Houston JG, Morris AD, Howie CA, Reid JL, McMillan N. Technical report: quantitative assessment of diaphragmatic movement--a reproducible method using ultrasound. Clin Radiol. 1992 Dec;46(6):405-7. [PubMed: 1493655]
23.
Fayssoil A, Behin A, Ogna A, Mompoint D, Amthor H, Clair B, Laforet P, Mansart A, Prigent H, Orlikowski D, Stojkovic T, Vinit S, Carlier R, Eymard B, Lofaso F, Annane D. Diaphragm: Pathophysiology and Ultrasound Imaging in Neuromuscular Disorders. J Neuromuscul Dis. 2018;5(1):1-10. [PMC free article: PMC5836400] [PubMed: 29278898]
24.
Wait JL, Nahormek PA, Yost WT, Rochester DP. Diaphragmatic thickness-lung volume relationship in vivo. J Appl Physiol (1985). 1989 Oct;67(4):1560-8. [PubMed: 2676955]
25.
Gottesman E, McCool FD. Ultrasound evaluation of the paralyzed diaphragm. Am J Respir Crit Care Med. 1997 May;155(5):1570-4. [PubMed: 9154859]
26.
Kokatnur L, Rudrappa M. Diaphragmatic Palsy. Diseases. 2018 Feb 13;6(1) [PMC free article: PMC5871962] [PubMed: 29438332]
27.
Simansky DA, Paley M, Refaely Y, Yellin A. Diaphragm plication following phrenic nerve injury: a comparison of paediatric and adult patients. Thorax. 2002 Jul;57(7):613-6. [PMC free article: PMC1746380] [PubMed: 12096205]
28.
DiMarco AF. Phrenic nerve stimulation in patients with spinal cord injury. Respir Physiol Neurobiol. 2009 Nov 30;169(2):200-9. [PubMed: 19786125]
29.
Dubé BP, Dres M. Diaphragm Dysfunction: Diagnostic Approaches and Management Strategies. J Clin Med. 2016 Dec 05;5(12) [PMC free article: PMC5184786] [PubMed: 27929389]
30.
Summerhill EM, El-Sameed YA, Glidden TJ, McCool FD. Monitoring recovery from diaphragm paralysis with ultrasound. Chest. 2008 Mar;133(3):737-43. [PubMed: 18198248]
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Bookshelf ID: NBK482227PMID: 29489218

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