eMedicine Specialties > Radiology > Chest

Diaphragm, Injury and Paresis

Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR, LRCP, Chairman of Medical Imaging, Professor of Radiology, NGHA, King Fahad National Guard Hospital, King Abdulaziz Medical City, Riyadh, Saudi Arabia
Sarah Al Ghanem, MBBS, Consulting Staff, Department of Medical Imaging, King Fahad National Guard Hospital, Saudi Arabia; Klaus L Irion, MD, PhD, Consulting Staff, The Cardiothoracic Centre Liverpool NHS Trust, The Royal Liverpool University Hospital, UK; Sumaira MacDonald, MBChB, PhD, MRCP, FRCR, Lecturer, Sheffield University Medical School; Endovascular Fellow, Sheffield Vascular Institute; Claire Barker, MB, ChB, FRCR, Consultant Radiologist, Christie Hospital, NHS Trust, UK
Contributor Information and Disclosures

Updated: Dec 1, 2008

Introduction

Background

Diaphragm injuries can be caused by both penetrating and blunt thoracoabdominal trauma. Diaphragmatic injury is thought to result from an abrupt increase in intra-abdominal pressure during blunt trauma. This leads to a clinically significant increase in the pressure gradient between the pleural and peritoneal cavities.^{1, 2, 3, 4, 5, 6}

Approximately 80-90% of diaphragm injuries are related to automobile accidents; falls or crush injuries to the diaphragm are rarer causes. Indeed, a lateral-impact automobile accident is 3 times more likely than any other impact to result in diaphragmatic rupture. The mechanism of injury is thought to involve distortion of the thoracic wall and ipsilateral diaphragmatic shearing.^{7, 8, 9}

Tears of the diaphragm typically originate at the musculotendinous junction, mostly in the posterolateral aspect of the hemidiaphragms. Some 64-87% of these tears are on the left side. This finding is thought to represent either relative weakness of the left hemidiaphragm compared with the right hemidiaphragm or the protective effect of the liver on the right side. Irrespective of the cause, right-sided rupture is associated with increased severity of injury and, therefore, increased mortality and morbidity rates.¹⁰

Patients with large diaphragmatic defects have critical problems shortly after trauma as a result of disturbed cardiorespiratory function associated with large herniation of abdominal contents into the pleural space. Other patients may be asymptomatic or have vague symptoms, which may cause the diagnosis to be delayed. Negative intrathoracic pressure during respiration presumably causes gradual herniation of the abdominal organs into the thorax and enlargement of the defect. The patient is at risk of strangulation, obstruction, and other life-threatening disorders if the diaphragmatic injury is not repaired. Penetrating injuries can produce small lacerations in the diaphragm. Organ herniation is uncommon, although not as uncommon as first thought.^{11, 12, 13, 14}

The most frequent cause of paralysis of the diaphragm is birth trauma or a postoperative complication as a result of cardiovascular surgery. Infections and tumors are less common causes of diaphragmatic paralysis. The consequence of diaphragmatic paralysis may be respiratory insufficiency. Diaphragmatic eventration, on the contrary, involves weakness or complete disappearance of the muscle fibers of the diaphragm. Eventration may be acquired with involvement of the phrenic nerve. It may also be associated with malformations; in this event, the prognosis is more guarded than it would be otherwise.^{15, 16, 17, 18}

Related eMedicine topics:
Diaphragmatic Injuries
Diaphragmatic Paralysis
Diaphragmatic Hernias

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Presentation

Demographics
 
The overall incidence of diaphragmatic injury is 0.8-5.8% in cases of blunt trauma (2.5-5% in cases of blunt abdominal trauma, and 1.5% in cases of blunt thoracic trauma).¹⁹

The incidence of diaphragmatic paresis in adults is not known. In infants, diaphragmatic paresis has been reported in 5-9% of brachial plexus injuries.

About 80-90% of cases are associated with injuries of the brachial plexus. Approximately 80% of lesions involve the left side; less than 10% are bilateral.

Mortality and morbidity are primarily related to the cause of diaphragmatic injury or paralysis and unilateral or bilateral involvement.

• In the newborn, the prognosis in diaphragmatic paralysis is not favorable, with an overall mortality rate of 10-15% for unilateral involvement and a rate close to 50% for bilateral involvement.²⁰
• About 50-60% of patients recover within the first 6-12 months of life. If recovery is to occur, improvement is seen within 2 weeks.

Diaphragmatic paralysis, eventration, or rupture can affect individuals of any age.

The diaphragm works in conjunction with the simultaneous contraction of the respiratory accessory muscles (the scalene, the parasternal portion of the internal and external intercostal muscles, the sternocleidomastoid, and the trapezius). The diaphragm also has an important role in speech, defecation, and parturition.

The peripheral muscular section is arranged into 3 groups of muscle fibers:

• A vertebral component arising from the crura and arcuate ligaments.
• A costal component arising from the inner aspects of the lower 6 ribs and costal cartilages.
• A sternal component arising from the deep surface of the sternum.

The 2 crura anchor the diaphragm to the spine. The right crus of the diaphragm arises from the anterior aspect of the first 3 lumbar vertebral bodies and the associated intervertebral disks. The left crus is attached to the first 2 vertebral bodies and disks. The arcuate ligaments are made up of a series of fibrous arches. The median arcuate ligament is formed by the medial fibrous borders of the 2 crura and the anterior surface of the aorta. Thickening of the fascia covering the psoas major muscle forms the medial arch. The lateral arch represents the fascia covering the quadratus lumborum muscle.

The diaphragm has 3 main openings:

• The aortic opening is at the level of the 12th thoracic vertebra and transmits the aorta, the thoracic duct, and often, the azygos vein.
• The esophageal opening is between the muscular fibers of the right diaphragmatic crus, usually at the level of the 10th dorsal vertebra and slightly to the left of midline. This opening transmits the esophagus, the vagi, and the branches of the left gastric artery and vein.
• The opening of the inferior vena cava (IVC) in the right side of the central aponeurosis at the level of the eighth or ninth dorsal vertebra transmits the IVC and the right phrenic nerve.

Embryologic development of the diaphragm is complex. As a result, several that can give rise to a variety of congenital hernias may occur, including herniation of upper abdominal contents through the canal of Morgagni, located anteriorly between the xiphoid and the costal margins; herniation through the posteriorly placed pleuroperitoneal canal (Bochdalek foramen); herniation through a deficient central tendon; and herniation through a congenitally large esophageal hiatus. Herniation through the central tendon is occasionally traumatic, particularly after steering-column injuries.¹³

Most humps represent localized eventration or simple herniation, but a variety of causes should be considered.

Presentation and natural history

Diaphragmatic paralysis may be bilateral or unilateral. In bilateral diaphragmatic paralysis, the accessory respiratory muscles assume some or all of the work of respiration by increasing their intensity of contraction. This increased workload on the accessory muscles may lead to muscle fatigue and respiratory failure. Bilateral diaphragmatic paralysis is characterized by profound abnormalities of pulmonary and respiratory muscle function. Patients with this condition develop severe restrictive ventilatory impairment, and their vital capacity and total lung capacity are often below 50% of that predicted for the patient. Lung capacity is further reduced when the patient assumes the supine position. The particular symptoms depend on whether the paralysis is unilateral or bilateral, on how rapid the paralysis occurs, and on the presence of underlying pulmonary disease.^{22, 23, 24, 25, 26}

The causes of unilateral diaphragmatic paralysis are many. The most common cause in adults is tumoral involvement of the phrenic nerve. In children, birth trauma and cardiorespiratory surgery are the most common causes. Diaphragmatic paralysis occasionally occurs as a complication of neurologic disease. Injury to the phrenic nerve from trauma to the thorax or cervical spine and pressure on the phrenic nerve from a substernal thyroid or aortic aneurysm can also cause diaphragmatic paralysis. Infectious disease involving the lungs, pleura, and/or mediastinum may result in temporary or permanent diaphragmatic paralysis. Finally, diaphragmatic paralysis may be idiopathic.^{10, 27, 28, 29}

Blunt or penetrating trauma to the abdomen can cause diaphragmatic rupture. Direct laceration may result from a penetrating object or from a fragment of a fractured rib. Diaphragmatic rupture is not a common finding in blunt abdominal trauma, and it may be overlooked because the dominant clinical symptoms may be related to other associated injuries.^{3, 30, 31, 32}

Dervisoglu et al described a case of a spontaneous rupture into the pleural space of a giant diaphragmatic hydatid cyst. The patient was admitted for dyspnea, nausea, vomiting, and right-sided thoracic pain. The diagnosis was reached by clinical findings, laboratory, and radiologic examinations (including a multislice computed tomography [CT] scan). This case shows that hydatid cysts of the diaphragm can spontaneously rupture into the intrapleural space.³³
 
About 80-90% of clinically diagnosed cases of diaphragmatic rupture involve the left diaphragm.³⁴


Unilateral diaphragmatic paralysis

Unilateral diaphragmatic paralysis is often discovered incidentally in patients undergoing chest radiography for some unrelated reason. Patients are usually asymptomatic at rest but have dyspnea on exertion and decreased exercise tolerance. If the patient has an underlying lung disease, dyspnea may occur at rest. Some patients may develop orthopnea, which is less intense than that observed with bilateral diaphragmatic paralysis.

Causes of unilateral diaphragmatic paralysis include the following:

• Tumoral invasion and/or compression of the phrenic nerve are the most common causes in adults, occurring in approximately 30% of patients.²⁷
• Other lesions near the phrenic nerve, such as pneumonia, pleurisy, aortic aneurysm, and retrosternal goiter, may be involved.
• Herpes zoster, cervical spondylosis, infection, vasculitis, and diabetes mellitus (which may be caused by peripheral neuropathy of the phrenic nerve) have been reported.
• Iatrogenic or surgical trauma is common and may result from thoracic surgery, manipulation of the cervical spine, central venous catheterization, or cardiac surgery.³⁵
• Idiopathic causes are possible.

Bilateral diaphragmatic paralysis

Patients with bilateral diaphragmatic paralysis present with respiratory failure or dyspnea, which may be clinically confused with heart failure. The dyspnea worsens when the patient is in the supine position. Tachypnea and rapid shallow breathing occurs when the patient is recumbent. Patients may also complain of anxiety, insomnia, morning headache, excessive daytime somnolence and fatigue, and poor sleep habits.²⁶

Patients are often tachypneic and use their accessory respiration muscles. A characteristic physical finding is a paradoxical inward movement of the abdomen with inspiration. The clinician should aim at diagnosing diaphragmatic paralysis and at evaluating its underlying cause, which will determine the ultimate management and prognosis.^{15, 36, 37, 38}

Traumatic diaphragmatic rupture

After abdominal and/or thoracic trauma, the diagnosis of traumatic diaphragmatic rupture (TDR) must always be considered, as diaphragmatic injuries occur in 0.8-8% of patients with blunt trauma. In fact, diaphragmatic injury is a predictor of the severity of injury in such patients; however, mortality usually results from other injuries rather than from the diaphragmatic injury itself. Moreover, TDR should be suspected when chest radiographic findings are abnormal. These imaging findings are 90% specific if visceral herniation has occurred in patients with multiple injuries.^{39, 40, 41, 42}

Predictors of mortality from diaphragmatic rupture after blunt trauma are age, injury severity score, and hemodynamic status.^{30, 43}

Diaphragmatic paralysis in the newborn

Diaphragmatic paralysis may occur in isolation or in association with injury to the brachial plexus. Causes that are rare in the newborn include spinal cord injury and neuromuscular disease. In the newborn, cardiac surgery for congenital heart disease is associated with a 0.5-1.5% incidence of diaphragmatic paralysis. Difficult extractions and breech delivery are the 2 most common precipitating causes of diaphragmatic paralysis in the newborn.^{20, 18, 29, 42}

Respiratory compromise affects infants more often than older children or adults. This is the result of a variety of factors, including poor intercostal muscle development, the ascending diaphragm (which reduces vital capacity), the infant's recumbent position, increased mediastinal mobility (which allows for compression of the contralateral lung), and the small caliber of the infant bronchial tree.

The clinical course of diaphragmatic paralysis is often biphasic. Immediately after birth and during the first hours of life, the patient has respiratory difficulty (often tachypnea), increasing oxygen need, hypercarbia, atelectasis, and a mediastinal shift. Pneumonitis eventually develops. During the next few days, the neonates' respiratory status may improve or stabilize. In severe cases, deterioration may recur over days to weeks; atelectasis or infection often provokes the progression.

Diaphragmatic paralysis in the newborn is clinically suspected when unexplained respiratory symptoms are present, especially when delivery was difficult or when a child undergoes thoracic surgery.

Paralysis of the diaphragm normally heals within a few weeks as long as permanent damage to the phrenic nerve has not occurred. The most frequent cause is birth trauma or a postoperative complication (eg, as a result of cardiovascular surgery). The consequence may be respiratory insufficiency; however, technical progress has improved respiratory reanimation. The indications for surgical plication are becoming rare.27, 44, 45

Diaphragmatic eventration involves atrophy or the complete disappearance of the muscle fibers of the diaphragm. More than two thirds of cases of eventration require surgical treatment. Eventration may result from an acquired affliction leading to permanent destruction of the phrenic nerve. It may also be associated with malformations; in this event, the prognosis is more guarded. Phrenic nerve stimulation may help in determining the prognosis. The goal of care is to provide ventilatory support to patients with bilateral diaphragmatic paralysis to prevent progressive respiratory failure and death. Unless a potentially fatal comorbid illness threatens the prognosis of the patient with unilateral diaphragmatic paralysis, death from respiratory insufficiency does not occur.^{46, 47, 48, 49}

Huault et al concluded that traumatic diaphragmatic hernias are usually associated with serious injuries in children. They stressed the importance of combining a high index of suspicion with imaging in patients at risk. Palpation and/or visualization of both diaphragms at laparotomy were extremely important for detecting these injuries when they were not suspected preoperatively.⁵⁰

Differential Diagnoses

Other Problems to Be Considered

The following diagnoses may be difficult to differentiate from bilateral diaphragmatic paralysis: 

• Alveolar hypoventilation is caused by disease of the brainstem or high cervical spine. Patients have normal respiratory muscle strength and can voluntarily hyperventilate to lower PaCO₂.
• Anterior horn cells and neuromuscular junction diseases may be difficult to differentiate from phrenic-nerve dysfunction.

References