Version July 2025
INTRODUCTION —
The most important respiratory muscle is the dome-shaped diaphragm, which separates the thoracic and abdominal cavities and is innervated by the phrenic nerve. Injury to the phrenic nerve associated with birth trauma or cardiothoracic surgery can result in diaphragmatic paralysis, which may lead to respiratory distress in newborns. The initial treatment is supportive, and spontaneous recovery occurs in most cases.
It is useful to review the embryology and physiology of the diaphragm before addressing the clinical features, diagnosis, and management of the disorder; this topic reviews these concepts.
Other related disorders are discussed separately. (See "Neonatal brachial plexus palsy" and "Eventration of the diaphragm in infants".)
DIAPHRAGM EMBRYOLOGY —
The diaphragm develops from four embryologic structures:
●Septum transversum
●Pluripotential membranes
●Dorsal mesentery of the esophagus
●Body wall muscles
The septum transversum is first recognizable at the third week of gestation as a mass of mesoderm located ventral to the cervical somites. During the fourth week, it descends and partially separates the thoracic and peritoneal cavities [1]. The openings that remain between the thorax and abdomen are the pleuroperitoneal ducts.
During the fifth week of gestation, myoblasts and neuronal elements from the third, fourth, and fifth cervical somites penetrate the developing diaphragm as the downward migration of the septum transversum continues. As a result, the phrenic nerve is comprised of the third, fourth, and fifth cervical nerve roots [2]. The migration continues until the eighth week of gestation. At that time, the septum transversum fuses with the pluripotential membranes and the mesenchyme ventral to the esophagus, closing the pleuroperitoneal ducts [1].
DIAPHRAGM PHYSIOLOGY
Diaphragm function — The diaphragm has two components: the noncontractile central tendon and the contracting muscle fibers. It is innervated by cervical motor neurons three, four, and five, conducted via the homolateral phrenic nerve through the neck and mediastinum.
Contraction of the diaphragm has the following effects that promote air movement into the lungs [3,4]:
●It decreases intrapleural pressure.
●It raises or inflates the rib cage using the abdomen as a fulcrum on which to lean.
●It expands the rib cage through its zone of apposition (the lower third of the rib cage apposed by the diaphragm) by generating positive intraabdominal pressure.
Anatomy of neonatal diaphragm — Anatomical differences between the newborn and adult result in decreased efficiency of the neonatal diaphragm. Compared with the adult, the newborn diaphragm differs in its attachment to the rib cage, its flatter shape, and its fiber composition [5,6]. Inefficiency of the diaphragm may be exacerbated by the newborn's highly compliant rib cage and horizontal configuration of the ribs, which reduce the mechanical advantage of the intercostal muscles in lifting the rib cage in inspiration. The newborn's recumbent posture, compared with that of the upright adult, also contributes to diaphragm inefficiency.
Rib cage attachments — The attachments of the diaphragm to the rib cage render the neonatal diaphragm less efficient than that of the adult. In the adult, the diaphragmatic muscle fibers radiate circumferentially and insert peripherally into the inner surface of the lower six ribs and costal cartilages anteriorly (costal part), and the upper three lumbar vertebral bodies posteriorly (crural part). In the newborn, muscle fibers from the anterior diaphragm radiate laterally and attach to the xiphoid process and the seventh rib [7]. Fibers from the posterior diaphragm join the eleventh rib, while posterolateral fibers blend with the transverse abdominal muscles. The large angle of insertion into the lateral wall limits the zone of apposition. As a result, most of the movement of the neonatal diaphragm is in the posterior portion, in contrast to the piston-like movement of the adult diaphragm [8].
Pressure generation — Because the neonatal diaphragm is flatter (that is, it has a larger radius of curvature) than that of the adult, the maximum transdiaphragmatic pressure generated by contraction is less [7]. This is expressed by Laplace's law:
P = 2T / r
where P is the transdiaphragmatic pressure, T is the tension developed by the diaphragm, and r is the radius of curvature of the diaphragm.
Fiber types — Adult and neonatal diaphragms differ in the relative proportion of type I and II muscle fibers, which affects their ability to withstand fatigue. Type I fibers are recruited first and generate a low level of force; they are relatively resistant to fatigue. Type II fibers are the last to be recruited, generate a high level of force, and are easily fatigued [9]. The proportion of fatigue-resistant type I fibers is less in the neonatal diaphragm compared with that of the adult (25 versus 55 percent) [10].
Body position — The diaphragm is less efficient in the recumbent newborn than in the upright adult. In addition, diaphragmatic function may be impaired more in the prone than supine position. In one study, diaphragm thickness and shortening were assessed by ultrasound in healthy term infants [11]. In the prone position, the diaphragm was thicker and shorter at both end-expiratory and end-inspiratory volumes, and diaphragm shortening was greater during tidal breathing, compared with in the supine position. The reduced resting diaphragmatic length in the prone position would be expected to impair diaphragmatic strength, while the additional shortening during tidal breathing would increase diaphragmatic work.
ETIOLOGY —
Diaphragmatic paralysis is typically caused by injury to the phrenic nerve. In almost all cases, this is caused by trauma during birth or cardiothoracic surgery. In rare cases, paralysis results from neuromuscular disorders [12,13]. (See "Neonatal birth injuries", section on 'Nerve injuries'.)
Birth injury — Extreme lateral traction on the shoulder during delivery can injure or transect the phrenic nerve and/or the brachial plexus by stretching their cervical roots [14]. The traction occurs during delivery of the shoulder in cephalic presentations and delivery of the head in breech presentations [15].
Involvement of the third to fifth, and especially the fourth, cervical roots results in diaphragmatic paralysis. Brachial plexus palsy is associated in 80 to 90 percent of cases, while diaphragmatic paralysis occurs in approximately 5 percent of brachial plexus injuries [15,16].
Factors associated with diaphragmatic paralysis are similar to those associated with brachial plexus injury. The risk of brachial plexus injury is greatly increased by vaginal delivery of a macrosomic newborn (>4500 g) (odds ratio 21, compared with normal weight) [14,17]. Shoulder dystocia may be a contributing factor. In one review, shoulder dystocia complicated the delivery of 75 percent of macrosomic newborns with brachial plexus injury [18]. Diaphragmatic paralysis occurs more often after breech than after cephalic deliveries [15]. Malpositioned forceps also may result in phrenic nerve injury [19].
Cardiothoracic surgery — Phrenic nerve injury is a recognized complication of cardiothoracic surgery [20]. Causes include electrocauterization, stretching, blunt trauma, or complete denervation [21]. The incidence of clinically diagnosed diaphragmatic paralysis after cardiothoracic surgery in children is variable, ranging from 0.5 to 2.2 percent of open and closed procedures in retrospective studies [21-24]. The incidence may be slightly higher (3 to 4.6 percent) in infants and younger children and occurs most often after Blalock-Thomas-Taussig shunts (commonly called Blalock-Taussig shunts) are performed [25,26]. (See "Tetralogy of Fallot (TOF): Management and outcome", section on 'Surgical repair' and "Management of coarctation of the aorta", section on 'Surgery'.)
Prospective assessment of injury by percutaneous stimulation of the phrenic nerve has detected a higher rate of injury than reported in retrospective studies. In a prospective study, unilateral phrenic nerve injury was detected after cardiac surgery in 6 of 50 infants and 4 of 50 children younger than 15 years of age [27]. All were symptomatic. No associations were found with age, type of surgery, length of bypass, aortic clamping, circulatory arrest, or degree of hypothermia.
In a single-center retrospective study, diaphragmatic paralysis occurred in 2.6 percent of pediatric patients following cardiac surgery (most frequently after bidirectional Glenn, arterial switch operations, and Blalock-Taussig shunts) and was associated with increased duration of mechanical ventilation and length of hospital stay [28].
Other procedures — Other procedures that may be performed in sick newborns can lead to phrenic nerve injury, although this complication seldom occurs. Diaphragmatic paralysis has been reported after cannulation of the internal jugular [29] or subclavian vein [30]. The disorder has also been associated with the insertion of chest tubes [31,32] and repair of esophageal atresia and tracheoesophageal fistula [33].
Neuromuscular disorders — Neuromuscular disorders are rare causes of diaphragmatic paralysis [12]. Causes identified in case reports include congenital myopathies [13,34], spinal muscular atrophy [35], myasthenia [36], and congenital diaphragmatic muscle hypoplasia [37]. Other causes include high spinal cord trauma and botulism. (See "Spinal muscular atrophy", section on 'Spinal muscular atrophy with respiratory distress type 1' and "Congenital myopathies", section on 'Other myopathies'.)
CLINICAL FEATURES —
Diaphragmatic paralysis occurring after birth injury typically is unilateral. The right side is involved most often (approximately 80 percent of cases) [15]. The most severely affected infants have bilateral involvement, which occurs in less than 10 percent [15,38,39].
Onset of symptoms — The onset of symptoms is variable and may occur soon after birth or later in the neonatal period. Recognition may be delayed in newborns receiving assisted ventilation. These patients usually do not become symptomatic until weaning from the ventilator is attempted.
Newborns do not tolerate diaphragmatic paralysis as well as older children or adults. Their anatomic differences result in increased respiratory dysfunction and earlier presentation of symptoms. (See 'Anatomy of neonatal diaphragm' above.)
Phrenic nerve injury associated with cardiothoracic surgery or other procedures usually is suspected when the infant cannot be weaned from the ventilator or develops respiratory distress after extubation [40]. Some infants present with complications of diaphragmatic paralysis, such as atelectasis, pleural effusions, aspiration, or respiratory infections [21,27].
Associated signs — Affected newborns typically have signs of respiratory compromise. These include tachypnea, mild to severe respiratory distress, cyanosis, apnea, or a weak cry.
Some affected newborns also have gastrointestinal symptoms. These typically include respiratory distress or tiring during feedings [41]. Patients with left-sided diaphragmatic paralysis may have frequent regurgitation as a result of displacement of the lower esophagus and/or stomach [42].
Most newborns with diaphragmatic paralysis caused by birth injury have an associated brachial plexus palsy [15,16]. This is usually the proximal type (Erb palsy), although it may be total. The affected limb typically assumes the characteristic "waiter's tip" position. (See "Neonatal brachial plexus palsy", section on 'Clinical features'.)
Physical examination — Affected newborns may have decreased movement of the rib cage on the affected side, with corresponding prominent movement of the unaffected side. This paradoxical movement of the diaphragm (ie, rising with inspiration and falling with expiration, also known as Kienboeck sign) may result in a "seesaw" movement of the abdomen. This "seesaw" movement may be absent in patients who are receiving positive pressure ventilation or continuous positive airway pressure (CPAP) because the affected diaphragm may not be elevated or move paradoxically. Rarely, newborns have the "belly dancer's sign" in which the umbilicus moves toward the affected side during inspiration [43].
Auscultation usually detects decreased air entry on the affected side. If the right diaphragm is affected, percussion (although rarely part of the newborn examination) may reveal dullness at the right lung base caused by the cephalic displacement of the liver [44]. Hyperresonance may occur over the left lung base if the left side is affected, due to the cephalic displacement of the gastric bubble.
DIAGNOSIS
When to suspect diaphragmatic paralysis — Diaphragmatic paralysis should be considered when respiratory dysfunction develops after a traumatic delivery, especially in a large newborn with breech presentation. However, respiratory distress and hypoxemia may also indicate primary pulmonary disease or congenital heart disease, so these diagnoses should be excluded. Diaphragmatic paralysis should also be considered when weaning from mechanical ventilation is unsuccessful after the child has undergone cardiothoracic surgery or another procedure, such as chest tube placement. (See 'Clinical features' above and 'Etiology' above.)
Confirming the diagnosis (preferred imaging) — We confirm the diagnosis of diaphragmatic paralysis with ultrasound; bedside echocardiography can also be used. In a spontaneously breathing newborn with diaphragmatic paralysis, we typically see paradoxical diaphragmatic movement (ie, rising with inspiration and falling with expiration). (See 'Physical examination' above.) However, the absence of paradoxical diaphragmatic movement does not exclude the possibility of diaphragmatic paralysis. In patients who are receiving positive pressure ventilation or continuous positive airway pressure (CPAP), the affected diaphragm may not be elevated or move paradoxically. Diagnosis in these patients is difficult unless an ultrasound can be done while they are spontaneously breathing.
Although we generally use bedside ultrasound, fluoroscopy can also confirm the diagnosis. We prefer ultrasound because it provides functional and dynamic images that can simplify diagnosis [45]. It also has the advantage of being done at the bedside and involves no exposure to ionizing radiation [46,47]. In addition, one study suggested that echocardiography was more reliable than fluoroscopy in detecting hemidiaphragms that required surgical plication [48]. It is even possible for the diagnosis to be made as an incidental finding on echocardiogram in the infant after cardiac surgery [49].
Other imaging tests
●Radiography – The affected hemidiaphragm typically is elevated on an anteroposterior chest radiograph (image 1). In general, an affected right hemidiaphragm is at least two intercostal spaces higher than the left, and an affected left hemidiaphragm is one intercostal space higher than the right [41]. Other radiographic findings that may be seen include atelectasis on the affected side and a shift of the mediastinum away from that side. The stomach bubble may appear elevated with left-sided paralysis.
●Magnetic resonance imaging (MRI) – Evaluation of the upper cervical spinal cord with MRI may be useful in newborns who present with diaphragmatic paralysis and quadriparesis. In a small series, this technique was used to demonstrate the extent and severity of the injury [50].
Limited role of electromyography and physiologic testing — Other methods are available to assess neonatal diaphragmatic function but are not used clinically because they are difficult to interpret and/or invasive. These include electromyography, measurement of maximal inspiratory pressure during crying, and phrenic nerve stimulation [20,27,51-53]. The technique of magnetic stimulation of the phrenic nerve may be a useful and noninvasive way to assess function but remains investigational in newborns [51].
MANAGEMENT
Initial supportive care — Initial treatment of diaphragmatic paralysis is supportive. With supportive care, spontaneous recovery of diaphragmatic function occurs in most cases.
Mildly affected newborns may respond to supplemental oxygen administered by hood or nasal cannula. If oral feedings are limited because of respiratory distress, nasogastric feedings can be used to provide adequate nutrition.
More severely affected newborns require mechanical ventilation. In less severe cases, continuous positive airway pressure (CPAP) may "splint" the diaphragm, reducing paradoxical motion, and allowing the newborn to breathe spontaneously [54,55]. Negative pressure ventilation also has been used [56,57]. Although the technique is cumbersome, it avoids endotracheal intubation.
Surgical treatment — If patients have persistent severe respiratory distress or a prolonged requirement for mechanical ventilation, surgical plication is performed. This procedure immobilizes and lowers the diaphragm, resulting in increased resting lung volume and improved action of the intercostal and abdominal muscles during breathing. Respiratory improvement after application of CPAP (8 to 10 cm H2O) may identify patients who will respond to plication because both interventions stabilize the diaphragm and increase functional residual capacity [58].
The appropriate timing for performing surgical plication is uncertain. In general, the procedure is considered if mechanical ventilation is required for at least two months and there are no signs of recovery [15]. However, some clinicians recommend earlier intervention to prevent complications of long-term mechanical ventilation, especially when injury follows cardiothoracic surgery or birth injury [14,59].
Surface recordings of diaphragmatic action potential amplitudes and phrenic nerve conduction times in response to percutaneous phrenic nerve stimulation may help predict whether recovery will occur [15,60]. Patients with absent or markedly reduced diaphragmatic action potentials or very prolonged conduction latencies are unlikely to recover and likely will need surgical plication.
Pacing — Diaphragmatic pacing may be considered in bilateral diaphragmatic paralysis, although experience in young infants is limited [61-64]. However, it is not helpful in unilateral paralysis because of the difficulty of synchronizing contractions of the normal and paralyzed hemidiaphragms.
OUTCOME
Conservative management — Most newborns with diaphragmatic paralysis associated with birth trauma recover in the first 6 to 12 months after birth with supportive care. Conservative management also usually is successful after cardiac surgery [26]. In some cases, symptoms will resolve with little objective evidence of improved diaphragmatic function [41].
After surgery — Plication usually is associated with rapid improvement in uncomplicated cases [23,65-67]. In general, mechanical ventilation can be discontinued within one week of surgery, even in preterm infants [68,69].
Data on long-term outcomes following plication are limited. In one report, six children with phrenic nerve injury due to surgery for congenital heart disease or birth trauma had return of normal function one to seven years following diaphragmatic plication [70].
Diaphragmatic paralysis caused by avulsion of the phrenic nerve is permanent. Loss of contraction leads to muscle atrophy and eventration of the diaphragm. (See "Eventration of the diaphragm in infants", section on 'Acquired eventration'.)
SUMMARY AND RECOMMENDATIONS
●Etiology – Diaphragmatic paralysis typically is caused by injury to the phrenic nerve. In almost all cases, this is caused by trauma during birth or cardiothoracic surgery. In rare cases, paralysis results from neuromuscular disorders. (See 'Etiology' above.)
●Signs and symptoms – Diaphragmatic paralysis occurring after birth injury usually is unilateral, and more commonly involves the right side. The onset of symptoms is variable and typically includes signs of respiratory distress, cyanosis, apnea, or a weak cry. Other associated findings include respiratory distress or tiring during feedings, gastrointestinal reflux, and brachial plexus palsy. (See 'Onset of symptoms' above and 'Associated signs' above.)
●Physical examination – The physical examination includes decreased movement of the rib cage on the affected side, with corresponding prominent movement of the unaffected side. There may also be a seesaw movement of the abdomen. Auscultation of the chest usually detects decreased air entry on the affected side. (See 'Physical examination' above.)
●Diagnosis – The diagnosis of diaphragmatic paralysis is confirmed by detecting paradoxical diaphragmatic movement (ie, rising with inspiration and falling with expiration) on ultrasound or echocardiography. Fluoroscopy can also make the diagnosis but involves ionizing radiation and cannot be performed at the bedside. An elevated hemidiaphragm on an anteroposterior chest radiograph is indicative of diaphragmatic paralysis. Other radiographic findings include atelectasis on the affected side, and shift of the mediastinum away from the affected side. (See 'When to suspect diaphragmatic paralysis' above and 'Diagnosis' above.)
●Supportive treatment – Initial treatment of diaphragmatic paralysis is supportive. With supportive care, spontaneous recovery of diaphragmatic function occurs in most cases. Supportive care includes supplemental oxygen and mechanical ventilation as needed by the newborn. (See 'Initial supportive care' above and 'Conservative management' above.)
●Surgical treatment – Surgical plication is indicated in patients with persistent severe respiratory distress and/or who require prolonged mechanical ventilation. Generally, surgical plication is associated with rapid improvement in uncomplicated cases, with discontinuation of mechanical ventilation within one week of surgery. (See 'Surgical treatment' above and 'After surgery' above.)
ACKNOWLEDGMENT —
The UpToDate editorial staff acknowledges Suzanne K Whitbourne, MD, who contributed to an earlier version of this topic review.
