Stridor in the Neonate and Young Child: Evaluation and Treatment of Underlying Causes

ABSTRACT: In the infant, especially the neonate, stridor often suggests a congenital abnormality, such as laryngomalacia. Stridor associated with a fever usually signifies an infectious cause, such as bacterial tracheitis or epiglottitis. In toddlers with acute onset of stridor who are afebrile, aspiration of a foreign body must be in the differential. In a patient who has been intubated, consider iatrogenic subglottic stenosis. Stridor must be differentiated from stertor, which is caused by obstruction in the nasopharynx or oropharynx. If obtainable, radiologic studies can help rule out certain diseases and can be diagnostic in some instances (eg, the steeple sign in croup).

Stridor is a harsh, vibratory, high-pitched sound caused by turbulent airflow through narrowed airways. In most cases, stridor can be classified as inspiratory, expiratory, or biphasic. It can be a sign of obstruction of the large airways that requires an immediate diagnosis and acute management. The causes of stridor vary from mild croup to severe epiglottitis. Knowledge of the levels of acuity, the pitfalls in diagnosis, and the initial treatment of any type of airway obstruction can be lifesaving in critical conditions. Awareness of the potential for rapid deterioration is crucial when evaluating stridor in children. Management of the cause of stridor usually requires a multidisciplinary approach.

Here, we provide an overview of potential causes of stridor, focusing on radiographic evaluation to help elucidate the underlying pathology.

ETIOLOGY AND
EVALUATION

Stridor may have an infectious, noninfectious, or congenital origin (Table 1). In the infant, especially the neonate, stridor often suggests a congenital abnormality, such as laryngomalacia or a tracheal web. Stridor associated with a fever usually signifies an infectious cause. In toddlers with acute onset of stridor who are afebrile, aspiration of a foreign body must be in the differential. In a patient who has been intubated, consider iatrogenic subglottic stenosis. It is important to keep in mind that the airway diameter in the child, and even more so in the infant and neonate, is small in comparison to the adult or adolescent. Thus, any decrease in the infant or young child’s airway is likely to have a greater impact on breathing and is more likely to require emergent intervention.

In general, stridor that is worse during inspiration usually signifies by extrathoracic obstruction, whereas stridor that is worse during exhalation typically represents intrathoracic obstruction. With an obstruction in the glottis region, stridor can occur during inspiration only or be biphasic. A fixed airway obstruction also leads to biphasic stridor. Stridor must be differentiated from stertor or snoring—the low-pitched inspiratory sound caused by nasopharyngeal or oropharyngeal obstruction—which is associated with choanal atresia, mandibular hypoplasia (Pierre-Robin or DiGeorge syndrome), and macroglossia (Beckwith-Wiedemann or Down syndrome).¹

In general, a plain radiograph can be obtained in the critically ill or unstable child if it can be done on site, such as in the emergency department. However, in some critically ill or unstable patients with respiratory distress and/or stridor, imaging studies may be impossible or even dangerous. For instance, placing the infant or child who is struggling to breathe in a supine position for CT evaluation may aggravate airway obstruction or precipitate complete obstruction of a partially blocked airway. If obtainable, radiologic studies can help rule out certain diseases and confirm the diagnosis in some cases. Table 2 lists the radiographic findings associated with the following causes of extrathoracic airway obstruction.

CROUP

Viral croup (acute laryngotracheitis). Viral croup is the most common cause of acute upper airway obstruction in children. It occurs mainly in children younger than 6 years, with a peak incidence of 7 to 36 months.² Parainfluenza viruses types 1, 2, and 3 account for more than 65% of cases of croup. Other viruses associated with this disease include adenoviruses, influenza type A (which causes the most severe disease), influenza B, respiratory syncytial virus, metapneumovirus, rhinovirus, enterovirus, and rarely measles virus and herpes simplex virus.³ The infection causes mucosal edema and, occasionally, fibrinous exudates that lead to narrowing of the airway in the subglottic region.

The clinical presentation of croup may include inspiratory stridor, barking cough, hoarse voice, and a variable degree of respiratory distress, with or without fever. Symptoms are characteristically worse at night and are aggravated by agitation and crying.⁴ Croup is essentially a clinical diagnosis. When the diagnosis is unclear, soft tissue neck radiographs may be helpful. An anteroposterior neck film showing the classic steeple sign of upper airway narrowing is diagnostic (Figure 1). However, only 50% of children with croup have this radiologic finding, and the steeple sign may be present in asymptomatic, healthy children.³

Corticosteroids are now recommended for all patients with croup regardless of severity. According to a recent Cochrane systematic review, use of corticosteroids is effective in reducing symptoms in children with severe, moderate, and mild croup as early as 6 hours and for up to at least 12 hours after administration.⁵ Corticosteroid treatment resulted in lower croup severity scores, fewer return visits or admissions, shorter hospital stay, and less use of epinephrine in most patients studied. Fluticasone appeared to be less beneficial than dexamethasone and budesonide. The authors of the study prefer the use of a single oral dose of dexamethasone, 0.6 mg/kg; however, they conclude that the optimal dose of dexamethasone (range, 0.15 to 0.6 mg/kg) needs to be defined. In a child who is vomiting, intramuscular dexamethasone or nebulized budesonide (2 mg in 4 mL of water) might be preferable.⁵

Nebulized L-epinephrine (diluted in 5 mL of saline at a ratio of 1:1000) and 2.25% racemic epinephrine (0.5 mL in 2.5 mL of saline) have been found to be equally effective in decreasing croup symptoms at 30 minutes after treatment.⁶ Nebulized racemic epinephrine is preferred by most providers because it is less expensive. Although racemic epinephrine was once thought to cause fewer cardiovascular adverse effects than L-epinephrine, no statistically significant difference has been found between the 2 drugs.⁶ Given its widespread use over several decades, nebulized epinephrine administered in 1 or even 2 doses would be unlikely to pose any significant risk to a child.⁶

In children with moderate to severe croup, both epinephrine and corticosteroids are given concurrently to reduce respiratory distress, while awaiting the effects of the corticosteroid treatment. The addition of intermittent positive pressure breathing to nebulized epinephrine treatment has been shown to be no more effective than nebulized epinephrine alone.

Humidified air (moist air) has been widely used and is commonly recommended as a home treatment. However, there is no evidence to support its use in an emergency setting.⁷ Heliox, which is 70% to 80% helium and 20% to 30% oxygen, can flow through the airways with less turbulence and resistance than pure oxygen; it should decrease the work of breathing in children with croup and perhaps can be used as a temporizing measure while waiting for corticosteroids to take effect. However, heliox has been found to be no more effective than racemic epinephrine and is more cumbersome to use and more expensive.⁸

Spasmodic croup (acute spasmodic laryngitis). Spasmodic croup presents as the acute onset of barking cough and stridor at night in an otherwise healthy child who may have minimal or no preceding upper respiratory tract infection (URI) symptoms.^2,9 As with viral croup, there is inflammatory edema in the subglottic area. The child can have repeated attacks on the same night and for the next 3 or 4 successive nights.^2,3 It is thought to be caused by an allergic phenomenon and is usually mild, requiring minimal treatment, if any.

BACTERIAL TRACHEITIS

This acute bacterial infection is characterized by inflammatory edema of the trachea with ulcerations and formation of microabscesses with pseudomembranes. It may have the same initial presentation as laryngotracheitis but evolves to a much more severe disease with high fever, toxicity, and severe airway obstruction. If imaging is obtainable, radiographic findings include narrowing of the subglottic area with diffuse haziness and irregularity of the trachea.

The illness is caused by Staphylococcus aureus (most commonly), group A streptococci, Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. Empiric antibiotic therapy should cover these organisms until culture results are available. Patients require treatment in an ICU setting; this almost always involves intubation and sometimes tracheostomy.⁹

EPIGLOTTITIS

Epiglottitis is an acute inflammation of the supraglottic structures—the epiglottis and aryepiglottic folds—characterized by rapid progression of symptoms. It usually begins with sore throat and fever that rapidly, over hours, progresses to difficulty in swallowing, airway obstruction, and death, if not treated promptly. Stridor is a late finding.¹⁰ Additional hallmarks of epiglottis are preference for a sitting position and refusal of food or drinks.¹¹ One study from Australia found that the diagnosis of epiglottitis was initially missed in 37% of 203 children who presented to a pediatric ICU between 1990 and 1993.¹⁰ Common misdiagnoses were pharyngitis, tonsillitis, URI, croup, asthma, influenza, and bronchilolitis.

Historically, the most common pathogen associated with epiglottitis was H influenzae type b (Hib). Since the introduction of the Hib vaccine, the incidence of epiglottitis in infants and children has decreased significantly.¹² Streptococccus species are now the most common organisms associated with epiglottitis, other causative pathogens include nontypeable H influenzae, S aureus, Neisseria, Klebsiella, Pasteurella multocida, and M catarrhalis. Failures of the Hib vaccine have been reported; 40% of vaccine failures were attributed to low serum immunoglobulin concentrations.¹³

Two types of epiglottitis have been described: the localized or “adult” form and the systemic or “pediatric” form.¹⁴ However, either form may occur in patients of any age. Children with the systemic form present with high fever, drooling, toxic appearance, and an elevated white blood cell (WBC) count with a shift to the left. These patients typically have rapidly progressive disease, difficulty in breathing, and stridor. Children with the localized form may have only a sore throat and lack any systemic symptoms initially.¹⁴

Suspected epiglottitis should be confirmed by direct laryngoscopy performed in controlled settings, such as the operating room or pediatric ICU. To avoid potentially worsening the airway obstruction, clinicians should defer any anxiety-provoking interventions (peripheral intravenous catheter insertions, examination of the oral cavity) until after the airway is secured. Diagnosis is based on direct visualization of the cherry red epiglottis. Lateral radiographs of the neck may reveal a thumbprint sign, which is caused by an inflamed and hypertrophied epiglottis and edematous aryepiglottic folds (Figure 2).

Treatment of children with epiglottitis consists of hospitalization and appropriate antibiotic coverage. Although one study of children aged 9 months to 11 years suggested that observation in the ICU without an artificial airway may be acceptable in certain circumstances,¹⁵ the general consensus is that the airway should be secured by intubation in the operating room.¹⁶ Because of the potential for rapid deterioration in patients with epiglottitis, the threshold for airway placement should remain low.

ABSCESS

Retropharyngeal abscess. The retropharyngeal space consists of loose connective tissue anterior to the cervical vertebrae between the prevertebral fascia and buccopharyngeal fascia. This space contains 2 chains of lymph nodes that drain the nose, adenoids, tonsils, sinuses, and middle ear. These lymph nodes are prominent in young children and involute in late childhood, explaining the higher incidence of deep neck infection in children younger than 6 years.¹⁷ In children, retropharyngeal abscess is mainly caused by the spread of infection from the nose, adenoids, tonsils, middle ear, or sinuses with suppurative changes within a lymph node.

Patients may present with fever, sore throat, anorexia, stiff and hyperextended neck, dysphagia, drooling, cervical adenopathy, torticollis, trismus, respiratory difficulty, and stridor.¹⁸ The diagnosis is based on the clinical presentation and radiographic findings. Lateral neck radiographs may show retropharyngeal edema and widening of the retropharyngeal space (Figure 3). A contrast CT scan can delineate the extent of the infection and help differentiate retropharyngeal abscess from other causes of dysphagia and stridor.¹⁹

Complications of retropharyngeal abscess include airway obstruction, spontaneous perforation, aspiration pneumonia, mediastinitis, and septicemia. Other more rare complications are empyema, thrombosis of the internal jugular vein, erosion of the internal carotid artery, and atlantoaxial dislocation.¹⁹

Treatment consists of drainage and antibiotics.^19-21 The predominant bacteria associated with deep neck infections are group A ß-hemolytic streptococci, S aureus, Haemophilus species, and anaerobes.¹⁹

Peritonsillar abscess. Although the most common abscess of the head and neck, peritonsillar abscess is a rare cause of stridor. It is commonly preceded by pharyngotonsillitis and occurs most often in adolescents. A typical presentation involves fever, sore throat, dysphagia, and trismus. Physical examination reveals an asymmetric tonsillar bulge with displacement of the uvula.²¹

Diagnosis is confirmed by the presence of pus on needle aspiration. In cases in which the diagnosis is unclear or the tonsils cannot be visualized because of trismus, a lateral soft tissue neck radiograph can aid in making the diagnosis. Contrast CT may be useful because it is highly accurate and minimally invasive, although expensive. Intraoral ultrasonography has been used to identify the size and location of the abscess with respect to the other anatomic landmarks, such as the carotid artery. This imaging technique is rapid, noninvasive, highly accurate, inexpensive, and easily accessible²²; however, it can be technically quite difficult in an ill patient with significant pain and trismus, so it has not been widely used.

Treatment of peritonsillar abscess is drainage and systemic antibiotics. Needle aspiration has a resolution rate of 96%. It is inexpensive, can be performed by non-head and neck specialists, and does not require specialized equipment.²³ Incision and drainage is indicated for acute failure of needle aspiration. Tonsillectomy is required for recurrent tonsillitis, failure of needle aspiration and antibiotics, recurrent peritonsillar abscess, or complications from a peritonsillar abscess.^21,23

LARYNGEAL
ABNORMALITY

Laryngomalacia. The most common cause of chronic stridor in infants is laryngomalacia. It usually becomes apparent during the first 2 weeks of extrauterine life and spontaneously resolves by age 12 to 24 months. The male to female ratio is approximately 2:1. The disorder produces a high-pitched inspiratory stridor that is exacerbated by viral infection, supine position, and exertion (eg, crying, feeding).²⁴ It can be diagnosed by flexible fiberoptic endoscopy. Gastroesophageal reflux disease has been associated with laryngomalacia, and in patients with both conditions, antireflux treatment is beneficial.²⁵

Treatment varies depending on the severity:

•Mild laryngomalacia is described as isolated, intermittent inspiratory stridor, with minimal work of breathing and normal growth and development. Management involves regular follow-up.²⁵

•Moderate laryngomalacia is characterized by continuous stridor and significant work of breathing, without other constitutional signs and symptoms. In addition to airway films and a chest radiograph, a barium swallow esophagogram may be indicated when dysphagia is present. Management is similar to that of mild laryngomalacia.²⁵

•Severe laryngomalacia is characterized by continuous inspiratory stridor, increased work of breathing, and respiratory distress requiring oxygen or airway support and surgical management.

Congenital vocal cord paralysis. Congenital vocal cord paralysis is the second most common congenital laryngeal abnormality in children after laryngomalacia.²⁶ Stridor is usually present and is often biphasic. Patients with unilateral vocal cord paralysis are more likely to have a hoarse voice and weak cry, without respiratory distress. Those with bilateral vocal cord paralysis may have a preserved cry and are more likely to be cyanotic and apneic.^25,26

Vocal cord paralysis is idiopathic in most cases. However, it has been associated with iatrogenic causes (postsurgical complications, intubation), birth trauma, neurological disorders (Arnold-Chiari malformation, hydrocephalus, meningomielocele, cerebral palsy, spinal muscle atrophy, myasthenia gravis), and cardiovascular anomalies (tetralogy of Fallot, ventricular septal defect, vascular ring, double aortic arch). Patients with vocal cord paralysis should undergo further evaluation for associated neurological or cardiovascular pathology.^25,26

Unilateral vocal cord paralysis can be managed with a nasogastric feeding tube or gastrostomy tube for adequate nutrition. Patients with bilateral vocal cord paralysis and stable respiratory status who have normal growth and development can be monitored with regular follow-up, which includes examination with flexible laryngoscopy. For patients who do not qualify for this management program, most pediatric otolaryngologists will place a tracheostomy tube as a temporary measure to secure the airway while waiting for spontaneous recovery. Spontaneous recovery within 6 months is common; however, the condition can persist up to 11 years after diagnosis.²⁶

Congenital subglottic stenosis. Congenital subglottic stenosis is the narrowing of the laryngeal lumen at the cricoid level (less than 4 mm in a full-term newborn and less than 3 mm in a premature infant). It is usually diagnosed in the first few months of life. Mild subglottic stenosis symptoms appear with URIs when there is edema of the laryngeal mucosa that contributes to a further decrease in the laryngeal lumen. Recurrent or persistent croup is a typical finding in children with subglottic stenosis. In severe cases, respiratory distress is present within the first days of life. The symptoms frequently resolve (with growth) in several years.²⁵ Anterior-posterior neck radiographs may show “hourglass” narrowing at the subglottic level.²⁵

Mild cases can be managed with regular follow-up. For severe cases, surgical intervention may be necessary. To avoid the complications from tracheotomy (eg, speech and language development retardation, accidental decannulation, increased risk of infection, and tracheotomy tube plugging), laryngotracheal decompression or reconstruction has been advocated.²⁵

FOREIGN BODY
ASPIRATION

One of the common causes of accidental death in childhood is foreign body aspiration. It is estimated that almost 600 children younger than 15 years die each year in the United States as a result of foreign body aspiration.²⁷ It is most common in children aged 1 to 3 years; a combination of factors contribute to foreign body aspiration, including poor swallowing coordination, immature dentition, activity while eating, and tendency to introduce objects in the mouth.²⁸ The most commonly aspirated objects are organic matter, such as peanuts, seeds, hot-dogs, and popcorn. Balloons are the most commonly aspirated nonfood item; other inorganic aspirated objects include toy parts, marbles, crayons, pins, nails, screws, and bullets.²⁹

Children with aspirated foreign bodies may choke, gag, or cough.³⁰ A history of choking is revealed in 80% of cases.²⁹ As the foreign body moves distally though the airway, the symptoms may become milder and may even subside completely.³⁰ A significant percentage of patients with foreign body aspiration are asymptomatic on presentation and can continue to be symptom-free for months.³⁰

Laryngeal and tracheal foreign bodies may manifest as cough and stridor and/or voice change; whereas cough, dyspnea, and unilateral wheeze or decreased air movement suggest a bronchial foreign body (Figures 4 and 5). A supraglottic foreign body may manifest with cough, dyspnea, gagging, drooling, or muffled voice.³⁰

Complications of retained foreign bodies include recurrent pneumonia, lung abscess, bronchopulmonary fistula, and bronchiectasis.³¹ For partial obstruction, removal of the foreign body is key.²⁹ For patients with complete obstruction, clinicians should follow the American Heart Association algorithm for choking.

A chest radiograph is indicated because some aspirated foreign bodies are radiopaque. A lateral view is helpful in visualizing the location of the foreign body. Soft tissue neck radiographs may be useful when the foreign body is in the upper airway. Atelectasis, obstructive emphysema, and pneumonia are indirect findings suggestive of foreign body aspiration. When the obstruction is partial, the chest radiographic findings may be normal.³⁰

Normal radiographic findings are found in a high percentage of airway foreign bodies diagnosed within the first 24 hours after aspiration; however, this percentage decreases substantially after the first day.³¹ Inspiratory and expiratory radiographs in children who can cooperate and decubitus radiographs in younger children may show unilateral hyperinflation and may help in diagnosis.²⁹ CT scanning can illuminate radiolucent foreign bodies and identify parenchymal changes. Spiral CT has been found to have 100% sensitivity and 66.7% specificity.²⁹

In cases in which the diagnosis is uncertain, flexible bronchoscopy is often used because it allows for complete airway evaluation. Rigid bronchoscopy is mainly used for removal of the aspirated foreign body. A foreign body at the level of the pharynx may be removed under direct laryngoscopy with a Magill forceps. Thoracotomy is useful in cases in which rigid bronchoscopy has failed. Patients are usually hospitalized for observation. Adjunct postoperative treatment with antibiotics and corticosteroids has been used despite little data to support its use.²⁹