1 What are the four primary diagnostic considerations in a febrile child with acute stridor?

TABLE 26-1 illustrates clinical criteria helpful in distinguishing among the four.

2 What is the most common cause of stridor in the pediatric population?

Laryngotracheobronchitis (croup) accounts for >90% of all emergency department visits for stridor in the pediatric population. The key features of croup include barky cough, stridor, and hoarseness, usually preceded by symptoms of a mild upper respiratory tract infection. Croup is most common in older infants and toddlers, though it is not uncommon in school-aged children.

eMedicine: Stridor. Available at www.emedicine.com/ped/topic2159.htm.

3 Name three animal sounds to which the croup cough has been compared.

The bark of a seal or sea lion, the bark of a dog, and the honking of a goose.

4 What is meant by the term spasmodic croup?

Spasmodic croup, also known as laryngismus stridulus, is a variant of croup that lacks the typical viral prodrome (low-grade fever, runny nose). Symptoms start suddenly, often in the middle of the night, and resolve quickly. Symptoms may recur for several nights in a row. The etiology of spasmodic croup is unclear. Since the diagnosis can be made only upon resolution of the symptoms, the distinction between viral and spasmodic croup during initial presentation lacks clinical relevance.

5 What is the characteristic radiographic finding in a patient with croup? In epiglottitis?

The classic radiographic finding in croup is the “steeple sign,” a narrowing of the laryngotracheal air column just below the vocal cords on an anterior-posterior view (Fig. 26-1). Another finding includes “ballooning” (distention) of the hypopharynx during inspiration, seen on a lateral view. The steeple sign has been show to lack sensitivity and specificity. The primary reason for obtaining radiographs in children with suspected croup should be to evaluate the possibility of other causes of stridor in atypical cases. The classic finding in epiglottitis is the “thumb sign,” referring to the lateral view of the swollen epiglottis resembling a lateral view of one’s thumb (Fig. 26-2). The thumb sign is also subjective, and radiographs alone should not be used to diagnose epiglottitis. If clinical suspicion is high, imaging should be deferred in favor of direct visualization of the airway under controlled circumstances.

Figure 26-1 Radiographic view of the steeple sign.

Figure 26-2 Radiographic view of the thumb sign.

6 Which bacterial infection of the upper airway most closely clinically mimics croup: Epiglottitis, bacterial tracheitis, or retropharyngeal abscess?

The clinical presentation of bacterial tracheitis is nearly indistinguishable from that of severe croup. In fact, croup caused by parainfluenza and influenza type A may lead to bacterial superinfection in some cases. Bacterial tracheitis presents with symptoms of stridor, fever, and toxicity generally worsening over a 3- to 7-day period. Racemic epinephrine and steroids are not effective, and many patients will require intubation and surgical debridement of the membranous tracheal exudates. The most common organism has generally been reported to be Staphylococcus aureus, though Moraxella catarrhalis infection is also prevalent and potentially more severe.

Salamone FN, Bobbitt DB, Myer CM, et al: Bacterial tracheitis reexamined: Is there a less severe manifestation? Otolaryngol Head Neck Surg 131:871–876, 2004.

7 Why are retropharyngeal abscesses uncommon in children over the age of 5 years?

A retropharyngeal abscess generally occurs in infants and toddlers, typically under the age of 4 years. The abscess is caused by seeding of the retropharyngeal nodes with bacteria, usually oral pathogens. After the age of 4, the retropharyngeal nodes atrophy.

8 What is stertor? How does it differ from stridor?

Stertor is the noise most aptly described as snoring. It refers to the low-pitched vibratory noise made when airflow is obstructed in the nose and soft tissues of the pharynx; stridor is higher pitched and refers to the noise of turbulent airflow through the larynx and trachea. Thus, a snoring patient is stertorous, and a “croupy” patient is stridulous (not stridorous!).

9 What is the most common cause of congenital stridor?

Laryngomalacia is the most common cause of stridor in infants. It is generally benign and resolves spontaneously as the child grows. The exact cause is unknown, though anatomically one finds one or more supraglottic abnormalities, including a long epiglottis that prolapses posteriorly, bulky arytenoids that prolapse anteriorly, or shortened aryepiglottic folds.

Manning SC, Inglis AF, Mouzakes J, et al: Laryngeal anatomic differences in pediatric patients with severe laryngomalacia. Arch Otolaryngol Head Neck Surg 131:340–343, 2005.

10 What is the best test for diagnosing laryngomalacia?

Clinical clues to the diagnosis of laryngomalacia include stridor that improves with prone positioning and worsens with crying. Airway fluoroscopy is suggestive of the diagnosis, but the gold standard for diagnosis is direct laryngoscopy in an awake, upright, spontaneously breathing infant. Direct laryngoscopy also rules out other less common causes of congenital stridor, including vocal cord paralysis and laryngeal webs and cysts.

11 Where in the airway is the likely site of pathology in a patient with stridor that is loudest in the expiratory phase?

Expiratory stridor suggests tracheal pathology. The differential diagnosis includes complete tracheal rings, primary tracheomalacia (faulty tracheal development), and secondary tracheomalacia (associated with external compression). External compression may be caused by vascular abnormalities or mediastinal masses, such as thymic cysts, cystic hygroma, thyroid hyperplasia, or mediastinal tumor.

12 What are the three most common vascular anomalies associated with tracheal compression?

Kussman BD, Geva T, McGowan FX: Cardiovascular causes of airway compression. Paediatr Anaesth 14:60–74, 2004.

13 A toddler born to an adolescent mother gradually develops hoarseness over a few-month period and presents with an acute exacerbation of stridor. What important pathologic condition must be considered?

Recurrent respiratory papillomatosis, caused by certain strains of the human papilloma virus (HPV), may cause significant airway obstruction preceded by an indolent history of hoarseness, chronic or intermittent coughing spells, or poor feeding. HPV is very common in sexually active females, with adolescent prevalence rates ranging from 20% to 40%, and about 1% of infants born to mothers with vaginal condyloma will develop recurrent respiratory papillomatosis. Treatment includes both surgical (laser) and medical (antiviral) modalities.

Wiatrak BJ: Overview of recurrent respiratory papillomatosis. Curr Opin Otolaryngol Head Neck Surg 11:433–441, 2003.

14 In a child who presents with stridor following a suspected foreign-body aspiration, where in the airway is the object likely to be found? What percentage of foreign bodies will be found in this location?

In two large retrospective studies of foreign body aspiration, stridor was reported as a symptom only when the object was located in the trachea. Conversely, the percentage of patients with tracheal foreign bodies reported as stridulous ranged from 15% to 50%. Of all respiratory foreign bodies, 10–15% were found in the trachea. Interestingly, tracheal foreign bodies resulted in normal radiographs in 50–80% of the cases, a higher percentage of normal radiographs when compared with foreign bodies in the lower respiratory tract.

Metrangolo S, Moneti C, Meneghini, et al: Eight years’ experience with foreign body aspiration in children: What is really important for a timely diagnosis? J Pediatr Surg 34:1229–1231, 1999.

Zerella JT, Dimler M, McGill LC, Pippus KJ: Foreign body aspiration in children: Value of radiography and complications of bronchoscopy. J Pediatr Surg 33:1651–1654, 1998.

15 Parents of an asymptomatic 2-year-old report that he coughed and choked while playing with small plastic blocks, but they are resistant to unnecessary bronchoscopy. What is the best diagnostic test?

Computed tomography (CT). Three-dimensional postprocessing of spiral CT images allows virtual views of the airway similar to those seen with endoscopy. CT has been shown to be accurate, and may be useful in both showing the exact location of a foreign body prior to bronchoscopy and ruling out a foreign body in patients with a low level of suspicion.

Kosucu P, Ahmetoglu A, Kormaz I, et al: Low-dose MDCT and virtual bronchoscopy in pediatric patients with foreign body aspiration. Am J Roentgenol 183:1771–1777, 2004.

16 Name five causes of stridor that are not directly related to the anatomy of the upper airway.

17 What electrolyte abnormality has been associated with stridor?

Hypocalcemia may be associated with laryngospasm and stridor, in addition to tetany and the characteristic Chvostek’s and Trousseau’s signs.