Congenital anomalies of the larynx

INTRODUCTION — Congenital anomalies are the product of errors in embryogenesis (malformations) or the result of intrauterine events that affect embryonic and fetal growth (deformations and disruptions) [1]. The more complex the formation of a structure, the more opportunities for malformation.

Defects in the formation and growth of the larynx lead to a variety of malformations. The embryology, clinical features, and management of congenital anomalies of the larynx are reviewed here. Congenital anomalies of the intrathoracic airways are discussed separately. (See "Congenital anomalies of the intrathoracic airways and tracheoesophageal fistula".)

EMBRYOLOGY — The formation of a median pharyngeal groove presages the appearance of the respiratory tract. At approximately 25 days of intrauterine life, the anlagen of the larynx, trachea, bronchi, and lungs arise from a ventromedial diverticulum of the foregut called the tracheobronchial groove. The cartilage of the trachea and connective tissue and muscle of the trachea and esophagus are derived from splanchnic mesenchyme. Lateral furrows develop on each side of the ventromedial diverticulum, deepen, and join to form the tracheoesophageal septum [2-4].

The distal esophagus can be distinguished from the stomach and the laryngeal primordia appear at approximately 33 days of intrauterine life. The T-shaped laryngeal slit (aditus) is formed anteriorly by the growth of the primordium of the epiglottis (from the hypobranchial eminence, arches III and IV) and laterally by the precursors of the arytenoid cartilages (ventral ends of arch VI) [2-4].

During the fifth and sixth weeks, the tracheoesophageal septum extends to the first tracheal ring. By the time the embryo is 13 to 17 mm in length, laryngeal cartilage and muscle development are clearly identifiable and lateral cricoid condensation is underway. By the seventh week of development, the cricoid ring is complete and the cartilaginous hyoid is visible below the epiglottis (picture 1). Definitive tracheal cartilage appears at this stage, and the esophagus has four discrete layers. The larynx, trachea, and esophagus are well formed by the end of the embryologic period (image 1) [2-4].

LARYNGOMALACIA — Laryngomalacia refers to collapse of the supraglottic structures during inspiration (movie 1 and picture 2) [5,6]. It is the most common congenital anomaly of the larynx [7,8]. It is distinct from tracheomalacia (an abnormally compliant trachea), which is far less common. Laryngomalacia causes inspiratory stridor, whereas tracheomalacia causes expiratory or biphasic stridor. In addition, tracheomalacia is often associated with other congenital malformations such as tracheoesophageal fistula or vascular rings. Tracheomalacia is discussed in greater detail separately. (See "Congenital anomalies of the intrathoracic airways and tracheoesophageal fistula", section on 'Tracheomalacia'.)

Etiology — The etiology of laryngomalacia is not clearly defined, and different mechanisms may apply in different infants. Proposed mechanisms include [8-10]:

●Delayed maturation or "hypotonia" of the supporting cartilaginous structures of the larynx

●Redundant soft tissue in the supraglottis

●A foreshortened or tight aryepiglottic fold

●Underlying neuromuscular disorders

●Supraglottic inflammation or edema

Gastroesophageal reflux (GER) has been reported to occur more commonly in children with laryngomalacia compared with other children [11]. Whether GER causes laryngomalacia is uncertain. It is quite possible that the two occur together because of a common underlying mechanism (immature airway and sphincter tone). Nevertheless, in clinical practice, it is widely noted that antireflux medications seem to improve laryngomalacia symptoms. The reason for this effect is unclear since infants typically do not produce much gastric acid.

In histologic studies, surgically excised supraglottic tissues from infants with laryngomalacia are not distinct from supraglottic tissues from infants without laryngomalacia, weakening the "malacia" or soft cartilage theory [12]. The frequent concurrence of GER, the variation in severity with state of consciousness, and the new onset of laryngomalacia after neurologic injuries support the hypothesis that it is a neuromuscular disorder [9].

Clinical features — Laryngomalacia manifests with intermittent low-pitched, "wet" inspiratory stridor, usually with onset in the neonatal period [7,8,13,14]. In most affected infants, stridor peaks at four to eight months of age and resolves by 12 to 18 months. Hoarseness is not a characteristic finding.

The degree of airway obstruction is dynamic, and, thus, the intensity of stridor fluctuates. Stridor is more intense during upper respiratory tract infections and is often worse in the supine position, improving when prone [7]. In infants with mild to moderate laryngomalacia, the stridor is usually loudest when feeding or sleeping and may disappear completely when crying (although this may be difficult to detect due to the noise of the cry). Patients with severe laryngomalacia, conversely, may have the loudest stridor during crying [7]. In some infants, the stridor may be present only during sleep or relaxation (state-dependent laryngomalacia) [13,14].

Other presenting features include [7,9,15-17]:

●Snoring and/or sleep-disordered breathing – 25 percent

●Swallowing dysfunction and/or feeding difficulties – 10 to 50 percent

●GER and laryngopharyngeal reflux (reflux beyond the esophagus to the larynx, oropharynx, or nasopharynx) – 60 to 70 percent

Children with mild forms of laryngomalacia breathe and feed well despite their noisy respiration. More severe forms result in suprasternal or substernal retractions, poor feeding, sleep-disordered breathing, and failure to thrive [16,17].

Up to 20 percent of infants with laryngomalacia have additional airway anomalies, but life-threatening anomalies are uncommon [5,18]. Laryngomalacia may be isolated or may occur in association with congenital syndromes (eg, Down syndrome, DiGeorge [22q11 deletion] syndrome) or other non-airway anomalies [5]. (See "Down syndrome: Clinical features and diagnosis" and "DiGeorge (22q11.2 deletion) syndrome: Clinical features and diagnosis".)

Natural history — In children who are otherwise healthy, laryngomalacia typically resolves over time as the child grows. In a review of three retrospective studies including a total of 411 infants and children with laryngomalacia, 89 percent had resolution of symptoms within the first few years of life (time to resolution ranged from 4 to 42 months) [19]. By contrast, laryngomalacia tends to persist in children who have underlying neuromuscular disorders and genetic syndromes.

Diagnosis — The diagnosis of laryngomalacia is usually suspected based upon the history and physical examination [7]. It is confirmed with flexible fiberoptic laryngoscopy (movie 1) [10].

●When to refer – An experienced pediatric care provider need not refer every infant with mild inspiratory stridor to a pediatric otolaryngologist. Endoscopic evaluation is warranted if the infant has any of the following:

•Moderate to severe stridor or stridor that is progressively worsening

•Apneic or cyanotic episodes

•Stridor that is atypical for laryngomalacia (eg, associated with hoarseness)

•Feeding difficulties or poor growth require

●Confirming the diagnosis – Diagnostic findings on laryngoscopy include an omega-shaped epiglottis and the collapse of the supraglottic structures during inspiration (movie 1). The term "omega-shaped" is used to describe an epiglottis that curls inward towards opening (picture 2). This is in contrast to a more rigid U-shaped epiglottis seen in healthy infants and older children (picture 3).

●Further evaluation – Once the diagnosis of laryngomalacia is confirmed with flexible fiberoptic laryngoscopy, the clinician should assess the severity and consider additional evaluation for associated airway abnormalities.

•Severity – The severity of laryngomalacia is determined by the degree and sequelae of airway obstruction and the response to conservative interventions (eg, position change, feeding modifications, treatment for GER). For example, intermittent, noisy breathing in an infant who is otherwise feeding and growing well would be considered mild, whereas an infant with considerable stridor associated with feeding difficulties, poor growth, apnea, or cyanotic episodes is considered to have severe laryngomalacia.

•Associated anomalies – Ancillary airway evaluation (eg, direct laryngoscopy and bronchoscopy or flexible fiberoptic bronchoscopy) for concurrent laryngotracheal malformations (eg, esophageal atresia, tracheoesophageal atresia) is warranted in infants with cyanosis, apnea, hoarseness, feeding difficulty, poor growth, or atypical stridor [5,10,18,20]. Ancillary airway evaluation is lower yield in infants with less severe symptoms, and performing it as a routine in this setting is controversial [5,10,18,20].

For children who have normal or equivocal findings on awake laryngoscopy yet have a clinical presentation highly suggestive of laryngomalacia, drug-induced sleep endoscopy (DISE) may be useful to evaluate for state-dependent laryngomalacia [21]. Some children show signs of supraglottic collapse only during sleep. DISE can identify this variant and help define the areas of supraglottic prolapse [22]. DISE is not without risk and thus should only be pursued in patients with considerable symptoms. We do not advise DISE in young infants. DISE is most commonly used to evaluate older children with residual obstructive sleep apnea following adenotonsillectomy. The procedure is discussed in greater detail separately. (See "Adenotonsillectomy for obstructive sleep apnea in children", section on 'Drug-induced sleep endoscopy'.)

Numerous other potentially dangerous airway abnormalities may have similar clinical presentations. Hoarseness is not characteristic of laryngomalacia. Other causes of stridor include subglottic stenosis, vocal cord paralysis, vascular ring, laryngeal mass (eg, cyst or hemangioma), subglottic hemangioma, and tracheomalacia (table 1). The assessment of stridor in children is discussed separately. (See "Assessment of stridor in children".)

Management — The management of laryngomalacia depends upon the severity. In the majority of otherwise healthy children, laryngomalacia is not dangerous and resolves spontaneously. (See 'Natural history' above.)

●Mild laryngomalacia – Infants with mild laryngomalacia (intermittent mild stridor with no other symptoms) may be followed clinically with frequent monitoring to make sure that weight gain is adequate [7,10]. Stridor usually resolves by 12 to 18 months of age. (See 'Natural history' above.)

●Moderate to severe laryngomalacia – Infants with moderate or severe laryngomalacia (stridor with feeding difficulty, dyspnea, tachypnea, cyanosis, apnea) should be referred to an otolaryngologist for full endoscopic evaluation and possible intervention [7,10]. Medical management may be adequate therapy for some infants with moderate laryngomalacia [23]; however, infants with severe laryngomalacia often require surgical intervention.

Medical management consists of acid suppression, speech and swallow therapy, and/or high-calorie formula. Infants known to have associated GER should be treated for reflux [10]. Therapy for GER is often empiric in patients with laryngomalacia, though a diagnostic evaluation may be appropriate for some children. Data supporting one approach versus the other are extremely limited [24-27]. Feeding evaluation and speech therapy services can help guide interventions to improve feeding (eg, texture modification, bottle pacing, augmenting feeding schedule). Management of GER and swallowing dysfunction are discussed in greater detail separately. (See "Gastroesophageal reflux in infants", section on 'Treatment options' and "Aspiration due to swallowing dysfunction in children", section on 'Management'.)

For children with severe laryngomalacia, supraglottoplasty (surgery removing redundant supraglottic tissue) can be helpful (picture 4). In experienced hands, supraglottoplasty can produce dramatic improvements in breathing, feeding, and growth with little morbidity [5,7,28-30]. Two meta-analyses found that for children with obstructive sleep apnea due to laryngomalacia, supraglottoplasty is associated with improvement in the apnea-hypopnea index and oxygen saturations; however, most children have residual symptoms after the procedure [31,32]. (See "Adenotonsillectomy for obstructive sleep apnea in children", section on 'Supraglottoplasty'.)

Possible complications of supraglottoplasty include supraglottic or glottic scarring and subsequent chronic aspiration or dysphonia.

The risks and benefits of supraglottoplasty should be carefully considered in children with underlying neuromuscular disease. Neuromuscular disease is not a contraindication to supraglottoplasty, but the benefit of improving airway obstruction must be weighed with the risk of worsening aspiration in this setting [10].

There is considerable institutional variability in the use of supraglottoplasty for management of laryngomalacia, with some specialized centers performing only a handful of procedures annually and other centers reporting >200 supraglottoplasties per year [33,34]. High levels of parental satisfaction with surgery should be balanced against the risks and expense of supraglottoplasty for what is a self-limited disease in most children [35]. In our practice, we reserve supraglottoplasty for severely affected patients. We generally do not offer surgery if the infant has mild symptoms, is otherwise healthy, and is feeding well with normal growth and development. While the infant's noisy breathing can be a source of concern and anxiety for some caregivers, this usually can be alleviated by appropriate anticipatory guidance and counselling regarding the typical course of laryngomalacia (ie, that it usually resolves as the infant grows). (See 'Natural history' above.)

MALFORMATIONS — The complex structure of the larynx and its numerous folds and outpouchings predispose this region to congenital malformations.

Cysts

Vallecular cysts — Congenital vallecular cysts contain respiratory epithelium and mucous glands. They arise in the hypopharynx between the epiglottis and base of tongue (picture 5A-B). Vallecular cysts are an uncommon cause of respiratory distress in infancy [36,37]. Infants with vallecular cysts typically present with feeding difficulty, failure to thrive, stridor, noisy breathing, respiratory distress, or a hoarse cry. Laryngomalacia is an associated finding [36-39]. Diagnosis is confirmed with flexible fiberoptic laryngoscopy.

Definitive treatment requires marsupialization, which can be performed transorally with microscissors or laser, or through a transhyoid resection [36,40-42]. Aspiration or rupture may provide temporary improvement in symptoms but seldom provides permanent treatment.

Laryngoceles and saccular cysts — Congenital laryngoceles and saccular cysts are abnormal dilations of the laryngeal saccule and arise in the region of the laryngeal ventricle. Laryngoceles are outpouchings of the saccular mucosa. They may remain within the confines of the cartilaginous larynx (internal laryngoceles) or extend through the thyrohyoid membrane to present as neck masses (combined laryngoceles). Saccular cysts are fluid-filled submucosal cysts that are covered by a normal mucous membrane and isolated from the interior of the larynx [43].

These anomalies typically are asymptomatic; however, they may cause upper airway obstruction (particularly in the neonate), hoarseness, dysphagia, dyspnea, and laryngeal discomfort [44-47]. The symptoms caused by laryngoceles are episodic because laryngoceles intermittently fill with air. In contrast, the symptoms produced by saccular cysts are constant [47].

Laryngoceles and saccular cysts usually are discovered incidentally during radiologic evaluation for unrelated symptoms. Laryngoceles are visualized as fluid- and air-containing cystic masses on plain radiography, ultrasound, or computed tomography (CT) [46]. CT is preferred for determination of the full extent of the lesion and its relation to the larynx (image 2).

Laryngeal atresia — Laryngeal atresia is thought to be caused by the failure of epithelial growth and recanalization in the vestibule and subglottic regions [48].

Most infants with laryngeal atresia present with asphyxia at the time of birth. Performing an emergency tracheotomy soon after delivery is necessary for survival because the imperforate larynx cannot be intubated [49]. Laryngeal atresia can be identified by antenatal ultrasonography in fetuses presenting with congenital high airway obstruction syndrome [50]. An ex utero intrapartum treatment (EXIT) procedure with tracheotomy is potentially lifesaving [51]. However, fetuses with laryngeal atresia often have other severe congenital malformations that may be fatal (eg, lung hypoplasia, tracheal agenesis, hypoplastic left heart syndrome, bilateral renal agenesis, esophageal atresia) [52].

Laryngeal webs — Laryngeal webs are rare congenital anomalies caused by failure of resorption of the epithelial layer that obliterates the laryngeal opening in normal development. This results in incomplete separation of the vocal folds (picture 6 and picture 7). Webs can occur anywhere along the anterior or posterior larynx. Laryngeal webs also can result from trauma to the airway (eg, from intubation, traumatic injury, or prior surgical manipulation). (See "Common causes of hoarseness in children", section on 'Trauma'.)

Laryngeal webs are categorized according to size [53]:

●Type 1 – Involving <35 percent of the glottis; they are typically thin or membranous

●Type 2 – Involving 35 to 50 percent of the glottis (figure 1)

●Type 3 – Involving 50 to 75 percent of the glottis, often extending to the anterior cricoid cartilage (picture 7)

●Type 4 – Involving up to 99 percent of the glottis

Approximately 10 percent of patients with laryngeal webs have other associated anomalies, principally of the upper respiratory tract (eg, subglottic stenosis, submucous cleft palate) [54,55]. In addition, laryngeal webs are associated with cardiac defects (particularly, ventricular septal defects [56,57]) and may occur in conjunction with 22q11 deletion as part of the DiGeorge/velocardiofacial syndrome. (See "DiGeorge (22q11.2 deletion) syndrome: Epidemiology and pathogenesis" and "Syndromes with craniofacial abnormalities", section on 'Velocardiofacial (Shprintzen) syndrome'.)

Patients with laryngeal webs usually present in infancy with respiratory distress and a weak or high-pitched cry [54,58]. Symptoms in those who present later in life include hoarse or weak voice, breathiness, and varying degrees of dyspnea and stridor depending upon the degree of airway compromise. (See "Assessment of stridor in children".)

Treatment of laryngeal webs depends upon the degree of airway obstruction. Simple anterior commissure webs are treated surgically, either by lysis of the web with a carbon dioxide (CO₂) laser or sharp division with a knife. Laryngeal reconstruction with or without a laryngeal stent may be indicated in patients with webs that involve larger portions of the anterior and posterior glottis. Recurrent webbing is common following attempts at either endoscopic or open repair [53].

Congenital subglottic stenosis — Congenital subglottic stenosis is a narrowing of the lumen of the cricoid region, possibly caused by incomplete canalization of the cricoid ring (diameter less than 4 mm in the term infant and 3 mm in the preterm infant) [48,59]. It presents most commonly as recurrent croup but may cause biphasic stridor in a newborn if severe. It is differentiated from acquired subglottic stenosis by the absence of history of trauma or instrumentation and by less severe symptoms. (See "Complications and long-term pulmonary outcomes of bronchopulmonary dysplasia", section on 'Glottic and subglottic damage'.)

Congenital subglottic stenosis typically improves as the larynx grows. Fewer than one-half of the children with this disorder require tracheostomy. Depending upon the severity of the obstruction and the need for supplemental oxygen therapy, congenital subglottic stenosis also may be treated by endoscopic division of cartilage with balloon dilation, anterior-cricoid split with posterior cartilage graft, or partial cricotracheal resection [48,60-63].

Laryngeal clefts — Posterior laryngeal clefts are thought to result from failed fusion of the two lateral growth centers of the posterior-cricoid cartilage at six to seven weeks of intrauterine life. The smallest clefts may involve only the interarytenoid region, whereas more extensive aborted development of the tracheoesophageal septum can result in a large laryngotracheoesophageal cleft that extends to the carina [64,65].

Laryngeal clefts occur in approximately 1 in 10,000 to 1 in 20,000 live births [66]. They are more common in boys than girls, with a male:female ratio of 5:3 [67,68]. Clefts of the larynx and trachea/esophagus can occur in isolation, or as part of a syndrome (eg, Opitz-Frias, VATER/VACTERL, Pallister-Hall, CHARGE), or with other associated malformations (gastrointestinal, genitourinary, cardiac, craniofacial) [69].

Children with posterior laryngeal clefts may present with increased secretions, feeding difficulty, failure to thrive, wheezing, stridor, noisy breathing, aspiration, respiratory distress, recurrent pulmonary infections, and/or hoarseness [48,70,71]. In one series of 41 children with type 1 posterior laryngeal clefts, the average age at onset of symptoms was five months and the average age at diagnosis was three years [70]. Children with posterior laryngeal clefts often have associated gastroesophageal reflux (GER), tracheomalacia, developmental delay, and/or additional congenital anomalies [48,70-72].

The diagnosis is based upon a high index of suspicion and is supported by modified barium swallow that shows leakage of barium into the airway [48,71]. Leakage occurs at the laryngeal introitus, rather than the distal trachea as is seen in H-type fistulae. Rigid endoscopy is the standard for diagnosis and should include endoscopic palpation of the interarytenoid area (picture 8) [70].

Posterior laryngeal clefts and laryngotracheoesophageal clefts may be classified according to anatomic or clinical criteria. The Benjamin classification describes five types (figure 1) [73]:

●Occult clefts can be appreciated only by palpation and measurement of the interarytenoid height

●Type 1 clefts are limited to the supraglottic, interarytenoid area (picture 8)

●Type 2 clefts show partial clefting of the posterior cricoid cartilage, sometimes with a mucosal bridge across the cartilaginous gap

●Type 3 clefts involve the entire cricoid and the cervical portion of the tracheoesophageal membrane, stopping above the thoracic inlet

●Type 4 clefts involve a major portion of the intrathoracic tracheoesophageal wall (picture 9)

The treatment for laryngotracheoesophageal clefts depends upon the type of cleft and severity of associated symptoms. Minor clefts (type 1 and occult clefts) sometimes can be managed without surgery if medical therapy can control GER and aspiration [48,70]. Injection of the interarytenoid region with fillers, such as hyaluronic acid, can help decrease aspiration temporarily as the child grows [74-76]. Local endoscopic procedures can also be attempted on smaller-sized clefts. Operative repair of extensive clefts typically requires collaboration of the otolaryngologist and thoracic surgeon [77]. (See "Management of gastroesophageal reflux disease in children and adolescents".)

Subglottic hemangiomas — Infantile hemangiomas are congenital vascular lesions that undergo a phase of rapid growth that is initiated during the first few weeks to months of life [78]. They may present as solitary lesions or as part of a segmental hemangioma syndrome [79,80]. The growth phase lasts for 12 to 18 months, after which the lesion stabilizes in size for a period of time. Finally, the lesion undergoes involution, typically with complete resolution of the lesion by age 5 in 50 percent of cases and age 12 in the remainder of cases. (See "Infantile hemangiomas: Epidemiology, pathogenesis, clinical features, and complications".)

Congenital subglottic hemangiomas are rare but potentially fatal lesions. They account for 1.5 percent of congenital laryngeal abnormalities. There is a higher prevalence in females, with a female:male ratio of 2:1. Presentation may be similar to that of subglottic stenosis, with recurrent croup and biphasic stridor.

Clinical diagnosis can be made based upon history and complete physical examination, including rigid endoscopy. Plain radiographs of the neck typically demonstrate asymmetric narrowing of the subglottis. CT with contrast may be useful in delineating large hemangiomas or those extending beyond the confines of the larynx. Rigid endoscopy reveals a red to blue, compressible, sessile lesion that is most commonly located in the posterolateral subglottis (picture 10 and picture 11).

Systemic therapy with propranolol is the first-line therapy for subglottic hemangiomas and has produced dramatic results in case series, with a low incidence of complications [81,82]. Historically, a watchful waiting approach with or without a tracheotomy was taken. Locally injected or systemic glucocorticoids may hasten resolution. Laser or open surgical resections have been used with mixed results. (See "Infantile hemangiomas: Management", section on 'Propranolol'.)

Subglottic hemangioma associated with cutaneous hemangiomas in a "beard" distribution may be seen in PHACE syndrome (posterior fossa brain malformations, hemangiomas of the face [large or complex], arterial anomalies, cardiac anomalies, and eye abnormalities) (table 2) [83,84]. (See "Infantile hemangiomas: Epidemiology, pathogenesis, clinical features, and complications", section on 'PHACE syndrome'.)

SUMMARY AND RECOMMENDATIONS

●Laryngomalacia – Laryngomalacia refers to collapse of the supraglottic structures during inspiration (movie 1 and picture 2). (See 'Laryngomalacia' above.)

•Clinical manifestations – Clinical manifestations include stridor that worsens in the supine position, during feeding, and with upper respiratory infections. Onset is usually in the neonatal period and symptoms typically peak at four to eight months of age. Hoarseness is not a characteristic finding.

•Diagnosis – Laryngomalacia is suspected based upon the history and physical examination and confirmed with flexible fiberoptic laryngoscopy (movie 1 and picture 2).

•Natural history – In most otherwise healthy children, laryngomalacia resolves spontaneously by 12 to 18 month of age.

•When to refer – Infants who have any of the following should be referred to a pediatric otolaryngologist for further evaluation:

-Moderate to severe stridor or stridor that is progressively worsening

-Apneic or cyanotic episodes

-Stridor associated with atypical findings (eg, hoarseness)

-Feeding difficulties or poor growth

●Vallecular cysts – Infants with vallecular cysts (picture 5A and picture 5B) typically present with feeding difficulty, failure to thrive, stridor, noisy breathing, respiratory distress, or a hoarse cry. Laryngomalacia is an associated finding. Diagnosis is confirmed with endoscopy of the hypopharynx. (See 'Vallecular cysts' above.)

●Laryngoceles and saccular cysts – Congenital laryngoceles and saccular cysts typically are asymptomatic; however, they may cause upper airway obstruction (particularly in the neonate), hoarseness, dysphagia, dyspnea, and laryngeal discomfort. The symptoms caused by laryngoceles are episodic because laryngoceles intermittently fill with air. The symptoms produced by saccular cysts are constant. (See 'Laryngoceles and saccular cysts' above.)

●Laryngeal atresia – Most infants with laryngeal atresia present with asphyxia at the time of birth. Emergency tracheotomy is necessary for survival. (See 'Laryngeal atresia' above.)

●Laryngeal webs – Laryngeal webs are rare congenital anomalies caused by failure of resorption of the epithelial layer at the laryngeal opening, resulting in incomplete separation of the vocal folds (picture 6 and picture 7). Patients with laryngeal webs usually present in infancy with respiratory distress and an unusual cry. Approximately 10 percent of patients with laryngeal webs have other associated anomalies. Treatment is surgical and depends on the degree of airway obstruction. (See 'Laryngeal webs' above.)

●Subglottic stenosis – Congenital subglottic stenosis is a narrowing of the lumen of the cricoid region. It presents most commonly as recurrent croup but may cause biphasic stridor in a newborn if severe. It is differentiated from acquired subglottic stenosis by the absence of history of trauma or instrumentation and by less severe symptoms. Congenital subglottic stenosis typically improves as the larynx grows; however, surgical intervention may be necessary in some children. (See 'Congenital subglottic stenosis' above.)

●Laryngeal clefts – Children with posterior laryngeal clefts may present with increased secretions, feeding difficulty, failure to thrive, wheezing, stridor, noisy breathing, aspiration, respiratory distress, recurrent pulmonary infections, and/or hoarseness. Contrast studies of the esophagus may show spillage of barium into the airway. Rigid endoscopy is the standard for diagnosis and should include palpation of the interarytenoid area (picture 8 and picture 9). (See 'Laryngeal clefts' above.)

●Hemangiomas – Congenital subglottic hemangiomas are rare but potentially fatal lesions. The presentation may be similar to that of subglottic stenosis with recurrent croup and biphasic stridor. Plain radiographs typically demonstrate asymmetric narrowing of the subglottis. The diagnosis is confirmed endoscopically (picture 10 and picture 11). Propranolol is generally the first-line therapy for subglottic hemangiomas. (See 'Subglottic hemangiomas' above and "Infantile hemangiomas: Management".)