Laryngeal tone and function is coordinated and modulated by a vagal nerve pathway called the laryngeal adductor reflex (LAR). Sensory information is gathered by superior laryngeal nerve fibers located in the aryepiglottic fold. Afferent signals pass through the nodose ganglion and are transmitted to the brainstem to synapses in the nucleus solitarius and nucleus ambiguous. These nuclei regulate breathing and swallowing. The efferent pathway is activated with signals propagating via the vagus nerve to the laryngeal muscles. In normal conditions, an involuntary motor response results in glottic closure and inhibition of respiration and swallowing, protecting the airway from the perceived laryngeal stimulus. This reflex also modulates baseline laryngeal tone. Abnormal sensorimotor integration of the LAR anywhere along the pathway results in decreased laryngeal tone, choking, aspiration, apnea, swallowing difficulty, and inability to clear secretions [1], all of which are within the spectrum of symptoms and clinical examination findings that may be seen in infants with laryngomalacia.

Laryngopharyngeal sensory testing in infants with laryngomalacia has demonstrated that the sensory stimulus threshold needed to begin the laryngeal adductor reflex is elevated in those with moderate and severe laryngomalacia. This finding suggests that peripheral afferent function and/or brainstem function are altered and lead to decreased laryngeal tone in patients with laryngomalacia. This theory is further supported by the finding of submucosal nerve hypertrophy in histological specimens of the supraarytenoid tissue in infants with severe laryngomalacia. It is unclear, however, if the noted nerve hypertrophy is the primary pathology or if it occurs secondary to inflammation from gastroesophageal reflux disease [4].

Alteration of brainstem responses may also contribute to the pathogenesis of laryngomalacia as they are often altered by states of hypoxia and hypercarbia, both of which may be seen in affected infants. The effect of brainstem modulation is further supported by case reports demonstrating reversal of laryngomalacia symptoms and findings after surgical decompression of the brainstem due to Chiari malformation or correction of a vertebral anomaly causing compression of the brainstem [3].

Gastroesophageal reflux likely plays an important role in the dysfunction of this neurological pathway by altering laryngeal sensation and causing tissue edema. Chronic acid exposure on the chemo- and mechanoreceptors of the larynx results in a functional denervation of the afferent response of the LAR. With decreased sensation the infant has difficulty handling secretions and initiating a swallow. Acid exposure also causes tissue edema, which can further exacerbate inspiratory prolapse of the supraglottic structures into the airway. Obstruction during inspiration can in turn increase negative intrathoracic pressure promoting further reflux and creating a vicious cycle. Until the airway obstruction/ reflux cycle is broken, the infant will continue to have symptoms.

Laryngomalacia is the most common congenital laryngeal anomaly, and is implicated in 45–75 % of infants with stridor. The exact demographic data of laryngomalacia is not known. There is a reported male predominance of an average 1.6:1 male to female ratio [1, 5–10]. The clinical significance of this is unknown. No racial differences have been reported, but the majority of published literature has reported on Caucasian infants [11].

Congenital laryngomalacia can occur in newborns of any gestational age. The condition is seen in premature infants but has not been shown to have an increased incidence in this population. There may be a trend toward an association of prematurity and severity of disease, but larger populations with documented gestational age data are lacking [1, 12]. When comparing the specific sites of supraglottic collapse, preterm infants were found to have more of the classic features of laryngomalacia compared to term infants [13].

Laryngomalacia is characterized by inspiratory stridor secondary to supraglottic tissue prolapse. The disease typically presents with stridor within 2 weeks of birth. The symptoms gradually increase until a peak is reached at 6–8 months of age. The majority of cases are self-limited and resolve by 18–24 months of age, but up to 20 % of infants will have significant airway obstruction and/or feeding issues requiring medical and surgical treatment [1, 14, 15].

Stridor is the primary symptom of laryngomalacia. On inspiration a high pitched, fluttering stridor is heard as the supraglottic tissues collapse over the glottis and vibrate against each other. Laryngomalacia increases with crying, agitation, and feeding due to the increase of negative intrathoracic airway pressures during these times. Supine positioning increases symptoms secondary to the posterior displacement of the base of tongue and laryngeal structures.

Feeding difficulties including regurgitation, emesis, cough, choking, and slow feeding are the most common associated symptoms of the disease. Airway obstruction interferes with the infant’s ability to coordinate the suck-swallow-breathe sequence needed for feeding. Weight loss and failure to thrive can occur when there is a high metabolic demand of feeding and breathing against an obstruction.

In severe disease, infants may also present with suprasternal and subcostal retractions, tachypnea, apneic pauses, cyanosis, pectrus excavatum, pulmonary hypertension, and cor pulmonale.

Diagnosis of laryngomalacia is primarily made by history and confirmed by an awake flexible nasopharyngoscopy. Caregivers often give a classic history of high pitched inspiratory stridor beginning within weeks of birth. The stridor is exacerbated with crying, agitation, supine positioning, and feeding. It is important to ask about feeding symptoms including cough, choking, regurgitation, and slow/fussy feeds. History of suprasternal and/or subcostal retractions, cyanosis, apnea, aspiration, and failure to thrive are worrisome and indicate severe disease. Cardiac, pulmonary, neurologic, gastrointestinal disease and the presence of a genetic disorder or syndrome history are important to note for treatment planning and prognostication.

The infant’s birth, intubation, and surgical history are important in determining congenital versus acquired causes of stridor. The differential diagnosis of congenital stridor in an infant includes subglottic stenosis, vocal cord paralysis, tracheomalacia, and tracheal stenosis. Conditions that cause inspiratory stridor in infants and can mimic laryngomalacia include unilateral vocal fold paralysis, vallecular cyst, or a saccular cyst of the larynx. These entities can be differentiated by flexible laryngoscopy. In contrast to the inspiratory stridor of laryngomalacia, infants with bilateral vocal fold paralysis or subglottic stenosis have biphasic stridor with both inspiratory and expiratory components. The stridor of tracheomalacia and tracheal stenosis has a characteristic expiratory phase.

As noted above, confirmation of laryngomalacia is made by an awake flexible nasopharyngoscopy (Fig. 1). The infant is gently retrained on the caregivers lap in an upright or semi-reclined position. Sedation is not necessary, and may lead to false positive findings due to the resultant decrease in neuromuscular tone. A flexible scope is passed and the nasopharyngeal, oropharyngeal, hypopharyngeal, and laryngeal structures are inspected.

During the procedure, arytenoid mucosa and cartilage prolapse, shortened aryepiglottic folds and an omega or tubular epiglottis may be visualized. A retroflexed epiglottis with posterior pharyngeal contact can also be seen in more severe cases. One must visualize dynamic collapse of the supraglottic structures on inspiration and obtain a consistent history to diagnosis laryngomalacia. The presence of an omega-shaped epiglottis is not pathognomonic for laryngomalacia as up to 50 % of normal infants have this shape to the epiglottis [16]. Inspiratory stridor is heard during a positive exam. In severe disease the infant may also exhibit retractions and/or brief cyanosis.

The larynx may prolapse at one or multiple supraglottic locations. Multiple anatomic classification systems have been described based on the supraglottic location and direction of collapse [13, 17–19]. When redundant arytenoid mucosa and accessory cartilages prolapse, this is recognized as posterior prolapse. Foreshortened aryepiglottic folds obstruct the airway in the lateral plane, and anterior collapse occurs with posterior displace of the epiglottis. The pattern of collapse may help to guide surgical treatment.

After confirmation of the diagnosis, other adjuvant studies may be indicated depending on symptomatology and severity of disease. Videofluoroscopic swallow study or functional endoscopic evaluation of swallow (FEES) can be used to assess feeding symptoms and aspiration. In infants with known chronic aspiration, a chest X-ray should be obtained to determine the amount of pulmonary injury present. Concomitant gastroesophageal disease such as malrotation or pyloric stenosis should be ruled out with an esophagram in those with severe recurrent emesis.