Introduction

Literally translated as “soft larynx”, laryngomalacia has an incidence of between 1 in 2000 to 1 in 3000 of the general population of infants and is the most common cause of noisy breathing in infants.^1,3 In laryngomalacia, the supraglottic tissues (those parts of the larynx that sit above the vocal cords) fall into the airway during inspiration, obstructing the airway. This causes stridor, a high pitched raspy sound, in the case of laryngomalacia during the inspiratory phase of respiration. Stridor is a sign of airway compromise, and whilst this can be caused by a wide variety of conditions, laryngomalacia is by far the most common cause in infants.¹ 

Understanding noisy breathing in infants

An infant with noisy breathing is a common presentation to the family physician or paediatric emergency room. There are broadly 3 types of noisy breathing: stridor, stertor and wheezing.¹ It is important to define these in the context of the diagnosis of laryngomalacia. Stridor is a high pitched raspy noise which can be present in inspiration, expiration or in both phases of respiration, depending on the level of the obstruction.

In the case of laryngomalacia, this is during inspiration, as inspiratory stridor occurs in obstruction above the level of the vocal cords. Stertor is a grunting/snoring noise present upon inspiration, found in enlarged tonsils and adenoids. Wheezing is a high pitched whistling noise, usually heard during expiration, indicating lung conditions such as asthma and bronchiolitis.

Laryngomalacia represents 45-75% of all causes of infant stridor.¹ Whilst many cases of laryngomalacia are benign and cause few complications or distress (except that of the child’s worried parents) and resolve spontaneously in 12-24 months, other cases cause significant feeding problems, and severe cases may require surgery due to significant breathing and feeding difficulties.^1,3

The presentation of laryngomalacia

The classical presentation of laryngomalacia is with inspiratory stridor, which worsens during feeding, crying and with the infant is lying on their back. Symptoms usually appear at birth or in the first few weeks of life, and typically are at their worst at 6-8 months. Resolution of symptoms occurs between 12-24 months of age.¹ 

However, not all cases present typically. One study found 3 main presentation types: classical stridor, snoring and sleep disordered breathing, and swallowing dysfunction. 64% of infants had classical stridor, 25% snoring / sleep disordered breathing and 11% swallowing dysfunction.²

In addition to stridor, other symptoms may occur. These are:^1,3

• Regurgitation during feeding
• Vomiting
• Cough
• Choking
• Slow or difficult feeding (this may be so severe that it causes weight loss or failure to thrive)

Less commonly, there are severe respiratory symptoms in the worst cases:^1,3

• Tachypnoea (rapid breathing)
• Suprasternal and substernal retractions (this is when hollows can be seen above and below the breastbone due to increased effort of breathing)
• Cyanosis (blue lips and extremities)
• Pectus Excavatum (a hollowed chest shape due to chronic breathing difficulty)
• Obstructive sleep apnoea (stopping breathing for short periods during sleep)
• Pulmonary hypertension due to chronic low blood oxygen levels

Laryngomalacia needs to be distinguished from other conditions causing noisy breathing, of which there are many, but the most common are asthma, bronchiolitis, and tracheomalacia.

How laryngomalacia is diagnosed?

The clinical history is the most important factor in diagnosis, however as explained above, this is not always the typical presentation described in medical textbooks, and laryngomalacia should be considered in babies who are feeding poorly, snoring at night, failing to gain weight or showing signs of breathing difficulty, even without stridor. Most diagnoses will be made in the first few months of life as this is when the symptoms first occur, advancing to their peak at 6-8 months.^1,2

Once laryngomalacia is suspected, referral should be made to an ENT specialist (Ear, Nose and Throat). The diagnosis will be confirmed by a flexible nasendoscopy procedure. This involves passing a thin fibre optic tube into the nose and above the larynx to visualise the larynx and supraglottis. The supraglottis is the area above and around the vocal cords and entry to the trachea (windpipe). The supraglottis comprises the epiglottis, false vocal cords, arytenoids, ventricle, and the aryepiglottic folds. In laryngomalacia the supraglottic structures are seen to collapse into the airway on inspiration and crying. An “omega” shaped epiglottis may also be seen. The procedure is done with the baby awake, held firmly in the seated position by a caregiver, and does not require general anaesthesia. Another advantage of the procedure is that it can identify other causes of stridor, such as a vocal cord paralysis or laryngeal cyst, which are rarer differential diagnoses for infant stridor. In severe cases however, there may be other lesions such as tracheomalacia, further down the airway, in which case a direct laryngoscopy/bronchoscopy in the operating room may be considered.^1,3,4

What causes laryngomalacia?

Whilst the exact cause of laryngomalacia is unknown, several theories abound. The anatomical theory suggests that an excess of flaccid supraglottic tissue is responsible. The cartilaginous theory suggests that the laryngeal cartilage is immature, and not sufficiently strong to support the supraglottic tissues. Finally, the most complex is the neurological theory that proposes that the nuclei and peripheral nerves involved in the control of coordinating breathing and movement of the supraglottic structures during breathing are underdeveloped, explaining why the condition spontaneously resolves at 12-24 months. It is the latter theory that currently has the most support in the scientific literature.^3,5

The spectrum of severity of laryngomalacia

Whilst most cases of laryngomalacia are diagnosed very early in life, the decision from the parents of the child to seek medical help and obtain a diagnosis is partly dependent on the severity of the disease. Severity is based not on the presence of the stridor, which, whilst distressing for parents, does not relate to the severity of the disease. Rather, this is evidenced by the effects laryngomalacia has on feeding and breathing. Laryngomalacia can be classified as mild, moderate or severe.¹

• Mild disease: stridor is present but is relatively inconsequential. There may be mild effects on feeding, such as coughing or choking, and the child may be a slow feeder or not feed comfortably, but weight gain is normal, and there is no failure to thrive. This accounts for about 40% of cases¹
• Moderate disease: stridor is present with significant coughing, choking and regurgitation of feeds, vomiting may be present. There is weight loss and feeding is markedly laborious. This also accounts for 40% of cases¹ 
• Severe disease: Breathing difficulties are marked. The child may be intermittently cyanosed (blue) and have apnoeic episodes where they stop breathing completely. Subcostal and suprasternal recessions are present and sometimes the child will develop a concave chest (pectus excavatum). These are the cases in which surgical intervention (supraglottoplasty) is frequently required and account for the remaining 20% of cases¹

Clearly in more severe disease and when weight loss or failure to thrive are key features, the child is likely to present early and thus be diagnosed early.

Clinical associations in laryngomalacia

Another factor that may aid early diagnosis of laryngomalacia is its association with other conditions. Laryngomalacia is associated with the following medical conditions in infants:⁶

• GERD (gastro-oesophageal reflux disease)
• Neurological diseases - seizures, hypotonia, cerebral palsy, microcephaly, quadriplegia
• Secondary airway lesions eg. subglottic stenosis, tracheomalacia
• Congenital heart disease
• Congenital abnormalities/syndromes, genetic disorders

Understanding why laryngomalacia is diagnosed in the first few weeks of life

The simple answer to this question is that the symptoms of stridor are striking and usually occur from birth to the first 2 weeks of life, and as up to 75% of all cases of infant stridor are laryngomalacia there is a high index of suspicion.¹ However this is not always the case as there are studies showing that in one series, only 64% of patients had stridor, demonstrating that clinicians need to be aware of atypical presentations.² Another factor is that in moderate and severe disease there is weight loss due to poor feeding or failure to thrive, which is usually picked up in routine postnatal checks of the baby’s growth and weight. Finally severe laryngomalacia causes profound breathing difficulties which will be evident from an early age. 

Summary

Meaning “soft larynx”, laryngomalacia is a condition in which the tissues above the vocal cords (the supraglottis) fall into the airway, obstructing breathing and causing a form of noisy breathing called stridor. Not all infants with laryngomalacia have stridor, however, it is something clinicians need to be aware of. In addition to stridor, laryngomalacia can cause feeding difficulties, poor weight gain and significant breathing difficulties. Symptoms begin at birth or in the first few weeks of life, and diagnosis is usually made in this period on the basis of clinical history and confirmation by nasendoscopy. Clinicians should be familiar with diagnosing laryngomalacia, as it is the most common cause of noisy breathing in babies.