Laryngomalacia In Neonates And Infants

Definition

Laryngomalacia is the dominant cause for a high-pitched respiratory sound, known as stridor, when breathing in,  in about 50-75% of neonates and infants. It results in intermittent airflow, characterised by noisy breathing, that may be a sign of the degree of respiratory disruption, and feeding concerns in approximately half of infants. However, the disorder is mostly self-limited, occurring within the first 24 months of life. Therefore, it is necessary for the diagnosis to be early as it may cause several concerns about growth.^1-4

Presentation

Laryngomalacia occurs due to the collapse of supraglottic structures, the upper portion of the larynx (voice box), during inhalation, thus, stridor or noisy breath develops as a result of intermittent airflow. It can be triggered by:

• Upper respiratory infections 
• Crying 
• Feeding 
• Agitation 

Stridor linked to laryngomalacia does not always appear at birth but might occur several weeks after. Symptoms may peak at 4 to 8 months of life and alleviate during sleep in mild to moderate cases. Some cases experience respiratory issues such as obstructive sleep apnea and recurrent aspiration pneumonia and could progress to pulmonary hypertension in severe cases. Feeding-related problems are present in about 50% of cases but in about all the severe cases including cough, emesis, cyanotic episodes, and regurgitation.³ 

Causes of laryngomalacia 

The causes of laryngomalacia are multifactorial, consisting of anatomic, neurological and inflammatory factors,  and several theories have been suggested.

Historically, the anatomic theory proposed that there is an abnormality in the laryngeal cartilage, but this theory failed to explain why some of the cases with similar laryngeal examinations were asymptomatic. 

However, one of the leading theories focuses on the neuromuscular concept, where neurologic dysfunction that impaired laryngeal tone (speech) was caused by an alteration of laryngeal nerves. No findings were reported by researchers regarding gastroesophageal reflux  as a causative factor for laryngomalacia.^1,3 

Prevalence 

Generally, the incidence of laryngomalacia is unknown and expected to be anywhere in about 1 in 3000. This may be due to the fact that mild laryngomalacia is clinically diagnosed and followed by a paediatrician rather than confirming it endoscopically. 

Previous evidence has proposed male predominance, however, recently other studies suggest that it is prevalent in both genders. Black and Hispanic neonates are at higher risk than white infants Moreover, low birth weight is a correlating factor due to prematurity.² 

Diagnosis and evaluation

History and examination

A clinical diagnosis can be applied based on the known symptoms of inspiratory stridor, triggered by feeding, crying, agitation, supine positioning, and upper respiratory tract infections.

Birth conditions that are taken into account include as:³

• Endotracheal intubation and gestational age 
• Congenital and genetic alterations 
• Respiratory symptoms 
• Feeding problems including slow growth, recurrent pneumonia, and reflux symptoms

Physical examination is typically carried out for:

• Height 
• Weight 
• Checking to time for the respiratory cycles 
• Listening to respiratory sounds 
• Watching chest movement 
• Observing retractions which refers to the movement of the chest wall during breathing and is a sign of breathing difficulty 
• Examining the chest wall if it is sunken inwards
• Listening to the breath sounds produced by the lungs using a stethoscope to figure out any abnormalities 

Laryngoscopy

Flexible fiberoptic laryngoscopy is the definitive diagnostic tool for laryngomalacia which can be performed alone on awake neonates and infants without the use of sedation. Topical anaesthetics should be avoided as they can impair the examination process and worsen airway collapse. 

This procedure gives the practitioner a complete view of the oropharynx, supraglottis, glottis, subglottis, and hypopharynx. Cases with laryngomalacia are observed to have characteristic findings as their aryepiglottic fold is shorter than normal, causing the epiglottis to be pulled backwards forming the shape of the Greek letter omega. Moreover, excess arytenoid tissue can be found prolapsed on the top of the opening of the vocal cords (glottis).² 

Swallowing mechanism

Conducting radiologic tests of swallowing is essential in neonates and infants who experience swallowing difficulties alongside laryngomalacia, and is usually performed by a speech therapist. Additionally, a modified barium swallow study is required, which is a procedure of consuming food or liquid mixed with barium sulphate, to be visualised on an x-ray. This is because aspiration might take place silently without any signs during a regular examination. 

Polysomnogram

Cases of laryngomalacia can be tested and quantified for the degree of obstructive sleep apnea. The test includes a drug-induced sleep endoscopy used to diagnose sleep disorders using certain physiological parameters during sleeping as eye movements, brain waves, breathing patterns, and heart rate. It may be useful for patients to have a supraglottoplasty, which is a surgical intervention to remove excess tissue, this procedure is to improve their sleep apnea.

Swallowing function and comorbidities 

Studies showed no significant differences in swallowing dysfunction or complications in cases with or without congenital heart diseases, neurologic defects, or Down’s syndrome. Moreover, there is no significant correlation between the severity of laryngomalacia and the presence of these abnormalities.¹

Treatment options and management

Conservative and medical treatment

Children with mild to moderate inspiratory stridor associated with no feeding problems can be followed up through observation after disorder confirmation. They should be closely monitored by checking their weight progress and worsening of feeding and respiratory symptoms.³ 

However, for children with mild to moderate respiratory symptoms and mild feeding problems, positional therapy and conservative management may be advantageous. Additional feeding strategies could be beneficial involving: 

• The use of breast milk 
• Slow flow feeding 
• Eating in an upright position 
• Use of thickened formula 
• Anti-reflux medications

Surgical treatment

Approximately 10% to 20% of infants will develop severe symptoms that require surgical intervention. In these cases, supraglottoplasty remains the most efficient option and the initial treatment of choice resulting in symptomatic improvement and reduced duration of symptoms in most cases. It also reduces sleep apnea episodes. 

Supraglottoplasty is conducted through multiple approaches, including using cold steel, laser, coblator, or laryngeal microdebrider.^2,4 

Patients are observed and monitored postoperatively, though it is generally well tolerated. Pharmaceutical therapy including steroid administration is highly recommended to avoid airway inflammation. 

Prognosis

The prognosis of laryngomalacia is expected between 12 to 18 months, but recent studies proposed a wider range of age of resolution. Surgical interventions have reliable outcomes with success rates up to 95%. However, some patients may require further intervention (revision surgery), especially those under 2 months old, with neurologic or cardiac comorbidities.²  

Complications

Aspiration after surgical intervention is uncommon anddoes not correlate to the surgical procedure. However, certain factors including age under 18 months at the time of surgery, neurologic concerns, and revision surgery are linked to postoperative aspiration. Nonsurgical treatments for laryngomalacia might be ineffective with no significant improvement in symptoms such as anti-reflux medication (proton pump inhibitors).

Consultations

Neonates and infants with laryngomalacia require multidisciplinary approaches and evaluations by specialists in neurology, gastroenterology, paediatrics, cardiology, genetics, and speech therapy. 

Patient education

Parents or caregivers should be aware that treatment is conservative-focused, but close follow-up and monitoring are mandatory to avoid the worsening of symptoms. Adherence to treatment approaches should be encouraged. Moreover, parents should be guided regarding the positional feedings and other advice. 

Summary

• Laryngomalacia is the most common cause of stridor during inspiration in neonates and infants. It results in intermittent airflow identified by noisy breathing. Laryngomalacia is due to the collapse of supraglottic structures during inhalation
• The causes of laryngomalacia are multifactorial and several theories have been suggested. It is a combination of anatomic, neurologic, and inflammatory factors that lead to the disorder
• Generally, the incidence of laryngomalacia is unknown and it is suggested to be anywhere from about 1 in 3000
• Physical examination should be done for height and weight, checking timing for the respiratory cycles, listening to respiratory sounds, watching chest movement, and observing retractions
• Laryngoscopy is the definitive diagnostic tool for laryngomalacia which can be performed alone
• Studies have shown no significant differences in swallowing dysfunction or complications in cases with or without congenital heart diseases, neurologic defects, or Down’s syndrome
• Children with mild to moderate inspiratory stridor associated with no feeding problems can be followed up through observation
• However, for children with mild to moderate respiratory symptoms and mild feeding problems, positional therapy and conservative management are required
• Approximately up to 20% of infants will develop severe symptoms that require surgical options
• Parents should be aware that treatment is conservative-focused, and close monitoring is mandatory to avoid complications