Laryngomalacia and Tracheomalacia

Overview

Definitions

Laryngomalacia is softening of or redundancy of supraglottic structures leading to collapse and narrowing of the airway during inspiration.

Tracheomalacia is an abnormality in tracheal compliance caused by a variety of factors, resulting in the dynamic airway narrowing.

Epidemiology

Laryngomalacia:

• Most common congenital laryngeal abnormality
• Estimated incidence 1 in 2,600 children
• 45%–75% of children with stridor have laryngomalacia. 
• No gender propensity
• More common in Hispanic or Black children
• Associated with prematurity and low birthweight 
• Can be associated with other congenital anomalies:
  • Down’s syndrome
  • DiGeorge’s syndrome

Tracheomalacia:

• Estimated incidence 1 in 2,100 children
• Can often develop as a complication of other conditions (e.g., vascular rings, post-surgical complication)
• Often accompanied by other upper airway malformations (e.g., tracheoesophageal fistula)
• More frequent in premature infants

Etiology

Laryngomalacia (not exactly known) presumed causes:

• Hypotonia (delayed maturation) of the supportive cartilage
• Redundant soft tissue
• Supraglottic inflammation
• Neuromuscular disorders
• Gastroesophageal reflux (seen in 60% of children with laryngomalacia)

Tracheomalacia:

• Congenital:
  • Hypotonia/cartilage weakness
    • Ehlers-Danlos syndrome
    • Bronchopulmonary dysplasia
  • Mechanical intrauterine pressure:
    •  Vascular rings
    •  Tracheoesophageal fistulas
• Acquired:
  • Cartilage injury:
    • Tracheostomy or intubation
    • External trauma
    • Surgery
  • External compression:
    • Thyroid goiter
    • Tumor
    • Vascular compression
    • Abscess/cyst
  • Recurrent infections:
    • Chronic bronchitis
    • Cystic fibrosis
  • Chronic inflammation:
    • Recurrent polychondritis
    • Emphysema/smoking

Pathophysiology

Embryology

1. 25 days: Anlagen of larynx, trachea, bronchi, and lungs form from tracheobronchial groove.
2. 33 days: Laryngeal primordia form.
3. 5th–6th week: Tracheoesophageal septum extends to the 1st tracheal ring.
4. 7th week:
   • Cricoid ring is formed.
   • Hyoid bone is visible.
   • Definitive tracheal cartilage appears.

Pathophysiology

Laryngomalacia:

• Abnormally soft laryngeal cartilage:
  • Inspiration → negative airway pressure → airway collapse
  • Narrowed airway → turbulent airflow → inspiratory stridor and increased work of breathing
• Dynamic obstruction: fluctuating obstruction with inspiration

Tracheomalacia:

• Cartilaginous:
  • Softening of the cartilage
  • Trachea is supported by 16 cartilaginous arches on membranous wall.
  • Weakening of cartilage causes collapse: 
    • Intrathoracic trachea during expiration
    • Extrathoracic trachea during inspiration
    • Can produce expiratory or biphasic stridor
• Membranous:
  • Anterior displacement of the membranous wall
  • Also called excessive dynamic airway collapse (EDAC)
• Classified by tracheal appearance:
  • Crescent: anteroposterior narrowing
  • Lateral: lateral narrowing (“saber sheath”)
  • Circumferential: anteroposterior and lateral narrowing

Clinical Presentation

Laryngomalacia

• Noisy breathing (stridor):
  • Present by 2 weeks of life
  • Loudest at 4–8 months
  • Mild: present during sleeping/feeding, but disappears with crying
  • Severe: intensifies with crying
• Hoarseness is not a feature of laryngomalacia.
• Frequent congestion without infection
• Snoring
• Feeding or swallowing difficulties (dysphagia)
• Failure to gain appropriate weight (severe cases)
• Laryngopharyngeal reflux: reflux of esophageal contents to the larynx, nasopharynx, and mouth

Tracheomalacia

• Can present in children (congenital) or adults (congenital or acquired)
• Inspiratory stridor (extrathoracic component)
• Barking cough, expiratory stridor (intrathoracic component)
• Respiratory distress
• Children:
  • Recurrent respiratory infections
  • Prolonged recovery
• Adults:
  • Dyspnea
  • Cough
  • Sputum retention
  • Frequent pneumonia
  • Syncope with forced exhalation/cough
  • Exacerbates other conditions (chronic obstructive pulmonary disease (COPD), asthma, bronchiectasis)

Diagnosis

Physical examination

Laryngomalacia:

• Lung exam:
  • Stridor occurs during inspiration.
  • Exacerbated by exertion (e.g., crying)
  • May be worse with feeding or supine positioning
• Face exam to rule out other causes of stridor:
  • Evaluate nasal patency to rule out choanal atresia.
  • Evaluate jaw for micrognathia.
• Neck exam: Assess for masses or vascular engorgement.

Tracheomalacia:

• Lung exam:
  • Stridor occurs during expiration or the stridor can be biphasic.
  • Exacerbated by upper respiratory infections
  • Subcostal retractions when accompanied by:
    • Asthma 
    • Bronchiolitis
• Signs of respiratory distress in severe cases:
  • Tachypnea:
    • Age 0–2 months: > 60/min 
    • Age 2–12 months: > 50/min 
    • Age 1–5 years: > 40/min 
    • Age > 5 years: > 20/min 
  • Dyspnea
  • Apnea
  • Retractions (suprasternal, intercostal, or subcostal)
  • Grunting
  • Nasal flaring
  • Altered mental status
  • Pulse oximetry < 90%
• Neck exam:
  • May have visible collapse of the trachea during swallowing
  • Child may lie with a hyperextended neck.
• General: failure to thrive

Imaging

Plain X-ray of the neck and chest:

• May or may not show a focal narrowing because the abnormalities are dynamic
• May show the cause of an extrinsic obstruction if an obstruction is present

Airway fluoroscopy:

• Dynamic imaging is performed during inspiration and expiration.
• Shows expiratory collapse
• Superior to the plain X-rays in demonstrating laryngo- and tracheomalacia

Computed tomography (CT) scan:

• Mostly for adult patients or children with a suspected external cause of tracheomalacia
• May show external obstruction:
  • Goiters
  • Tumors
  • Vascular rings/slings
• Dynamic expiratory image will show:
  • Posterior tracheal wall flattening or bowing forward
  • Small anteroposterior diameter
  • Increase in lung attenuation

Endoscopy and functional studies

• Flexible intranasal laryngoscopy: shows collapse of the cuneiform cartilages (laryngomalacia)
• Bronchoscopy: airway collapse during expiration (< 70% of its original diameter; tracheomalacia)
• Pulmonary function testing:
  • Decreased peak flow 
  • Flattening of the flow-volume loop
• Esophageal pH impedance: if the reflux component is present/suspected

Management

Laryngomalacia

Mild:

• Most cases are self-limited and non–life threatening.
• Infants need to be checked for appropriate weight gain.
• Stridor usually resolves by 12–18 months of age.

Moderate/severe:

• Medical management:
  • Acid suppression for associated reflux
  • Speech and swallow therapy (adjustment of food texture, schedule, pacing)
  • High-calorie formula to help growth and weight gain
• Surgery:
  • Reserved for severe cases unresponsive to medical management
  • Supraglottoplasty: removal of redundant supraglottic tissue
  • Can produce dramatic improvements in breathing and feeding

Tracheomalacia

Children: 

• Self-limited condition in the majority
• Indications for intervention:
  • Episodes of life-threatening airway obstruction
  • Recurrent respiratory infections
  • Respiratory failure
  • Failure to thrive
• Medical management: continuous positive airway pressure (CPAP)
• Surgical interventions:
  • Tracheal stents:
    • Endoluminal stents should only be used short term.
    • External stents: less complications
  • Aortopexy:
    • Suspension of the aorta to the sternum
    • Reduces pressure on the trachea caused by vascular malformations
    • Pulls the anterior tracheal wall toward the sternum, opening the airway

Adults:

• Medical:
  • Optimization of associated conditions (COPD, asthma)
  • Intermittent CPAP
  • Breathing techniques
  • Airway clearance techniques
  • Pulmonary rehabilitation
• Surgical approaches:
  • Tracheal stents
  • Tracheobronchoplasty
  • Tracheal resection and reconstruction
  • Tracheal replacement
  • Tracheostomy: last resort

Prognosis in children

• Most cases of laryngomalacia and tracheomalacia in children resolve by 2–3 years of age due to airway growth.
• Laryngomalacia and tracheomalacia increase the severity of respiratory infections.
• Some tracheomalacia cases can persist as exercise intolerance into adulthood.
• Prognosis is worse in children with:
  • Untreated reflux
  • Associated genetic disorders/congenital anomalies
  • Neuromuscular disorders

Differential Diagnosis

• Supraglottic webs: thin webs of squamous epithelium due to embryologic arrest of larynx development in the area near the vocal cords. Cause obstruction of the extrathoracic airway and produce symptoms that are similar to laryngomalacia. 
• Airway hemangioma: a “blood vessel” overgrowth in the airway. During crying, increased blood flow causes swelling and may cause partial obstruction of the airway, creating biphasic stridor, much like tracheomalacia.
• Vascular ring (e.g., double aortic arch): an anomalous structure that results from the abnormal development of the aortic arch complex and compresses the trachea and/or esophagus. Children with vascular rings often present with respiratory distress, dysphagia, stridor, and a cough similar to that seen in croup.
• Thyroglossal duct cyst: a benign midline neck mass created by persistent thyroglossal duct cells. Aside from airway obstruction, children with a thyroglossal duct cyst may present with dysphagia.