STRIDOR IN AN INFANT

(20 Marks - MS ENT University Examination Pattern)

DEFINITION

CLASSIFICATION

A. By Phase of Respiration

B. By Onset

• Congenital - present at or shortly after birth
• Acquired - develops after an initial symptom-free period

C. By Age of Presentation

• < 6 months: predominantly congenital causes (laryngomalacia, tracheomalacia, vocal cord paralysis, subglottic stenosis)
• 6-18 months: croup, subglottic hemangioma (peak growth phase)
• > 18 months: foreign body, papillomatosis, epiglottitis

CAUSES / ETIOLOGY

Supraglottic

1. Laryngomalacia - most common, accounts for 60% of all neonatal laryngeal problems
2. Saccular cysts and laryngoceles
3. Macroglossia, micrognathia (Pierre Robin sequence)
4. Epiglottitis (older infants/children)

Glottic

1. Vocal fold paralysis (VFP) - second most common cause of neonatal stridor
2. Laryngeal webs
3. Laryngeal cleft
4. Papillomatosis

Subglottic

1. Subglottic stenosis - congenital or acquired (post-intubation)
2. Subglottic hemangioma
3. Croup (acute laryngotracheobronchitis)

Tracheal

1. Tracheomalacia
2. Vascular rings and slings (double aortic arch, pulmonary artery sling)
3. Congenital tracheal stenosis (complete tracheal rings)

PATHOPHYSIOLOGY

INDIVIDUAL CAUSES IN DETAIL

1. LARYNGOMALACIA (Most Important)

• The epiglottis is long, narrow, and omega-shaped
• Aryepiglottic folds are short and tightly tethered
• Redundant mucosa of arytenoids prolapses into the airway on inspiration
• Underlying neuromuscular hypotonia affects the laryngeal adductor reflex (LAR), a vagal nerve-mediated reflex; dysfunction of the afferent-brainstem-efferent pathway results in poor laryngeal tone
• GOR (gastro-oesophageal reflux) is found in the majority and may be causative or self-perpetuating (high negative intrathoracic pressures promote reflux)

• Type 1: Foreshortened/tight aryepiglottic folds
• Type 2: Redundant supraglottic tissue
• Type 3: Posterior epiglottic collapse (associated with underlying neuromuscular disorders)

• High-pitched, fluttering inspiratory stridor onset within first 2 weeks of life
• Worse when supine, crying, feeding, or during intercurrent URTI
• Improves in prone position and with neck extension
• Most severe around 6-9 months, spontaneous resolution by 18 months in ~90%
• Severity increases with activity, may disappear during sleep
• Severe cases: feeding difficulties, failure to thrive, sternal/intercostal recession, pulmonary hypertension, cor pulmonale

• Awake flexible fibreoptic nasopharyngoscopy (gold standard, outpatient)
• Shows: omega-shaped epiglottis, short aryepiglottic folds, prolapse of arytenoid mucosa into glottis on inspiration, normal vocal fold mobility
• MLB (microlaryngoscopy and bronchoscopy) under GA: indicated for severe stridor, failure to thrive, atypical features, or suspicion of synchronous airway lesion (10-20% incidence)
• Note: MLB requires spontaneous ventilation under light anaesthesia; beak of laryngoscope in the vallecula - deep anaesthesia masks supraglottic collapse

Fig: Laryngomalacia - progressive airway obstruction on inspiration. Note the omega-shaped epiglottis. (Cummings Otolaryngology)

• 90% - observation with regular weight monitoring and reassurance
• Antireflux medication (PPI/H2 blocker) for 4 weeks if GOR present
• Surgical - Aryepiglottoplasty / Supraglottoplasty (endoscopic): for failure to thrive, cyanosis, apnoeic episodes, or pulmonary hypertension
  • Division of each aryepiglottic fold, excision of redundant mucosa/submucosal tissue over arytenoids; cuneiform cartilages may be partially excised
  • The interarytenoid "bridge" of mucosa is preserved to prevent scarring
  • Minimal bleeding; no routine antibiotics or steroids; immediate improvement post-op
• Tracheotomy: rarely required for most severe cases
• Caution: CHARGE syndrome - supraglottoplasty can worsen epiglottic collapse

2. VOCAL FOLD PARALYSIS (VFP)

• Birth trauma/forceps delivery (traction injury to vagus nerve)
• Iatrogenic left VFP after PDA ligation or interrupted aortic arch repair (left RLN passes around ductus arteriosus; incidence 1-7.4%)
• CNS anomalies: Arnold-Chiari malformation, hydrocephalus, nucleus ambiguus dysgenesis
• Cardiomegaly, TEF repair
• Idiopathic

• Unilateral VFP: weak cry, inspiratory or biphasic stridor, feeding difficulties, aspiration
• Bilateral VFP: normal voice but stridor, dyspnoea, cyanosis, apnoeic episodes; bilateral VFP may paradoxically abduct on expiration and adduct on inspiration, mimicking normal movement to the untrained eye

• Awake flexible nasolaryngoscopy (to avoid sedation artefact on cord movement)
• Laryngeal ultrasound (sensitivity 0.84, specificity 0.95)
• Laryngeal EMG under light anaesthesia to differentiate paralysis from arytenoid fixation
• Imaging (MRI/CT) to rule out cardiac and neurological causes
• Barium swallow to detect aspiration

• Mild/unilateral: observation; most idiopathic cases resolve spontaneously
• Severe/bilateral: tracheotomy; lateralization procedures in older children

3. SUBGLOTTIC STENOSIS (SGS)

• Grade I: <50% obstruction
• Grade II: 51-70%
• Grade III: 71-99%
• Grade IV: complete obstruction

4. SUBGLOTTIC HEMANGIOMA

• Benign endothelial tumours that enlarge throughout year 1; not always apparent at birth
• Cutaneous hemangiomas in a "beard distribution" are a clue to airway hemangioma
• Biphasic stridor appearing after first month of life without another explanation should raise suspicion
• Spontaneous regression by age 5 years
• Treatment: Propranolol (beta-blocker) - first line; systemic steroids, laser, or surgery for large lesions

5. VASCULAR RINGS AND SLINGS

• Double aortic arch (most common vascular ring), right-sided aortic arch, pulmonary artery sling
• Compress trachea and/or oesophagus
• Symptoms from birth; worsen with URTI; dysphagia if oesophagus compressed
• CXR may show tracheal narrowing; contrast oesophagram shows posterior indentation; CT/MRI angiography is definitive
• Treatment: surgical division of the ring

CLINICAL ASSESSMENT

History

• Age of onset: congenital causes present at/shortly after birth; hemangiomas develop after 1 month
• Duration: chronic = congenital; acute = infective, foreign body
• Positional variation: prone improves laryngomalacia; position-independent = subglottic lesion
• Feeding difficulties and failure to thrive: severity marker
• Associated symptoms: cyanosis, apnoea, voice change, cutaneous lesions
• Birth history: difficult delivery (VFP), prematurity/intubation (acquired SGS)
• Family history; syndromic features (CHARGE, Down syndrome)

Examination

• Phase and pitch of stridor
• Degree of respiratory distress (recession, use of accessory muscles, SaO2)
• Voice quality (aphonia = laryngeal web/atresia; weak cry = VFP; muffled = supraglottic)
• Weight and growth chart (failure to thrive)
• Cutaneous hemangiomas (beard distribution)
• Dysmorphic features, macroglossia, micrognathia

Investigations

1. Awake flexible fibreoptic nasopharyngoscopy - first-line, dynamic assessment of supraglottis and vocal fold movement
2. MLB under GA - gold standard for complete airway assessment; performed under spontaneous ventilation and light anaesthesia
3. CXR: mediastinal widening (vascular anomaly), subglottic narrowing (steeple sign in croup), radiopaque foreign body
4. CT/MRI neck and thorax: vascular rings, masses, extent of stenosis
5. Barium swallow: oesophageal compression, aspiration
6. Echocardiogram: associated cardiac anomalies, PDA
7. pH monitoring / impedance study: to quantify GOR
8. Laryngeal EMG: differentiate VFP from arytenoid fixation

MANAGEMENT SUMMARY TABLE

COMPLICATIONS OF UNTREATED SEVERE STRIDOR IN INFANTS

1. Failure to thrive - increased work of breathing + feeding difficulties
2. Pulmonary hypertension - due to chronic hypoxia
3. Cor pulmonale
4. Pectus excavatum - permanent chest wall deformity from chronic severe sternal recession
5. Obstructive sleep apnoea
6. Death - from acute airway obstruction

IMPORTANT EXAM POINTS

• Laryngomalacia: 60% of all neonatal laryngeal problems; resolves spontaneously by 18 months in 90%; surgical threshold = failure to thrive / cyanosis / apnoea / pulmonary hypertension
• VFP: second most common cause; left cord more often affected; left RLN at risk during PDA ligation
• Subglottic hemangioma: think of it with beard-distribution cutaneous hemangiomas; treat with propranolol
• MLB should be under spontaneous ventilation, light anaesthesia, laryngoscope beak in vallecula
• 10-20% of laryngomalacia cases have a synchronous second airway lesion - always screen
• GOR is found in the majority of laryngomalacia patients; may be causative or a consequence of high negative intrathoracic pressures
• Biphasic stridor = glottic or subglottic level pathology