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© Borgis - New Medicine 3/2004, s. 80-82
Lidia Zawadzka-Glos, Beata Zając, Anna Kaczmarczyk
Causes of laryngeal stridor in children
Department of Paediatric Otorhinolaryngology, Medical University of Warsaw, Poland
Head: Prof. Mieczysław Chmielik MD, PhD
Laryngeal stridor may pose a diagnostic and treatment problem. Congenital anomalies of the cricoid cartilage, postintubation stenosis, subglottic haemangioma, laryngomalacia, congenital malformations such as: laryngeal webs and cysts, inflammatory lesions and foreign bodies should be considered in differential diagnoses. Laryngeal stridor occurring in children with subglottic stenosis has to be differentiated with vocal cord paralysis.
Laryngeal stridor is always a symptom, not a disease. It is a sound which is produced by tissue vibration and a turbulent flow of the air through the obstructed lumen of air passages. Stridor never occurs in health; it is a pathological symptom, evidence of an impaired patency of the respiratory tract. The assessment of stridor characteristics such as its loudness, sound pitch, respiration phase, allows establishing a likely localization of stenosis. Stridor may be described as inspiratory, biphasic, i.e. inspiratory – expiratory, or expiratory, dry or wet; sound pitch may be low or high. Stenosis of the air passage under the rima of the glottis causes an inspiratory stridor, stenosis at the level of the glottis and the subglottic portion produces an inspiratory-expiratory stridor with inspiratory prevalence. Stenosis of the trachea and lower respiratory tract leads to stridor with a prolonged expiratory phase. Impaired patency of the upper respiratory tract at the level of the nose or nasopharynx produces a characteristic anterior or posterior nasal stridor. An obstruction at the level of the middle and inferior pharynx results in a hoarse and wet inspiratory stridor.
Laryngeal stridor may be a symptom which occurs rapidly and causes acute laryngeal dyspnoea; it also may be chronic, usually present since the child´s birth and causing progressive restriction in respiratory tract patency. Slowly increasing stenosis of the laryngeal lumen results in adaptation to deteriorating breathing. In such cases, mild mucosal oedema in the course of infection may give rise to a rapid laryngeal obstruction, may exceed the patient´s adaptation possibilities, which may result in severe respiratory distress.The most frequent causes of laryngeal dyspnoea are caused by:
1. inflammatory diseases of the larynx
2. internal and external trauma to the larynx, postintubation stenosis
3. congenital abnormalities
4. papillomatosis of the larynx
5. haemangioma of the larynx
6. endogenous and exogenous foreign bodies
7. congenital and acquired paralysis of the vocal cords
8. laryngospasm
– tetanus
– irritation of the laryngeal vestibule mucosa
– epileptic seizures
– episodes of hysteria
9. non-inflammatory oedema
– allergic oedema
– lymphatic oedema
– Quincke´s oedema
– oedema associated with venostasis (superior vena caval syndrome, circulatory insufficiency, status post cardiosurgery)
10. oedema due to a diminished oncotic pressure (hypoalbuminaemia in nephrotic syndrome, cirrhosis of the liver).
Inflammatory disease of the larynx is the most frequent cause of laryngeal stridor. Acute laryngeal inflammation in paediatric patients has a different course than that in adults because of a specific anatomical structure of the larynx in a young child and a high predisposition of the laryngeal mucosa and loose connective tissue of the submucosal layer to develop oedema. Among many types of acute laryngitis, acute subglottic laryngitis is the most frequent. Laryngeal stridor in this condition is characteristically harsh, inspiratory or inspiratory-expira-tory with inspiratory prevalence; the associated cough is dry and barking. The symptoms are pathognomonic for acute subglottic laryngitis. The inflammation of the laryngeal mucous with specific symmetrical oedema at the subglottic portion, constricts the lumen of the air passages to a few millimeters. Subglottic laryngitis is typical in infants and young children. If the symptoms of laryngitis occur in children under 6 months of age, and are refractory to conventional treatment, or the episodes of laryngitis develop a few times in the first year of life, another concomitant pathology of the larynx should be considered.
Among different types of acute laryngitis, epiglottitis deserves special attention. The disease has been known for ages, but it still carries a high risk of fatalities. The risk is often due to a late diagnosis (lack of prodromal symptoms, the patient´s late presentation to the phy-sician), inadequate treatment procedures on diagnosing acute epiglottitis (not restoring the patency of the respiratory passages), or high virulence of Haemophilus influenzae, sepsis or multiorgan insufficiency. Stridor in epiglottitis is inspiratory, damp and low-pitched. It is a late-stage symptom which indicates obstruction of the inferior pharynx and laryngeal vestibule by a large oedematous epiglottis.
Laryngeal stridor occuring at birth or immediately after birth may suggest congenital abnormalities of the larynx, i.e. laryngeal cyst, laryngeal web, congenital contraction of the cricoid cartilage, congenital paralysis of the vocal cords. Laryngomalacia is one of the most frequent types. The diagnosis may be made only on directoscopy, and on assessment of the function of the larynx on swallowing and breathing. The symptoms of laryngomalacia are closely associated with the degree of flaccidity of the laryngeal cartilage. Inspiratory stridor varies in severity,and increases on effort, irritation or crying. The flaccid epiglottic structure of the larynx collapses on inspiration and obstructs the lumen of the air passages. Stridor in laryngomalacia depends on body position; it increases in the supine position, increases on prone positioning. The flexion of the head down to the chest increases stridor. Gastro-oesophageal reflux is frequently a coexisting condition in this group of children. In severe laryngomalacia with a hypoplastic epiglottis, choking episodes occur on feeding, and during infection the patient develops dyspnoea or respiratory insufficiency.
A rapid onset of laryngeal stridor following a chocking episode is suggestive of a foreign body lodged in the subglottic airway. A careful history of the size and type of the foreign body is crucial to remove the cause of stridor. The course of the condition is rapid, with a likely severe dyspnoea, choking or sudden airway obstruction. Removing the foreign body from the subglottic airway is one of the most difficult procedures.
Subglottic laryngitis is very rare in infants under 6 months of age. In this age group, the stridor may be associated with laryngomalacia, subglottic haeman-gioma or congenital subglottic stenosis.
Stridor in children after cardiosurgical procedures or operations on the neck, and in children with hydro-cephalus, may suggest paralysis of the vocal cords.
Difficulty in removing the endotracheal tube after prolonged or traumatic intubation may be due to subglottic stenosis. Laryngeal stridor related to the body position is typical of laryngomalacia, cysts and haeman-giomas of the larynx. In vocal disturbances, e.g., hoarseness, the vocal cords are also involved.
Conditions such as gastro-esophageal reflux predispose to a recurrent laryngitis, lesions on the vocal cords, and inflammation of the subglottic airway, which, consequently, leads to secondary stenoses.
Laryngeal stridor in children always requires laryngo-logical examination both in a normal or urgent course depending on the severity of the stridor, associated symptoms and the patient´s general condition. The laryngological diagnostic procedure includes an endo-scopic examination and additional investigations, e.g., ultrasonography. Computed tomography and NMR are used in justifiable cases. The diagnostic procedures should often include evaluation of the central nervous or circulatory system. Depending on the main cause of the stridor, the child is referred either for conservative treatment or surgical procedure.
Practical guidelines
Laryngeal stridor present at or shortly after birth may indicate congenital laryngeal abnormalities, e.g., laryngeal cyst, laryngeal web, congenital contraction of the cricoid cartilage, congenital paralysis of the vocal cords, haemangioma, laryngomalacia.
A rapid onset of laryngeal stridor following a choking episode raises a suspicion of a foreign body lodged in the subglottic airway.
Subglottic laryngitis is infrequent in infants under 6 months of age, therefore, other laryngeal abnormalities should always be excluded.
The stridor which appears in children after cardiosurgical procedures or after operations on the neck, and in children with hydrocephalus, may suggest paralysis of the vocal cords.
Difficulty in removing the endotracheal tube, and the stridor developing between 7 and 21days after extu-bation suggest postintubation stenosis.
Gastro-esophageal reflux predisposes to recurrent inflammation of the larynx, and consequently, leads to secondary stenoses.
The stridor resulting from an excessive use of the voice or during/after respiratory infection suggests haemangioma of the larynx.
Laryngeal stridor is an important issue in paediatric laryngology. The problem requires frequently not only laryngological but also cardiological or neurological diagnostic procedures. The laryngologist should re-member about congenital anomalies of the larynx, especially if the symptoms occur in infants under 6 months of age. A careful history and a thorough physical examination determine an appropriate evaluation plan and an early diagnosis.
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