Discussion:
Stridor is one of the common respiratory finding observed in pediatric
age group which is caused mostly by some obstruction in the upper
airway. Stridor is not exclusively present in respiratory distress but
could also have some central nervous system etiology. In the first year
of life, Laryngomalacia is the most common cause of stridor (1). It
presents typically in the first few weeks after birth, may worsen in the
first 4 - 8 months and usually resolves by 18 – 20 months of age (4).
It is usually managed conservatively; but surgical management is
necessary in cases with worsening respiratory distress (5). However,
secondary airway lesions other than laryngomalacia may also be observed
to cause stridor in pediatric age group. FB plays an important role in
determining these causes of airway anomalies.
Various studies were performed worldwide to evaluate the cause of
stridor in this age group by bronchoscopic evaluation (6,7,8). Most of
the studies had laryngomalacia as the most common cause of stridor with
an associated secondary lower airway anomaly. Laryngomalacia may be
caused by multiple reasons. One of the most common cause of
laryngomalacia is neurological, i.e. altered laryngeal tone due to
abnormality of the laryngeal nerve (9). Reflux is said to be another
important cause of irritation and edema of the supra-glottic airway
which worsens airway obstruction (10). Laryngomalacia is mainly a
clinical diagnosis having stridor which worsens with feeding and in
supine position and decreases on prone positioning. Other associated
features involve weight loss of failure to thrive. Infants with
laryngomalacia are observed to have shortened aryepiglottic folds,
floppy omega shaped epiglottis and redundant arytenoid tissue which
prolapses over the glottis in every breathing cycle. In our study, there
was a good correlation (95.23%) between clinical diagnosis and
bronchoscopic findings in cases with suspicion of Laryngomalacia.
There may be other causes of stridor beyond laryngomalacia. In a study
conducted by Martin et al, infra-glottic stenosis, laryngeal
inflammation and vocal cord paralysis were the most common findings on
bronchoscopy in children with stridor (11). In other study by Erdem et
al, laryngomalacia was the most common cause for stridor followed by
other causes like subglottic stenosis, tracheal compression, laryngeal
cyst which comprised of 16.5% of the cases evaluated for stridor (1).
In our study, laryngomalacia was the most common cause of stridor
(29.41%) followed by subglottic stenosis (13.23%) and tracheomalacia
(11.76%). Other findings included subglottic stenosis, tracheomalacia,
foreign body aspiration, external airway compression etc. Subglottic
stenosis involves narrowing of the airway encircled by the cricoid
cartilage, below the glottis and above the first tracheal ring (12). It
could be congenital or acquired. More than 90% of the acquired
subglottic stenosis is secondary to endotracheal intubation (13).
Foreign body aspiration is a very common cause of acute onset noisy
breathing in pediatric age group. Classic history of acute onset choking
or coughing might not be present in such cases. In the above study done
by Erdem et al, 15% of the children with stridor required surgical
intervention (1) as compared to 10.35% of the children requiring
surgical intervention in our study.
Stridor improved with time in all cases as observed on follow up.
Children with an underlying neurological ailment tend to have persistent
stridor for a relatively longer duration (1). However, Yuen et al
reported in his study that neurological abnormalities did not alter time
to resolution of symptoms (14).
On the basis of various studies done in the past, it can be concluded
that bronchoscopic evaluation is necessary in accurately diagnosing the
exact cause of stridor as prompt treatment could be initiated. Pediatric
bronchoscopy can be done by a trained pulmonologist, intensivist,
surgeon or anesthetist and should be included among the primary
investigations in evaluation of children with stridor.