Onset, Sound Patterns Help Pinpoint Cause of Stridor

January 2008

By Betsy Bates
Elsevier Global Medical News

STANFORD, CALIF. - Be a good listener to distinguish the cause of stridor in children, Dr. Anna H. Messner stressed at a recent pediatric update sponsored by Stanford University.

Tuning in to the pattern and the tone of a child's noisy breathing will certainly help clinch the diagnosis, but it's also important to pay careful attention to the details when parents describe how the illness developed.

"Whenever you're trying to figure out what a kid has, you want to try and classify stridor in your mind," said Dr. Messner of the departments of pediatrics and otolaryngology/head and neck surgery at the university.

First, decide whether the audible part of the child's breathing is inspiratory, expiratory, or both (biphasic).

"Sometimes I make my own chest go in synch with the kid to see which it is," she suggested.

Inspiratory stridor points to a lesion at or above the vocal cords. Examples of inspiratory stridor include epiglottitis (supraglottitis), laryngomalacia, and bacterial tracheitis.

Audible expiratory breathing, or wheezing, suggests a narrowing of the trachea or the bronchus.

Biphasic stridor suggests involvement at or below the vocal cords, as in the case of croup, in which an obvious audible inspiratory component may be paired with an expiratory barking cough.

Vocal cord paralysis may present with inspiratory stridor, but may have an expiratory component as well.

Other clues are also important when considering various conditions underlying stridor:

Croup (laryngotracheitis). It is highly likely to be preceded by nasal congestion and/or a discharge in a baby 6-36 months old. Fever may be present, but the onset is gradual. On x-ray, look for the "steeple sign" indicating swelling of the subglottis.

"It would be really unusual to see croup without a nasal discharge," said Dr. Messner.

Epiglottitis (supraglottitis). This disease, on the other hand, was historically known for its extremely rapid onset, she explained. "It's not the kid who's had a cold for a few days. This was the kid who was active, playing, healthy in the morning and was sick as a dog in the afternoon."

Symptoms include fever, sore throat, and drooling, but most telling is the child's behavior and posture. Often, they lean forward at an awkward angle. "When you see these kids, what you notice is, they won't move. They don't lie down if they can help it. If they're moving around, they do not have epiglottitis," Dr. Messner commented.

Widespread vaccination against Haemophilus influenzae type b (Hib) beginning in 1991 sharply reduced the number of cases in the United States from 100 per 100,000 to 0.3 per 100,000.

Today, epiglottitis is seen rarely, mostly in children who failed to respond to the vaccine and in those infected with influenza type A, Streptococcus pneumoniae, and Staphylococcus aureus.

More worrisome is the population of immigrant children who have never received the Hib vaccine, and could well show up with symptoms of a disease that is becoming less recognizable to pediatricians.

"That's why we need to know a lot about it." Urgent action is required with epiglottitis, she emphasized. "They all get intubated. You don't wait for respiratory distress, because often that's too late."

Laryngomalacia. This is the most common cause of stridor in newborns. This disorder of immature laryngeal and pharyngeal tone is noteworthy for its distinctive low-pitched, coarse cry.

"Some people have described it as a turkey gobble," said Dr. Messner.

Laryngomalacia stridor is strictly inspiratory, and generally intermittent, worse during feeding and sleeping, but abating during crying.

Importantly, laryngomalacia can be diagnosed and evaluated by an otolaryngologist using a flexible laryngoscope in the clinic.

Babies often recover without treatment when they are aged between 12 and 18 months; until then, pediatricians should monitor weight, be alert to feeding difficulties such as choking and aspiration, and consider treating their gastroesophageal reflux disease, which affects virtually 100% of children with laryngomalacia.

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