QUESTION:

I am a graduate student in my medical externship and I’m trying my best to understand this:

It’s my understanding that the internal branch of the recurrent laryngeal nerve mediates sensation below the vocal folds and mediates a cough reflex. This is why we’d expect a cough if material is sensed below the level of the vocal folds in a pt with an intact cough response. If material gets below the vocal folds and no cough is produced, we call that silent aspiration.

It’s my understanding that the superior branch of the laryngeal nerve mediates sensation above the vocal folds and an expected response to material above the level of the vocal folds is a swallow.

What about material sitting on top of the vocal folds (level 5 of the pen-asp scale)? Is that expected to elicit a cough or a swallow?

If material sitting on top of the vocal folds is considered penetration (because it did not go below the vocal folds) and is expected to elicit a cough, wouldn’t that mean that there is such a thing as silent penetration?

DR. JAMES COYLE’S ANSWER:

Good for you in accurately describing the sensory innervation of the larynx. 

In a healthy state the stimulus of foreign material on the vocal folds should elicit a response of some sort.  However, people who frequently exhibit laryngeal penetration, people who smoke, and people with other conditions that desensitize the mucosal receptors’ or the sensory system’s response to irritation can lead to the need for a higher threshold of stimulation to elicit a response (attenuated response).  So that is why the distinction is important.  “Silent” laryngeal penetration to this level (PAS 5) would be unlikely in a person with intact laryngeal sensation while more likely in these other situations.

Also, it is perfectly normal for material (thin liquid especially) to just barely enter the vestibule and then spontaneously be ejected to the pharynx during laryngeal closure (PAS 2).  So if you wanted to use these terms I suggest including the depth of penetration in the descriptions (as the PAS scores include).  For instance, “silent deep laryngeal penetration” is different from “silent shallow laryngeal penetration” as explained above.

 

CATHERINE’ S FOLLOW-UP COMMENT:

Thank you, Dr. Coyle, as always for your input that informs our practice, whether in pediatrics or adult populations.

This paper below may be of interest to you. While it was published in 2000, it was a study well-done from the team Children’s of Colorado. It remains foundational in the world of pediatric dysphagia. In the setting of particular co-morbidities, especially CLD in our littlest ones, such understanding becomes critical in developing an algorithm for each infant that helps peel apart the likely impact of physiology on risk to invade the airway, not just in the moment in radiology, but in the course of a true feeding,

Friedman, B., & Frazier, J. B. (2000). Deep laryngeal penetration as a predictor of aspiration. Dysphagia, 15(3), 153-158.

Abstract: This study describes the incidence of laryngeal penetration in 125 dysphagic children ranging in age from 7 days to 19 years who were seen over a 6-month period at The Children’s Hospital in Denver, Colorado. Laryngeal penetration was identified in 60% of the study group, with 31% demonstrating deep laryngeal penetration. Of the children exhibiting deep laryngeal penetration, 85% aspirated, suggesting a strong correlation between these two events. It was noted that children exhibiting deep laryngeal penetration often began to aspirate further into their feedings. Use of extended feedings during videofluoroscopy is discussed as a diagnostic strategy in the presence of deep laryngeal penetration.

I hope this is helpful in your key learnings.
Keep up the critical thinking!