Laryngeal Penetration In The Normal Swallow: Does Penetration Suggest Pathology in the Aging Population?
Dagger (2006) examined a group of healthy normal individuals and found that laryngeal penetration was a common occurrence in the swallow. Starting at age 50 she found penetration to occur in 16.8% of swallow.
Significantly more penetration occurred on larger liquid boluses. There was no relationship between gender and frequency of penetration. Non of the subjects that penetrated showed a sensorimotor response to the penetration, which may related to relatively shallow depth of the penetration.
Harris-Martin (2007) found 100% of her participants penetrated with a Penetration Aspiration Scale (PAS) of 1-3 on one clinical trial.
What to Consider:
We often anticipate a cough response with laryngeal penetration. However the internal branch of the superior laryngeal nerve provides innervation to the hypo pharynx and it is NOT responsible for a cough response. Therefore there should be no anticipated cough response to laryngeal penetration.
Instead: When the sensory and motor function of the larynx is intact, the entry of foreign material into the supraglottic space can be expected to serve as a physiologic stimulus that will trigger an immediate swallow response with laryngeal vestibule closure, thereby enabling the biomechanics squeezing of penetrated material back out of the larynx. (PAS of either 2 or 4).
Penetration into the supraglottic space that does not trigger an immediate swallow response with effective clearance of the penetrant (PAS 3 or 5) should be considered abnormal response and should bring into question the integrity of the reflexive sensory-motor responses that are usually initiated with the excitation of iSLN receptors.
What to Do with this Information:
Laryngeal penetration is a normal variance, particularly in the aging population when it occurs inconsistency, shallow, and is cleared spontaneously. Pooled material that sits in the laryngeal vestibule and does not clear spontaneously is much more likely to be productive of aspiration and more likely to be related to a true dysphagia.
Too often clinician see laryngeal penetration in any context and recommend more conservative diets and/or thickened liquids unnecessarily. “Silent laryngeal penetration” is a NORMAL response. With more information on the normal aging swallow, clinician can limit conservative diet restrictions to improve patient’s quality of life.
Dagget A, Logemann J, Rademaker A, Pauloski B: Laryngeal penetration during deglutition in normal subjects of various ages. Dysphagia. 21(4): 270-274, 2006.
Harris, Bonnie & Brodsky, Martin & Michel, Yvonne & Lee, Fu-Shing & Walters, Bobby: Delayed Initiation of the Pharyngeal Swallow: Normal Variability in Adult Swallow: Normal Variability in Adult Swallows. JSLHR. 50:585-94, 2007.
Ludlow, Christy: Laryngeal Reflexes: Physiology, Technique, and Clinical Use. Journal of Clinical Neurophysiology: official publication of the American Electroencephalographic Society. 32:284-293, 2015.