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Dun Dun Dun… the ever important Vagus nerve! The vagus nerve, know as CN X or TEN reminds me of Las Vegas in that its got so much crazy shit going on all the time! It provides both motor and sensory innervation to several different muscles.
Honestly, this nerve is probably the most overwhelming. There’s a lot of mind numbing neuro words going on here, but I promise to try to stay low key. I’ll first discuss the important muscles that are innervated, but also include the specific branches if your feeling ultra fancy.
The pharyngeal branch of CN X innervates:
- The superior, middle, and inferior constrictors
A. The inferior constrictor includes the cricopharyngeus (innervated by the pharyngeal plexus) and is the primary muscle of the UES. It is tonically active, but relaxes during swallowing to open so that the bolus can pass through,
- All of the muscles of the soft palate EXCEPT the tensor veli palatini (which is CN V)
- ALL intrinsic laryngeal muscles (via the L recurrent laryngeal nerve)
- Cricothyroid (via the external branch of the superior laryngeal nerve) <– yes I know thats an intrinsic laryngeal muscle too, but different innervation kids!)
Sensory innervation of CN X is carried by a mix of various vagus branches, some of the recurrent and some of the superior, and are responsible for the:
- mucous membrane at the valleculae, epiglottis, aryepiglottic folds, and most of the larynx (via the internal branch of the superior laryngeal nerve)
- mucous membrane below the level of the folds (via the recurrent laryngeal nerve)
- special sensory taste to the epiglottis
- general sensory to the soft palate, posterior tongue, lower pharynx (beyond where CN IX stops), and the UES
The vagus nerve plays a very large role in the pharyngeal phase of the swallow. CN X is rather difficult to assess at the bedside also. An MBSS or a FEES will give you much more information regarding any sensory and motor impairments, but there are a few things you can do clinically if you’re suspecting vagus nerve involvement:
You are able to assess the vagus nerve at the bedside by inspecting the palate. If it is lower, and less arched, and you have the patient say “aaah”, and see a deviation to one side or the other, then you know there is some sort of CN X pharyngeal branch impairment.
You can also listen to the patient’s voice. By having the patient converse or sustain phonation, listen for changes in vocal quality, pitch, loudness levels, and control.
Any sort of vagus nerve involvement can lead to reduced laryngeal adduction, and/or poor cough effectiveness all leading to aspiration during the swallow, poor UES opening leading to aspiration of residue after the swallow, and any type of sensory impairment of the vagus nerve can lead to the ever dreaded silent aspiration.
These are obviously VERY general techniques that can be used, but if something doesn’t seem quite right here, this is a patient that you REALLY should pursue an instrumental assessment on. If for some reason, you work at one of those antiquated facilities that makes you cry, plead, and beg for an instrumental, insert temper tantrum here. Nothing grinds my gears more than an unethical, cheap a$$ administrator that wont provide the necessary diagnostics for their residents, but in this case, you are able to throw around the big scary words such as “high risk of silent aspiration.”
A few exercises that may be beneficial include the Shaker, CTAR, Mendelsohn, supraglottic exercise, super-supraglottic (barring any contraindications), and possibly NMES in the submental placement. Now notice I only said exercises and NOT compensatory strategies. Unless you have trialed the compensatory strategies under fluoro or FEES, don’t you dare do it. I know you’re a wonderfully sweet and well-intentioned person, but the reality is that several compensatory strategies done while eating can have the opposite effect and actually throw the bolus in to the airway. You don’t need none of that.
In conclusion, the vagus is not for the faint of heart and controls a crap ton in there. The vagus nerve has involvement with poor velopharyngeal seal, decreased closure of the larynx, weak pharyngeal constrictor contraction, esophageal motility (via the autonomic Dorsal Motor Nucleus), and UES opening/closure.
Resources: (And a special thank you to Dr. Kate Krival for verifying that I might know what I’m talking about 🙂
Corbin-Lewis, K, Liss, J.M., & Sciortino, K.L., 2005, Clinical Anatomy & Physiology of the Swallow Mechanism, Thomson Delmar Learning, Clifton Park, NY
Murray, J., 1999, Manual of Dysphagia Assessment in Adults, Singular Publishing Group, Inc., San Diego