This video from our Cleveland team is a great way to start a discussion on the complicated relationship of the cricopharyngeus and hyolaryngeal elevation. It’s important to know that the MBS really can't be used to determine CP dysfunction.
Appropriate passage of the bolus depends upon:
1: adequate relaxation of the CP muscle
2: adequate hyolaryngeal elevation to provide traction to help pull open the PES and
3: adequate pharyngeal pressure to propel the bolus through.
Any one of these (or all of these) can be inadequate and will appear functionally the same on the MBS, since they can “make up” for one another.
An MBS can be a part of the picture...but to really tease out that CP dysfunction is THE problem, we need more info, because of the interaction between events. A person can have perfectly adequate relaxation of the CP, but inadequate traction force provided by the hyolaryngeal elevation, so the CP is not pulled open further...which looks exactly the same on fluoro as a person with CP dysfunction, but adequate hyolaryngeal elevation. If we see a video like this, and we are suspicious, it would require a GI referral to get more data to make an appropriate plan of care.
See the link below for more info on this relationship: