Palatal Instability- Surgical TREATMENT

Palatal instability is a relatively new diagnostic term. However the incidence of this upper airways dysfunction according to recent research places it at the top of the list of possibilities when breathing problems are suspected. That is it appears to be the most common!


The history behind this new finding is of particular interest. 

Palatal instability (PI)  is said to occur when a seal between the tongue and the soft palate is broken. Whilst the seal is intact the palate doesn’t move about and thus is ‘stable’. Once the seal is broken the palate can move or billow into the airway reducing the aperture through which air passes. That is it becomes ‘unstable’.

This seal mechanism ( Oropharyngeal seal - OPS) was first discussed in the early 1990’s in conjunction with the beginnings of a surgical procedure that aimed to improve the function of this seal. In 1998 the concept was discussed with veterinarians at Bristol University and the decision was made to explore these concepts. In 2013 Allen K and Franklin S published the results of their research.

Their Article -

Characteristics of palatal instability in Thoroughbred racehorses and their association with the development of dorsal displacement of the soft palate.

Allen K, Franklin S.

Equine Vet J. 2013 Jul;45(4):454-9. doi: 10.1111/evj.12004. Epub 2013 Jan 7.


TREATMENT 


There are only two surgical approaches that attempt to deal with this issue directly.

( Other procedures may ‘indirectly’ affect function at the OPS)


The two procedures are (i) ‘Ahern Procedure’ ( Oral Palatopharyngoplasty)

                                       (ii) ‘Soft Palate firing’ ( Thermal Palatoplasty)

Both these procedures attempt to tighten the ‘valve’ that forms the first part of the OPS. This valve is referred to as the Isthmus Faucium. 

There are however subtle but important differences between the two approaches.

Thermal Palatoplasty -

Firing causes an increase in tension of the superficial tissues of the underside of the soft palate. As a result the circumference of the Isthmus is reduced. This can improve the seal but also reduces the size of the cavity that houses the tongue. Improvement is often said to be temporary ( several months only) which may be explained by the fact that the more important tissues to tense are the ‘deep’ tissues of the palate which support the action of the ‘natural’ tensing mechanism which is the ‘broad tendon’ or aponeurosis. With firing these tissues are only secondarily tensed by the inflammatory process which accompanies the firing. As the inflammation settles (6-8 weeks) this effect is lost and symptoms can return. 

Oral Palatopharyngoplasty -

This surgical technique has evolved over the last 25 years with the present form being described as the ‘Modified Ahern Procedure’. The surgery has two components.

  1. a.Tension Palatoplasty (TPP) with ‘Tension Release’ incisions. This creates tension in the deep tissues of the mid and rostral soft palate which is the region tensed by the broad tendon. The tension release incisions maintain the aperture at the Isthmus so the tongue is not squeezed out of the back section of the mouth (oropharynx). This increase in tension should be permanent.

  2. b.Subepiglottal mucosae stripping. This is performed to improve stability at the other valve that functions to maintain the OPS. The Intrapharyngeal Ostium.

Note (i):- both procedures can be repeated at later dates to further increase tension. Approximately 1 in 4 OPP’s undergo maximum tensing at 1 to 3 years after the original procedure. 

             Soft Palates are often repeat ‘fired’ up to 3 times in some instances.

Note (ii) OPP surgery is also used to treat DDSP (Dorsal Displacement of the Soft Palate) and ADAF ( Axial Deviation of the Ary-epiglottic Folds).