OPS

CASE REPORT


An unusual presentation of the Oropharyngeal Seal (OPS) associated with a case of permanent epiglottal entrapment.


The oropharyngeal seal  ( ref 1,2 ) had been proposed as the primary mechanism responsible for the maintenance of ventral positioning of the soft palate in horses during exercise. This proposal had been supported by the examination of palatine contour and positioning during treadmill endoscopy. When the OPS was in place the caudal soft palate would appear to be drawn or sucked ventrally into the glossoepiglottic trough and piriform recesses. At the same time the mid ventral section of the epiglottis sat mostly above and therefore not in contact with the palate. The exception was of course at the free border of the palate and occasionally at the tip of the epiglottis where this tip was curled ventrally. Conversely if air entered the oropharynx with relaxation of and thence via the Isthmus faucium, the caudal palate would immediately flatten out and would then lie in contact with the ventral surface of the epiglottis. At this moment the ventral positioning of the palate became reliant on  palatoepiglottic contact or the‘ palatoepiglottic hinge’ mechanism.


More recently a 9 year old standardbred racehorse presented with a history of chronic intermittent ‘roaring’ or biphasic stertor. Standing endoscopy revealed permanent dorsal displacement of the soft palate above  the epiglottis. This was not in itself an unusual finding. However normally speaking when the palate is dorsal to the epiglottis it is not possible to confirm epiglottic contour or integrity without  lateral radiography or an oropharyngeal examination under GA. In figure 1 this is in fact the case. However in figure 2 one can can clearly make out the epiglottic contour. This is because the palate has been drawn into the piriform recesses either side of the epiglottis. In this case an oropharyngeal seal has been formed with the palate in a super rather than subepiglottic  position.


In an attempt to explain this unusual presentation the horse was anaesthetised so that the epiglottis and oropharynx could be better examined. Palpation within the oropharynx revealed an epiglottic entrapment. The epiglottis itself was best described as short and thick whilst having a bilaterally symmetrical contour. The apparent inability of the caudal free border of the soft palate to assume a subepiglottic position was associated with the physical absence of a subepiglottic notch. With an epiglottis of adequate or normal length an entrapment in some ways serves to augment the substance of the epiglottis without obliterating the ventral notch into which the free border of the palate slots. In this case the notch had been obliterated by thickened entrapping subepiglottic mucosas.


The entrapping mucosas were then resected in total without disturbing the aryepiglottic folds. A ventral notch was now palpable. A tension palatoplasty (TPP) (ref 2, 3 ) was also performed to add further tension at the isthmus faucium.


At a subsequent post operative examination the soft palate was seen to be maintained in a normal subepiglottic position.


References


1.   Ahern TJ.  Pharyngeal dysfunction during exercise. J of Eq Vet Sci 1999;19:226-

       231.


2.  Ahern TJ. Oral palatopharyngoplasty . J of Eq Vet Sci 1993;13:185-188.


3.  Ahern TJ: A review of the anatomical components, and the process of

    entrapment of the epiglottis in the horse, with a comparative synopsis of surgical

    treatments, J Equine Vet Sci 1996;16:408-414.



Figure A : caudal soft palate conforming and adherent to the ventrally placed epiglottis


Figure B : caudal soft palate flattened and dorsal to the epiglottis



A

B