Page 660 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Respir atory system: 3.2 Surgical conditions of the respir atory tr act 635

VetBooks.ir 3.71 3.72

Fig. 3.72 Endoscopy of the oropharynx, showing
a deformed apex of the epiglottis in a horse under
Fig. 3.71 Permanent dorsal displacement of the soft general anaesthesia. The nasotracheal tube can be
palate, despite withdrawal of the endoscope. seen in the top of the picture.

Prognosis or complete pharyngeal collapse has been observed.
The prognosis depends on the cause. Generally, a Ventral pharyngeal collapse has been implicated as
physical cause that can be treated, such as a subepi- a precursor to DDSP. Treadmill studies have shown
glottic cyst, is associated with an excellent progno- clinically that almost all cases of DDSP are preceded
sis. A neurological cause is associated with a guarded by billowing of the soft palate up into the airway.
prognosis. Some pharyngeal function will return in
some horses treated successfully for guttural pouch Aetiology/pathophysiology
mycosis. Surgical management with tie forward and The nasopharynx is an unsupported muscular tube
staphylectomy has been reported with a success rate and can contract completely, notably during degluti-
of over 80%. Other causes of pharyngeal paralysis tion. As a result, without appropriate muscular tone
have a poor prognosis. the pharynx is unable to resist the changes in air-
way pressure at exercise. Neuromuscular weakness
PHARYNGEAL COLLAPSE will result in collapse of the nasopharynx, similar
to the pathogenesis of DDSP. Attention has focused
Definition/overview on pharyngeal inflammation, including previous
Pharyngeal collapse can be the result of a space- evidence of pharyngeal lymphoid hyperplasia, and
occupying lesion in the peripharyngeal tissues, inflammation in the region of the pharyngeal nerves
resulting in severe compromise of the airway. The in the guttural pouch, but a causal relationship has
guttural pouch can distend downwards resulting in not been established. Ventral pharyngeal collapse is
dorsal pharyngeal collapse while distended retro- quite specifically associated with dysfunction of the
pharyngeal lymph nodes can compress the pharynx tensor veli palatine muscle. Other causes of pharyn-
caudally and laterally. geal collapse in the literature include rostral respira-
Dynamic pharyngeal collapse is another one of the tory tract obstructions leading to increased negative
causes of airway obstruction that has become appar- pressure in the pharynx (nasal deformities or masses),
ent since the development of treadmill endoscopy. myopathies causing weakness, and neuropathies.
Dynamic dorsal, ventral, lateral, dorsal and lateral Physical compression from surrounding pathology