Page 649 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

624 CHAPTER 3

VetBooks.ir Management Dorsal pharyngeal cysts may be remnants of the cra-
niopharyngeal duct or Rathke pouch, while palatal
Treatment may not be necessary if there is no loss of
performance. Mild cases frequently respond to laser
incidental endoscopic findings, but can be associated
ablation of the scar tissue. Cutting of the cicatrixes cysts may have a salivary origin. Cysts are usually
and bougie dilation have also been used in a few with respiratory noise and, presumably, obstruction
cases. Treatment of other associated lesions may also in some horses.
be required. Medical treatment with antibiotics and
anti-inflammatories is generally ineffective. If there Aetiology/pathophysiology
is severe webbing or marked swelling of the aryte- There are no reports detailing the aetiology and
noid cartilages then permanent tracheostomy, or pathophysiology of pharyngeal cysts, but they are
insertion of a permanent tracheotomy tube, is indi- speculated to be of embryological origin. They are
cated. Prevention in the Texas region has included more commonly reported in Thoroughbreds and
‘dry lotting’ (i.e. removal of access to pasture). This Standardbreds.
is imperative to prevent recurrence in treated cases.
Alternatively, the horse can be moved to a more tem- Clinical presentation
perate climate. Cysts are usually identified during endoscopic
examination. The significance of the cysts is hard
Prognosis to determine, but some clients who learn that their
Recurrence following treatment is very common, horse has one will seldom be happy until something
especially if the horse returns to the same environ- has been done about it.
ment. If the horse can be moved to a different cli-
mate, then the outlook is fair. Differential diagnosis
Pharyngeal lymphoid hyperplasia and other pharyn-
PHARYNGEAL CYSTS geal masses should be considered.

Definition/overview Diagnosis
Developmental cysts are rare but may occur most The endoscopic appearance is usually quite typical
commonly in the subepiglottic position (see p. 625), (Fig. 3.54) and no further diagnosis is necessary.
and occasionally on the dorsal pharynx or soft palate. Transendoscopic aspiration is feasible but the diag-
nostic value is questionable. The probable loss of
volume and hence definition of the cyst would limit
3.54 further therapy.

Management
If accessible, then surgical resection or laser abla-
tion of the cyst could be considered. The author
has treated these cysts with intralesional injec-
tions of formalin using a procedure similar to that
described for PEH (Fig. 3.55). Usually up to 5 ml
of serous fluid can be withdrawn from the cyst
before the cyst is re-filled with a similar volume of
10% formalin.

Prognosis
Prognosis is good. These cysts are seldom clinically
significant. Ablation or injection with formalin usu-
ally results in a small, scarred area on the pharyngeal
Fig. 3.54 A dorsal pharyngeal cyst on endoscopy. wall. Recurrence has not been observed.