For the Health of It
The epiglottis is a triangular shaped cartilage located
in the throat at the base of the entrance to the airways.
During normal breathing, it is situ- ated above the soft
palate and facilitates air move- ment. When eating, the
epiglottis moves upwards and backwards to allow swallowing
and to prevent food from entering the airways.
To allow for such movement, the lower surface of the
epiglottis has a loosely attached, elastic mucosa (subepiglottic
mucosa). Epiglottic entrapment occurs when
the subepiglottic mucosa becomes positioned above the
epiglottis, restricting movement.
The most common presenting sign in cases of epiglottic
entrapment is abnormal respiratory noise. The
abnormally positioned subepiglottic mucosa creates a
slightly narrowed airway, as well as increased air turbulence,
which creates a harsh respiratory noise. Horses in
a higher plane of work, racehorses for example, can also
present with exercise intolerance. In horses performing
at high speeds, even mild narrowing of the airway can
result in decreased athletic performance, and, as a result,
decreased earnings. Coughing and nasal discharge occur
in some cases, as an abnormally functional epiglottis can
contribute to disruption of airflow and slightly interfere
with the swallow- ing process. As none of these changes
indicate a specific cause of disease, transnasal endoscopy
is often used to further investigate horses exhibiting these
clinical signs. This procedure is commonly done in many
cases with suspected upper airway disease and involves
the passage of a small, flexible camera up the horse’s nose
to visualize the airway. Most horses tolerate this intervention
well with minimal restraint or sedation.
The majority of cases have persistent epiglottic entrapment;
however, a small number of horses experience
intermittent epiglottic entrapment, which is relieved
when the horse swallows. The membrane entrapping the
epiglottis can vary in thickness, width, and can become
ulcerated. In addition to endoscopic evaluation, a radiograph
of the laryngeal region can also be obtained to
assess the patient for epiglottic hypoplasia (a smaller than
normal epiglottis) as this can be an uncommon cause of
epiglottic entrapment.
Surgery is the most common treatment option for this
condition. An incision is made through
the abnormally positioned subepiglottic mucosa to
12 • Walking On
Epiglottic Entrapmnent
Reprinted with permission from Equine Disease Quarterly, Volume 29, Number 2
release the entrapped epiglottis. The procedure can be
performed either under sedation and lo- cal anesthesia
or under general anesthesia and typically takes less than
30 minutes. There are several surgical methods available,
namely use of a transnasal endoscopically guided laser,
transen- doscopic electrosurgical instrument, or transnasal
or transoral curved surgical knife. Surgical excision
can also be performed via incision into the airway via the
pharynx or larynx, however, these methods will result
in an external scar and can contribute to surgical site
complications. These procedures are therefore typically
reserved for cases with ad- ditional complications.
The potential complications of surgical inter- vention
include thermal trauma to the epiglot- tis, adhesions,
and cicatrix (scar) formation. To reduce the risk of these
occurring, horses should receive systemic and topical
anti-inflammatory medications. Dorsal displacement
of the soft pal- ate can occur regardless of the treatment
method employed, particularly when epiglottic hypoplasia
is present.
Local inflammation is common following sur- gical
correction of epiglottic entrapment. Horses should
therefore receive transnasal endoscopic evaluation each
week following surgery until the larynx has a normal appearance.
Throat sprays con- taining anti-inflammatory
agents are also strongly recommended. In order to reduce
inflammation in the laryngeal region; horses require a
period of rest following surgery. Depending on the severity
of the condition and the treatment method employed,
horses can return to work 3-8 weeks post-operatively,
providing transnasal endoscopic evaluation is normal.
Reoccurrence is not uncom- mon and can be treated by
surgical excision of the excess subepiglottic mucosa. The
majority of horses with epiglottic entrapment without
epiglottic hypoplasia are able to return to their original
level of activity.
CONTACT:
Alex Gillen, MA, MS, VetMB, CertAVP, DipACVS, DipECVS,
MRCVS alexandra .gillen@liverpool .ac .uk
Phillip Leverhulme Equine Hospital University of Liverpool
United Kingdom