LARYNGEAL PROSTHESIS:POST OPERATIVE DYSPHAGIA
A laryngeal prosthesis is the most common surgical procedure performed to treat laryngeal abductor (ability to open the entrance to the trachea or windpipe) weakness. The weakness most often occurs on the left side of the throat and only occasionally on the right. A single or double heavy suture is implanted to mimic the action of a dysfunctional muscle and thence the airway is held (or half of it ) permanently open. The surgery has proven to be quite successful in improving air supply in these horses. A major downside of the procedure however is the occasional occurrence of dysphagia (difficulty in swallowing food) post operatively.
DYSPHAGIA my occur soon after surgery and then may dissipate several weeks to months there after. Coughing whilst eating and the nasal return of feed and or water are the most common signs of this anomaly.
POSSIBLE CAUSES: (none have been explicitly implicated.)
1) over lifting (abduction ) of the affected side of the larynx such that
(I) the larynx cannot be closed to stop food entering the upper
trachea during swallowing.
, (II) the passage of food on the surgical side is inhibited (blocked) by
the over abducted larynx (corniculate process of the arytenoid
cartilage).
2) possible neuritis or nerve trauma as a result of
(I) reactions to the prosthetic implant (inflammation)
(II) nerve compression or torsion intra-operativily as the surgical site
is extremely difficult to expose.
NB- Over abducted implants can be removed and horses often race successfully after this procedure.
-Dysphagic symptoms often settle between 80 to 110 days post operatively.
The answer to this occasionally encountered sequela of prosthetic laryngoplastys may well be found in a new procedure referred to as a NERVE MUSCLE PEDICLE GRAFT. Rather than anchor this protective apparatus (the corniculate cartilage of the larynx) this procedure attempts to restore function. That function can be restored though be it slightly altered as a different nerve to the original dysfunctional one is used.
Further reading:
Fulton I C: The nerve muscle pedicle graft for treatment of idiopathic laryngeal hemiplegia:current status, In: The Diagnosis and Treatment of Respiratory Disease, Dubai International Equine Symposium ,Pub,Mathew R. Rantanen Design 1997, 407-418.
Ahern T J : Laryngo-pharyngeal desensitisation following a prosthetic laryngoplasty. J of Eq Vet Sci 1996 ;16:120-2.
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