Matamata Veterinary Services | Latest News

Latest News


November 22, 2011

Endoscopic evaluation of a horse’s upper airway is most commonly performed at rest. Resting endoscopic examination of the upper airway is an effective diagnostic tool for identifying structural abnormalities of the larynx.
These include:

  • Laryngeal hemiplegia
  • Rostral displacement of
  • The palatopharyngeal arch
  • Epiglottic entrapment
  • Lymphoid hyperplasia
  • Epiglottic hypoplasia
  • Subepiglottic cysts
  • Arytenoid chondritis
  • Persistent dorsal displacement of the soft palate

Abnormalities that decrease the diameter of the airway and increase airway resistance can cause respiratory noises due to air turbulence. This is heard as a roar or a whistle during inspiration at exercise. If the degree of obstruction is severe enough, then exercise intolerance or poor performance may result.

In marginal or subtler cases the evaluation is repeated using video endoscopy, which results in an easier procedure for the examiner. Videotapes of the examination may then be reviewed at a slower rate to accurately assess the type and degree of obstructive abnormality. Ultimately, this can be done while the horse is exercising on a treadmill to show dynamic changes that may not be seen at rest.

Laryngeal Hemiplegia … in more detail

This is a disorder whereby the symmetry in movement of the rim and vocal cords of the larynx are affected causing a functional obstruction during exercise. This is due to a partial or complete paralysis of the nerve that supplies, usually the left, vocal cord. These abnormalities in resting laryngeal function involve the corniculate process of the arytenoid cartilage (vocal cord) and have been categorised into five grades:

  • Grade I: all movements are synchronised
  • Grade II: all major movements are symmetrical and full abduction is achieved, although it may be delayed, especially on the left side
  • Grade III: full abduction is still achieved although activity on the left side is reduced and it may appear asymmetrical at rest
  • Grade IV: the left side is not capable of full abduction. Asymmetry is obvious
  • Grade V: true hemiplegia. Complete paralysis and no movement on the affected (usually left) side

Grades IV and V fail the scoping panel examination and Conditions Of Sale (Section 16) at the Karaka Yearling Sales as it is likely severe enough to limit the horse’s performance.
Treatment of horses exhibiting laryngeal hemiplegia involves performing a prosthetic laryngoplasty (tie-back procedure). Prognosis for a successful return to previous level of work after laryngoplasty is reported to be 50% to 70%. Resection of the vocal cords and Hobday operation (ventriculectomy) may also be performed at the same time to help enlarge the opening (rima glotties) during exercise and this will help with eliminating the roaring noise usually heard.