Page 708 - The Veterinary Care of the Horse

be palpated through the skin.

VetBooks.ir These signs can develop anytime up to 6 years of age and the condition is often progressive.

Thoroughbred yearlings destined for racing are frequently wind tested prior to sale.

Diagnosis

Diagnosis is made on the clinical findings.

• Abnormal inspiratory noise. The horse is examined at canter. At this gait, the horse’s

stride pattern and the respiratory cycle are linked. The horse breathes out as the leading
foreleg contacts the ground and so by careful observation it can be determined whether
the noise occurs on inspiration or expiration,

• Laryngeal palpation.

• Endoscopy.

• Ultrasound examination of the dorsal cricoarytenoid muscle.

ENDOSCOPIC FINDINGS

The larynx is examined at rest and during or immediately after strenuous exercise. In some

veterinary practices endoscopes that can be attached to the bridle are now used and the
function of the larynx observed whilst the horse is ridden. This gives a more accurate picture

of the dynamic changes that take place whilst the horse is exercising.
The degree of laryngeal dysfunction is graded according to the endoscopic findings.

1 Normal (Figure 15.22). All movements of the larynx are equal and occur at the same

time on both sides. The larynx opens maximally after strenuous exercise.

2 The opening of the left side of the larynx may occur fractionally after the opening of the
right side during inspiration. The movement of the left side may have a slight ‘flutter’ or
else open in two stages. However, when the horse exercises, the larynx opens fully. This

is not considered to be significant as it occurs in many horses and their performance is
not affected.

3 There is definite asynchrony of movement between the right and left sides of the larynx.
Following exercise the left side no longer opens fully.

4 There is no active movement of the left side of the larynx. The opening appears

markedly asymmetrical and the left arytenoid cartilage and vocal cords obstruct the
airway (Figure 15.23).