Dynamic Scope – Laryngeal Paralysis

Dynamic Scope – Dorsal Displacement of the Soft Palate

As the majority of conditions affecting the equine heart are often only visible during intense exercise, this new diagnostic tool will be invaluable in gaining vital information about the cardian function of the equine athlete. The ecg machine can be attached to the horse as it is ridden on the gallops, in the arena, or attached to a lunging roller if  required. It can be used in combination with the DR Scope, or on its own, as part of an assessment of poor performance.

Most of these horses have been presented for either making an abnormal inspiratory noise or for poor performance on the racecourse. This revolutionary piece of equipment allows us to examine live footage of the horses’ upper respiratory tract whilst working under normal conditions on a gallop during training.

The conditions which we have diagnosed in these horses have been wide ranging. Indeed the equipment has on occasions been very useful in ruling out conditions and diagnosing normal function as well as the wide range of obstructive airway conditions.

• In about 10% of cases the anatomy and function of the pharynx and larynx was found to be normal but mucus and evidence of lung disease was detected towards the end of the piece of work. A follow up broncheoalveoar lavage (lung wash) identified the causative problem which when treated got the horse back to full potential, thus saving the owner from unnecessary wind surgery.

For those horses (80%) which were found with anatomical / functional problems of the upper airway the DRS is a revelation. In approximately half of the horses we have examined we have found that they have more than one obstructive condition compromising the horses’ airway.

1) Axial Deviation of the Aryepiglottic Folds (ADAF) was found on its own but more frequently in combination with other conditions. It is very often seen as a precursor to Dorsal Displacement of the Soft Palate (DDSP). Horses which exhibit ADAF usually make a “whistle” which is quite similar to the noise associated with Laryngeal Hemiplegia (Left Recurrent Neuropathy). Indeed we have seen a number of horses where the ADAF was accompanied by Vocal Cord Collapse (VCC) either single or bilateral.

2) Laryngeal Hemiplegia – now we can grade this condition more accurately according to the degree of paralysis seen during fast exercise. This influences the decision as to which surgery is necessary – a Hobday or a Tie Back. Vocal Cord Collapse (Left Recurrent Neuropathy) can of course occur as the primary condition and in such instances can be treated by the standard Hobday operation.

The rate of progressive deterioration associated with Left Recurrent Neuropathy was captured by some video footage which we obtained from a NH gelding who over a period of 7 months went from whistling and evidence of left vocal cord collapse to exercise intolerance with marked signs of right sided ADAF and left arytenoid collapse. Following a Tie Back operation I am happy to report that he won his first race!

3) Dorsal Displacement of the Soft Palate (DDSP) is definitely the most common obstructive airway disease which we have seen. Many horses (30% of those with DDSP) do not make a noise but only show symptoms of cutting out or pulling up in a race or piece of work. The degree by which the palate displaces varies with no correlation with the symptoms. As stated previously this condition may be in combination with others such as ADAF or VCC.

The most successful surgery for DDSP we have found is a Tie Forward procedure. One of the benefits of this surgery is that it doesn’t keep the horse out of training for very long.

In many instances we find that there is severe instability of the palate without it achieving full displacement. In these cases the palate billows in front of the Larynx thus reducing the airway. These horses respond well to a soft palate cautery where the tissues are tightened and the stability of the structures is increased.

The use of the DRS has taken the guesswork out of the diagnosis of upper airway conditions and this more accurate diagnosis has resulted in more targeted surgeries with much better results. In the same way the DRS also identifies those horses which have conditions which cannot be helped by surgical intervention and of course this is a great saving to the owner. Conditions such as Pharyngeal Collapse and Retroversion of the Epiglottis are not usually suitable for surgery.

It is because the DRS is such a good prognostic indicator that we would advise anyone who is considering subjecting their horse to wind surgery that they have a DRS examination performed first to determine exactly what surgery carries the best prognosis.

Following the DRS examination the recording can be sent to the surgeon of your choice or it can be performed by our resident surgeon Mario Antignani DVM., or Prof. Geoff Lane FRCVS. who visits Lisadell Equine Hospital monthly.

To View Videos of the Dynamic Scope Please Go to News Section of Website, or access our youtube channel “Lisadellvet”