AThe cause of pharyngeal cicatrix (tightened scar tissue from wound healing) is usually unknown, but is assumed to be inflammation based on scarring present in the pharynx. Unfortunately, most obstructions are diagnosed when the cicatrix is mature, and the cause of the insult difficult to determine. If the cicatrix is mature in your horse, it is probably safe to assume that the lesion will not worsen unless the inflammation recurs. As far as agricultural spraying is concerned, it depends on what is being sprayed. If the sprayed compound causes airway inflammation, it could cause further problems.

If considering treatment, there can be other abnormalities (structural laryngeal or fungal infections) associated with the cicatrix, so a thorough exam of the upper airway should be done. Transendoscopic (through the scope) treatment with either electrosurgery or a laser is used to cut the wall of the cicatrix (which is usually pretty thin). A stent of the area might be used after surgery to help hold the cicatrix open, as recurrence is the major problem. My experience with cicatrix is that they can be very frustrating, although decent results have been reported in the literature in a very small number of cases. My advice would be to attempt treatment only if you can’t work around his exercise intolerance.