Treatment of idiopathic headshaking in horses with pulsed high-dose dexamethasone.

The research investigates if the use of a high-dose of the anti-inflammatory drug, dexamethasone, can reduce signs of idiopathic headshaking in horses. It confirms that environmental factors can increase headshaking but finds that the drug does not significantly affect headshaking behavior.

Objective

The main aim of the study was to see if a high-dose, pulsed-administered dexamethasone could alleviate signs of idiopathic headshaking in horses in a real-world setting. Idiopathic headshaking in horses was previously hypothesized to have an inflammatory cause, suggesting corticosteroids such as dexamethasone could have potential beneficial effects.

Methods

• The study was designed as a prospective, blinded clinical trial and included a convenience sample of 20 adult horses exhibiting signs of idiopathic headshaking.
• Horses were selected from the general population and were diagnosed by practicing veterinarians.
• Two groups were created: one receiving the dexamethasone and the other a placebo. Each horse was treated orally with 60 mg of dexamethasone per day for 4 days; this was repeated every three weeks over 4 months, mimicking a pulsed dosing regime.
• Horse owners were kept in the dark about the horses’ group designation and were asked to score the severity of headshaking in their horses three times a week, with a score of 0 denoting no headshaking and 4 denoting the most severe.
• The researchers then used ordinal logistic regression to compare the changes in these scores between the dexamethasone-treated and placebo groups over each treatment pulse.

Results

• Of the initial 20 horses, 12 completed the trial. For those that finished, there was no statistically significant difference found between the two groups concerning headshaking scores—a result indicating that dexamethasone had no significant effect on alleviating idiopathic headshaking in horses.
• However, the study did confirm the significant impact of environmental factors, such as sunshine (P ≤ .001), wind (P = .028), and exercise (P ≤ .045), on increasing headshaking behavior in the horses, echoing similar findings in earlier reports.

Conclusion

• Despite a well-considered study design and careful observation, the researchers were unable to show a benefit of dexamethasone treatment for idiopathic headshaking in horses. The reasons for this lack of effect remain unclear and may be rooted in the still imperfect understanding of the pathophysiology underlying idiopathic headshaking.