Internal neurolysis of the maxillary branch of the trigeminal nerve for the treatment of equine trigeminal mediated headshaking syndrome.

A 5-year-old Hannovarian warmblood gelding was presented for recurrent headshaking exacerbated with exercise. The horse displayed clinical signs of repetitive vertical head movements, face rubbing on the forelimbs and on the ground, repetitive sneezing, and striking the muzzle with his forelimbs. The clinical signs resulted in a horse that could not be ridden and was dangerous. Clinical signs were most persistent in direct sunlight, but occurred with excitement, exercise, or bridling indoors. A diagnosis of equine trigeminal mediated headshaking syndrome was made. Surgical treatment was performed with a supraorbital approach to the maxillary branch of the trigeminal nerve as it exits the round foramen, where an internal neurolysis (nerve combing) was conducted on both the left and right nerves. Severe headshaking behavior resolved after surgery. The horse displayed face rubbing of the muzzle which began 96 hours after surgery and resolved over 12 days with corticosteroid and vitamin E therapy. The horse became pasture sound and the clinical signs had resolved in the presence of sunlight, but repetitive vertical head movements persisted under saddle which left the horse unpleasant to ride.