A new procedure may bring relief for headshaking horses.
Idiopathic headshaking is not an uncommon problem, and proves very frustrating to treat. It is thought to be due to pain in the sensory nerves supplying the face (trigeminal nerve).
Surgeons at the Philip Leverhulme Equine Hospital at the University of Liverpool have developed a technique that uses small coils implanted alongside the nerves.
The procedure is carried out under general anaesthetic with the horse lying on its side. One side is treated, and then the horse is turned over to operate on the other side.
Platinum embolisation coils (used in human medicine to block damaged blood vessels) are introduced into the infraorbital canal under fluoroscopic guidance. (The canal carries the infraorbital branch of the trigeminal nerve through the maxilla.) The coils are placed towards the back of the canal, just in front of the last cheek tooth, where they lie adjacent to the nerve. Between two and five coils are inserted on each side.
Compression of the nerve is believed to block the pain sensation that causes the headshaking.
Veronica Roberts and her colleagues reported their experience of this technique in the Equine Veterinary Journal. Twenty-four horses were treated. All other causes of headshaking had been ruled out, confirming the diagnosis of idiopathic headshaking. The horses had shown no response to conservative treatment such as nose nets.
Overall 84% of cases had a successful outcome. The procedure was successful at the first attempt in 59% of horses. It had to be repeated in six horses and performed three times in one horse.
A side effect seen in 46% of horses was nose rubbing, leading to damage to the skin of the face and muzzle. This usually lasted for less than a month, but in one horse it persisted for five months.
"The side effect is distressing" Dr Roberts adds. "Recently we have been also using a laser at the same time as putting in the coils to try to reduce this side effect but it is too early to see if it has made a difference."
When should the benefits of the treatment be seen? The clinicians suggest that one month after treatment the owners expose the horse to the conditions that previously set off the headshaking. (For horses that showed the nose-rubbing complication after surgery they suggest waiting until two weeks after that has subsided.)
If the headshaking is still present at that time, they suggest testing at monthly intervals. If there has been no improvement by three months after surgery it is unlikely that waiting further will help. Repeating the procedure could be considered..
"The surgery needs to be much better, but it is the best we can offer at the moment" Roberts explains. "Certainly some horses are totally better, some merely significantly improved to the point they can be ridden. The first horse was operated 5 years ago and is still ok. A few others have relapsed but not many."
Since moving to Sweden, Dr Roberts has had a good result in one horse, a very good result in one and excellent results in three more.
The technique seems to have a good chance of substantially improving the signs of headshaking. It needs refining so that fewer cases need to be treated more than once.
For more details see:
Caudal compression of the infra-orbital nerve: A novel surgical technique for treatment of idiopathic headshaking and assessment of its efficacy in 24 horses.
VLH Roberts, SA McKane, A Williams, DC Knottenbelt.
Equine Vet J (2009) 41, 165 - 170