British researchers have reported some success in treating headshaking in horses through electrical nerve stimulation using a probe beneath the skin.
Veronica Roberts and her colleagues carried out their study on seven horses diagnosed with trigeminal-mediated headshaking.
There are currently no consistently safe and effective methods for treatment of the problem. In the condition, the trigeminal nerve is sensitised, appearing to result in neuropathic pain. This can result in headshaking.
The researchers employed what is known as Percutaneous Electrical Nerve Stimulation (PENS) therapy, a minimally invasive treatment used in people to manage neuropathic pain.
The seven horses were sedated before undergoing treatment. A tiny area of skin was desensitised with local anaesthetic to facilitate probe insertion.
A disposable PENS probe was advanced beneath the skin under ultrasonographic guidance to sit next to the nerve.
The nerve was stimulated for 25 minutes following a protocol of alternating frequencies and a perception threshold based on human clinical data.
The probe was then removed and the procedure repeated on the other side.
Each horse underwent a series of three or four treatments, with treatments being repeated when signs of headshaking recurred.
All horses tolerated the procedure well, the researchers reported in their findings, which have been accepted for publication in the peer-reviewed Equine Veterinary Journal.
Three horses developed a haematoma at the site on one occasion and two had increased clinical signs of headshaking for up to three days after their first treatment.
Six horses showed a positive response to their first treatment, returning to ridden work at the same level as before the onset of headshaking, with five continuing to respond.
The median remission time for the first treatment was 3.8 days, with the horses ranging from 0 to 7 days.
The median remission time increased with each treatment. It was was 2.5 weeks after the second treatment and 15.5 weeks after the third treatment, with some of the horses enjoying relief of up to 24 weeks.
The fourth and final treatment provided a median remission time of 20 weeks. The return of headshaking for five of the horses ranged from 12-28 weeks, with two of the animals getting ongoing relief.
The researchers concluded that PENS therapy was a safe, well-tolerated, minimally invasive, repeatable management option for trigeminal-mediated headshaking. It proved effective at easing clinical signs in the short to medium term, which was encouraging, they said.
Roberts, from the School of Veterinary Sciences at the University of Bristol, was joined in the research by W.H. Tremaine, who is also from the university; and N.K. Patel, from the Institute of Neurosciences at Southmead Hospital Bristol.
V.L.H. Roberts, N. K. Patel and H. Tremaine.
Neuromodulation using percutaneous electrical nerve stimulation for the management of trigeminal-mediated headshaking; a safe procedure resulting in medium term remission in five of seven horses.
The abstract of the study can be read here.