EquiPENS(TM) Neuromodulation for Trigeminal Mediated Headshaking


Chine House Veterinary Hospital is now offering EquiPENS (per-cutaneous electrical nerve stimulation) neuromodulation therapy for equine trigeminal mediated headshaking. Clinical trials undertaken by the University of Bristol has shown EquiPENS to be a safe, well tolerated, repeatable management option for trigeminal-mediated headshaking, with encouraging efficacy for improvement of clinical signs.  

 Trigeminal-mediated headshaking:

Horses with trigeminal mediated headshaking show violent, usually vertical, shaking of the head, rubbing of the muzzle and snorting which we believe is caused by nerve pain. Such nerve pain is very difficult to treat and does not respond to anti-inflammatories and pain killers. Research involving Dr Kirstie Pickles from Chine House has shown that the trigeminal nerve (the main nerve providing sensation to the face) fires at an inappropriately low threshold in headshaking horses such that harmless stimuli e.g. rain, UV light are perceived as painful. The cause of this misfiring is incompletely understood but the nerve appears normal when examined under a microscope indicating that the nerve itself is not physically damaged and therefore the nerve dysfunction is potentially reversible.

PENS neuromodulation in people:

Trigeminal-mediated headshaking shares some clinical similarities to human trigeminal neuralgia which sufferers describe as itching, tingling, burning, electric shock-like sensations in the face. One therapy, available as a course of treatment on the NHS under NICE guidelines, for these patients is PENS neuromodulation. A probe is placed under the skin next to the affected nerve and a small current applied. Patients report that, once the probe is in place, it is quite a pleasant sensation. The only side effect reported in people is slight bruising at the site of probe insertion. Not all patients respond but, if they do, pain relief lasts from a few hours up to a week following the first treatment, a few days to two weeks following the second treatment and an average of two months after the third and subsequent treatments. It is important to repeat treatments as close as possible to the return of signs of pain. Some people only respond to later treatments. Equally, it is possible to respond to the initial treatment but then not respond to later treatments.

EquiPENS neuromodulation in horses:

A published clinical trial of EquiPENS neuromodulation in seven headshaking horses at the University of Bristol has shown the procedure to be tolerated well under standing sedation. Five horses returned to ridden work following their third procedure, with an average remission time of 15.5 weeks. One horse responded to the first procedure but not to later ones. A few horses had minor bruising at the site of probe insertion. The University of Bristol has now performed the procedure 138 times on 48 horses. Of these, 39% returned to their previous level of ridden work for at least 2 months, some up to 2 years and ongoing. Some horses have a few bad headshaking days after one or more procedures but may still cease headshaking. Length of remission may increase with repeated procedures. However, some horses have not responded and others have responded for too short a time to be practical. Results suggest that three procedures should always be performed before deciding if the horse will respond to treatment.