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

REASONS FOR PERFORMING STUDY: There are no consistently safe and effective methods for the treatment of trigeminal‐mediated headshaking in horses. In affected horses, the trigeminal nerve is sensitised, appearing to result in neuropathic pain. Percutaneous electrical nerve stimulation (PENS) therapy is a minimally invasive neuromodulatory treatment used in people to manage neuropathic pain. OBJECTIVES: To determine whether PENS therapy is safe, tolerated and effective for the management of trigeminal‐mediated headshaking in horses. STUDY DESIGN: Descriptive case series. METHODS: Seven horses diagnosed with trigeminal‐mediated headshaking and currently showing clinical signs were studied. All procedures were carried out in sedated horses with a needle‐prick sized area of skin desensitised with local anaesthetic to facilitate probe insertion. A disposable PENS probe was advanced subcutaneously adjacent to the nerve, rostral to the infraorbital foramen under ultrasonographic guidance. The nerve was stimulated for 25 min following a protocol of alternating frequencies and a perception threshold based on human clinical data. The probe was removed and the procedure repeated on the contralateral side. The protocol used comprised a series of 3 or 4 treatments, with treatments being repeated when signs of headshaking recurred. RESULTS: All horses tolerated the procedure well. Three horses developed a haematoma at the site on one occasion and 2 had increased clinical signs for up to 3 days following first treatment. Six horses demonstrated a positive response to their first treatment, returning to ridden work at the same level as prior to onset of headshaking, with 5 continuing to respond. Median remission time for first treatment was 3.8 days (range 0–8 days, n = 7), second treatment 2.5 weeks (0–8 weeks, n = 7), third treatment 15.5 weeks (0–24 weeks, n = 5) and fourth treatment 20 weeks (12–28 weeks ongoing, n = 2). CONCLUSIONS: Percutaneous electrical nerve stimulation therapy is a safe, well tolerated, minimally invasive, repeatable management option for trigeminal‐mediated headshaking, with encouraging efficacy for amelioration of clinical signs in the short‐ to medium term.