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Background: Oral administration of magnesium and boron might have a beneficial effect on headshaking behavior in horses., Objective: Evaluate the effects of oral magnesium alone or in combination with boron on headshaking behavior in affected horses., Animals: Twelve geldings (6 healthy controls and 6 affected)., Methods: Prospective randomized controlled dietary trial over 42 days in 12 horses (6 horses diagnosed with trigeminal-mediated headshaking and 6 unaffected healthy controls). All horses received a hay diet and were randomized into 3 treatment groups: pelleted feed combination (PF), pelleted feed combination with magnesium (M), and pelleted feed combination with magnesium-boron (MB) with a week washout of hay only between treatments. Headshaking behavior and biochemical blood variables were assessed at baseline (hay only) and then after each week of supplementation., Results: All 3 diet interventions increased blood ionized and total magnesium. Groups M and MB further increased Mg 2+ when compared to PF. Horses receiving treatments had a significant reduction in headshaking behavior, as measured by incidence rate ratio (IRR), when compared to unsupplemented hay diet (44% for PF, IRR, 0.558; CI, 0.44, 0.72; P < .001; 52% for M, IRR, 0.476; CI, 0.37, 0.62; P < .001; and 64% for MB, IRR, 0.358; CI, 0.27, 0.48; P < .001)., Conclusions and Clinical Importance: Magnesium in combination with boron had the greatest decrease in headshaking. Oral supplementation with magnesium or magnesium in combination with boron should be considered in horses affected with headshaking., (© 2019 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.)

Background: Trigeminal-mediated headshaking results from a low threshold for firing of the trigeminal nerve. A seasonal component has been implicated in onset of clinical signs, which occur during the spring and summer months. Geldings are overrepresented in the affected population and hormonal differences as compared to a healthy control population of geldings might contribute to headshaking., Objective/hypothesis: To assess concentrations of luteinizing hormone (LH) over an 8-hour period in gelded healthy controls and horses affected with headshaking. Our hypothesis was that geldings with seasonal headshaking would have higher concentrations of LH over an 8-hour period compared to control horses during the summer when affected horses manifested headshaking., Animals: Twelve geldings (6 controls and 6 affected)., Methods: Prospective controlled trial. Blood samples were drawn every 15 minutes over an 8-hour time period during summer from all horses to measure circulating LH concentrations by using a radioimmunoassay for equine LH. All affected horses were actively affected by headshaking at the time of sample collection., Results: No statistically significant differences in LH concentrations were found throughout the study period in headshakers as compared to control horses. Time had no significant effect, but a slight decrease in LH concentrations was observed for all horses. The main limitation of the study was the low number of horses., Conclusions and Clinical Importance: Horses affected with headshaking did not have significant differences in circulating LH during the late summer as compared to control horses., (© 2019 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.)

Background: Trigeminal-mediated headshaking results from low-threshold firing of the trigeminal nerve resulting in apparent facial pain. Magnesium may have neuroprotective effects on nerve firing that potentially dampen signs of neuropathic pain. This hypothesis has not been investigated in horses with trigeminal-mediated headshaking., Objective: To investigate head-shaking behavior in affected horses after IV magnesium sulfate infusion., Animals: Six geldings with trigeminal-mediated headshaking., Methods: Prospective randomized crossover study. Horses were controlled for diet and infused IV with 5% dextrose solution (DS; control solution at 2 mL/kg body weight [BW]) and MgSO 4 50% solution (MSS at 40 mg/kg BW). Head-shaking behavior was recorded at times T0 (baseline, before infusion) and T15, T30, T60, and T120 minutes post-infusion. Venous blood variables such as pH, HCO 3 - , standard base excess (SBE), Na + , Cl - , K + , Ca 2+ , Mg 2+ , total magnesium (tMg), glucose, and lactate were measured; strong ion difference (SID) and anion gap (AG) were calculated for each time point., Results: Blood variables including pH, Na + , Cl - , K + , SID, AG, lactate, Ca 2+ , tMg, and Mg 2+ had significant changes with MSS as compared to DS treatment. Glucose, SBE, and HCO 3 - did not have significant changes. A 29% reduction in head-shaking rate occurred after MSS treatment but no change occurred after DS treatment., Conclusions and Clinical Importance: Administration of MSS IV increased plasma total and ionized magnesium concentrations and significantly decreased head-shaking behavior in horses with trigeminal-mediated headshaking., (© 2019 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.)

Trigeminal-nerve-mediated headshaking represents a major welfare challenge for owners and veterinarians and is caused by a low threshold firing of the trigeminal nerve resulting in pain manifested as violent head jerking that often terminates the horse&rsquo;s career and life due to poor quality of life and suffering. As metabolic changes such as acid⁻base status and electrolytes play a role in nerve firing, this study sought to assess the effects following administration of hypertonic solutions on headshaking behavior in affected horses. This prospective randomized controlled crossover design utilized six horses affected with trigeminal-mediated headshaking and three treatment groups receiving intravenous administration of 5% dextrose solution at 2 mL/kg bwt (DS), NaCl 7.5% at 4 mL/kg bwt (HS), or NaHCO₃ 8.4% at 2 mmol/kg bwt (HB). Horses were assessed for headshaking behavior changes at times T0 (baseline, before infusion) and T15, 30, 60, 120 min post infusion. Venous blood variables: pH, HCO₃ &minus; , standard base excess (SBE), Na⁺, Cl &minus; , K⁺, Ca 2+ , Mg 2+ , total magnesium (tMg), glucose, and lactate were measured at T0 (baseline, before infusion) and T5, 15, 30, 60, 120 min post infusion. Strong ion difference (SID) and anion gap (AG) were calculated for each time point. With HB treatment, there was greater than 50% reduction in headshaking rate. There was an effect of time on increasing headshaking rate. There was an effect of breed on headshaking rate. Changes in blood parameters following DS were virtually absent. Infusion of HS caused mild changes and did not vary much from baseline except for SID and AG. Only infusion of HB caused blood pH and HCO₃ &minus; to be outside of the physiologic range (alkalemia and metabolic alkalosis, respectively), SBE to double or triple, AG to decrease, and SID to increase compared to baseline. Infusion of DS was followed by increase in blood glucose and decrease in blood Na⁺. Infusion of HS was followed by increase in Na⁺ and Cl &minus; and decrease in Mg 2+ . Infusion of HB was followed by decrease in Mg 2+ . Blood tMg, K⁺, and Ca 2+ decreased slightly, but did not vary greatly from baseline following any of the treatments, remaining within physiologic ranges. Changes in blood composition were transient. Among all treatments, only HB had an effect on headshaking rate. The limited effects following these fluids were likely due to normal mechanisms of regulation of blood levels of pH and electrolytes. Further investigations of changes in electrolytes that might affect nerve firing should be explored.