Sensory nerve conduction and somatosensory evoked potentials of the trigeminal nerve in horses with idiopathic headshaking.

This research article investigates the significance of sensory nerve activity and evoked potentials of the trigeminal nerve in horses suffering from idiopathic headshaking. The researchers tested the nerve’s activity in healthy horses and compared it to those with the disorder, finding meaningful differences which might signify trigeminal nerve hyperactivity in the affected horses.

Details of the Study

• The study aimed to find out if there were differences in the sensory function of the trigeminal nerve in healthy horses versus those suffering from idiopathic headshaking (HSK), a disorder yet to be fully understood in terms of cause and physiological effects.
• Twelve horses, both healthy and those affected by the HSK, were used in the study, which is prospective in nature.
• The researchers evaluated the sensory nerve action and somatosensory evoked potentials of the horses, with the stimulus being applied to the mucosa dorsal to the maxillary canine.
• The sensory path of the trigeminal complex was traced and recorded using electrodes at various points (infraorbital nerve, maxillary nerve, spinal tract of trigeminal, and somatosensory cortex).

Results

• The researchers discovered a significant difference in the threshold for activation of the trigeminal nerve between the affected horses (≤ 5 mA) and the healthy ones (≥ 10 mA).
• Post-activation, no differences in nerve action potential parameters were observed between the groups or between the left and right sides of the individual horses.
• Interestingly, a horse showing seasonal symptoms of HSK had an activation threshold similar to the control group when tested during a symptom-free period.

Conclusions

• This study supports the hypothesis of trigeminal nerve hyperexcitability being involved in the pathophysiology of idiopathic headshaking.
• The findings also suggest that the disease may induce functional changes in the sensory pathway of the trigeminal complex rather than permanent structural alterations, evidenced by variability in symptoms across seasons.
• Moreover, the research posits that horses could potentially serve as a natural model for studying similar conditions in humans, such as idiopathic trigeminal neuralgia.