Clinical Research Abstracts of the British Equine Veterinary Association Congress 2013
Reduced Threshold Potential of the Trigeminal Nerve in Equine Headshaking
Article first published online: 9 SEP 2013
© 2013 The Author(s). Equine Veterinary Journal © 2013 EVJ Ltd
Equine Veterinary Journal
Special Issue: Clinical Research Abstracts of the British Equine Veterinary Association Congress 2013
Volume 45, Issue Supplement S44, page 18, September 2013
How to Cite
Aleman, M., Pickles, K.J., Williams, D.C. and Madigan, J.E. (2013), Reduced Threshold Potential of the Trigeminal Nerve in Equine Headshaking. Equine Veterinary Journal, 45: 18. doi: 10.1111/evj.12145_44
- Issue published online: 9 SEP 2013
- Article first published online: 9 SEP 2013
- Cited By
Although the aetiopathogenesis of headshaking remains elusive, trigeminal neuralgia is regarded as the likely explanation of observed clinical signs. The aim of this study was to compare sensory nerve conduction threshold and velocity of the trigeminal nerve using the infraorbital nerve in control and headshaking horses.
Control group (n = 6 horses) and headshaking group (n = 6) were subject to general anaesthesia. A Nicolet Viking IV evoked potential system was used for sensory nerve conduction study. Stimulating, recording and reference electrodes were used. A pair of stimulating electrodes was placed at the gingival mucosa, one each at the rostral and caudal aspects of the maxillary canine tooth. Four pairs of recording electrodes were placed at 4 different points along the tract of the infraorbital nerve (point 1 at infraorbital foramen), maxillary nerve (point 2 at exit of trigeminal canal), spinal somatosensory (point 3 at level of C1 spinal cord segment), and cortical somatosensory evoked potentials (point 4 at level of frontal cerebral cortex). A reference electrode was placed at a distance half way between the stimulating and recording electrodes at point 1. Stimuli were applied at 2.5, 5, 10, 15, 20 mA. The duration of each stimulus was 0.1 ms. Thresholds were recorded and conduction velocities calculated for each group.
The threshold of sensory nerve action potential occurred at low stimuli (2.5 and 5 mA) in horses with headshaking; and at higher stimuli (10 mA in 3 horses, 15 mA in 1 horse, and 25 mA in 2 horses) in control horses. Although there were differences in conduction velocity between groups, this was not significant.
Conclusions and practical significance
Headshaking horses have a low threshold for inducing sensory action potentials upon minimal stimulation compared with control horses supporting involvement of the trigeminal nerve in the pathogenesis of affected horses.
Ethical animal research
Study approved by the UC Davis IACUC. Sources of funding: Private donation. Competing interests: None.