School of Veterinary Medicine, Department of Medical Sciences, 2015 Linden Drive, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
Photic headshaking in the horse: 7 cases
Article first published online: 23 APR 2010
© 1995 EVJ Ltd
Equine Veterinary Journal
Volume 27, Issue 4, pages 306–311, July 1995
How to Cite
MADIGAN, J. E., KORTZ, G., MURPHY, C. and RODGER, L. (1995), Photic headshaking in the horse: 7 cases. Equine Veterinary Journal, 27: 306–311. doi: 10.1111/j.2042-3306.1995.tb03082.x
- Issue published online: 23 APR 2010
- Article first published online: 23 APR 2010
- Received for publication: 10.11.93; Accepted: 12.11.94
Seven horses with headshaking are described. No physical abnormalities were detected in any of the cases. Six of these horses had onset of clinical signs in the spring. The role of light was assessed by application of a blindfold or dark grey lens to the eyes, covering the eyes with a face mask and observing the horse in total darkness outdoors. Cessation of headshaking was observed with blindfolding (5/5 horses), night darkness outdoors (4/4 horses) and use of grey lenses (2/3 horses). Outdoor behaviour suggested efforts to avoid light in 4/4 cases. The photic sneeze in man is suggested as a putative mechanism for equine headshaking. Five of 7 horses had improvement with cyproheptadine treatment (0.3 mg/kg bwt b.i.d.). Headshaking developed within 2 calendar weeks of the same date for 3 consecutive years in one horse. Neuropharmacological alterations associated with photoperiod mechanisms leading to optic trigeminal summation are suggested as possible reasons for spring onset of headshaking.