Familial occurrence of narcolepsy in Miniature Horses

Abstract

Summary In an investigation of 2 closely related Miniature Horses with a history of excessive sleepiness, depression and episodes of collapse, a diagnosis of narcolepsy was made on the basis of neurological examination and pharmacological testing. Further investigations included electroencephalographic examination (KEG), and analysis of protein content, cell count and monoamine metabolite concentrations of lumbosacral cerebrospinal fluid (CSF). There were no abnormalities noted in the EKGs, and no consistent changes in CSF neurotransmitter metabolites in the narcoleptic horses when compared with 3 normal, unrelated Miniature Horses and 2 related, clinically unaffected animals. The breeding background of the 2 affected horses was investigated and a limited survey of Miniature Horse breeders in North America was conducted. These investigations have shown that narcolepsy is a rare but distinct syndrome in the Miniature Horse, and that the cases described here appear to represent a familial occurrence of the disease.

Familial narcolepsy in the Lipizzaner horse: a report of three fillies born to the same sire

“…The regression of clinical signs as seen in two of our cases also was observed over an 8-month period by Lunn et al (1993) in Miniature horses. In comparison, Sweeney et al (1983) observed one case of narcolepsy over 39 months with no progress noted and in this case clinical signs of narcolepsy did not change during this time period.…”

“…In the papers by Lunn et al (1993) and Sweeney et al (1983), physostigmine increased uncoordination and weakness but did not cause complete collapse in the affected horses. The only complete collapse in narcoleptic horses was described by Sheather (1924) in Suffolk foals and by Lunn et al (1993) in Miniature horses. The forms of cataplexy may vary among animal species.…”

“…Onset of the syndrome was as foals and excessive sleepiness gradually regressed as the horses aged. An early onset of signs also was observed in two closely related Miniature horse foals (Lunn et al 1993), in an Icelandic foal (Bathen-Nothen et al 2009) and in three Suffolk foals (Sheather 1924). On the contrary, Sweeney et al (1983) and Hines (2005) described the onset of clinical signs in adult horses ranging from 2 to over 20 years.…”

“…Sporadic (Sweeney et al 1983;Bathen-Nothen et al 2009) and familial cases (Sheather 1924;Lunn et al 1993) of excessive sleepiness in horses have been described. Primary sleeping disorders characterised by excessive daytime sleepiness in human beings can be distinguished as narcolepsy with cataplexy, narcolepsy without cataplexy, idiopathic hypersomnia with long sleep time and idiopathic hypersomnia without long sleep time (ICSD-2 2005).…”

“…Sleep deprivation caused by painful orthopaedic disorders must be ruled out in these horses (Aleman et al 2008). A positive physostigmine and/ or atropine provocation test, which aggravates or improves narcoleptic symptoms, respectively, has also been proposed (Lunn et al 1993;Bathen-Nothen et al 2009). In the case-series presented here, the occurrence of sleep disorders in three Lipizzaner fillies is described.…”