FAMILIAL OCCURRENCE OF NARCOLEPSY IN MINIATURE HORSES

In an investigation of 2 closely related Miniature Horses with a histo ry of excessive sleepiness, depression and episodes of collapse, a dia gnosis of narcolepsy was made on the basis of neurological examination and pharmacological testing. Further investigations included electroe ncephalographic examination (EEG), and analysis of protein content, ce ll count and monoamine metabolite concentrations of lumbosacral cerebr ospinal fluid (CSF). There were no abnormalities noted in the EEGs, an d no consistent changes in CSF neurotransmitter metabolites in the nar coleptic horses when compared with 3 normal, unrelated Miniature Horse s and 2 related, clinically unaffected animals. The breeding backgroun d of the 2 affected horses was investigated and a limited survey of Mi niature Horse breeders in North America was conducted. These investiga tions have shown that narcolepsy is a rare but distinct syndrome in th e Miniature Horse, and that the cases described here appear to represe nt a familial occurrence of the disease.