Horner's syndrome in cats and dogs: a review

The literature was reviewed and reference made to a retrospective study of cases of Horner's syndrome seen at the Royal (Dick) School of Veterinary Studies. It was concluded that the cardinal diagnostic sign of Horner's syndrome is miosis. Ptosis, prolapse of the third eyelid and apparent enophthalmos are frequently presented but other signs of sympathetic deficit such as facial or aural vasodilatation are observed less consistently. The clinical diagnosis may be confirmed by pupillary response to cocaine. Horner's syndrome was frequently associated with trauma and less commonly with neoplasia. In a significant number of cases the cause was undetermined. Lesions of central neurons are reported infrequently while lesions of preganglionic and postganglionic neurons are described more often and appear to have a similar incidence. Preganglionic lesions most frequently involve the thoracic spinal cord and cervical sympathetic trunk while postganglionic lesions usually result from middle ear and retrobulbar disorders. The site of the lesion may be determined on the basis of clinical signs and pupillary response to phenyladrenalin or hydroxyamphetamine which both distinguish postganglionic lesions from preganglionic and central lesions.