Horner's Syndrome in Dogs: Welfare and Diagnosis

Key Welfare Considerations

• Horner's syndrome results from disruption of the sympathetic nerve supply to the eye and face.
• Classic welfare signs include ptosis (drooped eyelid), miosis (constricted pupil), enophthalmos, and third eyelid protrusion.
• The three-order neuron classification (first, second, third order) guides welfare diagnostic investigation.
• First-order (central) Horner's results from brainstem or cervical spinal cord disease — serious welfare implications.
• Second-order (preganglionic) Horner's from thoracic/neck lesions requires welfare investigation for masses.
• Third-order (postganglionic) Horner's is most commonly idiopathic in dogs — excellent welfare prognosis.
• Middle ear disease is a significant welfare cause of Horner's in dogs — otitis media welfare assessment is important.
• Pharmacological testing with phenylephrine differentiates pre- and postganglionic welfare lesion location.
• Third-order Horner's resolves within 6-16 weeks in idiopathic cases — welfare prognosis is excellent.
• MRI brain and spinal cord imaging identifies welfare-relevant central or preganglionic disease.
• Chest radiography screens for welfare-relevant mediastinal masses in second-order Horner's.
• The cosmetic welfare appearance of Horner's causes owner concern — reassurance about prognosis is important.
• No welfare treatment is required for idiopathic third-order Horner's — resolution with time.
• Welfare management focuses on identifying and treating any underlying cause rather than the eye signs.
• Golden Retrievers have breed predisposition to idiopathic Horner's — welfare prognosis in this breed is excellent.