This cat has been presented by the owner saying that, having been awol for a few days, the animal arrives back home with her eyes looking like this. What is your provisional diagnosis and what test would you perform to confirm it. I know we only have the eyes to see here, but would it be worth looking at the rest of the animal too?!
The narrower eyelid in the right eye and the narrower pupil, together with the protrusing third eyelid showing an enophthalmos with the globe sunken back in the orbit, are pathognomonic of Horner’s syndrome. But to be sure, and to localise the site of the nerve lesion, topical phenylephrine gave this amelioration of signs in 28 minutes. That shows that the second order neuron between the spinal cord and the cranial cervical ganlion is affected. Actually you’ld have to be very remiss not to notice that the cat had an elbow flexion ipsilaterally too, showing a radial nerve palsy suggesting that the sympathetic denevation is related to trauma to the brachial plexus. This must have resulted only in neuropraxia, for over the next two months the radial and sympathetic nerve dysfunction gradually resolved.