Anyone experienced with feline Horner's Syndrome??

[Hell Hath No Fury]

Last Tuesday I discovered my cat in a fair bit of distress -- long story (and $900+) short, he has been diagnosed with Horner's Syndrome.

I have been doing a bit of reading on it and it certainly fits - he was in not good shape when I found him, suggesting some sort or traumatic injury -- but he has a few symptoms that I am finding puzzling.

He is not talking (he's a HUGE chatterer) and when he does meow, it is very soft and hoarse -- think Marlon Brando in "The Godfather". And he is also not purring. He is enjoying getting petted and makes bisquits, but he breathes heavily through his nose instead of pouring.

Other than that, he is eating/drinking/pooping well, and appears to be recovering from whatever traume he experienced.

Any help/suggestions?