Question: Our 18 month old cat was stricken with paralysis beginning in his hind legs and progressing to the front. After treatment he is in full recovery. We saw him vomit a blade of what looked like mondograss (we have lots of it) the night before onset of the paralysis. He had another long piece of what looked like mondo grass in his stool the next morning. Have you ever heard of mondograss or its berries causing toxic paralysis in domestic animals?
I can't tell you that mondograss is definitely NOT toxic to cats. I can say however that I have never heard of such a concern and after an exhaustive search could find no reference to mondo being toxic to cats or other pets.
It is not unusual for cats to consume grasses and other such plants and then regurgitate to remove something from their stomach. Ask you vet about this and perhaps he could offer some other possible causes.