Never have had a case/patient with it. Very rare, but it can happen. There are several other neurological and neuromuscular condition a little more common but still rare that present with similar symptoms.
If current therapy is unsuccessful, I recommend getting a diagnosis from a neurologist (will probably need to go to a large specialty practice or a vet school). These things are so rare they are very difficult for a general practitioner to come up with a correct diagnosis.
Doug, DVM
Doug & Sandy
Kaylee
Winnie 6 1/2 year old golden
2008 Southwind 2009 Honda CRV