Nystagmus

Question
My 18 year old Jack Russell terrier, Roxy, looks as though she has Nystagmus.  She was going around in circles yesterday so we took her to the vet who says if this doesn't resolve in a couple of days we should think about Roxy's future.  What I forgot to ask though is that if this resolves will it return?  
Thanks for your help

Answer
Sincere apologies for the delayed response.

Nystagmus is a sign of a problem with the vestibular system.  This can be temporary as with an ear infection or physical trauma or can be long term as with idiopathic vestibular syndrome, which happens in older dogs and is a progressive degeneration.  Your veterinarian likely was looking to see if the nystagmus persisted which might lend strength to a diagnosis of IVS.  If however it resolved I would not expect it to return.

Please let me know if I can be of any further assistance and again apologies for the delay.