On a similar note... I have very little AS pain, but began to experience numbness/tingling/coldness in my extremities. I became alarmed had it checked out and doctor confirmed the disease had got in my nervous system. An injection and some NSAIDs for some time calmed down the symptoms and they never returned (now over 15 years ago).
We must always be wary of any such symptoms as it could mean permanent nerve damage (Neuropathy) or Cauda Equina Syndrome. It is something that must be checked out by an experienced doctor as late treatment is seldom of much use. Nerve damage whether caused by Cauda Equina Syndrome or by any other cause is rare but need urgent treatment. Check out Cauda Equina Syndrome on Google.