I, also have IC with severe Hunners Ulcers and experience the same thing that you go through.  I also have a very rare nerve disorder called CIDP (Chronic Inflammatory Demyelinating Polyneuropathy) which causes severe pain in my wrists and hands when it flares up and causes me to have bilateral wrist drop and the loss of both of my hands, which can last for a few hours, weeks or months.  My longest episode was 13 months of having no use of my hands and extreme pain to go along with my IC.  Of course, I have issues with classification of IC as well.  Personally, I think that the diagnosis of IC should only be used in patients with Hunners Ulcers, which is rare.  In patients with symptoms only, I think it should be referred to as Irritated Bladder Disorder (or something similar).  This way, doctors can know immediately what they are dealing with when they look at your chart.  Of course, most doctors I've seen have to be educated on the disorder anyway!!