Whether or not you can work depends on how progressed the disease is, how soon after symptoms started that you received a diagnosis with treatment commencing, how well you're responding to treatment (including side effects from the medications) and what kind of work you're in.
Forget high stress jobs, those where there's a lot of noise, motion, emotional distress, places you might receive even a light touch, open areas. These are all things that are triggers that can set off an episode of spasms, stiff or rigid muscles, falls, difficulty breathing and a number of problems associated with the disease.
Consider whether or not you can drive or have transportation to go to and from work. If your disease is advanced, how many days in a month would you miss work because of the disease. This can make a difference in whether or not you'd be considered by anyone for hire or if you should consult an attorney for the purposes of filing for disability. These are just some of the things I've gone through over time.
Though I don't know the percentage of people with SPS that may work, I know there are few people known to have the disease and few doctors that know what to look for or understand how to cope with it so it takes roughly seven years to diagnose if you have the GAD65 antibodies (though mine took 15-16 years). Not everyone has the antibodies. That said, I imagine even the undiagnosed keep working until they miss too much work or can't stand the pain and other symptoms.