The leg cramps could be from something totally unrelated to your spinal problem and that is why the doc may have appeared skeptical to you. Those muscle cramps can be extremely painful. They can be related to many different things. Dehydration, metabolic changes, circulatory issues, etc. There are many causes.

If you are being followed by a PCP, I would discuss the muscle cramps with him and have some blood work done if you have not already done so. If they are persistent, which it sounds like they are, you definitely need to find some relief. Quinine was usually the drug used for leg cramps but it has proven ineffective in most cases from what I have read.

Be sure you stay hydrated and request further investigation into the matter. You need your sleep and you don't need the daytime pain either.

I am not suggesting that the cramps are not related to your spinal issues, just that they MAY not have anything to do with it.