Re: Cervical stenosis, what are the rules?
The rules are not hard and fast, but up to interpretation by your doc when they compare MRI results with your symptoms and other tests such as nerve conduction. No one test can determine what needs to be done.
But you have some incorrect info.. the signs of cord compression from spinal stenosis are reversible if caught and the cord allowed to expand back to a reasonable size. I've been through cord compression in my cervical, thoracic and lumbar spine and surgery has relieved the compression and I got back most of the feeling and all of the strength. And I have cord compression again in my neck after having it relieved twice before.
Seeing spinal fluid around the cord does help them to know you are okay. But when there is frank compression of the cord, that is when they start to measure the cord width. Since the pressure is done so slowly over a period of many years, we can take more cord compression than someone who has had it happen abruptly such as in breaking one's neck or dislocating a vertebrae suddenly. The cord averages 11-12mms in width. I personally had compression down to 5-6 mms at more than 1 level in my neck and it was 7-8mms. in the remaining levels...from C3 to C7. Others here have similar stories.
So you have a good way to go before you will need surgery. I opted to have a laminoplasty that opens the back of the spinal canal and re-builds it to double the size of the canal, yet continue to protect the cord with bone. You may need the same thing down the road.
So as far as rules go...it's not just how many millimeters or that you have numbness in your feet or that your reflexes are hyper or hypo, indicating nerve compromise, but all of them together. The MRI can show the cord width and that is important but not the be all and end all of cord analysis. I recently was operated on for cauda equine syndrome from lumbar compression. The MRI said I didn't have it. The nerve studies said I had something more wrong than the MRI showed. When the surgeon got in there, he was blown away as to how bad it really was and my symptoms were correct for what was really wrong. BTW, everything came back.
So it is all of it and no one study or symptom rules the diagnosis or what needs to be done to manage or correct it.