The sural nerve is a sensory nerve that runs along the calve and into the outer part of the foot. I have damage to my sural, tibal, and peroneal nerve in my left leg and sural and peroneal in my right leg. I am considered idiopathic at this time, all my blood work has come back normal so far. The damage I have is affecting the mylen covering and also the axons. affecting my sensory and motor functions. I have mild sysmptoms most of the time with occassional burning sensations is my thigh and left calve. What bothers me the most is the weakness in my left knee and the falling asleep feeling in both feet and ankles. I am only 41 and was diagnosed 7 months ago. By reading the other posts, it looks like it can take a long time to find a cause.