Yes to the burning zapping, pins and loss of sensation from the knees getting more pronounced approaching the toes. The muscle loss above the waist is limited to the soaz. (phoenetic spelling). The muscle that lifts the knee. My Endo RXd me Foltanks, methylated b-12 plus folic acid. I took everything that was not contraindicated as I was in quite a panic. Mrs. D was a lifeline to me and I took the shotgun approach. I still take fish oil because I work on a gyro bike almost daily and now am able to stand up and pedal 40 strokes. Once upon a time I would have fallen off. As far as spasms, I could not tell pain from spasm. They (muscles) would not harden up or try to work involuntarily but I would lie and rub deeply for the pain. Mt knees will stiffen and ankles and hips thus the gyro bike to keep the juices flowing, haha,sob. You might search Piriformis Syndrome, also Amyotrophy. The latter has an acute phase. I experienced some relief by performing Pifirormis stretches and these are close kin to stretches designed to release soaz. My b-12 number was at 114 when accident happened and b-12 deficiency can have wide array of effects. 400 is the low acceptable these days. Hoping for your betterment, Ken in Texas.