20yr ago herniated disc/sciatica,8 yr ago calf atrophy began.5yr ago clean emg. today still full mobility but further calf atrophy leg twitching,als?

Talk with your neuro: logist post EMG to find out what nerve damage may have occurred that is contributing, especially since your EMG was normal. What was his/her advice to you? Herniated discs and sciatica don't normally cause calf atrophy. Ask him/her about your concerns with ALS, as you're not saying you have the typical symptoms of spasticity, spasms, cramps, fasciculations, or spreading of atrophy to other areas.