Muscle atrophy

Hello

So I discovered the size of my leg muscle became smaller than the other leg but I didn't care that time) and this year I decided to go to a neurologist and after I had CT scanner and an EMG it showed that I have lumbar herniated disc and the EMG showed that I didn't have neuropathy so I went to a neurosurgeon he said that I don't really have a herniated disc and the problem of my back can never be the reason of my muscle atrophy , so he doesn't understand what caused my muscle to atrophy and so he asked me for an MRI .

*My muscle atrophy stopped ( I'm not losing any more muscle ) I also did exercises but it didn't change

Can someone tell me what would my problem ( just give me the possibilities of what I may have)

And thank you so much