My hand bellow the elbow is getting thinner

Hello! First of all I would like to ask you to forgive my bad English because I am only 17 and come from Europe. Thank you for understanding!

Now allow me to explain my syndromes. In past 3 years I have been noticing that my hand bellow the elbow is getting thinner. It all started with my little finger which jumps strangely when I try to move it. At the same time I had cramps in my left hand. I didn't really pay attention to it, and I didn't even notice my hand was getting thinner. I noticed it last year when I was at the doctor (to get medical permission for driving license) and I had to stretch out my arms. My fingers were shaking, I couldn't move little finger close to my third finger and I couldn't straighten out the forefinger. That is when I have decided to pay a visit to my doctor. He sent me to a hospital and I went through all kind of tests but they couldn't give the diagnosis. They also thought the reason could be virus meningitis which I had had in a summer one year earlier, but I can assure you this is not the reason because I have found pictures from before I had meningitis and my hand was already thinner as normal. They sent me to another, bigger hospital. I went through the same tests mostly and some new ones, but they couldn't figure it out either. It's been almost a year now since I first went to a doctor, but I still don't know what's going on.

They think one possible theory is muscle atrophy, but don't understand why it progressed that fast, besides, the atrophy is usually symmetrical, but my right hand is absolutely fine.
The other theory is that it might be something genetic, but I am not sure about this one.

I had EMG about 3 times and they didn't find anything strange. I also had many other tests like x-ray, CT of head and arm, MR of spinal marrow, MLPA test and some others.
MLPA showed presence of SMN1 and SMN2 and <5% of something. Maybe you know what it means, I don't.
MR showed between C6 and middle of C7 thinner atrophic spinal marrow (translation may not be exact). Some doctors say that this can not cause my problems, because the deformation is minimal, but some others think this could be the main reason but none ventures to confirm any of it.
Others didn't show anything unnormal.

Doctors are trying hard to find the reason why this started, but I don't remember having any kind of injury. I never even had a broken bone or anything like it. One of the doctors even said that this is the point where Slovenian knowledge needs help from foreign countries, but I only want to know if there is a way of treatment that could improve the condition of my hand? Because I will have to decide about further education soon and I really want to pick something computer related.

Thank you again. I really appreciate your effort!